The 1999 Superoutburst of QY Per

(Superhump light curve by the VSNET QY Per collaboration team: Taichi Kato, Makoto Uemura, Gianluca Masi, Alessia Cassetti, Lew Cook, Katsura Matsumoto, Lasse Teist Jensen, Brian Martin, Tonny Vanmuster, Denis Buczynski)

Enlarged light curves:

(CCD image by courtesy of Gianluca Masi)

(CCD image by courtesy of Lew Cook)

(CCD image by courtesy of Massimiliano Martignoni)

(Outburst light curve from reports to VSNET)

Successful international collaboration ongoing!

(vsnet-alert 3867)

QY Per likely very rare outburst, observations requested

We have been informed by Mike Simonsen (AAVSO, MI USA) that the large- amplitude SU UMa-type candidate (potentially a WZ Sge-like object) QY Per is currently undergoing a very bright outburst.

Recent observations:

   YYYYMMDD(UT)   mag  observer
   19991129.935  <156  (G. Poyner)
   19991201.842  <149  (G. Poyner)
   19991202.740  <150  (T. Kinnunen)
   19991203.946  <158  (G. Poyner)
   19991205.039  <158  (G. Poyner)
   19991205.919  <150  (T. Kinnunen)
   19991207.926  <156  (G. Poyner)
   19991209.030  <150  (T. Kinnunen)
   19991213.980  <152  (G. Poyner)
   19991214.860  <152  (T. Kinnunen)
   19991216.890  <150  (T. Kinnunen)
   19991219.860  <144  (T. Kinnunen)
   19991219.972  <149  (G. Poyner)
   19991228.645   135  (M. Simonsen)
   19991228.666   136  (M. Simonsen)
Confirmatory observations are most urgently requested.

QY Per was discovered by Hoffmeister in 1966. Hoffmeister recorded two outbursts (mag 14.2 on 1964 Sep. 12 and mag 16.0 on 1969 Oct. 5), the small recorded number of outbursts already indicates the low frequency of outbursts. A further outburst at mag 14.9 was recorded by Risino in 1989 (IAUC 4900).

(Extracted report from vsnet-obs 997):

  from Veroeff. Sternwarte Sonneberg 9, 125 (1979)

    JD      mag
  2438642  <17.0
       51   14.2
       52   14.15
       53   14.7
       69  <17.0

  2440484   16.8:
      500   16.0
      501   16.5:
      504   16.1:
      511   16.1:

The authors (H. Busch & K. Haeussler) states that the cycle length is about 370 days (probably concluded from other outburst observations not listed in their table).

  from IAUC No. 4900  (Rosino)

  mag ~ 14.9 on 1989 Oct. 30 & 31.

Since the start of systematic monitoring by amateur observers, three outbursts have been known: 1994 Oct 25.889 mv=14.0, by Tonny Vanmunster, 1995 Aug. 21.979 (mv=14.1, Vanmunster), 1996 Dec. 7.88 (mag 14.3 by J. Pietz). The first two of them were immediately followed by several observers, and were shown to fade quickly. The exact location of QY Per was first measured by N. James during the 1994 outburst: 03h 15m 36s.82 +42o 28' 13".8 (J2000.0).

Taichi Kato commented in [ vsnet-obs 991]:

>    Judging from this information, it seems to me that the 1994 outburst
> is a normal (short) outburst rather than a superoutburst as suggested
> in CVC 54.  It is rather surprizing that this outburst may have surpassed
> the brightest recorded outburst, but still seems to be a normal (short)
> one.  A similar cases can be found in BZ UMa, DV UMa etc.  I have vague
> impression that some TOADs behave unlike many TOADs, in that they rarely
> show superoutbursts in spite of their very low outburst frequency
> (this is just the opposite how WZ Sge-type dwarf novae usually behave).
> Can someone comment on this?  Or are we only missing superoutbrusts?
> I would be eager to know what has been the case of the 1995 outburst of
> QY Per.

The exact nature of QY Per is still unknown. The present reported magnitude being still above all previously recored outbursts, the present outburst, if confirmed, can be a genuine superoutburst (first ever since the discovery).

We will undertake, when confirmed, an intensive observing campaign on this object, as we have had (still ongoing) a very successful one in DV UMa. Please post timely to vsnet-alert confirmatory observations, new findings, the progess of the outburst and observations.

Taichi Kato and Makoto Uemura

(vsnet-alert 3868)

We have just confirmed the rare outburst of QY Per. Although the magnitude is still uncertain because of the twilight, the object is clearly visible on CCD frames (around mag 14?). We hope we will be able to report the details later.

Taichi Kato and Makoto Uemura

(vsnet-alert 3871)

Bill Worraker (Didcot, UK) reports QY Per is undergoing a bright outburst, thus confirming Mike's detection.

His observations are as follows...

Dec 28.909    13.8
    28.943    13.8

Illness prevented me from posting this alert earlier - sorry!

Happy New Year,

Gary Poyner

(vsnet-alert 3872)

PERQY 991223.190 <175C Scp
PERQY 991228.168  139C Scp
Sequence:   VSNet
Instrument: IRO (0.5-m RCT + AP-8)
(report delayed due to a computer problem)

The most recently recorded outburst was detected by J. Pietz on 1996 Dec 7.88 UT at mv= 14.3 (cf. vsnet-obs 4521, vsnet-alert 624). I would suppose that several (normal) outbursts were missed in the last three years. The mean cycle length appears to be about one year, but may be as short as five months.


