Identification of 3 cataclysmic variables detected by the ART-XC and eROSITA telescopes aboard SRG during the all-sky X-ray survey. (arXiv:2107.05611v1 [astro-ph.HE])

Identification of 3 cataclysmic variables detected by the ART-XC and eROSITA telescopes aboard SRG during the all-sky X-ray survey. (arXiv:2107.05611v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Zaznobin_I/0/1/0/all/0/1">I. Zaznobin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sazonov_S/0/1/0/all/0/1">S. Sazonov</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Burenin_R/0/1/0/all/0/1">R. Burenin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Uskov_G/0/1/0/all/0/1">G. Uskov</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Semena_A/0/1/0/all/0/1">A. Semena</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gilfanov_M/0/1/0/all/0/1">M. Gilfanov</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Medvedev_P/0/1/0/all/0/1">P. Medvedev</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sunyaev_R/0/1/0/all/0/1">R. Sunyaev</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Eselevich_M/0/1/0/all/0/1">M. Eselevich</a>

We report the discovery of three previously unknown cataclysmic variables in
the data of the first year of the all-sky X-ray survey by the SRG orbital
observatory. The sources were selected due to their brightness in the 4–12 keV
band in the data of the Mikhail Pavlinsky ART-XC telescope. They are also
detected by the eROSITA telescope, which provided accurate localizations and
spectral data for broad-band spectral analysis. All three objects had been
previously known as X-ray sources from the ROSAT all-sky survey and XMM-Newton
slew survey, but their nature remained unknown. The X-ray spectra obtained by
eROSITA and ART-XC are consistent with optically thin thermal emission with a
temperature kT>~15 keV for SRGAJ194638.9+704552 and SRGAJ225412.8+690658 and
kT>~5 keV for SRGAJ204547.8+672642. This, together with the inferred high X-ray
luminosities ($2times 10^{32}$-$3times 10^{33}$ erg s$^{-1}$), strongly
suggests that all three sources are CVs. We have obtained optical photometry
and spectroscopy for these objects using the AZT-33IK 1.6-m telescope of the
Sayan Observatory. The optical properties confirm the CV nature of the objects.
We conclude that SRGAJ194638.9+704552 is an intermediate polar,
SRGAJ204547.8+672642 is most likely a polar or an intermediate polar, and
SRGAJ225412.8+690658 can be either a magnetic or a non-magnetic CV. We also
measured an orbital period of 2.98~hours for SRGAJ204547.8+672642, based on
TESS data. Three out of the planned eight SRG all-sky surveys have now been
completed. We expect to find plenty of new CVs during the survey and to
continue our optical follow-up program.

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