J/A+A/690/A243 Cataclysmic variables in SRG/eROSITA surveys (Schwope+, 2024)
A first systematic characterization of cataclysmic variables in
SRG/eROSITA surveys.
Schwope A.D., Knauff K., Kurpas J., Salvato M., Stelzer B., Stuetz L.,
Tubin-Arenas D.
<Astron. Astrophys. 690, A243 (2024)>
=2024A&A...690A.243S 2024A&A...690A.243S (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Binaries, cataclysmic ; X-ray sources ;
Stars, distances
Keywords: surveys - stars: dwarf novae - novae: cataclysmic variables
Abstract:
We present an account of known cataclysmic variables (CVs) that were
detected as X-ray sources in eROSITA X-ray surveys and have Gaia DR3
counterparts. We address standard CVs with main sequence donors and
white dwarfs accreting via Roche-lobe overflow (RLOF) and related
objects, the double degenerates (DDs), and the Symbiotic Stars
(SySts). We discern between non-magnetic (dwarf novae and nova-likes)
and magnetic CVs (polars and intermediate polars, IPs). In the
publically available eROSITA catalog from the recent DR1, typically
65% of known cataloged and classified CVs are detected. This fraction
rises to over 90% if the stack of all eROSITA X-ray surveys (called
S45 in this paper) is considered and the search volume is restricted
to a radius of 500pc. We examine the various classes of CVs in
various diagnostic diagrams relating X-ray and optical properties
(luminosity, absolute magnitude, color, X-ray spectral hardness,
optical variability) and establish their average class properties. We
derive spectral properties for the 22 brightest polars and confirm an
increase in the ratio of soft to hard X-rays with increasing magnetic
field in the accretion region. We report three new soft IPs and
present a spectral analysis of all soft IPs. Their blackbody
temperatures agree well with published values. The DDs represent the
bluest and faintest sub-category but reach the same identification
fraction as the standard CVs. The SySts are the most distant systems;
only 20 (13%) were detected as X-ray sources in S45, and seven of
those are first-time detections. Using an upper limit flux of the
non-detected CVs we investigate their mean properties. Their X-ray
non-detection is a distance effect in the first place. All the
combined properties were used to select candidate CVs for all-sky
optical identification programs with the ultimate aim to compose large
CV samples to better constrain the impact of magnetic fields on the
evolution of CVs, to derive space densities, luminosity functions, and
quantify the contribution of white-dwarf accreting systems to the
Galactic Ridge X-ray Emission (GRXE). The results of the optical
identification program will be presented in forthcoming papers.
Description:
Known cataloged CVs with Gaia DR3 entries detected in eROSITA DR1.
Given are per object the IAU name from DR1, the CV name and its type
(IPs with 4 and 5 stars are labeled IPs, those with 2 and 3 stars are
labeled IPcands), the Gaia source ID, the X-ray coordinates (RA and
DEC), the separation between the eROSITA X-ray and the Gaia optical
coordinates in arcsec, the number of photons collected in DR1 in the
energy band 0.2-2.3 keV, the logarithm of the derived flux (in units
of erg/cm^2/s), the Gaia G-band magnitude, the distance (in
pc), the logarithm of the derived X-ray luminosity (in units of
erg/s), the X-ray to optical flux ratio, the absolute magnitude in the
G-band, and the Gaia color.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
tablea1.dat 306 416 Known cataloged CVs with Gaia DR3 entries
detected in eROSITA DR1
--------------------------------------------------------------------------------
See also:
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
J/A+A/682/A34 : SRG/eROSITA all-sky survey catalogs (eRASS1) (Merloni+, 2024)
Byte-by-byte Description of file: tablea1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 23 A23 --- 1eRASS IAUNAME of eRASS1 source,
1eRASS JHHMMSS/s+DDMMSS
25- 48 A24 --- CVName Nsme of CV
50- 57 A8 --- CVtype Subtype of CV
59- 77 I19 --- GaiaDR3 Associated Gaia source ID
79-110 A32 --- DetUid String unique detection ID
112-132 F21.17 deg RAdeg X-ray right ascension (J2000)
134-155 F22.18 deg DEdeg X-ray declination (J2000)
157-176 F20.17 arcsec Sep Positional offset X-ray to optical
178-189 F12.7 ct MLcts1 Number photons in eRASS1
191-202 E12.6 mW/m2 MLFlux1 Associated flux in eRASS1 (0.2-2.3keV)
204-212 F9.6 mag Gmag Gaia G-band magnitude
214-234 F21.15 pc Dist Distance to CV according to Bailer-Jones
et al., 2021AJ....161..147B 2021AJ....161..147B, Cat. I/352
236-253 F18.15 [10-7W] logLX log(X-ray luminosity) (0.2-2.3keV)
255-275 F21.18 --- log(FX/Fopt) log(X-ray to optical flux ratio)
277-296 F20.17 mag gMAG Absolute G-band magnitude
298-306 F9.6 mag Bp-Rp Gaia color Bp-Rp
--------------------------------------------------------------------------------
Acknowledgements:
Axel Schwope, aschwope(at)aip.de
(End) Axel Schwope [AIP, Germany], Patricia Vannier [CDS] 29-Jul-2024