The 2001 Shiny, Powerful, Magnificent, Enigmatic, Incredible!
Mega-Hyper-Ultra-Super-Outburst of

WZ Sagittae (WZ Sge)

The King of Cataclysmics!!!!

VSNET is permanently superoutbursting...

Amazing!
Unbelievable!
Wonderful!
Fantastic!
Miracle!
Fascinating!
Crazy!
...
The star has left no time of rest for observers...
There is no other choice than to observe WZ Sge...
WZ Sge, WZ Sge, WZ Sge...

(Light curve of WZ Sge during the 2001 outburst.)

Outburst detection and rapid brightening on July 23

(vsnet-alert 6093)

T.Watanabe reported the outburst of WZ Sge (observed by M. Oshima). The reported observation is

SGEWZ 200107232233 97 Oht

Kyoto team confirmed this now, and continue the observation. More details will be reported later.

Regards,
Ryoko Ishioka and Makoto Uemura

VSOLJ news (in Japanese)

WZ Sge: rapidly brightening!

Our preliminary photometry of WZ Sge shows a rapidly brightening of the object. We started time-series observation at 14:30 (UT) and the object was about 9.5mag at that time, and then, now (17:00 UT) we estimate the object is about 9.1mag, which indicates the rising rate is about 3.8 mag/day.

As in the recent case of RZ Leo and AL Com, WZ Sge stars show "early superhump" during the very early phase of their outbursts. Tonight observations are important to study the birth of early superhumps. As well as follow-up photometric observations, tonight spectroscopy is strongly urged.

As reported by Dr. Kuulkers, the object may show short-period oscillations during the rising phase, so observers should take CCD images with an exposure time as short as possible. The Kyoto team is now observing with an exposure time of 10s (25-cm SC + ST-7E).

Regards,
Makoto Uemura

Spectrum taken on the first night of the outburst

(vsnet-alert 6110)

WZ Sge spectrum at Bisei Observatory

K. Ayani (Bisei Astronomical Observatory) has kindly provided the following spectrum of WZ Sge taken on July 23, between 17h 39m 40s and 17h 49m 37s UT. Balmer lines are in generally absorption (likely filled with emission). More detailed analysis is under way.

VSNET Collaboration team

Evolution of spectrum

(Spectrum on July 23 taken by K. Ayani (Bisei Astronomical Observatory.)

(Spectrum on July 25 taken by K. Ayani (Bisei Astronomical Observatory.)

Time-resolved spectra during the early phase

(vsnet-alert 6123)
WZ Sge: short-term variations in optical spectra

Accorging to the report from Dr. Sadakane, observing at Okayama Astrophysical Observatory, both emission and absorption components of H-beta show strong short-term variation (reported on July 24).

Since the object is very bright, even small telescope will be able to obtain time-resolved low resolution spectra. Such time-series spectroscopy will provide enormous hints for the dwarf nova outburst and the early superhump. Observations are strongly encouraged. If possible, observations covering more than one orbital period are prefered.

Regards,
VSNET Collaboration team

(vsnet-alert 6125)

Dear all,

Time-resolved spectroscopic observations taken by K. Sadakane, Osaka-Kyoiku University were done between July 24 UT 13:50 and UT 16:50, at OAO 36-inch with coverage of 400-500nm. A spectrum taken about at the middle of the eclipses shows that He II 4686 A is a strong emission with doubled profile. The estimated peak separation is about 14 A, but the peaks vary with the orbital period. The CIII - NIII complex at 4640 A is also in emission with double peak. On the other hand, H-beta shows both of emission and absorption feature like P Cyg profile, which varies with the orbital period. Higher Balmer series H-gamma and H-delta are broad absorption features, as is He I 4471 A. More detailed analysis is under way.

The emission feature resembles to the beginning of the 1978 outburst reported in IAUC 3311, and Ortolani et al. (1980) taken at four days after maximum, but does not resemble the spectra taken by K. Ayani at Bisei during the rising stage (vsnet-alert 6110), which shows no emission component around the wavelength of HeII and C-N complex.

Best Regards,
Hajime BABA and Kozo Sadakane
VSNET Collaboration team

(vsnet-alert 6128)

WZ Sge: time-resolved spectra

H. Baba provided an image of spectra taken by Dr. K. Sadakane at Okayama Astrophysical Observatory on July 24. The spectra can now be seen in VSNET WZ Sge web page:

http://www.kusastro.kyoto-u.ac.jp/vsnet/DNe/wzsge01.html

In these figure, double peak emission lines of He II 4686 and C III/N III blend are clearly seen. We can see the variations of their profiles. More detailed information will be presented by H. Baba.

Regards,
VSNET collaboration team

Evolution of early superhumps

(Light curve of the early phase. Observers: Kyoto team (R. Ishioka, M. Uemura, H. Ohashi, T. Kato, K. Matsumoto, G. Masi)

(vsnet-campaign 1025)

Kyoto team started tonight observation at 11:10 (UT). We plan to take a run on WZ Sge whole night. The object is clearly brighter than bright comparison star (GSC 1612.1830 V=8.5). We estimate the object is about 8.1 mag now (12:10 UT).

Last night observation during 23.6 - 23.8 UT shows that WZ Sge was rapidly brightening. Its magnitude was Rc~9.7 mag at the start time and Rc~8.7 mag at the end time. The rising rate was about 5 mag / day. In addition, short-term modulations with time-scales of 0.01 - 0.03 d are superimposed on the rising trend.

Following observations are urgently encouraged!!

Regards,
Ryoko Ishioka, Makoto Uemura, Hiroyuki Ohashi

(vsnet-alert 6115)

Dear Colleages,

to me, my data for this star look terrific. I've recorded three ecplises and they agree with ephemerides reported here by Taichi Kato. It is very well visible a rising trend, saying thatthe star was brightning again during my run. Also, there are some other minor peaks, maybe superhumps (early or complete?) superimposed to the eclipse profile.

The maxima are about 0.057 days apart, that is about 82 minutes and the same time is amomg eclipses.

As I said, the curve is visible at

http://www.eurolink.it/comets/wzsge.htm

Tonight I will be observing only this amazing star.

Regards,
Gianluca

(Average profile of early superhumps)

(Average profile of early superhumps on July 26)

(Average profile of early superhumps on July 27)

(Average profile of early superhumps on July 28)

(Average profile of early superhumps on July 29)

(Average profile of early superhumps on July 30)

(Average profile of early superhumps later on July 30)

(Average profile of early superhumps on July 31)

(Average profile of early superhumps later on July 31)

(Average profile of humps on August 2)

(Average profile of humps on August 3)

(vsnet-alert 6133)

WZ Sge: change of profiles of early superhump

Dear Colleagues,

The profile of early superhumps is starting to show a dramatic change. The profile is starting to vary from cycle to cycle.

The "V"-shaped fadings (corresponding to the eclipse phase) were getting broader, and became "U"-shaped in the middle part of the July 25 run. The overall amplitude of variation was getting smaller, which tendency had not been observed until July 25. These changes may be a result of the changing precession rate of the accretion disk, which needs to be confirmed by further observations. We have already analyzed and received 8160 data points, steadily growing in number!

The profile of early superhumps starting to vary significantly, long, continuous observations (as long as possible!) are strongly encouraged.

Regards,
Taichi Kato
VSNET Collaboration team

Evolution of superhumps

(vsnet-alert 6196)

WZ Sge superhumps finally!?

Dear Colleagues,

The partial analysis of the Kyoto Aug. 4 run (Ohashi et al.) has shown that the secondary hump (with respect to the main peak of early superhumps) has now become stronger than the main peak. This may indicate the true evolution of genuine superhumps! Please keep the closest watch! More later.

We have received additional data from Donn Starkey, which will be duly incoporated in the analysis.

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6197)

Dear Colleagues,
I've just reduced my last night run, which resulted to be of very high-quality. The lightcurve is simply amazing! Where we had two series of maxima (primary and secondary) now we have two, close, almost superimposed maxima, resembling the shape of the letter "M". A very rough estimates of the period, based on the peaks, give me someting around 0.058d, but I need to do a better analysis.

I'll provide full details asap, with curves and PDM analysis.

Regards,
Gianluca

(vsnet-alert 6199)

Dear Colleagues,

I have already given a preliminary description of my latest results with WZ Sge in vsnet-alert 6197 (BTW: I did a typo while giving the period: please read 0.056d instead of 0.058). Please find this more detailed note.

The sky was clear on Aug.04 and I observed for 7 hours, once again getting more than 1500 images. The resulting curve is amazing. The maxima are now almost equivalent (with some exceptions) and they look superimposed, resembling the shape of the letter "M". Respect to the previous night, the modulation is now larger, of about 0.2 mag. PDM analysis of this run indicates as the better period 0.05609d (using pdm.exe from vsnet website). The dramatic changes (once again!) in the light curve can suggest emerging superhumps (negative???). Of course better conclusions will be available just after combining several datasets from different station right now, Michael Richmond is getting photometry under good sky conditions).

Updated light curves at

http://www.eurolink.it/comets/wzsge.htm

Enjoy!

Follow-up, as well as further analysis are urgently requested.

Regards,
Gianluca Masi

(vsnet-alert 6200)

WZ Sge genuine superhumps!

Dear Colleagues,

The analysis of the combined data on Aug. 4 (D. Starkey, Kyoto data, G. Masi, 3218 points, still growing in number) has clearly shown the presence of a signal with an amplitude of 0.10 mag and a period of 0.057197 +/- 0.000046 d. The phase-averaged light curve at this period shows sharply defined maxima, resembling those of "usual" superhumps of SU UMa stars, and the phase 0.4 "shoulder", which had been the main peak of early superhumps. WZ Sge now started to show long-waited superhumps. The earliest strong evolution of this signature was observed around Aug. 4.53 UT. We have confirmed the all findings in [vsnet-alert 6196, 6197 and 6199].

Congratulations!

Regards,
Taichi Kato
VSNET Collaboration team

(Average profile of humps on August 5, genuine superhumps!)

(vsnet-alert 6217)

Dear Colleagues,

The combined PDM analysis of Aug. 5-6 data (D. Starkey, Kyoto, G. Masi and F. Mallia, J. Pietz) has given an average period of 0.057796 +/- 0.000023 d, which siginificantly differs from the periods determined from Aug. 5 and Aug. 6 data only. The theta profile also suggests that the period is indeed changing. The superhump period has thus changed within a day (or even within 0.5 d). Please keep the closest watch of the evolution of superhumps!

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6221)

Dear Colleagues,

We have apparently found the final answer! The there was an interchange of maxima from early superhumps to true superhumps around Aug. 5.8 UT, this affected the period analysis on Aug. 5. Before then, the maxima of true superhumps were superimposed on the profile of early superhumps. By taking this finding into account, we have been able to determine the period of true superhumps as 0.057157 +/- 0.00077 d. This period well expresses all maxima up to Aug. 7.07 UT.

Regards,
Taichi Kato
VSNET Collaboration team

(Average profile of humps on August 6-7, genuine superhumps!)

(vsnet-alert 6223)

WZ Sge O-C variation

Dear Colleagues,

We have newly put a preliminary O-C diagram of early superhumps and newly appearing superhumps, as identified in [vsnet-alert 6221].

[Please note that:
 1) The times were only roughly extracted; please don't cite
    this figure as the final result ;-)
 2) Secondary hump structures are omitted.]

This figure corresponds to Figure 1 of Bohusz and Udalski (1979) in IBVS 1583, which first correctly idenified the signal of WZ Sge in 1978 as superhumps.

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6229)

WZ Sge: superhump period update

Dear Colleagues,

Brian Martin, Michael Richmond and Donn Starkey have kindly provided high quality data on August 5-7 (some of these announcements were already made in vsnet-campaign-dn or vsnet-obs). We have been able to extend the baseline, and refined the superhump period as 0.0571372 +/- 0.0000050 d. This period well fits all superhump maxima up to Aug. 7.425 UT.

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6233)

WZ Sge: superhump period update

Dear Colleagues,

The PDM analysis of the data (4906 points) between Aug. 6.785 and 8.070 UT has yielded a period of 0.057132 +/- 0.000015 d. This value should be rather regarded as an "instataneous" period, because both superhump and early superhump (or modulations related to the orbital motion) are superimposed.

