Discovery of a cataclysmic variable with a sub-stellar companion

Abstract

Abstract. We find that the ROSAT source 1RXS J105010.3-140431 is a cataclysmic variable with orbital period of 88.6 min and a spectrum closely resembling WZ Sge. In particular, emission lines are flanked by Stark-broadened absorption wings probably originating in the photosphere of a compact object. The Balmer absorption lines can be modeled by the spectrum of a DA white dwarf with 13 000 < T eff < 24 000 K. The strong absorption lines allowed us to obtain direct radial velocities of the white dwarf using the cross-correlation technique. We find an extremely low white dwarf radial velocity half amplitude, K wd = 4 ± 1 km s −1 . This is consistent with the upper limit obtained from the Hα emission line wing K < 20 km s −1 . The corresponding mass function is incompatible with a main sequence secondary, but is compatible with a post orbital period minimum cataclysmic variable with a brown dwarf-like secondary. The formal solution gives a secondary mass of 10-20 Jovian masses. Doppler maps for the emission lines and the hypothesis of black-body emission indicate a steady state (T ∼ r −3/4 ) accretion disk mainly emitting in Hα and an optically thicker hotspot with a strong contribution to the higher order Balmer lines and He I 5875. As in other long cycle length dwarf novae, evidence for inner disk removal is found from the analysis of the emission lines.

Doppler tomography of the dwarf novae VY Aquari and WX Ceti

“…Skidmore et al 2000;Mennickent et al 2001). The fact that we find different structures in our Hα and Hβ maps shows that in the case of VY Aqr and WX Cet, this ratio is not constant across the disc, suggesting density and temperature variations along the disc azimuthal direction.…”

“…Figure 3 shows our results along with theoretical isoparametric curves from Smak (1981). In this figure, we also include the data for SU UMa stars given by Mennickent & Arenas (1998) and the position of 1RXS J105010.3-140431, a candidate for WZ Sge-type dwarf novae (Mennickent et al 2001). We found that the Hα A 84 − A 41 pair for WX Cet (A 84 = 0.14 ± 0.01 and A 41 = 0.16 ± 0.01) practically coincides with that found by Mennickent & Arenas (1998) in spectra taken in 1992 (viz.…”

Astrophysics in 2002

“…The events ϩ12 37 Ϫ7 trace the bulge light, as do, more or less, galactic novae, though the census is less complete. Dwarf novae with long recurrence times do indeed have very light weight secondaries (Mennickent et al 2001). WZ Sge, the prototype of the class, blew its stack again in July 2001 (Cannizzo 2001).…”

WX Ceti: a closer look at its behaviour in quiescence and outburst

“…On the other hand, there are two independent determinations of the radial-velocity curve of the primary in WX Cet, one by Mennickent (1994, original data published by Mennickent et al 2001), the other by Thorstensen et al (1996). Since the observations in both cases are limited to a few subsequent nights, the determined periods are not very accurate.…”