Detection of superhumps in the CV 1RXS J053234.9+624755

1RXS J053234.9+624755 is a recently discovered CV that has been reported in outburst by W. Kriebel (cvnet-outburst, 2005 Mar 16) and P. Schmeer (cvnet-outburst, 2005 Mar 16) on Mar 16.8 UT, 2005.
This cataclysmic variable is located at R.A.=05h32m33.87s and Decl.=+62o47'52.1" (J2000.0). 

Mar 18/29, 2005 - Detection of superhumps

I started a time-series photometry session on this target at CBA Belgium Observatory on 2005, Mar 18.797 UT, using a 0.35-m f/6.3 telescope and unfiltered ST-7 CCD. The observing session lasted for > 5.5 hours (to be stopped for clouds), and the resulting light curve clearly shows superhumps with an amplitude of approx. 0.2 mag, superimposed on a fading trend (decline rate of 0.6 mag/d). 

The light curve below (fig. 1) - obtained after removing the linear trend of decline - depicts  the superhumps. A superhump period analysis, using the ANOVA method of Peranso (fig. 2), yields a value of 0.0574 /+- 0.0010 d, classifying this object as a new very short-period UGSU-type dwarf nova. The phase diagram, folded over this best period fit, is shown in fig. 3. 

Fig. 1. Superhumps in 1RXS J053234.9+624755 on 2005, Mar 18/19, after removal of linear trend of decline

Fig. 2. ANOVA period analysis yielding a Psh of 0.0574 d

Fig. 3 Phase diagram by folding the above mentioned Psh

March 23/24, 2005 observations

The next opportunity to observe 1RXS J053234.9+624755 from Belgium was on Mar 23/24, 2005. Although the sky conditions were not very favourable (moonlight and haze), I succeeded in accumulating unfiltered data for about 7 hours, resulting in the light curve below. Superhumps were very dominant, with an amplitude of about 0.09 mag, but less intensive than during their detection night (see above). Using >500 observations, I derived a superhump period of 0.0569 +/- 0.0008 d for Mar 23/24, using the ANOVA method of Peranso.

Fig. 4 Superhumps in 1RXS J053234.9+624755 on 2005, Mar 23/24, after removal of linear trend of decline

Fig. 5 Phase diagram by folding a Psh of 0.0569d

Second stage of outburst

The first stage of the outburst, described above, revealed a quite stable superhump period at 0.0571 +/- 0.0002d, when using a total of 1069 observations obtained by CBA observer Tom Krajci (CBA Albuquerque) and myself. It covers the time interval between JD 2,453,448.2 and JD 2,453,457.8.

The second stage of the outburst has been pretty well covered by CBA observations too. We here present an analysis of 1705 CBA observations, obtained between JD 2,453,460 and 2,453,464. Data were submitted by Arto Oksanen, Tom Krajci and myself.

The behaviour of 1RXSJ053234.9+624755 during this second stage of the outburst is entirely different from the first stage. The stable superhump has been replaced by considerable flickering, showing irregular variations with an amplitude of up to 0.9 mag over 40 min (!), and 0.6 mag variations over 15 min time intervals. See extracts in Fig. 6 and 7 below.

Fig. 6 Flickering with amplitudes up to 0.9 mag is clearly present in this data set of Tom Krajci (CBA New Mexico)

Fig. 7 Another example of short-term flickering in 1RXS J053234.9+624755. Light curve of Apr 02/03, 2005.

The observations of Apr 01/02, 2005, obtained by Arto and myself, seem to indicate a superposition of flickering on a longer-term periodic signal (Fig. 8). Using various period analysis techniques in Peranso, I tried to determine this long-term signal. The various period analysis methods gave quite different results, indicating there is no stable period in the data. I also performed a multi-periodic analysis, using the CLEANest method in Peranso. This again confirmed the absence of a dominant signal. Extending the analysis to all observations related to this second stage of the outburst, revealed similar results.

Fig. 8 - Apr 01/02, 2005 light curves of Arto Oksanen (CBA Finland - brown dots) 
and Tonny Vanmunster (CBA Belgium - pink dots)

Also on Apr 02/03, 2005 the light curve of 1RXSJ053234.9+624755 was still dominated by large amplitude flickering (Fig. 7).

Flickering all over the place. What's next in the light curve of this intriguing variable ?




Copyright © 2005 - Tonny Vanmunster.