Long-awaited outburst of an eclipsing SU UMa-type dwarf nova, HT Cassiopeiae

complied data from VSNET reports

The Alert!

(vsnet-alert 273, G. Poyner)

Dear Colleagues,

Bill Worraker (Didcot, UK) has reported an outburst of HT Cas, which is monitored as part of the TA/BAA Recurrent Objects Programme. I have just confirmed the outburst. Details....

     Nov 17.9049 UT    mv=13.4    Worraker, 26cm  Seq. TA
         17.9132       mv=13.4    Poyner, 40cm   Seq. TA

There is no need to emphasise the importance of this outburst!

Gary Poyner

Details of the Recurrent Objects Programme can now be found on 
'THE ASTRONOMER' WWW pages at http://www.demon.co.uk/astronomer

Immediate preoutburst observations

(vsnet-alert 274)

Dear Colleagues,

We Ouda-team observed HT Cas on Nov 15 with a CCD with V filter attached to a 60-cm reflector. HT Cas was found to be already somewhat brighter than usual quiescent level at that time with an averaged level of V=16.14 outside eclipses. An eclipse was observed approximately centered at HJD24450037.147, with a duration of 12 min which is apperently longer than mentioned (~6 min) by Welsh (vsnet message #317). No evidence of orbital hump was observed.

For follow-up observers, a PostScript finding chart with V-magnitude is available at :


The forecast time of eclipses of HT Cas are listed below

(times are geocentric).

   YYMMDD hh:mm:ss (UT)
   951118 05:16:20
   951118 07:02:23
   951118 08:48:27
   951118 10:34:30
   951118 12:20:33
   951118 14:06:36
   951118 15:52:39
   951118 17:38:43
   951118 19:24:46
   951118 21:10:49
   951118 22:56:52

   HJD (mid-eclipse) = 2443727.93721 + 0.0736472039E

And the table of comparison stars are listed below.

    AAVSO         Misselt(1995)     VSNET
  (Alert 217)      V      B-V      approx. V
     109         11.88   +0.59      11.84
     134         13.62   +0.85
    anon         13.92   +0.85      13.90    just south of HT Cas
     143         14.33   +1.59      14.23
    anon         14.61   +1.02      14.62    west to AAVSO (109)
     151                            14.70
     155         15.19   +1.86      15.19
     156                            15.02
    anon         15.58   +1.79      15.57    faint star just SE to HT Cas
     159                            15.82
     163                            16.18
     166                            15.91

Needless to say, close monitoring is highly encourged.

Best Regards,
Hajime Baba and Ouda-team

Eclipse observations at Ouda

(vsnet-alert 277)

Dear Colleagues,

A total of high quality 1081 V-band CCD frames of HT Cas were obtained by a 60-cm reflector at Ouda Station (Kyoto University) with a typical time resolution of 23s (20s exposure + 3s dead time). A prelimary analysis gives following mid-eclipse times (heliocentric correction has not been applied intentionally). Magnitudes were determined using V=11.88 star by Misselt (1995).

    JD (Geo)    eclipse center   outside eclipse   depth
 2450039.86757      14.45 V          13.16 V        1.29 V
      40.01482      14.45            13.17          1.28
      40.08851      14.50            13.22          1.28
      40.16218      14.57            13.26          1.31
      40.23583      14.72            13.29          1.43

Eclipses last ~12 min. The above data seem to indicate HT Cas has already started a rather rapid decline at a rate of ~0.5 mag/day. However, broad hump features (amplitude ~0.05 mag) around 2450040.108 and 2450040.190 may be indicative of the appearance of superhumps. Further observations are strongly encouraged.

Ouda team (Daisaku Nogami and Hajime Baba observing)

A story of this night ..

Start of a rapid decline

(vsnet-alert 278)

Dear Colleagues,

We Ouda Team observed HT Cas on Nov 19.47. The object seems to be declining. Based on our CCD image on CRT, we estimate that the magnitude out of eclipse is V~13.7 mag, which is about 0.6 mag fainter than that of Nov 18. This indicates that this outbutst seems to be a normal one ?

Further monitoring is highly encourged !

Best Regards,
Hajime Baba and Daisaku Nogami
Ouda Team ( at observatory )

Eclipse observation by Makoto Iida

This image contains consecutive eight panels, from the upper left to the lower right as time proceeds. HT Cas is the northern component of an aggregate of three stars at the center of each panel. The fourth panel represents the center of an eclipse. The images were taken by a 16-cm reflector with an ST-6 CCD camera. (Courtesy of Makoto Iida)

Outburst image by the Ouda team

CCD photometry by Nick James

(vsnet-alert 280)

Dear all,

Attached to this e-mail is a postscript graph showing two consecutive eclipses of HT Cas. Photometry was unfiltered using a Sony CCD and 30cm Newtonian and the brightness of HT Cas was measured relative to the nearby GSC 4030.00719. Eclipse duration was 550 sec in each case and the times of minima were:

1995 November 19, 18:24:20 UTC (JD 2450041.26690)
1995 November 19, 20:10:30 UTC (JD 2450041.34063)

These agree very well with predictions based on Kato's vsnet-alert 277 message.

The sample period in the following plot is approximately 25s (20s exposure + 5s read-out). My location is Chelmsford, UK.

More information, including a CCD image of the field is available on the pages of The Astronomer at http://www.demon.co.uk/astronomer/htcas.html

Regards Nick James.

get a full message containing a PS file

Post-outburst behavior

(vsnet-alert 287)

Dear HT Cas observers,

HT Cas seems to have stopped fading. The post-outburst object is now staying about 1 mag brighter than its "high-state" quiescence. Nightly averaged preliminary magnitudes outside eclipses are below:

    mid-UT     mag   S.D.  N  band
  951118.618  13.27 0.075 904 V
  951119.505  13.98 0.086  71 V
  951120.534  15.55 0.130  91 V
  951121.554  15.89 0.141 477 V
  951122.494  15.93 0.210 303 V

  (S.D.: for a single point)

The light curves on Nov. 21 and 22 show broad undulations with a time- scale of few hours, together with short-term flickering and QPOs. Although the averaged system brightness has changed little these two nights, the shapes of eclipses have changed considerably; the system is now exhibiting rather sharp ingresses and egresses which are usually observed in quiescence.

Ouda team (Taichi Kato, observing)

Related objects

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