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6235)

The hump at phase 0.5 (of the superhump phase) corresponds to the best exemplification of the residual main hump of early superhumps. [Note they are moving respect to the superhump phase. Other smaller humps at other phases also correspond to some of early superhump structures observed at different epochs, quite complex!]

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6238)

WZ Sge: superhump period update

Dear Colleagues,

We have receieved new data from the RIT observatory team (M. Richmond, S. Davis, T. Davis), D. Starkey and partly analyzed the Kyoto Aug. 8 run.

The general fading has almost stopped.

We have updated the superhump period as 0.057231(30) d, by a least-squares fitting, rather than the PDM analysis. As the baseline becomes longer, the analysis tends to give a longer period than the 'canonical' period obtained during the 1978 superoutburst. The profile of superhumps strongly vary with time. Further observations are strongly encouraged!

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6241)

WZ Sge: superhump period update

Dear Colleagues,

We have received a high-quality run from G. Masi. Combined with earlier observations, as well as the new Kyoto data, we have refined the superhump period as 0.057211(22) d. The most recent superhump profile shows a secondary maximum on the fading branch, as G. Masi has noted.

The results and revised figures will appear on the VSNET WZ Sge page in due time.

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6245)

WZ Sge: August 9

Dear Colleagues,

We have receieved the high-quality set of the latest data from G. Masi. Together with the partially analyzed Kyoto data on Aug. 9, we have refined the superhump period as 0.057171(17) d.

The residuals to this ephemeris a systematic variation, with a likely period of 4 d. This variation is most likely caused by the beat between the orbital and superhump periods. As noted by G. Masi, the superhumps show 'secondary superhumps' at phase 0.4 in the August 9 observations. On the contrary to Masi's suggestion, the O-C analysis favors the main peak as genuine superhumps. The secondary superhumps were already present in the earlier Kyoto observations, but had a smaller amplitude. The phases of these secondary superhumps do not seem to vary very significantly, pending immediate more observations. This feature seems to more resemble secondary superhumps sometimes seen in other SU UMa-type dwarf novae, but whose nature is still poorly understood.

Please follow the evolution of superhumps as much as you can, and as follow the fate of secondary superhumps as quickly as possible!

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6246)

Dear Colleagues,
just to clarify myself:

>As expected, the light curve is definitely different from
>last night and it is really outstanding. The curve looks 
>like in my  previous Aug. 04/05 run, where it had the "M" 
>shape. But this time the lower peak is the right one.  

Regards,
Gianluca

(vsnet-alert 6251)

WZ Sge: superhump profile Aug. 9-10

Dear Colleagues,

The analysis of the combined data between Aug. 9 and 10 (G. Masi, B. Martin, Kyoto team) has yielded a remarkable superhump profile!

The "secondary superhumps", as seen in Masi's light curve, became even stronger hours later. These two hump structures are of approximately similar strength on Aug. 10.

The phase-averaged light curve folded at the orbital period shows a shallow (0.03 mag) fading at the predicted times. However, this does not seem to be directly related to the two humps above.

Either of the main hump structures (more likely the secondary one) now has a orbital phase close to what is expected for the main hump of early superhumps. It may be possible that the present unique profile is caused by the somwhow enhanced early superhumps at this stage.

Further analysis is in progress. More observations are strongly encouraged!

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6252)

WZ Sge: nightly averaged magnitudes

Dear Colleagues,

The table is very preliminary (zero-point corrections are still approximate, some data have not been yet included) nightly averaged magnitudes reported to the VSNET Collaboration team.

  1) One can see how the growth of superhump slowed the rate of fading.
  2) The initial rapid fading looks slower than what has been belived
     from the historical outbursts.
  3) Marvellous nightly coverage!  Even a single night doesn't exist
     having less than 1000 observations!

     mid-UT      V-C   err   N
 ---------------------------------
  20010723.774  0.087 0.012 1665
  20010724.704 -0.469 0.002 3906
  20010725.610 -0.216 0.002 5947
  20010726.686 -0.063 0.002 1848
  20010727.588  0.099 0.001 8387
  20010728.686  0.318 0.002 3985
  20010729.515  0.410 0.001 5754
  20010730.667  0.571 0.001 5317
  20010731.636  0.687 0.001 6043
  20010801.630  0.777 0.001 9442
  20010802.470  0.900 0.002 2379
  20010803.614  0.984 0.001 6199
  20010804.634  1.095 0.001 5104
  20010805.524  1.144 0.001 6777
  20010806.464  1.177 0.002 2800
  20010807.493  1.255 0.002 1976
  20010808.513  1.306 0.001 3293
  20010809.604  1.351 0.002 1913
  20010810.248  1.417 0.002 1283

(vsnet-alert 6255)

WZ Sge: superhump period and structure on Aug. 10-11

Dear Colleagues,

G. Masi has just provided an excellent run. Combined with the earlier data, and the partially analyzed Kyoto 10 data, we have updated the superhump period as 0.057153(16) d. On August 9 the superhumps showed prominent 'secondary superhumps' at phase 0.4, which became even stronger on August 10, and gradually merged into singly-peaked superhumps on August 11.1.

The discrimination of true superhump signal among peaks has become even more difficult, but we have selected the first (in terms of the chronological order) peak as genuine superhumps based on O-C analyses (this identification may be subject to revision, as new data become available). There is a tendency of peak merging. Further observations are very strongly encouraged.

Masi's latest data also suggests some decline of the mean magnitude. This also needs to be confirmed by further (immediate) observations.

Regards,
Taichi Kato
VSNET Collaboration team

Emerging eclipses

(vsnet-alert 6256)

WZ Sge: eclipse and superhump structure

Dear Colleagues,

The analysis of the Aug. 10-11 data (B. Martin, Kyoto, G. Masi) using the same technique as in [vsnet-alert 6251] shows the persistence of a shallow dip (0.04 mag) at the predicted phase of eclipses.

The hump features reported in [vsnet-alert 6251] have moved with respect to the orbital phase -- they are not therefore associated with the early superhumps, but are moving superhumps with complex multiple peaks.

More detailed analysis is in progress.

Regards,
Taichi Kato
VSNET Collaboration team

(Average profile of humps on August 11 Kyoto observation, prominent eclipses are superimposed on superhumps)

(vsnet-alert 6261)

WZ Sge: deep dips following the superhump maxima

Dear Colleagues,

We have received further excellent data from D. Starkey, M. Richmond and the RIT team, J. Pietz and G. Masi. We have also received data from B. Martin, but they seem to suffer from a transmission problem. We are also analyzing the Kyoto data, taken by K. Matsumoto-san.

A quick-look at the light curve shows deep dips just following the superhump maxima. The feature started to appear on Aug. 10, and looks strongest during the Kyoto Aug. 11 run. The feature seem to have become weaker in later runs (Masi and Jensen).

More analysis is intensively in progress.

Our latest result (up to yesterday) appeared in IAUC 7680.

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6262)

We have confirmed that the "dips" exactly corresponds to eclipses. WZ Sge is now confirmed to be an "eclipsing SU UMa-type dwarf nova, which shows eclipses even during superoutburst" !!

It looks like that the precessed disk was most favorably situated for eclipses at the time of Kyoto observation. We will be able to learn much about the nature of superhumps and spot(s) of WZ Sge (still poorly known in this system) from the analysis of eclipses! Please don't miss the predicted times of eclipses!

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6264)

Re: WZ Sge: nature of the dip

Dear Masi and Colleagues,

> >     It looks like that the precessed disk was most favorably situated
> > for eclipses at the time of Kyoto observation. 
> 
> Could this "geometric" factor explain why, on my Aug. 09/10 
> run, I had a very clear vision of those ecplises, where in 
> other sessions they were weaker?

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6265)

WZ Sge: superhump period

Dear Colleagues,

We have updated the superhump period of WZ Sge as 0.057194(15) d using new epochs of superhumps. As reported in the recent postings, recent superhump maxima have been highly affected by the overlapping eclipses. The period should be therefore treated as a preliminary one.

We have also confirmed the trend of the increased fading rate. The observed increased fading rate in conjunction with the overlapping eclipses on superhumps seems to suggest a "beat phenomenon" as the possible origin of the fading (as observed in DV UMa and IY UMa). But this needs to be confirmed by the subsequent observations.

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6268)

WZ Sge: eclipse feature and new data

Dear Colleagues,

We have received new data from T. Vanmunster. The data comprise the last segment of the outburst light curve presented on the VSNET WZ Sge page.

We have further analyzed the Kyoto data. The consecutive three eclipses between 11.45 and 11.65 are very prominent, while the next one became suddenly shallower. The profile and depth of eclipses thus vary with a short time scale! This indicates that "we should observe every eclipse", as much as we can! Please don't miss predicted epochs.

We will later put more representative analysis on the Web page.

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6270)

WZ Sge: update

Dear Colleagues,

We have received further data from T. Vanumnster, J. Pietz, B. Martin, and are analyzing the Kyoto data last night. Preliminary analysis of the data suggest that the relatively rapid fading trend still continues. (The slowing of the general fade looks like to have been only observed during the emerging stage of superhumps).

The eclipses are have become difficult to discern! It may have been that the eclipses have become shallower and broader. The profile is indeed strongly varying!

Regards,
Taichi Kato
VSNET Collaboration team

(Average profile of humps on August 12-13 G. Masi and Kyoto observation, eclipses became very weak)

(vsnet-alert 6283)

WZ Sge superhump period update

Dear Colleagues,

We have received new data from B. Martin, J. Pietz, G. Masi, M. Richmond and the RIT team. We have also received data from D. Starkey, but they have not been yet incorporated for analysis because of a potential phase problem (now checking). The results of the new Kyoto data are being produced, and are incrementally incorporated to the data set.

The analysis of superhump timings has yielded the following refined superhump period: 0.057191(8) d. The O-C's have become less noisier, probably because of the reduced effect of the beat phenomenon.

There seem to be a hint of emeregence of QPOs on the declining branch from superoutbursts. More detailed analysus is under way.

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6284)

WZ Sge eclipse on August 13-14

Dear Colleagues,

We have received additional data from J. Pietz. New Kyoto data have been also added.

The analysis of the Aug. 13-14 data show eclipse just on the ascending branch of superhumps. They are difficult to discern, but may become more evident when eclipses fall on more slowly changing intervals.

It is now evident eclipses are most sharply detectable when they are slightly later than the superhump maxima.

Regards,
Taichi Kato
VSNET Collaboration team

(Average profile of humps on August 14-15 Kyoto and Pietz preliminary data, eclipses are strong again!)

Revised superhump period of the 1978 superoutburst

(vsnet-alert 6285)

WZ Sge superhump period

Dear Colleagues,

The most recent estimate of the superhump period better agrees that of Bohusz and Udalski 1979 (IBVS 1979), P=0.057213, than that of Patterson et al. 1981 (ApJ 248, 1067), P=0.05714, obtained on the occassion of the 1978 superoutburst.

We have more closely examined these original data. The cycle counts in Bohusz and Udalski 1979 have been found to be correct (to the present knowledge of the new superhump period), while there seem to be ambiguities in superhump identifications in Patterson et al. 1981. We have securely identified three superhump timings on Dec. 22-25, and probable one on Dec. 28. Three possible superhump timings on Dec. 19 and 26 do not match the currently determined period, and the ephemeris by Bohusz and Udalski 1979. It is very likely the period of 0.05714 d was strongly affected by these "noisy" identifications. Using new secure identifications of superhump times, from Bohusz and Udalski 1979 and Patterson et al. 1981, we obtained a refined superhump period of 0.05722 d for the 1978 superoutburst. This superhump period is 1.0% longer than the orbital period.

This would indicate that WZ Sge has the perfectly same fractional superhump excess as in AL Com!

Regards,
Taichi Kato
VSNET Collaboration team

Late stage of the main superoutburst

(vsnet-alert 6288)

WZ Sge eclipses again!

Dear Colleagues,

We have received the new data and a comment from J. Pietz:

first results from the current night suggests a major change in the lightcurve compared to the last night. The eclipse is more deep and dominates now the lightcurve.

