J/other/AstL/51.412 SRG/eROSITA sources in Hyades (Khamitov+, 2025)
Observations of the Hyades Open Cluster during the SRG/eROSITA All-Sky Survey.
Khamitov I.M., Bikmaev I.F., Gilfanov M.R., Sunyaev R.A., Medvedev P.S.,
Gorbachev M.A., Sklyanov A.S., Efremova P.D., Panarin S.S.
<Astronomy Letters, 51, 412-435 (2025)>
=2025AstL...51..412K 2025AstL...51..412K (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; X-ray sources
Keywords: X-ray sources - stars - open clusters: Hyades -
instruments: SRG/EROSITA, ROSAT/PSPC
Abstract:
Using data from the all-sky X-ray survey with the eROSITA telescope
onboard the SRG orbital observatory and the optical catalog of Hyades
cluster members constructed from Gaia data (2023A&A...678A..75Z 2023A&A...678A..75Z), we
have investigated the X-ray emission from cluster stars. Of the 395
cluster members located in the eastern Galactic part of the sky,
eROSITA detects X-ray emission from 290 stars, 171 of which have been
found for the first time in X-rays. At the Hyades distance (∼47pc) the
median eROSITA sensitivity in this sky region corresponds to a
0.3-2.3keV luminosity LX∼2.6x1027erg/s, allowing 100% of the stars
with spectral types from F0 to K5 to be detected within the Hyades
tidal radius. We have also investigated objects in the Hyades tidal
tail (2019A&A...621L...3M 2019A&A...621L...3M, 2019A&A...621L...2R 2019A&A...621L...2R), where X-ray emission
was recorded from 114 of the 281 known tidal tail members, 59 of which
have been found in X-rays for the first time.
Description:
The catalogue of SRG/eROSITA sources associated with Hyades within
three tidal radii at the Eastern Galactic hemisphere with X-ray
characterstics is presented in table1. The catalogue of SRG/eROSITA
X-ray sources associated with Hyades stars in the Eastern Galactic
tidal tail with X-ray characterstics is presented in table7. The list
of coincidences of ROSAT and eROSITA sources in the Hyades is
presented in table8.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 129 305 eROSITA X-ray sources in the Hyades
table7.dat 142 114 eROSITA X-ray sources in the Hyades Eastern
Galactic tidal tail
table8.dat 78 108 Hyades coincidences of eROSITA and ROSAT sources
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See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
J/A+A/621/L2 : Hyades tidal tails revealed by Gaia DR2 (Roeser+, 2019)
J/A+A/621/L3 : Hyades tidal tails with Gaia DR2 (Meingast+, 2019)
J/ApJ/931/45 : The factory + the beehive. IV. Praesepe + Hyades (Nunez+, 2022)
J/A+A/678/A75 : Young nearby open clusters members photometry (Zerjal+, 2023)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 16 A16 --- SRGe SRGe+ designation (JHHMMSS.s+DDMMSS)
18- 36 I19 --- GaiaDR3 Gaia DR3 identifier (1)
38- 47 F10.7 deg RAdeg Gaia DR3 right ascension (ICRS)
at Ep=2016.0 (1)
49- 58 F10.7 deg DEdeg Gaia DR3 declination (ICRS) at Ep=2016.0 (1)
60- 69 F10.7 mag Gmag Gaia DR3 G-band mean magnitude (1)
71- 75 F5.2 arcsec r98 eROSITA source position error
77- 81 F5.2 arcsec Sep Separation between X-ray eROSITA and
optical GAIA DR3 positions of source
83 I1 --- Ngaia [1/3] Number of GAIA DR3 sources within r98
85- 91 F7.3 10+21W LX X-ray luminosity in 0.3-2.3keV band according
to 5 eROSITA surveys (in 10+28erg/s unit)
93- 97 F5.3 10+21W e_LX 1-sigma error of X-ray luminosity in
0.3-2.3keV band according to 5 eROSITA
surveys (in 10+28erg/s unit)
99-106 F8.5 --- logRX Log of ratio X-ray in 0.3-2.3keV to
bolometric luminosities (4)
108 I1 --- f_Xvar [0-2] Flag on Xvar (2)
110-119 F10.7 --- Xvar ? Factor of X-ray variability (3)
121-125 A5 --- SpType Spectral type (4)
127 I1 --- N6d [1/2] Number of Hyades stars within r98
129 I1 --- bflag [0/1]? binarity parameter,
1 indicates the system with binarity
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Note (1): From Zerjal et al., 2023A&A...678A..75Z 2023A&A...678A..75Z; Cat. J/A+A/678/A75.
Note (2): Flag on Xvar as follows:
0 = Xvar measured value
1 = lower limit on Xvar determination
2 = Xvar not determined
Note (3): Xvar is the X-ray variability factor defined as the ratio of
the maximum and minimum fluxes recorded in five eROSITA surveys including
the flux measurement error.
