J/A+A/704/A107 eRASS1 source properties and classifications (Bao+, 2025)
Unveiling the soft X-ray source population toward the inner Galactic disk with
XMM-Newton.
Bao T., Ponti G., Haberl F., Mondal S., Morris M.R., Mori K., Mandel S.,
Xu X.-J.
<Astron. Astrophys. 704, A107 (2025)>
=2025A&A...704A.107B 2025A&A...704A.107B (SIMBAD/NED BibCode)
ADC_Keywords: Galactic plane ; X-ray sources ; Binaries, X-ray
Keywords: novae, cataclysmic variables - Galaxy: disk -
Galaxy: stellar content - X-rays: binaries - X-ray: stars
Abstract:
Across the Galactic disk lies a diverse population of X-ray sources,
with the fainter end remaining poorly understood due to past survey
sensitivity limits. We aim to classify and characterize faint X-ray
sources detected in the eROSITA All-Sky Survey (eRASS1) toward the
inner Galactic disk (350<l<360, -1<b<1) using deeper XMM-Newton
observations (∼20 ks). We analyzed 189 eRASS1 sources, combining X-ray
spectral fitting (0.2-10keV) with Gaia astrometric and photometric
data for robust classification. Our results show that the eRASS1
catalog toward the Galactic disk is overwhelmingly dominated by
coronal sources (∼74%), primarily active stars and binaries, with ∼8%
being wind-powered massive stars and ∼18% being accreting compact
objects. We propose an empirical hardness-ratio cut (HR>-0.2) to
efficiently isolate these non-coronal sources. By stacking the
classified population and comparing with the Galactic Ridge X-ray
Emission (GRXE) surface brightness, we estimate that ∼6% of the GRXE
flux in the 0.5-2.0keV band is resolved into point sources above the
eRASS1 flux limit (∼5x10-14erg/cm2/s). This resolved
soft-band emission is dominated by active stars, while hard-band flux
originates primarily from X-ray binaries. We conclude that the eRASS1
catalog retains a non-negligible population of compact objects that
can be effectively distinguished using X-ray color selection.
Description:
This table provides X-ray spectral properties for 189 X-ray sources
detected toward the inner Galactic disk in the eROSITA All-Sky Survey
(eRASS1) catalog. For each source, the data includes the potential
Gaia counterpart identification, associated photometric information,
X-ray spectral parameters (thermal temperature kT or photon index
Gamma) and luminosity derived from XMM-Newton data, and the final
source classification. The reported errors for the X-ray spectral
fitting results are given at the 1-sigma confidence level.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
tablea1.dat 107 189 X-ray properties and classification for 189
eRASS1 sources toward the Galactic disk
--------------------------------------------------------------------------------
See also:
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
IX/69 : XMM-Newton Serendipitous Source Cat. 4XMM-DR13 (Webb+, 2023)
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- 4 A4 --- ID Source identifier
6 A1 --- n_ID [*] Note (1)
8- 16 F9.5 deg RAdeg XMM Right ascension (J2000)
18- 26 F9.5 deg DEdeg XMM Declination (J2000)
28- 33 F6.2 arcsec sepXE Angular separation between XMM and
eROSITA position
35- 38 F4.2 arcsec sepXGaia ?=- Angular separation between XMM and
Gaia positions
40- 43 F4.2 --- Pfalse ?=- The false-matched rate of the
Gaia counterpart
45- 49 F5.2 kpc D ?=- Photometric distance from Gaia DR3
52 A1 --- n_D [+] Note (2)
54- 59 A6 --- Type ?=- Source classification from this work
61- 68 A8 --- Simbad ?=- Source type in the SIMBAD
69- 73 F5.2 keV kTmean ?=- The mean plasma temperature
75 A1 --- Gamma [G] Note (3)
76- 80 F5.2 keV e_kTmean ?=- Negative error on kTmean
82- 86 F5.2 keV E_kTmean ?=- Positive error on kTmean
88- 91 F4.2 --- redchi2 ?=- Reduced chi^2 of spectra fitting
93- 97 F5.2 [10-7W] logLX ?=- The unabsorbed 0.2-10keV luminosity
99-102 F4.2 [10-7W] e_logLX ?=- Negative error on logLX
104-107 F4.2 [10-7W] E_logLX ?=- Positive error on logLX
--------------------------------------------------------------------------------
Note (1): n_ID labeled with "*" meaning they have "strong" association in the
eRASS1 Hard catalogue.
Note (2): n_D labeled with "+" mean their distance are taken from literature.
Note (3): label_Gamma labeled with "G" are those fitted by power-law model and
the best-fitted photon index is presented in kTmean column.
--------------------------------------------------------------------------------
Acknowledgements:
Tong Bao, xzbaotong(at)gmail.com
(End) Patricia Vannier [CDS] 29-Oct-2025