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6293)

Dear Colleagues, Once again, the WZ Sge light curve experienced a dramatic change. Eclipses (as announced by Dr. Kato on previous vsnet messages) are now dominating the curve and they occurr at the predicted times. Maxima are quite elaborate: at the beginning of the run there were two main humps, with the one on the left being the stronger. In the middle of the run the y were almost equivalent (on Aug 14.985), while at the end of the session the one on the right is dominant and even higher!

The ascending branch shows aparticular "curvature" on the middle.

The star is at the same magnitude of the end of my previous observing session.

The curve has been posted at:

http://www.eurolink.it/comets/wzsge.htm

Regards,
Gianluca

(vsnet-alert 6294)

WZ Sge fading stopped!

Dear Colleagues,

We have received high-quality data from G. Masi. We are also approaching to our final analysis of the Kyoto Aug. 14 data. The changing profile of eclipses and humps is exactly what is described by G. Masi in vsnet-alert 6293.

We must draw reader's attention to the general trend of the light curve (which will be posted on the Web later). These observations indicate that WZ Sge has almost stopped its linear fading trend continuously observed in the past several days. This may be indicative of a new stage of the superoutburst, or the effect of the beat phenomenon. The latter possibility looks more likely, but the hump and eclipse profile look different from the previous beat cycle. Further observations are naturally very wanted!

Regards,
Taichi Kato
VSNET Collaboration team

Late superhumps

(vsnet-alert 6295)

Date: Wed, 15 Aug 2001 09:29:45 +0100 (BST)
From: tom marsh 
Subject: [vsnet 2108] Late superhumps in WZ Sge

its now the 22nd day of the WZ Sge outburst and quiescence must be coming soon. However rather than think its all over then, I wanted to encourage everyone looking at this star to carry on intensively now and well after the outburst because of an interesting paper by Rick Hessman and others on the dwarf nova OY Car. (Hessman et al 1992, Astronomy & Astrophysics, 263, 147). In this paper they observed eclipses of the bright spot where the gas stream hits the disk after a superoutburst. This can be used to determine the radius at which the stream/disk impact occurs. This revealed that an elliptical disk remained even after the outburst. This disk precesses slowly relative to our line of sight and so varying radii are measured for the stream impact. We might be able to do the same for WZ Sge. It just requires as-fast-as-possible photometry in the lates stages and following the outburst (less than 1 minute exposure to exposure, preferably less than 30 seconds). If the superb coverage obtained so far keeps up, it may be possible to map out the shape of the disk in exquisite detail, which would be a nice finale to a great campaign,

regards,

Tom Marsh

(vsnet-alert 6296)

Dear Colleagues,

Just a comment. If WZ Sge may fade, and become difficult to measure with conventional photometry softwares, please send us raw images. We are fully prepared to make necessary PSF photometry even under difficult conditions. Just to ensure bright stars (PSF standard candidates) are not saturated. At 15-th mag, there is no problem to measure 10-s exposures (or even 5-s exposures) with 20-30 cm telescopes. Please continue observing as long as you can! For WZ Sge, a duration of 100 d since the start of the outburst would be a roughly acceptable estimate of the required intensive campaign. (Please note the cooling time of the white dwarf was a few times longer than this on the occasion of the 1978 outburst; white dwarf specialists should stay longer :-)

Regards,
Taichi Kato
VSNET Collaboration team

Unexpected superhump profile

(vsnet-alert 6300)

WZ Sge: unexpected profile!

Dear Colleagues,

We are currently analyzing the newly reported data (the details will be summarized later). The most striking is the latest run by J. Pietz. The run shows that the main hump now resides in the "pre-eclipse" phase. This probably indicate that the next "sharp eclipse" stage is coming soon!

Another noteworthy feature is that eclipses have become less apparent. On the other hand, there is a signal of phase 0.6 dip, which rather looks like eclipses.

WZ Sge is experiencing an important stage of evolution. Please continue your observations as long as possible, and record as many eclipses and dip features as possible!!

Regards,
Taichi Kato
VSNET Collaboration team

(Average profile of humps on August 15-16 from Pietz and Masi data)

(vsnet-alert 6310)

WZ Sge: sharp eclipses emerging again!

Dear Colleagues,

We have received new data from A. Oksanan, J. D. West, M. Richmond and the RIT team, and B. Martin. We are also analyzing the Kyoto Aug. 16 data. The coverage is excellent, reflecting the best longitudinal spread of observers!

Sharply defined eclipses, just after the hump maxima, are emerging again as expected! The first indication of this signal appeared in the latter half of Martin's observation on Aug. 16. Please see how this evolves! (Multicolor photometry and spectroscopy around these phases are also very helpful in understanding the nature of these variations).

More detailed analysis will be presented by Ishioka-san and Uemura-san, later.

Regards,
Taichi Kato
VSNET Collaboration team

Rapid fading!

(vsnet-alert 6311)

WZ Sge: rapid fading?

Dear Colleagues,

With the newly analyzed Kyoto data, the fading trend seems to have become unprecedentedly apparent during the present outburst. The mean decline rate between Aug. 17.09 and 17.67 UT is 0.32 mag/d, largest ever observed during this outburst. Although superhumps (or pre-eclipse humps) are still very prominent, WZ Sge may be experiencing another very important stage of the outburst! This may be a transient dip, as observed in AL Com.

We will continue analyzing the rest of the data. Please keep your closest eye on this object, and keep us informed!

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6312)

(Average profile of humps on late August 16 from J. Doug West, M. Richmond, S. Davis, B. Martin, Kyoto, S. Kiyota)

Dear Colleagues,

The phase-average light curve on Aug. 16 (later half) is found to be totally amazing! The light curve consists of sharply defined eclipses (short ingress and egress) and giant humps, close to the phase of orbital humps of ordinary dwarf novae. The light curve is extraordinarily similar to that of quiescent light curve of WZ Sge (there are known alternations in the quiescent light curves of WZ Sge; the present light curve in outburst closely matches one of them!).

The light curve is placed on the VSNET WZ Sge page.

Please don't miss the present important moment!!

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6319)

WZ Sge: rapid fading!

As suggested in the previous alerts, we have confirmed the rapid fading of WZ Sge.

B. Martin has kindly sent us his data on Augsut 16/17, which clearly shows the rapid fading with an apparent decline rate of 1.16 mag/d. In the light curve taken by S. Kiyota just before this phase, we can see superhumps with amplitudes of about 0.15mag. On the other hand, the Martin's new data does not show such prominent humps while it shows some hints of modulations.

The Kyoto team is now having a run on WZ Sge. The current magnitude is ~11.8 mag.

Time-series observations are strongly urged to reveal the evolution of superhumps and/or orbital modulations during this phase. Although the object is fading, however, the historical event of WZ Sge will continue. The object will probably show re-brightening events as the other WZ Sge type stars. In the case of AL Com, the temporary dip lasted only for a couple of days. So, as well as photometry, spectroscopic monitoring during these few days can give enormous information about the physics of the re-brightening and accretion disk.

Observations are strongly encouraged.

Regards,
Makoto Uemura
VSNET collaboration team

(vsnet-alert 6321)

WZ Sge: rapid fading continues!

Dear Colleagues,

J. Pietz has kindly sent the new data, and informed the following:

Attached you will find the data. Will be interesting 
to see other data if the following features are real:
a) fading with 1mag/day
b) two short fadings 15 minutes apart 
c) a peak after the second fading

(vsnet-alert 6322)

WZ Sge: rapid fading from Kyoto observation

Dear Colleagues,

Very preliminary, partial analysis of the Kyoto Aug. 17 data confirms the precipitous fading at a rate of 1.2 mag/d! A quick look at the data shows that, even at this fading stage, short exposure times are sufficient and still very useful. Please continue observing with your configuration, which has been used during the superoutburst maximum. Unless there is a special reason, you don't have to change the exposure time.

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6323)

WZ Sge: rapid fading and hump structure

Dear Colleagues,

The analysis of the combined data on Aug. 17 (B. Martin, partially analyzed Kyoto, J. Pietz) has shown the following new features:

   1) During the early decline stage, the humps have became smaller in
      amplitude and complex
   2) Later on, early half of the Kyoto data shows little evidence of
      eclipses!  Humps have become even less apparent, and the light curve
      looks rather flat, except for small-scale fluctuations.
   3) Later in Pietz's observations, a new sharp hump structure emerged.
      The humps have an orbital phase of 0.35-0.4, which is ~0.5 different
      from the giant humps seen on Aug. 16.   This feature may be
      "late superhumps" finally!  Eclipses are not very evident

    Further analysis of this combined data set has shown very shallow
fading (<0.02 mag in average) at orbital phase 0.1.  There is no hint of
sharp eclipses seen on Aug. 16.  The light source responsible for the
Aug. 16 eclipse should have suddenly faded!  The phase 0.4 hump seen in
Puetz's data has not emerged yet.  This structure (possible late superhumps)
should have emerged suddenly.

    There is no indication of the slowing of the fading rate until the
Pietz's last run.

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6328)

WZ Sge: rapid fading continues

Dear Colleagues,

Donn Starkey's most recent data suggest that the rapid fading of WZ Sge still continues. The speed of decline may have become slightly slower, which may be an indication of an immediate rebrightening. Please keep the closest watch!

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6333)

WZ Sge: Kyoto successful observation last night

Dear Colleagues,

The Kyoto team (Ishioka-san et al.) used 5-s integration time (as we have been mainly using). A quick look at the light curve is excellent! The hump structure (late superhumps?) is clearly detected.

Even at 5-s integration, we have confirmed that this yields sufficiently high S/N for single exposures. Unless the object dramatically fades to quiesence, please keep you strategies up to now, and follow the evolution of WZ Sge closely. Even at quiescence, we recommend to use 10-s integrations, base on our past experience.

Regards,
Taichi Kato
VSNET Collaboration team

After the rapid fading, superhumps again emerged!

(vsnet-alert 6334)

WZ Sge giant humps emerging! Dear Colleagues,

The analysis of Pietz's data and partially analyzed Kyoto data indicates large-amplitude humps are emerging! The humps had a smaller amplitude in the early Kyoto data, but have grown to full-amplitude humps comparable to those of superhumps.

The phase is different from the "hump" observed on Aug. 17, and is located close to the pre-eclipse phase. The humps on Aug. 17 and 18 are therefore of different nature! We may be witnessing the regrowth of superhumps, or other unexpected features. The decline of the system has substabtially slower on Aug. 18. Beware of rebrightening(s)!!!

Regards,
Taichi Kato
VSNET Collaboration team

(Average profile of humps on late August 18 from J. Pietz, M. Moilanen, and D. Starkey)

(vsnet-alert 6335)

WZ Sge: growing superhumps (Moilanen data)

Dear Colleagues,

Marko Moilanen, Nyrola observatory, has sent very high-quality data (22 sec net time resolution) between Aug. 18.844 and 19.033 UT. The data show a strong hump signal with an amplitude of 0.35 mag! The period analysis suggests this signal is the reappearance of superhumps. Small dip-like eclipses are also present at the predicted times. More detailed analysis, combined with earlier data, will be later presented by Uemura-san et al.

We strongly encourage immediate observations, since the humps are very rapidly evolving!

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6336)

WZ Sge: almost stopped fading!

Dear Colleagues,

We have received a new set of very high quality data from J. Pietz. The data show prominent humps, as reported from Moilanen's data. We have confirmed the structure of the hump feature, and the presence of fadings at the predicted times of eclipses.

The following very preliminary (still on a limited sample of the data) nightly averaged magnitudes indicate that WZ Sge has almost completely stopped fading.

     mid-UT      V-C   err   N
 --------------------------------
  20010817.532  2.941 0.215 1451
  20010818.874  3.827 0.140 770
  20010819.021  3.825 0.134 183

(vsnet-alert 6337)

Re: WZ Sge: growing superhumps

We have received a new data from J. Pietz which is perfectly consistent with the data sent from M. Moilanen (vsnet-alert 6335). Using the combined data, we performed period analysis and calculated the period of humps to be 0.05704(15) d. The period is significantly longer than the orbital one, which confirms that the current humps appearing during the bottom of the dip is superhumps.

Regards,
Makoto Uemura
VSNET collaboration team

Rebrightening!

(vsnet-alert 6345)

WZ Sge rebrightening!

Dear Colleagues,

We have receievd new data from G. Masi, A. Oksanen, T. Vanumunster, M. Moriyama, and revised from by B. Martin. We are also intensively analyzing the Kyoto data.

