CBA Belgium Observatory
1RXS J232953.9+062814 - a new SU UMa dwarf nova with 
  orbital period below 'period minimum' 


1RXS J232953.9+062814 - 2001, Nov 5/6  (CBA Belgium Observatory)

On Nov. 3.926 UT, P. Schmeer detected an outburst (at mag 12.5) of this object,that is classified as a dwarf nova by Jingyao et al. (1998, Ann. Shanghai Obs. 19, 235). On November 5th, the Kyoto team announced their detection of superhumps in this system (vsnet-alert 6836), with a very short period of about 0.043d, which is the shortest one among hydrogen rich cataclysmic variables, except for V485 Cen. The corresponding orbital period definitely is below the so called 'period minimum'.

We were able to confirm the interesting findings of the Kyoto team a few hours later, through an observing run at CBA Belgium Observatory, using the 0.35-m f/6.3 telescope and unfiltered SBIG ST-7 CCD (Nov 5/6, 2001). Our observations are presented in the figure at left, and clearly show a 0.2 mag superhump. Combining these data with the Kyoto date revealed a superhump period of 0.04633(2) d, as reported in vsnet-alert 6838.

Further observations from other observatories finally led to a more accurate superhump period value of 0.046311(12) day, as was announced in IAUC 7747 by the VSNET Collaboration team.


After our November 6th observations, 1RXS J232953.9+062814 gradually started to fade. However, on the night of November 9/10, 2001, we were surprised to find the object rebrightening again, rising to a new maximum. 

Such a post-superoutburst rebrightening  has also been observed in V485 Cen, but was related to a normal outburst. My November 9/10 light curve, depicted at right, seems to point to the absence of superhumps too. 

The gaps in the light curve are due to cloud fields.

          1RXS J232953.9+062814 - 2001, Nov 9/10  (CBA Belgium Observatory)

The night of November 10/11 was extremely clear and stable over CBA Belgium Observatory. We observed 1RXS J232953.9+062814 for a total of 6.2 hours, and the resulting light curve (shown at right) revealed the following findings :
  • this object is again showing superhumps with a period of 0.04639 +/- 0.00010 d (PDM technique, after removing linear trend of decline)
  • The average superhump amplitude was 0.24 mag
  • The object was fading at a rate of 0.09 mag per hour
  • The phase diagram (see below) shows at least one, and likely two, additional humps, superimposed on the main superhump.

1RXS J232953.9+062814 - 2001, Nov 10/11  (CBA Belgium Observatory)

Below are the period diagram and (averaged) phase diagram of 1RXS J232953.9+062814, corresponding to the Nov 10/11 observations, based on 306 datapoints. 



  (c) Copyright Tonny Vanmunster, 2001