I think Mike Simonsen's observations were actually made 0.5 days later than stated. The current outburst is very likely a supermaximum, so time-resolved photometry is strongly recommended.

(vsnet-alert 3875)

Dear colleagues,

I just finished a 2.5 hours CCD photometry run on QY Per, using the = 0.35-m f/6.3 telescope at CBA Belgium Observatory [1999, December = 29/30]. Right now, clouds are entering the sky and chances are quite = high I will have to completely abort the observing session.

All FITS images were acquired with an ST-7 CCD camera without filters, = and were instanteneously processed and reduced (PSF photometry). The = resulting real-time light curve clearly shows the presence of a 0.20 mag = modulation, to be attributed to superhumps. A first rough estimate of = the superhump period yields a value of 0.0723d +/- 0.0009d. These = observations thus establish QY Per as a new (and likely interesting) = member of the UGSU type of cataclysmic variables.

Further high-speed photometry is highly recommended, to settle the = precise superhump period value.

Best regards,

Tonny Vanmunster
CBA Belgium Observatory

(vsnet-alert 3877)

Dear Colleagues,
I've finished a 3.5 hours CCD run on this target (from 20:40 UT to 00:10 UT) , using a SBIG ST-7, unfiltered camera and a 28cm, f/3.3 telescope (CBA Italy).

A VERY preliminary analysis shows the following features:

- clear superhumps, with an amplitude of about 0.2 magnitudes;
- a superhump period of about 0.08 days (this is a rough estimate,
  done with my own eyes,
as I have not a software able to perform PDM analysis).
I will post a light curve on my website as soon as possible.

All the best.. and best wishes for the incoming y2k!


CBA Italy

(vsnet-alert 3884)

Dear Colleagues,

Congratulations to all who detected the outburst, and succeeded in observation! Special thanks to all who quickly responded to the alert and recorded superhumps. Please continue your nice observations as long as possible on this rare occasion!

As for the Kyoto observation, we (T. Kato and M. Uemura) observed QY Per for 8 hour's nearly continuously last night. A very preliminary analysis of the (partly reduced) data has yielded a superhump period of ~0.082 d, close to the one reported by Gianluca Masi. The relatively long superhump period and the rare outburst occurence seem to strengthen the relationship with DV UMa, whose spectacular superoutburst is still fresh in our memory. We would like to inform more detailed information after finishing the present reduction and collating incoming information.

We would like to set up a special page on QY Per, as we have had on DV UMa. We would be extremely happy to receive the data to be reflected to the Web page (Y2K and time permitting...). The data should be sent to

Congratulations and thanks again to all! We will be having the second- night run soon after this.

Taichi Kato and Makoto Uemura

(vsnet-alert 3889)

QY Per updated superhump period

The application of PDM to Gianluca Masi's dataset (cf. vsnet-alert 3877, 3883) has yield the most likely superhump period of 0.0828 day. The combination with the Kyoto data on Dec. 29 (moderately affected by the extinction and passing clouds) tends to give a slightly longer period (0.0825 - 0.0840 day depending on the data segment used). The Kyoto team is currently taking a long run under excellent sky condition. Although the present analysis firmly support the long-period nature of QY Per, we hope we can provide a far better-defined superhump period after finishing the analysis of the present run, and the scheduled successive run by Masi.

Best regards,
Taichi Kato, Makoto Uemura, Gianluca Masi

(vsnet-alert 3894)

QY Per fully grown superhumps

The Kyoto team finished the analysis of the very successful 8.5-hour run on Dec. 30. Four fully grown superhumps are impressively caught. Compared to Dec. 29 observations by Masi and the Kyoto team, the growth of the superhump was apparent, whose amplitude is now around 0.3 mag. This growth probably explains the unstable period solution from the Dec. 29 data only, when the superhumps are still under way to a growth. Combined period analysis of Dec. 29 data by Masi and Dec. 30 data by the Kyoto team has yield the best superhump period of 0.0779 d. We will be able to inform the updated results after finishing the analysis of successive Dec. 31 data by Masi and his colleagues. The data indicate that the observation covered the most important part of the early stage of the rare superoutburst. We thank again to Mike Simonsen for timely notifying us of this rare event.

Best regards,
Taichi Kato, Makoto Uemura, Gianluca Masi

(vsnet-alert 3901)

Dear Colleagues,
I posted a light curve for this star, as it was during my last time-resolved CCD photometric run (30/31 Dec.). As said earlier, the humps are growing, and here they appear to be 0.4 magnitudes large.

A mean every two points has been performed (while the data I sent to Dr. Kato are the original ones)

Gianluca Masi

CBA - Italy

QY Per: refined superhump period

Based on the data between Dec. 29 and 31, the best superhump period of QY Per has been determined as 0.0789 d. The data used for analysis are

        UT    points
   Dec. 29-30   251 Gianluca Masi
        30       65 Lew Cook
        30      840 Kyoto team
        30-31   312 Gianluca Masi
        31      207 Lew Cook
The Kyoto Dec. 29 data have been excluded from this analysis because they covered the initial growing stage of superhumps. (It has become evident the early part of the Kyoto Dec. 29 data reflects the rapid decline stage from the superoutburst peak).

The value will be updated when the ongoing analysis of the early part of Dec. 30 (Masi) and Dec. 31 (Kyoto) becomes available.

Good luck to all!

Taichi Kato, Makoto Uemura, Gianluca Masi, Lew Cook, Katsura Matsumoto,
The VSNET QY Per collaboration team

VSNET light curve (requires Java)

Light curve

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The 1999 normal outburst

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