The latest data have confirmed the brightening trend, as well as the further growth of superhumps! This indication of the brightening was also detected visually (vsnet-obs 35257, H-.G. Lindberg).

The short duration of the fading suggests that the present fading is "dip"-type, as observed in AL Com (1995, 2001) and V2176 Cyg. The object may enter its second superoutburst (the nomenclature proposed by Nogami et al. in AL Com), as inferred from the strong reappearance of superhumps. Observations are most urgently requested!

Since the system will be back to its "outburst" magnitude, please use short exposure times, and a brighter comparison star, as you have used during the main superoutburst.

More detailed analysis and Web presentation will be announced by Uemura-san and Ishioka-san.

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6345)

WZ Sge: reappearance of sharp and deep eclipses

Dear Colleagues,

The analysis of the latest Oksanen's run revealed the appearance of deep (0.15 mag), sharp eclipses, as were observed in the later stage of the main superoutburst. The giant superhumps just precedes these eclipses, and the eclipses are superposed on the declining branch of superhumps. Further observations (high time-resolution is better) are most emergently requested.

More details will be presented on the Web by Uemura-san.

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6356)

WZ Sge: striking eclipses and superhumps!

Dear Colleagues,

G. Masi has kindly provided the latest data. As already reported by Masi, the amplitudes of the eclipses have become comparable to those of giant superhumps! The Masi's obseravation terminated at the still growing eclipses! The depth of the last eclipse was already unprecedented during this entire superoutburst.

Please continue observing as long as possible, as many superhumps and eclipses as possible, to get the data at this previously unobserved stage of this important object!! We are keenly analyzing the most recent data, and will be able to inform the result in due time (by Uemura-san et al.).

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6361)

WZ Sge: slowly re-brightening

The Kyoto observation last night (Ishioka et al.) shows the object becomes 0.05mag brighter than August 19, which indicates that the the rate of re-brightening is quite gradual. In the last night light curve, we can see a hump with an amplitude of about 0.35mag.

Follow-up observations are encouraged!

Regards,
Makoto Uemura
VSNET Collaboration team

(vsnet-alert 6367)

WZ Sge: rebrightening, more analysis

Dear Colleagues,

We have received additional high-quaility data from B. Martin. Combined with the previous data, and the new analysis of Kyoto data, there seems to have been a minimum of brightness in early Aug. 20 (UT). The object has a more rapid brightening trend during the latter half of Aug. 20. This may be an indication of an immediate full rebrightening. Please keep the closest watch!!

The profiles of eclipses vary, but the sharp, deep eclipses are present throughout this brightening phase.

More detailed analysis, and Web update, will be presented later by Uemura-san.

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6369)

WZ Sge: superhump period analysis

Dear Colleagues,

S. Kiyota-san has sent the latest set of observations. The rising trend is less marked in this observation. We need to closely observe whether there is hours-to-day modulations (observed in AL Com in the past), or there is a steadily rising trend.

The more detailed timing analysis of newly appeared superhumps have shown that these hump maxima are well represented by a period of 0.05681 d, which is consistent with the PDM analysis from the earlier data. The hump timings have O-C's (aboslute values) less than 0.002 d for at least the latest 35 cycles. Such a high degree of stability of the superhump period was not observed during the main superoutburst; it may be either the beat phenomenon has become weak, or we are observing a stable segment of new superhumps by chance. The rapid growth of new superhumps was observed during the Aug. 18 full-night Kyoto run, and the amplitude became full (0.3-0.4 mag) on late Aug. 18 (UT), which was closely followed by M. Moilanen and A. Oksanen (Nyrola Observatory team), J. Pietz, G. Masi and B. Martin. The coherence of superhumps was confirmed up to the latest run by Kiyota-san.

Further observations are strongly wanted, since eclipses are expecteded to coincide with the superhump maxima.

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6371)

WZ Sge: rising!

Dear Colleagues,

D. Starkey's latest data today (vsnet-obs 35298) reported to the VSNET Collaboration team indicate a clear rising trend. The trend seems to be getting rapid! The humps are now doubly peaked, and have become less pronounced than before. More detailed analysis is underway.

Please keep observing as long as possible!

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6372)

We have confirmed that the maxima of superhumps fall on the predicted times of eclipses. Sharp, narrow eclipses are present on the top of superhumps. This explains why the humps looked doubly peaked!

(vsnet-alert 6374)

According to the new data observed by D. Starkey (vsnet-obs 35311), the rapid rising trend continues. The rising rate is about 1.5mag/d. In his light curve, we can see humps with an amplitude of 0.15mag on the rising trend. Eclipses are also seen on the top of the humps.

The beginning of the rebrightening has been confirmed. Tonight observations will be important to catch the hump and eclipse evolution. Sano-san (Nayoro, Japan) informed us that he performed time-series observation tonight.

Regards,
Makoto Uemura
VSNET collaboration team

(vsnet-alert 6390)

WZ Sge rebrightening! (messsage from Pietz)

J. Pietz has kindly sent two sets of new data, the latter of which covers the ongoing rebrightening phase!

Message from Pietz:

WZ Sge is still rising -> 0.8mag/day
and possible humps with an amplitude of 0.04mag

WZ Sge rebrightening! and humps, eclipses

(vsnet-alert 6391)

Dear Colleagues,

By combining the reported data, it has become evident that the amplitude of superhumps decayed on late Aug. 20 (UT). The system started to brighten, as reported in earlier messages. The superhumps decayed as the system rebrightened. The most recent data from Pietz indicate the presence of only weak superhumps with amplitudes 0.03-0.04 mag. However, the phase of the superhump maxima is on an extension from the pre-rebrightening observations.

Eclipses have become weaker as well. The center of eclipse seems to be slightly earlier than the predicted times, though this needs to be confirmed by further observations. It is not clear yet whether this change in the eclipse phase and depth is more associated with the rebrightening phenomenon, or the beat with the orbital period.

Intensive observations are very urgently requested, since some of WZ Sge-type dwarf novae (AL Com, V2176 Cyg) showed a rapid decrease of brightness after reaching the second maximum (maximum of rebrightening), followed by an immediate brightening returning to the (second?) superoutburst plateau.

Please also remind HST and CXO observations are scheduled today!

Regards,
Taichi Kato
VSNET Collaboration team

Rapid fading from the first rebrightening

(vsnet-alert 6396)

Dear colleagues,

I have just uploaded the August 21/22 light curve of WZ Sge, that I obtained at CBA Belgium Observatory, to my web site (see address below).

It was not a particularly favourable photometric night, hampered also by low clouds. I nevertheless managed to collect a dense time-series, over a period of about 6 hours. The resulting light curve clearly shows a number of interesting features. First, the rebrightening of WZ Sge, which was still very obvious in the hours preceding our observations, seems to have come to an end. The superhumps are much smaller than in any of our previous observing nights, having an amplitude of 'barely' 0.06 mag. In between superhumps, there are a number of dips. The most pronounced dip (the one immediately preceding the superhump peaks) likely is to be attributed to eclipses.

Best regards,
Tonny Vanmunster
CBA Belgium Observatory

http://www.lunarpages.com/cbabelgium

(vsnet-alert 6400)

WZ Sge: rapid fading from the rebrightening maximum

Dear Colleagues,

The Kyoto and Ouda teams have completed Aug. 22 observations under clear conditions. The data are now being intensively analyzed.

We have also received new data from Y. Sano, M. Richmond and S. Davis (RIT observatory team), T. Vanumunster and S. Kiyota. All the data, together with visual observations, show clear fading trend soon after WZ Sge attained its maximum of the rebrigtening. Although this may suggest that the present revrightening may be a normal outburst, one must remind that such a rapid fading was immediately followed by a second rebrightening in some past WZ Sge-type outbursts (AL Com, V2176 Cyg), together with a regrowth of superhumps. Such a transition took a very short time (usually within a day) compared to the usual evolution of dwarf nova outbursts, and they are very difficult to catch. Most intensive follow-up observations are encouraged, with your best parameters used in outburst.

More detailed analysis of all the data are keenly in progress, and will be duly announced and/or reflected on the VSNET WZ Sge page.

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6405)

WZ Sge: observation on Aug. 22

Dear Colleagues,

From the partial analysis of the Aug. 22 WZ Sge data, the linear fading at a rate of 0.82 mag/d is confirmed. The rate of decline is close to that observed at the termination of the main superoutburst.

Hump features are also superimposed on the fade, and seems to be growing in amplitude as the system faded. The profile is triangular, having a sharp edge-like maximum. The total ampliude (in average) was 0.06 mag. The entire profile differs from all other past hump profiles observed during the current superoutburst. The hump minimum corresponds to the predicted times of eclipses, but whether they represent real eclipses or hump minima needs to be tested by further observation. Sharply defined, short eclipses have totally disappeared.

More analysis is ongoing, and more result will be presented by Uemura-san and Ishioka-san.

Regards,
Taichi Kato
VSNET Collaboration team

Super-QPOs on August 22

(vsnet-alert 6411)

(Details of super-QPOs on August 22)

WZ Sge: strong super?-QPOs on Aug. 22 data

Dear Colleagues,

As reported by Uemura-san, the Ouda team succeeded in taking high S/N, high speed (net resolution 3s) photometry of WZ Sge on Aug. 22 (and Aug. 23). The analysis of the Aug. 22 data shows the presence of strong QPO signal, with characteristic periods of 3-5 min, and amplitudes up to 0.1 mag.

The long coherence of the QPO signal strongly resembles so-called super-QPOs (Kato et al., PASJ 44, L215, 1992) observed only during superoutbursts. The period of superhumps seems to show secular changes, as was observed in EF Peg during the 1991 superoutburst.

The correlation analysis with the simltaneous Kyoto data shows that the "noise-looking" signals in the Kyoto data are actually these QPOs. These QPOs are detectable only with the highest resolution (10-15s or better). Please continue your present configuration, if your equipment is able to get the data at such a high rate.

Regards,
Taichi Kato
VSNET Collaboration team

Second rebrightening!

(vsnet-alert 6413)

WZ Sge: stopped fading or even rising, and humps!

Dear Colleagues,

The partial analysis of the Kyoto Aug. 23 data (observation by Ishioka-san) shows that the rapid fading has stopped! The analysis even shows a hint of further rebrightening. The humps are becoming prominent again!!

The star may undergo the next rebrightening immediately. Please keep the vigil!

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6414)

WZ Sge: humps! eclipses!

Dear Colleagues,

Further analysis of the Kyoto Aug. 23 data shows the emergence of new hump structure (at binary phase 0.8), and the reappearance of sharply defined, deep eclipses (up to 0.1 mag)! Another spectacular change is definitely happening!

Regards, Taichi Kato VSNET Collaboration team

(Average profile of humps on August 23: on its way to the second rebrightening!)
(Average profile of humps and eclipses on August 23, from Ouda high-speed photometry data)

(vsnet-alert 6432)

WZ Sge rapidly fading from the second rebrightening

Dear Collgeaues,

We have received new data from T. Vanmunster, D. Starkey and S. Kiyota. Newly analyzed Kyoto data have been also added.

The data confirm the rapidly fading trend reported by T. Vanmunster. The fading continues during Starkey's latest observation. The rate of the fading is 0.85 mag/d, and seems to be accelerating.

The eclipses are even more prominent, and have a mean depth of 0.07 mag. The sharp superhumps are seen at phase 0.85 (the actual hump maxima are probably slightly later, being deformed by the overlapping eclipses). Other small hump structures are also seen at other phases (the phase-averaged light curve will be later posted on the VSNET WZ Sge page).

The present fading trend and rate are very reminiscent of the rapid fading following the first rebrightening. The main difference is the presence of strong superhump signals even at maximum. The present behavior look as if the star is trying to stuck to the superoutbursting state, but so far failed. Since the time-scale of vasriaitons have become quite short, continuous observations are most urgently needed.

Regards,
Taichi Kato
VSNET Collaboration team

(Averaged profile, later on Aug. 24 to early Aug. 25, during the fading stage from the second rebrighteng)

(vsnet-alert 6415)

WZ Sge: slow brightening and humps

Dear Colleagues,

We have further received new data from J. Pietz, T. Vanmunster and Y. Sano. The latest data from J. Pietz also confirm the slowly brightening trend. The amplitude of the humps is now 0.3 mag. More detailed analysis is in progress.

