X-ray and ultraviolet observations of the eclipsing cataclysmic variables OV Bootis and SDSS J103533.02+055158.3 with degenerate donors. (arXiv:2101.03059v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Schwope_A/0/1/0/all/0/1">Axel Schwope</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Worpel_H/0/1/0/all/0/1">Hauke Worpel</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Traulsen_I/0/1/0/all/0/1">Iris Traulsen</a>
The majority of cataclysmic variables are predicted to be post-period minimum
systems with degenerate donor stars, the period bouncers. Owing to their
intrinsic faintness, however, only a handful of these systems have so far been
securely identified. We want to study the X-ray properties of two eclipsing
period bouncers, OV Bootis and SDSS J103533.02+055158.3, that were selected for
this study due to their proximity to Earth. We have obtained XMM-Newton
phase-resolved X-ray and ultraviolet observations of the two objects for
spectral and timing analysis. Owing to a recent dwarf nova outburst OV Boo was
much brighter than SDSS J103533.02+055158.3 at X-ray and ultraviolet
wavelengths and the eclipse could be studied in some detail. An updated eclipse
ephemeris was derived. The X-rays were shown to originate close to the white
dwarf, the boundary layer, with significant absorption affecting its spectrum.
There was no absorption in SDSS J103533.02+055158.3, despite being observed at
the same inclination indicating different shapes of the disk and the disk rim.
The white-dwarf temperature was re-determined for both objects: the white dwarf
in OV Boo was still hot (23,000 K) five months after a dwarf nova outburst, and
the white dwarf in SDSS J103533.02+055158.3 hotter than assumed previously
(Teff = 11,500 K). All three cataclysmic variables with degenerate donors
studied so far in X-rays, including SDSS J121209.31+013627.7, were clearly
discovered in X-rays and revealed mass accretion rates dot(M) >= 8 x 10^(-15)
Msun/ yr. If their X-ray behavior is representative of the subpopulation of
period bouncers, the all-sky X-ray surveys with eROSITA together with
comprehensive follow-up will uncover new objects in sufficient number to
address the remaining questions concerning late-stage cataclysmic variable
evolution.
The majority of cataclysmic variables are predicted to be post-period minimum
systems with degenerate donor stars, the period bouncers. Owing to their
intrinsic faintness, however, only a handful of these systems have so far been
securely identified. We want to study the X-ray properties of two eclipsing
period bouncers, OV Bootis and SDSS J103533.02+055158.3, that were selected for
this study due to their proximity to Earth. We have obtained XMM-Newton
phase-resolved X-ray and ultraviolet observations of the two objects for
spectral and timing analysis. Owing to a recent dwarf nova outburst OV Boo was
much brighter than SDSS J103533.02+055158.3 at X-ray and ultraviolet
wavelengths and the eclipse could be studied in some detail. An updated eclipse
ephemeris was derived. The X-rays were shown to originate close to the white
dwarf, the boundary layer, with significant absorption affecting its spectrum.
There was no absorption in SDSS J103533.02+055158.3, despite being observed at
the same inclination indicating different shapes of the disk and the disk rim.
The white-dwarf temperature was re-determined for both objects: the white dwarf
in OV Boo was still hot (23,000 K) five months after a dwarf nova outburst, and
the white dwarf in SDSS J103533.02+055158.3 hotter than assumed previously
(Teff = 11,500 K). All three cataclysmic variables with degenerate donors
studied so far in X-rays, including SDSS J121209.31+013627.7, were clearly
discovered in X-rays and revealed mass accretion rates dot(M) >= 8 x 10^(-15)
Msun/ yr. If their X-ray behavior is representative of the subpopulation of
period bouncers, the all-sky X-ray surveys with eROSITA together with
comprehensive follow-up will uncover new objects in sufficient number to
address the remaining questions concerning late-stage cataclysmic variable
evolution.
http://arxiv.org/icons/sfx.gif
