ibvs2.sty

Eclipsing cataclysmic variables (CVs) are important because through detailed modeling of the eclipses it is possible to deduce the physical properties of the system. This paper reports the discovery of two new eclipsing CVs: PHL1445 and GALEXJ003535.7+462353.

PHL1445 (= PB9151) is listed in the Palomar-Haro-Luyten catalogue as a faint blue object (Haro & Luyten, 1962). A spectrum (6dFGSg0242429-114646) taken by the 6dF Galaxy Survey (Jones et al., 2004 and 2009) showed it to be a cataclysmic variable (Wils, 2009). Because of the split emission lines and a number of anomalously faint points in the light curve of the Catalina Real-time Transient Survey (CRTS; Drake et al., 2009), it was suspected to be an eclipsing variable as well. Follow-up observations at the Astrokolkhoz Observatory with a C14 Schmidt-Cassegrain and an unfiltered CCD camera, showed this indeed to be the case. As shown in Fig. 1, the light curve shows deep eclipses lasting about 6 minutes, with an amplitude of more than two magnitudes. In addition the period is very short, 76.3 minutes, near the minimum orbital period for CVs (Gänsicke et al., 2009). Such a short orbital period is usually observed in WZSagittae type dwarf novae like GWLib (orbital period 76.8 minutes) and SDSSJ074531.91+453829.5 (76.0 minutes), with rare large amplitude outbursts. Only SDSSJ150722.30+523039.8 has a shorter orbital period among the eclipsing CVs (Savoury et al., 2011).

Table \[ToM\] lists the observed times of eclipses. From these, the following eclipse ephemeris was derived: $$\label{PHL1445}
  HJD Min = 2455202.5579(1) + 0\fday05298466(8) \times E$$

Since not many deeply eclipsing CVs are known at this orbital period, high speed photometry of the eclipses, such as done by Southworth and Copperwheat (2011) and Savoury et al. (2011) would certainly be of value for this object.

\[ToM\]

  ----------- ----------- ------------
    PHL1445               
               SuperWASP   This paper
   5202.5579   4330.553    5477.5621
   5202.6108   4331.589    5478.4228
   5202.6640   4332.622    5478.5954
   5202.7169   4333.655    5479.4560
   5241.6075   4334.688    5479.6284
   5242.6144   4335.551    5480.6625
               4360.703    5481.3519
               4407.388    5481.5239
               4408.424    5482.3856
                           5483.4192
                           5486.6920
                           5495.3052
                           5495.6516
                           5576.6190
                           5577.6526
                           5579.7207
  ----------- ----------- ------------

  : Observed times of eclipse for PHL1445 and GALEXJ003535.7+462353. The times are given as HJD - 2450000 (UTC based). The uncertainty on the times is about 0.0001 days for PHL1445 and 0.0005 days for GALEXJ003535.7+462353 for the minima obtained from our data, and 0.001 days for the minima obtained from SuperWASP data.

GALEXJ003535.7+462353 was discovered as a variable source by the GALEX satellite (Martin et al., 2005) on 30 August 2008. Although the object is too faint itself, both the Northern Sky Variability Survey (NSVS; Woźniak et al., 2004) and SuperWASP (Butters et al., 2010) observed the combined magnitude of GALEXJ003535.7+462353 and GSC3249-1603, which lies some $18\arcs$ to the West. Both surveys show a number of brightenings in the combined light curve, lasting several days, with an amplitude of up to 0.2 magnitudes from the normal combined magnitude of 12.9, indicating the possible variability of GALEXJ003535.7+462353 rising to about magnitude 14.5, from its normal magnitude of around 16.5. These may be an indication of a dwarf nova outburst with a fairly small amplitude. In addition, during these bright phases SuperWASP showed short periodic dimmings back to the normal combined magnitude with a period of around 0.1723 days. The likely cause of these periodic fadings are eclipses of the variable.

GALEXJ003535.7+462353 was therefore followed extensively by the authors. The eclipses with a duration of about 30 minutes, could be easily confirmed. At quiescence the eclipse depth is about 2 magnitudes in $V$, but varying slightly. In a timespan of three months one definite outburst was observed, lasting about a week (see Fig. 2), and possibly a few shorter outbursts. At the end of the observing season, the object was entering another outburst. The rise to outburst seems to be more gradual, like in some other dwarf novae with a short outburst cycle and relatively small amplitude (often classified as Z Cam type variables). During the long outburst, the eclipses could also be observed with a similar amplitude as during quiescence. Fig. 3 shows eclipses observed during quiescence, during a rise to outburst and one during outburst.

From the list of observed times of eclipse in Table \[ToM\], together with the times of minimum that could be derived from the SuperWASP data, the following eclipse ephemeris was deduced:

$$\label{J003535}
  HJD Min = 2455477.5615(4) + 0\fday17227503(11) \times E$$

[**Acknowledgements:**]{} This study made use of the Simbad and VizieR databases (Ochsenbein et al., 2000), and of data provided by the NASA GALEX mission. Part of the data were obtained through AAVSONet, run by the American Association of Variable Star Observers, through the Tzec Maun Foundation and by using the Bradford Robotic Telescope.

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