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6417)

WZ Sge definitely rising!

Dear Colleagues,

We have finished analyzing the Kyoto Aug. 23 data. The rising trend is apparent. We have also received data from D. Starkey today (early Aug. 24 UT), which clearly shows a rise at a rate of 0.3 mag/d. (Super)humps become increasingly evident. We shall see today the full return to its outbursting state!

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6419)

WZ Sge: humps on Aug. 23

Dear Colleagues,

The period analysis of the combined data onm Aug. 23 has yield P=0.05716(13) d, which is significantly longer than the orbital period. They are genuine superhumps!

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6421)

Visual magnitude estimates by P. Schmeer, Bischmisheim, Germany:

 
WZ SAGITTAE  (UGSU)
Aug. 23.911 UT,  12.4 ; 24.878,  11.3 ; 24.917,  11.3
Sequence:   AAVSO
Instrument: 203-mm SCT
 
Regards,
Patrick

(vsnet-alert 6426)

WZ Sge second rebrightening maximum

Dear Colleagues,

We have recieved a large number of data of the past few nights from many observers around the world. The review of these data are keenly in progress, and will be reported later.

We have also partly analyzed the Kyoto Aug. 24 run. The preliminary analysis shows the object brighter than the first rebrightening! Superhumps with amplitudes of 0.10 mag (probably reduced by the overlapping eclipses) and clear eclipses with a mean depth of 0.10 mag are seen. The center of eclipses are slightly earlier than the predicted eclipse times.

The persistence of large-amplitude superhumps, in contrast to the weakening of the superhump signal during the first rebrightening, may suggest that the present rebrightening is the genuine "second superoutburst", as was observed in AL Com in 1995.

Intensive observations are strongly encouraged in order to see the evolution of the superhumps, general outburst behavior, and details of each eclipses. High-speed photometry to follow the evolution of QPOs are also very encouraged.

More later.

Regards,
Taichi Kato
VSNET Collaboration team

WZ Sge fading getting slower

Dear Collgeaues,

In spite of the initial rapid fade from the second rebrightening, the fading has apparently become slower now. The reported magnitude of 12.0 is considerably brighter than those recorded at the bottom of the previous "dips". This may suggest that WZ Sge may be on its way to the third rebrightening (what a hasty star!). Please keep the closest watch on its behavior.

Time-series analysis of the new data (during the second dip) is keenly in progress.

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6437)

WZ Sge: fading

Dear Colleagues,

On the contrary to the preceding message, the latest data from J. Pietz shows that the object is still fading. Humps have become less intensive. The overall behavior strongly mimics the fading from the first rebrightening.

We have also received data from J. Pietz (two nights), M. Richmond and J. Kern (RIT team), high-speed photometry data from A. Oksanen (Nyrola Observatory). The analysis of the Kyoto data is also ongoing. They are being analyzed intensively.

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6440)

Dear Colleagues, after some days of silence, finally I've been able to track again this amazing star. I observed for 5 hours, starting at 21:00 UT. Images were grabbed every 14 seconds, each exposure being of 9 seconds. I reduced about 50% of the run and here are some preliminary results (I have also one hour of data between 18:50 UT and 20:00 UT).

The curve is very interesting. While there are no large humps (>0.2mag), some short-term modulation seems to be clearly present (period of 0.015d), mainly during the first hour; the final part shows a little "dip" . Eclipses have a weak importance, at least in this part of the run. I confirm a fading trend for the star.

The light curve, with others curves from previously unpublished datased will be added later today.

Kind Regards,
Gianluca

Note on the close companion and data analysis

(vsnet-alert 6428)

WZ Sge: note on the close companion and data analysis

Dear Colleagues,

WZ Sge is currently experiencing the most unknown period of its superoutburst. The object may rise or fall with very short intervals, as have been experienced in EG Cnc (six post-superoutburst rebrightenings), AL Com (looking most similar to the present WZ Sge outburst; AL Com in 1995 showed undulations with time-scales of hours to days, whose nature have not been yet clear) and WZ Sge in 1978 (rather sparcely sampled visual data suggest day-scale variations). Please keep your eye on this object as long as you can -- we may not have a next similar chance within some decades.

However, as Arne Henden has commented, there is close companion (10 arcsec away) which may partly degrade CCD photometry (esp. in red or unfiltered ones). One may include this companion within the same aperture, and subtract its contribution. However, this process has a caveat: the companion is red, and is affected by differential extinction differently from WZ Sge and/or comparison stars. One must also know exactly the system color response to exactly determine the contribution. The contribution from the companion (and the sky background when including both stars in a large aperture) dominates when WZ Sge fades. The combination of these effects causes both systematic errors and a reduced S/N. It is therefore recommended to treat these measurements only as preliminary ones (to be used as real-time assessment of the behavior of the object). Observers are thus strongly requested to store all images (please don't erase them!), and make more elaborate analysis (PSF photometry) to separate these two stars. The VSNET Collaboration team is fully prepared to receive these raw images, and to make necessary PSF photometry. We can receive the data either via ftp or CD-ROM (please consult us if you use other media).

For those who are familiar with IRAF/DAOPHOT or other professional softwares may perform PSF photometry by themselves. We recommend to use GSC 1621.1830 (200733.72 +174000.1) = SAO 105719 as the primary PSF standard, if the star is not saturated. The second best selection is GSC 1621.1758 (200733.52 +173916.0). Please don't use the "automatic centering" function of the software [even the combination of professional softwares and long focal length images can easily fail], but use calculated PSF positions from the rest of the stars in the frame. Please don't rely on old positions (e.g. in the past literature, from DSS scans, etc.) since WZ Sge has a high proper motion.

A sample of such PSF photometry (separation of two stars) in quiescence can be seen at:

ftp://ftp.kusastro.kyoto-u.ac.jp/pub/vsnet/DNe/WZ_Sge/wzq.gif

for which we used a frontside-illuminated (low Q.E.) CCD attached to a 60-cm telescope, V-filter and 10 sec exposures. If your analysis cannot attain this level of constancy for the companion, it may be possible that something is wrong with the analysis. Please refer to this light curve in assessing your analysis.

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6442)

WZ Sge: new hump structure and possible QPOs

Dear Colleagues,

The analysis of the latest data (J. Pietz and A. Oksanen) has revealed the emergence of new (super)humps at phases completely different from the previous superhumps (during the second rebrightening). This phenomenon may be some sort of "late superhumps" to newly appeared superhumps during the second rebrightening (how complex!). There seem to be no "true" eclipse signals.

Furthermore, large-amplitude modulations with time-scales of ~20 min. Although they may be substuctures of (super)hump signals, they may represent the emergence of new QPOs. Since some super-QPOs are known to arise from these slow modulations (cf. EF Peg in 1991), observers are strongly urged to record the evolution of short-term oscillations, as well as evolution of (super)humps.

Regards,
Taichi Kato
VSNET Collaboration team

The third rebrightening!

(vsnet-alert 6458)

WZ Sge: third rebrightening maximum, complex humps!

Dear Colleagues,

We have received new data from G. Masi (two nights), T. Vanmunster and J. Pietz. We have also added newly analyzed Kyoto and Ouda data.

The data clearly show that WZ Sge reached the maximum of the third rebrightening around mid Aug. 26 (UT), and the object has already started to fade! The latest observation by J. Pietz (26.80 - 26.98 UT) shows a linear fading at a rate of 0.38 mag/d.

The hump structure has again become complex. Although the full amplitude of the humps are 0.09 mag, there are at least two distinct hump components: one seems to correspond to "late superhumps" persisting since the fading branch of the second rebrigtening, another seems to be new superhumps, which are very likely highly distorted by the eclipses. The exact identification would require a further detailed study (in progress, by Ishioka-san and Uemura-san). Eclipses have become again less prominent. The deepest dip-like feature may correspond to eclipses, but they occur 0.1 phase earlier than the predicted eclipses. The development of these features also should be followed intensively.

Since WZ Sge is up and down with a very short time scale (three times faster than in EG Cnc!), dense and continuous observations are most highly wanted!

More later.

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6463)

WZ Sge: further fading from the third rebrightening

Dear Colleagues,

We have received new data sets from G. Masi and D. Starkey. G. Masi's data impressively depicts the rising phase of the first rebrightening.

Starkey's latest data confirms the fading trend (vsnet-alert 6458). The present rebrightening looks like to follow the same pattern as in the preceding ones.

Time-series analysis has shown that the complex hump strutures (vsnet-alert 6458) have become even weaker, associated with phase shifts. However, two maxima are still clearly visible. Eclipse-like fading 0.1 phase preceding the predicted eclipses also persists. Observers are strongly urged to continue observing the object, using the same technique as in the past similar episodes.

Regards,
Taichi Kato
VSNET Collaboration team

We have updated the overall light curve on the VSNET WZ Sge page. The durations and depths of the fadings (dips) during the outburst seem to have become progressively shorter and shallower. It may be that the star may be stuck to the superoutbursting state at the next or the following rebrightening. Please keep the vigil!

Super-QPOs again!

(vsnet-alert 6471)

We have performed preliminary analysis of observations last night at Ouda. We have obtained over 6000 images with integration time of 1-2s. The object is rapidly fading with 1.1mag/d. There are humps with amplitudes of about 0.1mag and a period near the superhump period. The QPOs of 3-5 minutes have again become strong, which is very similar to the previously reported one during the rapid fading phase from the rebrightening.

Regards,
Makoto Uemura

WZ Sge: strong super-QPOs on Aug. 27 data (Ouda, Kyoto)

(Phase-averaged light curve on August 27)

(vsnet-alert 6474)

WZ Sge further fading and humps! QPOs!

Dear Colleagues,

We have receive a great number of data, which will be reported later.

The latest data from J. Pietz (up to early Aug. 28 UT) have confirmed the continuing fading trend as inferred from the Ouda observation.

The superhumps have again become prominent, and large-amplitude QPOs reported by Uemura-san highly distort the hump profile. The present apprearance of large-amplitude superhumps may suggest that a new rebrightening is approaching. Keep a close watch!!

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6476)

WZ Sge: double humps!

Dear Colleagues,

We have further analyzed the data, which were kindly sent by B. Martin, J. Pietz, and data at Ouda and Kyoto (the latter being analyzed).

The averaged profile shows fadings at phase 0.0 and 0.5, the former being possible broad eclipses. Two hump maxima and two minima show a double profile. The overall feature of the phase-averaged curve is similar to those of early superhumps.

The averaged curve is also posted at the VSNET WZ Sge page.

Regards,
Taichi Kato
VSNET Collaboration team

The fourth rebrightening!

(vsnet-alert 6493)

WZ Sge: already fading from the fourth rebrightening, message from J. Pietz

We have received the following message and data from J. Pietz:

Date: Wed, 29 Aug 2001 01:19:55 +0200 (MEST)
From: Jochen.Pietz@t-online.de (Jochen Pietz)
Subject: WZ Sge: first results of run 27

I will try to get some additional data for a more reliable analysis.

Regards,
Jochne Pietz

(vsnet-alert 6494)

WZ Sge: fourth rebrightening

Dear Colleagues,

We have received new data from T. Vanmunster, J. Pietz, D. Boyd (two nights) and M. Richmond, S. Davis, M. Aggeleton (RIT team), and are intensively analyzing the Kyoto Aug. 28 observation (observed by Ishioka-san).

A quick look at the data have shown that the system has undergone its fourth rebrightening, slowly starting near the end of Vanmunster's run, major rise during the RIT observation, and peaking at the beginning at the Kyoto Aug. 28 run. The peak brighteness may even surpass those of the three preceding ones (pending more accurate zero point adjustment). The object has already stared a slow fading, as reported by J. Pietz.

The complex hump features are observed to grow during the Vanunster's run, stronger in RIT runs. The profile has become a "triple wave" at the time of the Kyoto observation, and its pattern persists in the latest Pietz's run. The system may fade rapidly again, but the recurrence time is peogressively getting shorter. One may witness the next rise at any time!

We will be undertaking on the phasing/period analysis, as well as further analysis of the Kyoto data. More information will be posted later.

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6502)

WZ Sge: fading from the fourth rebrightening, eclipses!

Dear Colleagues,

We have received new data from J. Pietz and D. Starkey. The data, together with the Kyoto data, confirmed the continuing fading trend from the maximum of the fourth rebrightening.

The fading was slow during the Kyoto observation (0.17 mag/d), but became more rapid (0.84 mag/d between Aug. 28.81 and 29.20), and is apparently continuing.

Among the "triple-hump" profile, one seems to be identified with persisting signal close to the quiescent orbital humps (and may also be identified with early superhumps?), and the others (weaker ones) are moving in phase. Eclipses became sharper and deeper as the system faded.

We have put representative phase-averaged light curves on Aug. 28-29 on the VSNET WZ Sge page.

Regards,
Taichi Kato
VSNET Collaboration team

(Phase-averaged light curve on August 28: eclipses became deeper as the star faded.)

(vsnet-alert 6505)

WZ Sge Aug. 28: QPOs at shorter periods

Dear Colleagues,

We have received high time-resolution data on Aug. 28 from Marko Moilanen (Nyrola observatory). The data show the intermittent appearance of QPOs with periods 2-3 min, which is significantly shorter than that recorded in the Ouda observation. There seems to be some correlation between the QPO amplitude and hump phase. More detailed analysis will be reported by Uemura-san.

We have also received a great number of new data, and analyzing the Kyoto observation last night. The result will be reported later, but the fading trend was already apparent in the Kyoto data. The recent pattern of renbrightenings may be represented by a 2-d period, which suggests a new rebrightening is ongoing NOW !!

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6509)

WZ Sge: humps and eclipses on Aug. 29

Dear Colleagues,

A quick look at the partly analyzed Kyoto data on Aug. 29 (around 29.55 UT, just before the bottom of the fading) has shown only weak (0.05 mag or less) presence of the hump structure, which had been evident on Aug. 28-early 29. The main hump is now observed at phase 0.5 (the main peak before the eclipse had almost disappeared!). Shallow, slightly broad, eclipses are also present, at slightly earlier than the predicted times. There must have been a subsequent dramatic change in the hump and eclipse profiles, as judged from the description and preliminary data from D. Starkey. Please follow the evolution of humps and eclipses, and the fifth rebrightening, as closely as possible!

Regards,
Taichi Kato
VSNET Collaboration team

The fifth rebrightening!

(vsnet-alert 6511)

WZ Sge: at the fifth rebrightening maximum

Dear Colleagues,

D. Starkey has reported the latest data, covering the rise to and the maximum of the fifth rebrighetening. The phase analysis, after removing the general trends, has yielded very weak periodic signals. Eclipses are no longer prominent. The strongest hump signal (about 0.05 mag in average) resides just after the eclipse times. It may be that altough superhumps may have newly grown, their existence may have been masked by the eclipse effect. If this possibility is confirmed by the following observations, the present hump phase suggests that either superhumps have newly appeared, or developed from the "pre-eclipse" hump signal predominantly seen in the Aug. 28 data. The latter interpretation may naturally explain the apparent absence of the strong hump signal in the Aug. 29 data. The present superposition of hump and eclipse phases at maximum is the first-ever seen during the rebrightening stage. Observers are requested to closely follow the evolution of eclipses and humps in order to determine the geometry of the eclipsed source.

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6514)

WZ Sge: maximum of the fifth rebrightening

Dear Colleagues,

We have received a large amount data, from K. Morikawa, University of Athens Observatory team (K. Gazeas, A. Yushchenko, P. Niarchos, 6 nights), T. Vanmunster, RIT observatory team (M. Richmond, M. Aggleton), B. Martin, and the Kyoto data. Thanks to all observers, the fifth rebrightnening has been recorded in unprecedented detail!

The most striking feature of the fifth rebrightening is the waekening of the superhump signal around the rebrightening maximum. It seems to be superhumps may be fading away, but this needs to be tested by further observations.

The phase-averaged light curve close to the rebrightening maximum shows a hump at phase 0.2, which siginifantly differs from the result from preceding observations, and qualifies the signal as superhumps, rather than some orbital signature. Eclipses are also weakly seen, and have a rather broad profile.

Observers are strongly urged to follow the evolution of (super)humps, eclipses, and the rebrightening itself, in order to further discriminate the possibilities of the intrinsic weakening of superhumps or the beat-related modulations.

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6515)

WZ Sge: hump structure, no ture eclipse?

We have further analyzed the data. The phase-averaged light curves between late Aug. 29 (slowly brightening stage) and early Aug. 30 (maximum of the fifth rebrightening) seem to suggest that there are no true eclipses (only shallow fadings 0.1 phase before the predicted times, and location is highly variable). There were three small hump maxima during the slowly brightening stage in one cycle, one of which (at phase 0.2) seems to be commonly, but more weakly, present when the system is at maximum.

We have put the figure of comparison on the VSNET WZ Sge page.

Regards,
Taichi Kato
VSNET Collaboration team

(Phase-averaged light curve on late August 29: slowly rising toward the fifth rebrightening and early Aug. 30: at maximum of the rebrightening)

(vsnet-alert 6522)

WZ Sge: fading from the fifth rebrightening, and rising again?

Dear Colleagues,

The partial analysis of the Aug. 31 Kyoto observations shows that WZ Sge was again fading from the present rebgithening. The course of the fading is similar to those recorded in the past rebrightenings (no anomaly?).

The later part of the Kyoto observation suggests that the fading has stopped, and may be even slowly rising. This may be an indication of the sixth rebrigtening! Humps have again become strong. Please observe closely! We will report later on, as the analysis proceeds.

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6523)

WZ Sge: reappearance of (super)humps and eclipses!

Dear Colleagues,

The partial analysis of the Kyoto data (Aug. 31.60 to 31.69) confirms the reappearance of sharp eclipses (depth 0.10 mag), which is phase 0.05 earlier than the predicted times, and large (super?)humps at phase 0.8. There is another hump around phase 0.15, but this may comprise a single entity, intervened by eclipses, with the phase 0.8 hump. The full amplitude of humps is 0.13 mag. The observed behavior strongly anticipates an immediate next rebrightening!

Regards,
Taichi Kato
VSNET Collaboration team

The sixth rebrightening!

(vsnet-alert 6524)

WZ Sge: sixth rebrightening!

Dear Colleagues,

The most recent D. Starkey's observations shows WZ Sge at its maximum of the sixth rebrightening! The major rise should have taken place during the European night.

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6525)

WZ Sge: modulation at the sixth rebrightening

Dear Colleagues,

We have completed the analysis of the Kyoto Aug. 31 data (observer Ishioka, Uemura et al.) The mean brightness of the object remained almost constant until the end of the run (31.775 UT), with prominent humps and eclipses.

Deep, sharp eclipses are also clearly present in Starkey's Sep. 1 data, which were taken at or just after the rebrightening maximum. The hump maxima, with a smaller amplitude, are seen at a phase close to that observed in the preceding Kyoto data. The clear appearance of eclipses and humps at the sixth rebrightening maximum (these features were not very clear during the fifth rebrightening) may suggest the presence of a precessing component (origin of superhumps?), which is eclipsed at certain times. Aug. 23 data showed similar eclipse and pre-eclipse humps, which may suggest the presence of a 8-d cycle.

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6526)

Dear colleagues,

I had a short observing session on WZ Sge last night (Aug 31 / Sep 01), between 31.81 UT and 31.90 UT (before clouds completely covered the sky). The resulting light curve shows another very steep brightening of WZ Sge, as predicted by Kato-san in [vsnet-campaign-dn 1456], by 0.41 mag in almost 2.2 hours. I'm not sure how long this brightening trend has continued (I hope others have been more successful in their observing run last night), but it must have been very spectacular !

There were furthermore some dips and humps in the rising trend of the variable, but I haven't further analysed this yet. I will make the light curve available on my web site, later this evening.

Best regards,

Tonny Vanmunster
CBA Belgium Observatory
http://www.lunarpages.com/cbabelgium
email : Tonny.Vanmunster@advalvas.be

(vsnet-alert 6534)

WZ Sge: fading from the sixth rebrightening!

Dear Colleagues,

We have received new data from T. Vanmunster, K. Morikawa, B. Martin, J. Pietz, and new data from Kyoto observation last night (observer R. Ishioka).

WZ Sge is now fading from its sixth rebrightening. However, the duration of the flat maximum exceeds 0.5 d, which seems to be the longest among all rebrightenings. The fading started during the Kyoto observation. Eclipses and (super)humps persist throughout this period, and a preliminary look at the light curve, the phase of the (super)hump maxima comes closer to the eclipse center. More detailed analysis will be presented later.

Another noteworthy feature from these data is the sudden brightening occurring at Aug. 31 13h UT. The system became systematically brighter by about 0.1 mag thereafter. The feature was first caught in the Kyoto observation, but we considered it as some unknown instrumental effect. However, simultaneously taken Morikawa's data have confirmed its reality. The phase is unrelated to an eclipse timing, and the cause of such a sudden change is unknown.

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6536)

WZ Sge: hump and eclipse profiles on Sep. 1 (sixth rebrightening)

Dear Colleagues,

We have put on the VSNET WZ Sge page the figures representing the recent variations of the hump and eclipse profiles. Please note the dramatic change of (super?)humps (phase and amplitude) and eclipses (phase and profile) across the rebrightening.

The phase of eclipses particularly changed to a great extent. At maxmum, the phase tended to be earlier than the predicted times. Later during the decline, the eclipses became quite asymmetric.

The phase 0.8 hump (orbital hump??) grew again as the system faded. However, the hump maxima were around phase 0.0 at the rebrightening maximum. It may be that these humps (at phase 0.0; superhumps?) were different ones from those at phase 0.8, and became strongest only when the system is close to the maximum. Close follow-up observations of these detailed structures are naturally very wanted. If the system brightens again (likely!), the number of rebrightenings will break the record of post-superoutburst rebrightenings!

Regards,
Taichi Kato

(vsnet-alert 6537)

Dear colleagues,

I just finished analysing my CCD observations of WZ Sge of Sep 01/02. It was mostly clear, with some cloud fields entering the sky towards the end of the run. WZ Sge showed a gradual decline from its 6th rebrightening (see light curve at my web site), but what is more obvious is the rather complex modulations. Dominating single-peaked (super?)humps are easy recognisable, and in between these humps are at least two smaller hump structures. Eclipses are still there too, and appear reasonably well at the predicted times.

It's cloudy over Belgium now, with lots of rain.

Tonny Vanmunster
CBA Belgium Observatory
http://www.lunarpages.com/cbabelgium
email : Tonny.Vanmunster@advalvas.be

(Later on Sep. 1.)

(Late Sep. 1 - early Sep. 2. Hump features and eclipses are prominent again.)

(vsnet-alert 6538)

WZ Sge: fading from the sixth rebrightening

Dear Colleagues,

We have received high-quality data from D. Starkey, T. Vanmunster, the RIT team (M. Richmond and S. Davis). New data from the Kyoto observation have been also added.

The most striking feature in the Sep. 2 observations is the fading trend, as observed in the past rebrightenings. The six rebrightening generally displayed the same evolution of the phenomenon as in the past five rebrightenings, despite a slight difference of the duration of the flat maximum.

Large-ampltude QPOs (super-QPOs?) with periods of 2-5 min are also transiently present, most notably between Sep. 2.05 and 2.07.

More detailed analysis will be presented later.

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6540)

WZ Sge: humps, eclipses, dips

Dear Colleagues,

The time-series analysis of the descending branch of the sixth rebrightening has revealed the re-appearance of the "phase 0.6 dip", just preceding the (super?)humps. The eclipses have become more prominent (depth 0.10 mag), with a sharply defined profile. The bottom of the eclipses seem to have become flatter, suggesting that some of the well-defined light sources is totally eclipsed. The pre-eclipse (super?)humps are also prominent, as reported by T. Vanumunster.

The representative phase-averaged light curve is placed on the VSNET WZ Sge page.

Regards,
Taichi Kato
VSNET Collaboration team

The seventh rebrightening!

(vsnet-alert 6546)

WZ Sge: fading from the seventh rebrightening, and yet another??

Dear Colleagues,

We have received new data from B. Martin. We are also anlyzing the Kyoto observation last night (observer R. Ishioka). Martin's observation suggests that the object was already fading from the seventh rebrightening at the time of the observation (Sep. 3.143 to 3.352). However, the subsequent Kyoto observation (only partly reduced) even suggests a rising trend again! Since both observations were not performed under ideal conditions, observers are strongly urged to observe the object as quickly as possible, and as long as possible, in order to check the current outbursting state and its trend. The most recent observation may even suggest that the object's behavior may be strongly changing! Please keep the vigil as much as you can!

Regards,
Taichi Kato
VSNET Collaboration team

(At maximum of the seventh rebrightening. Humps have smaller in amplitude, and moved in phase.)

(vsnet-alert 6555)

WZ Sge: time-series analysis of the 7-th rebrightening

Dear Colleagues,

We have put on the VSNET WZ Sge page representative averaged profiles on Sep. 3 and 4 (at maximum of the 7-th rebrightening and the following minimum, respectively). At maximum of the 7-th rebrightening, eclipses were still present (shallow, but still sharp). Humps have become smaller in amplitude, and siginificantly moved in phase. The strongest humps are seen at phase 0.2-0.3, which is largely different from the phase of the large humps seen on preceding nights. Other small-scale structures are seen on the descending branch; among them a dip at phase 0.7-0.8 is distinct.

During the minimum following the 7-th rebrightening, large-amplitude humps again appeared! The humps are triangular in shape and have a sharp peak at phase 0.3. The systenatic phase shift between these two nights suggest that they are superhumps. Eclipses have become again inapparent.

Please have a look at the light curves on the WWW for more details.

Regards,
Taichi Kato
VSNET Collaborationt team

(At minimum after the 7-th rebrightening. Superhumps appear at a different phase. Eclipse have become inevident.)

The eighth rebrightening!

(vsnet-alert 6552)

WZ Sge: eighth rebrightening confirmed

Dear Colleagues,

We have received new data from the RIT team (M. Richmond, B. Conrad, M. Aggelton, S. Davis, two nights), and the latest data from J. Pietz.

Together with the partly analyzed Koyto data last night (observer R. Ishioka), we have confirmed the eighth rebrightening as reported by L. Cook. More result will be reported later. Although the moon is bright, please continue observing!

Regards,
Taichi Kato
VSNET Collaborationt team

(vsnet-alert 6554)

WZ Sge: already fading from 8-th rebrightening!

Dear Colleagues,

We have received new data from L. Cook (two nights) and B. Martin. We have also newly added the Kyoto data. The data by L. Cook and B. Martin very clearly depict the rising branch of the 8-th rebrightening. The Kyoto observation last night was found to be done at maximum of the rebrightening. The last data from J. Pietz already shows the fading trend, indicating that the period of rebrightening has shortened to 1.5 d!

The next rebrightening is expected to start rising at around September 5.6-5.7 UT (best for the east Asia), and will be at maximum during European nights. Please keep the vigil as much as you can!

The phase analysis and WWW update will come soon.

Regards,
Taichi Kato
VSNET Collaborationt team

(vsnet-alert 6558)

WZ Sge: fading from the 8-th rebrightening

Dear Colleagues,

We have received new data from D. Starkey, and added new data from Ouda observation (observer M. Uemura) and Kyoto observatin (observer R. Ishioka). Starkey's data between Sep. 5.05 and 5.21 clearly show the fading trend, as was observed during the 7-th rebrighetening. The overall behavior of the 8-th rebeightening is similar to the 7-th rebrightening, except for remarkable changes in the hump and eclipse profiles. The flat maximum (or the outburst duty cycle) seems to have become longer in recent rebrightenings. The star may be around maximum of the 9-th rebrightening now (?)

Time-series analysis will be presented later.

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6559)

WZ Sge: Sep. 4-5 time-seires analysis, eclipse and humps appeared again!

Dear Colleagues,

As reoorted by Uemura-san, at the (8-th) rebrightening maximum, there seemed to be no "true eclipses" at the predicted phase. The profile is very complex, and there was an eclipse-like fading 0.1 phase preceding the predicted times. The maxima of humps appear at phase 0.4 and 0.6 (double peaks). There is also a dip-like feature at phase 0.1-0.2, making the overall appearance as "triple humps".

Later on the fading of the rebrightening, eclipses at predicted phases appeared again! There is also growing hump signal preceding eclipses (the feature commonly seen in the past rebrightenings).

A representative light curve is presented on the VSNET WZ Sge page.

Regards,
Taichi Kato
VSNET Collaboration team

(Maximum and fading stage of the 8-th rebrightening. At rebrightening maximum, Eclipse-like fading appeared 0.1 phase before the predicted eclipses. Later on the fading stage, eclipse and pre-eclipse hump appeared again.)

The nineth rebrightening!

(vsnet-alert 6560)

WZ Sge: 9-th rebrightening!

Dear Colleagues,

With the most recent data just sent from J. Pietz (Sep. 5.960-6.074 UT), we have confirmed the occurrence of the 9-th rebrightening! The object seems to be past maximum, and apparentlt started fading. Relatively large-amplitude complex modulations are superimposed. Please continue observing the object, as the next minimum (and regrowth of hump features) is expected to be ongoing now.

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6562)

WZ Sge: 9-th rebrightening at maximum

Dear Colleagues,

The most recent data from D. Starkey clearly shows that WZ Sge stays at its maximum of the 9-th rebrightening. Time-series analysis (combined with the data from J. Pietz) shows the main humps at phase 0.7-0.8, which occurs earlier than before. A negative phase shift or a new feature? Two dip-like minima are seen, at the predicted eclipse times and phase 0.4. The overall light curve is very complex.

Starkey's data show a slight tendency to fade. We may expect the 10-th rebrightening within 1.5 d.

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6567)

WZ Sge: details of the 9-th rebrightening

Dear Colleagues,

We have received new, very excellent, data from B. Martin. The data covered the 9-th rebrightening maximum to early decline, and confirmed the lengthening of the maximum phase.

Time-series analysis of the 9-th rebrightening revealed that relatively broad, but distinct, eclipses appeared slightly earlier than the predicted eclipses. The phase 0.7-0.8 hump becomes also prominent. The overall appearance of the light curve is double-humped, whose profile strongly resemble that of quiescent humps (and possibly early superhumps). The figure is placed on the VSNET WZ Sge page.

The similar profile during the rebrightening was seen on Aug. 28 (the 4-th rebrightening). The recent systematic variation of hump/eclipse profiles during the rebrightening stages seems to support the presence of a 9-d beat period, seemingly closely related to the "beat phenomenon" observed during the main superoutburst! This fact indicates that we have covered a full precession of the post-superoutburst eccentric disk, and recorded systematic change of the associated eclipse profile and hump profile across rebrightening -- the long-wanted observation in these CVs, and probably the first successful one in WZ Sge-type dwarf nova! The present success is expected to solve the "enigma" of the WZ Sge-type post-superoutburst rebrightening!!

It has become increasingly evident that the present WZ Sge outburst provides the chance in a thousand in the CV research! Please keep the present very excellent and impressive coverage, until the star completely fades away!

Regards,
Taichi Kato
VSNET Collaboration team

(Maximum and fading stage of the 9-th rebrightening. Broad eclipses and double humps are prominent.)

The tenth rebrightening!

(vsnet-alert 6575)

WZ Sge: 10-th rebrightening!

Dear Colleagues,

The most recent data from D. Starkey (Sep. 7.071-7.135 UT) clearly showed another fading branch from the 9-th rebrightening, and likely quick turning-up to the next (10-th) rebrightening! More detailed analysis will be presented later.

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6582)

WZ Sge: damping oscillation

Dear Colleagues,

18 days have passed since the first post-superoutburst rebrightening. Up to now, ten distinct rebrightenings have been recongnized. As the time passes, it has been increasingly evident that these rebrightenings are a damping oscillation in nature, both in amplitude and period. The maxima of these rebrightenings have strictly followed the smooth extension of the decline of the main superoutburst. This general trend would suggest the continous shrinkage of the overall disk, through which the heating and cooling wave propagated. The damping nature of the oscillation may be naturally explained at a constant mass-transfer to the progressively shrinking accretion disk. The system now keeps relatively constant brighteness at about 11.5 mag. Further detailed, intensive observations are still strongly requested in order to follow the fate of the diminishing rebrightening oscillation.

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6587)

WZ Sge: fading from the 10-th rebrightening (Sep. 8)

Dear Colleagues,

We have received new data from B. Martin and M. Moilanen. We are also analyzing the Kyoto data last night (observer R. Ishioka). The most recent data clearly show the fading from the 10-th rebrightening.

Clear orbital or superhump signal, as well as likely eclipses, is also superposed, as observed in the fading branches of the past rebrightenings. More detailed time-series analysis will be presented later.

The data suggests the next rebrightening may be just ongoing!

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6588)

WZ Sge: fading from the 10-th rebrightening update

Dear Colleagues,

We have received new data from J. Pietz (data up to just an hour ago). The data in on the same extension of the fading trend as observed in the Kyoto data. The rate of the fading seems to be larger than that of the preceding rebrighteing. Close, continous, observations are most urgently requested in order to see whether the current fading trend still continues (and enters the final fading?) or the object again rebrightens!

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6589)

WZ Sge: hump and eclipses during the 10-th rebrightening

Dear Colleagues,

Time-series analysis of the early fading stage of the 10-th rebrightening has revaled the following structure.

   1) Eclipses: present on the ascending branch of the humps.  Sharp but
      rather shallow.  The eclipse center slightly earlier than the predicted
      times.

   2) Humps: large main hump at phase 0.2-0.3.  Phase 0.8 hump disappeared.

   3) Possible phase 0.7 dip.

Regards,
Taichi Kato
VSNET Collaboration team

(Early-to-mid fading stage of the 10-th rebrightening. Eclipses and humps become less prominent.)

The 11th rebrightening!

(vsnet-alert 6597)

WZ Sge: 11-th rebrightening

Dear Colleagues,

We have received new data from B. Martin and L. Cook. The both sets of data clearly show a sharp rise toward the 11-th rebrightening, which should have peaked late on Sep. 9 (the system may have just started fading now). Hump modulations are clearly visible, while eclipse are not very evident. Time-series analysis will be presented later.

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6598)

WZ Sge: time-series analysis of the Sep. 9 data

Dear Colleagues,

We have analyzed the rising portion of the 11-th rebrightening. The main hump is located at phase 0.3-0.4, and not at 0.8-0.9, seen in the rising stage of some of past rebrightenings. This would imply either the main hump is moving in phase (i.e. superhumps) or the 0.8-0.9 phase pre-eclipse humps have become weaker. In the former case, it may be possible superhumps may be somehow (physically or geometrically) enhanced when they occur at pre-eclipse phases. As reported earlier, eclipses are not evident on Sep. 9 observations. This may have been an effect of superposition of eclipses with some of hump structures.

Further observations are strongly encouraged to discern the possibilities, and to record the expected fade of the 11-th rebrightening. The system is expected to undergo a next rebrightening within 1.5 d, if the present activity continues.

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6604)

WZ Sge: fading from the 11-th rebrightening (Sep. 10)

Dear Colleagues,

We have received new data from T. Vanumunster and L. Cook. Cook's latest data clearly indicate the fading from the 11-th rebrightening. The rate of decline is comparable to that of the 10-th rebrightening. Hump structure is very apparent on the light curve. The overall light curve suggests that the system may undergo the next rebrightening soon. Time-series analysis will be presented later.

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6605)

WZ Sge: strikingly different profile! (Sep. 10)

Dear Colleagues,

WZ Sge has shown another veru striking change in its orbital light curve! The analysis of the most recent data (L. Cook) has revealed that the profile has now become "sinusoidal", i.e. smooth maximum at phase 0.5 and minimum at phase slightly before 0. The overall appearance of the profile even resembles that of a reflection-type variable! Although it is not unlikely that we are observing the illuminated surface of the secondary star (reflection effect), the chance seems to be small because the disk light should have dominated at present. Anyway, such a profile has not been observed so far even during the entire rebrigtening period. Observers are strongly requested to follow the evolution of the light curve, and record the dramatic change!

The representative light curves of the 11-th rebrightening have been posted on the VSNET WZ Sge page.

Regards,
Taichi Kato
VSNET Collaboration team

(Rising and fading branch of the 11-th rebrighitening. Note the remakable change of the profile!)

(vsnet-alert 6606)

WZ Sge: further fading from the 11-th rebtightening, hump again!

Dear Colleagues,

B. Martin jas just sent the most recent data. WZ Sge has further faded from the 11-th rebrightening. The mean magnitude is fadinter than the minimum after the 10-th rebrightening.

There is a striking hump at phase 0.8-0.9, which is remarkably different from the humps (phase 0.5) seen during the early fading stage of the 11-th rebrightening. The reappearance of strong humps suggest that a new rebrightening is just coming now!

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6607)

WZ Sge: finaly faded!?

We have started time-series observations at the Ouda observatory with the 60-cm telescope from 9:40 (UT). The object is about R=13.0mag and not in rebrightening. This indicates that the historical event of WZ Sge 2001 entered a new period or finally faded.

Confirmations and follow-up observations are encouraged.

Regards,
Makoto Uemura

(vsnet-alert 6615)

WZ Sge fading: recovering?

Dear Colleagues,

Very preliminary analysis of the Kyoto data last night (observer R. Ishioka) confirms the rapid fading as reported by Uemura-san. The object reached the faintest magnitude since the discovery of the outburst.

However, there was a steep rise between 11.51 and 11.55 UT (analysis of the following times still in progress). Further observation is still most urgently requested in order to follow the observed trend!

We have also confirmd PSF photometry has yielded sufficiently good quality data even at minimum and with short (4s) exposures. Please continue observing with your usual protocols.

Regards,
Taichi Kato
VSNET Collaboration team

The 12th rebrightening!

(vsnet-alert 6616)

WZ Sge: 12-th rebrightening!

Dear Colleagues,

The most recent data from D. Starkey clearly shows that the 12-th rebrightening has taken place, as suggested by the Kyoto observation! Since the course of the 11-th rebrightening and the subsequent fading was different from those of the earlier ones, observers are strongly requested to observe the behavior following the latest change. More detailed analysis is in progress.

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6621)

WZ Sge: 12-th rebrightening, a different one!

Dear Colleagues,

Very preliminary analysis of the Kyoto data last night has shown that WZ Sge took a (very) slow rise between Sep. 11.5 and 12.5. The object has further risen since the preceding observation by D. Starkey.

The rise time of ~1 d is extremely long compared to those of the previous rebrightenings. This suggest that the present rebrightening has a different nature from the past rebrightenings. It would be noteworthy that the 6-th (last) rebrightening of EG Cnc had a substantially slower rise, accompanied with a slow rise lasting more than a day before reaching maximum (Kato et al. 1997). Observers are most strongly and urgently requested to follow the behavior of WZ Sge!

The time-series light curve looks rather flat, pending further detailed analysis. More later.

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6622)

WZ Sge: fading from the 12-th rebrightening!

Dear Colleagues,

Further analysis of the Kyoto data, and the most recent Starkey's data again show the fading of WZ Sge! The object may be entering the stage of precipitous decline, or the amplitude of oscillations (rebrightenings) may have become larger. Further observations are strongly requested to follow the behavior at this important stage.

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6623)

WZ Sge: amazing humps on Sep. 11!

Dear Colleagues,

We have completed the detailed analysis of the Sep. 11 runs, taken during the deep minimum preceding the 12th rebrightening.

The result is awful! There were HUGE humps at phase 0.85! Sharp eclipses and phase 0.5 dip are also seen. We have put a preliminary, representative lught curve on the VSNET WZ Sge page. Please note the difference in the vertical scale! (The relatively noisy appearance in some phases is just an artifact of the failure of automatic removal of poor data).

These large-amplitude humps may be appearing again as the system fades (now!) from the 12th rebrightening.

Regards,
Taichi Kato
VSNET Collaboration team

(Deep minimum preceding the 12th rebrightening. Very strong humps and relatively sharp eclipses are seen.)

(Deep minimum after the 12th rebrightening. Humps and eclipses are overlapped.)

(vsnet-alert 6626)

WZ Sge: fading from the 12-th rebrighteng, Ouda and Kyoto observation

Dear Colleagues,

The rapid fading from the 12-th rebrightening has been confirmed both in Ouda (observer M. Uemura) and Kyoto (observer R. Ishioka) observations. The preliminary magnitude on Sep. 13.5 UT is comparable to that on Sep. 11.5 UT, the minimum after the 11-th rebrightening. The speed of decline is also comparable to that of the fading from the 11-th rebrightening.

We have also confirmed that the hump structure was also present during the maximum of the 12-th rebrightening. There also seems to be a hint of QPO signals.

Further analysis is in progress, and we encourage intensive observations of this very important stage of the outburst.

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6628)

WZ Sge: stopped fading!

Dear Colleagues,

We have finished the full analysis of Sep. 13 data (Kyoto and Ouda). The observation consistently showed rapid linear fading, as reported in the preceding reports.

We have just received new data from B. Martin. Martin's data clearly indicate that the fading trend has completely stopped or even brightened (though the zero-point uncertainly has made direct comparison rather difficult). Martin's observations also clearly show large-amplitude complex modulations, which may suggest the next rebrightening is just ongoing. The hump feature on Martin's data seems to be different from that observer during the preceding minimum phase on Sep. 11. Further analysis is keenly in progress.

The star may be brightening now, and further intensive observations are most strongly wanted!!

Regards,
Taichi Kato
VSNET Collaboration team

(vsnet-alert 6629)

WZ Sge: humps and eclipses on Sep. 14

Dear Colleagues,

The analysis of the Sep. 14 data have revealed that humps are reduced in amplitude (compared to the Sep. 11 deep minimum), and significantly moved in phase. The peak of humps is presumably located near the eclipse center, which would explain the reduction of the hump amplitude.

The rather broad eclipses occur slightly before the predicted times. There is also a slight hint of phase 0.6 dip.

A comparison of light curves between two minimum epochs (Sep. 11 and Sep. 14) is presented on the VSNET WZ Sge page. Please have a look, and share the wonders of the king of cataclysmics!

Regards,
Taichi Kato
VSNET Collaboration team

Fading after the 12th rebrightening

(Giant humps and sharp eclipses observed 4 day after the 12th rebrightening. The object stayed at 2 mag brighter than quiescence, and slowly fading).

(Comparison of humps and eclipses. Eclipses become strongest on early Sep. 17. QPO-like modulations were also seen on early Sep. 17)

(Light curve on Sep. 18. Humps and eclipses are superposed in phase. Eclipse became very narrow).

(Light curve on Sep. 20. Humps and eclipses became prominent again. There was a remarkable growth of these features within one day).

(Light curve on Sep. 22. Humps became most prominent.)

(Light curve on Sep. 23. Eclipse became very sharp.)

(Light curve on Sep. 24. Humps and eclipses became less apparent.)

(Light curve on late Sep. 25 - early Sep. 26. No sharp eclipses. Humps have moved.)

(Light curve on late Sep. 28. Large-amplitude humps and sharp eclipses.)

Averaged profile during the post-rebrighteing state

(CLEAN-ed spectrum)

Nightly light curves

(Early superhumps on July 24. Observers: Kyoto team, G. Masi, J. Pietz, M. Richmond, T. Davis)

(Early superhumps on July 25. Observers: Kyoto team, G. Masi, G. A. Good, J. Pietz)

(Early superhumps on July 26. Observers: M. Moilanen, G. Masi, F. Mallia, J. Pietz, M. Richmond, T. Davis, M. Fiaschi, D. Starkey, G. A. Good)

(Early superhumps on July 27. Observers: Kyoto team, G. Masi, J. Pietz, R. Novak, G. A. Good)

(Early superhumps on July 28. Observers: G. Masi, R. Novak, J. Pietz, L. Cook, Kyoto team)

(Early superhumps on July 29. Observers: Kyoto team, S. Kiyota, J. Pietz, D. Starkey)

(Early superhumps on July 30. Observers: D. Starkey, Kyoto team, S. Kiyota, R. Novak, J. Pietz, L. Kral, M. Richmond)

(Early superhumps on July 31. Observers: Kyoto team, B. Martin, G. Masi, J. Pietz)

(Early superhumps on August 1. Observers: Kyoto team, B. Martin, F. Mallia, G. Masi, J. Pietz, M. Richmond, L. Kral, D. Starkey)

(Early superhumps on August 2)

(Early superhumps on August 3, transition to usual suerphumps)

(Enlarged light curve of early superhumps on July 28)

Genuine superhumps!

(Fully developed superhumps on August 5. Observers: B. Martin, Kyoto team, J. Pietz, G. Masi, D. Starkey)

(Fully developed superhumps on August 7)

(Fully developed superhumps on August 8)

(Superhumps on August 11)

Unprecedented coverage and emails

(vsnet-chat 4775)

Many people have been contributing measurements of WZ Sge to the VSNET effort over the past month. From one of Kato-san's messages (sent Aug 27), I see that over 160,000 data have been reported in a little more than one month.

Is this some sort of record for astronomical measurements of a single object? I can't think of any other object which has been scrutized so intensely by so many people in such a short time, but I've been working on CVs for only a short time. Are there other examples of such intense observation? I wonder if SN 1987A is a possible contender -- though I doubt that people measured it several times a minute for nights on end.

Perhaps we fall short of one of the campaigns of the Whole Earth Telescope on a white dwarf? Or one of the searches for stellar oscillations by Gilliland and his colleagues? Maybe radio astronomers studying the rotation of millisecond pulsars leave us in the dust ... Does anyone know?

When I told one of my colleagues here at RIT about the global effort over the past month, he suggested that it might make a good press release. Now, I really, really dislike the number of press releases in astronomy these days (especially those stupid "hook" sentences at the very beginning), and their endless claims of "first" and "best" and "groundbreaking discovery". But if it turns out that the entire VSNET team has, say, beaten the old record by a factor of 3 or 4, I wonder if a joint press release from all contributing institutions and individuals would make sense?

                                         Michael Richmond

(vsnet-chat 4776)

Michael wrote:

>> over 160,000 data have been reported in a little more than one month.

>> I really, really dislike the number of press
>> releases in astronomy these days...
>> and their endless claims of
>> "first" and "best" and "groundbreaking discovery".

>> But if it turns out that the entire VSNET team has, say, 
>> beaten the old record...

\Brian

(vsnet-chat 4778)

> Are there other examples of such intense observation?  I wonder
> if SN 1987A is a possible contender -- though I doubt that
> people measured it several times a minute for nights on end.

Not sure which of the many radio astronomy projects would win this contest; but the University of Tasmania's 14 metre radio telescope has continuously observed the Vela Pulsar since 1981. And it's a circumpolar object at their latitude. See this link for a description:=20 http://www-ra.phys.utas.edu.au/observatories/14m-intro.html

>   When I told one of my colleagues here at RIT about the global
> effort over the past month, he suggested that it might make a good
> press release.

There will be a seminal article published in one of the journals about "The WZ Sge Outburst Of 2001". No doubt with a long list of acknowledgements, contributors, and a zillion references to VSNET. That takes care of getting noticed by the professionals.

But who gets to write the item for Sky & Telescope, so that the unwashed masses also know of this accomplishment?

cheers,
Fraser Farrell

Kuulker's comparison of outburst light curves of WZ Sge

(1913, 1946, 1978)
(URL: http://saturn.sron.nl/~erikk/wzsge/wzsge_1913_1946_1978.gif)

(2001)
(URL: http://saturn.sron.nl/~erikk/wzsge/wzsge_2001.gif)

Charts

Chart by Japan Variable Stars Study Association

Finding chart to accompany Landolt photometry of WZ Sge field (Richmond)

VSNET light curve (requires Java)

Light curve

VSNET data search

Search!

VSNET WZ Sge page

VSOLJ news (in Japanese)

Initial letter on WZ Sge 2001 by the VSNET Collaboration (Ishioka et al.) Initial spectroscopy letter (Baba et al.) Interpretation of early superhumps (T. Kato)

A guide to CCD observation (in Japanese)

Related systems (WZ Sge-type dwarf novae) observed by the VSNET Collaboration team

HV Vir (2001)

RZ Leo (2000-2001)

RZ Leo paper (PASJ in press)

AL Com (2001)

EG Cnc (1996-1997)

HV Vir (1992) paper (PASJ in press)

SU UMa-type dwarf novae in general

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