Note (4): The bolometric luminosities (used in R_X determination) and the
spectral types were estimated by interpolating the dependence of these
parameters on the absolute magnitude (MG) in the G band (Gaia DR3) for
main-sequence stars. For this purpose we used the version of Mamajek's
tables (the version of April 16, 2022) originally published in
Pecaut and Mamajek, 2013ApJS..208....9P 2013ApJS..208....9P.
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Byte-by-byte Description of file: table7.dat
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Bytes Format Units Label Explanations
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1- 16 A16 --- SRGe SRGe designation (JHHMMSS.s+DDMMSS)
18- 36 I19 --- GaiaDR2 Gaia DR2 identifier (1)
38- 57 F20.16 deg RAdeg [] Gaia DR2 right ascension (ICRS)
at Ep=2015.5) (1)
59- 76 F18.15 deg DEdeg Gaia DR2 declination (ICRS) at Ep=2015.5) (1)
78- 87 F10.7 mag Gmag Gaia DR2 G-band mean magnitude (1)
89- 92 F4.1 arcsec r98 eROSITA source position error
94- 98 F5.2 arcsec Sep Separation between X-ray eROSITA and optical
Gaia DR2 positions of source
100 I1 --- Ngaia [1/8] Number of Gaia DR2 sources within r98
102-108 F7.3 10+21W LX X-ray luminosity in 0.3-2.3keV band according
to 5 eROSITA surveys (in 10+28erg/s unit)
110-114 F5.3 10+21W e_LX 1-sigma error of X-ray luminosity
in 0.3-2.3keV band according to 5 eROSITA
surveys (in 10+28erg/s unit)
116-123 F8.5 --- logRX Log of ratio X-ray in 0.3-2.3keV to
bolometric luminosities (4)
125 I1 --- f_Xvar [0/2] Flag on Xvar (2)
127-136 F10.7 --- Xvar ? Factor of X-ray variability (3)
138-142 A5 --- SpType Spectral type (4)
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Note (1): From Roser et al., 2019A&A...621L...2R 2019A&A...621L...2R; Cat. J/A+A/621/L2 and
from Maingast and Alves, 2019A&A...621L...3M 2019A&A...621L...3M; Cat. J/A+A/621/L3.
Note (2): Flag on Xvar as follows:
0 = Xvar measured value
1 = lower limit on Xvar determination
2 = Xvar not determined
Note (3): Xvar is the X-ray variability factor defined as the ratio of the
maximum and minimum fluxes recorded in five eROSITA surveys including the
flux measurement error .
Note (4): The bolometric luminosities (used in logRX determination) and the
spectral types were estimated by interpolating the dependence of these
parameters on the absolute magnitude (MG) in the G band (Gaia DR3)
for main-sequence stars. For this purpose we used the version of
Mamajek's tables (the version of April 16, 2022) originally published in
Pecaut and Mamajek, 2013ApJS..208....9P 2013ApJS..208....9P.
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Byte-by-byte Description of file: table8.dat
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Bytes Format Units Label Explanations
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1- 16 A16 --- SRGe SRGe+ designation (JHHMMSS.s+DDMMSS)
18- 21 A4 --- Instr ROSAT instrument (1)
23- 26 A4 --- Source Source of X-ray data (1)
28- 37 F10.7 deg RAdeg Right ascension (J2000) of the
ROSAT source (1)
39- 48 F10.7 deg DEdeg Declination (J2000) of the ROSAT source (1)
50- 53 F4.1 arcsec Sep Separation between the ROSAT and eROSITA
sources
55- 56 I2 arcmin offaxis ? Distance of the ROSAT X-ray source from
the telescope axis in arcmin (1)
58- 61 F4.1 10-16W/m2 FX-ROSAT 0.1-2.4keV X-ray flux of the source from
the ROSAT (10-13erg/s/cm2 units) (1)
63- 65 F3.1 10-16W/m2 e_FX-ROSAT Measurement error in the X-ray flux of the
source from the ROSAT data in the
0.1-2.4keV energy
(10-13erg/s/cm2 units) (1)
67- 70 F4.1 10-16W/m2 FX-Ero X-ray flux of the source from the eROSITA
data in the 0.3-2.3keV energy band
(10-13erg/s/cm2 units)
72- 74 F3.1 10-16W/m2 e_FX-Ero Measurement error in the 0.3-2.3keV X-ray
flux of the source from the eROSITA
data (10-13erg/s/cm2 units)
76 I1 --- Nero [1/2] Number of eROSITA sources in the
Hyades that fell into the error circle of
the ROSAT source identified previously
with a cluster star
78 I1 --- Ngaia [1/2] Number of Gaia DR3 optical
counterparts in the r98 error circle of
the eROSITA X-ray source
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Note (1): From Nunez et al., 2022ApJ...931...45N 2022ApJ...931...45N; Cat. J/ApJ/931/45.
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Acknowledgements:
Irek Khamitov, irek_khamitov(at)hotmail.com
License: CC-BY-4.0 [see https://spdx.org/licenses/]
(End) Patricia Vannier [CDS] 10-Mar-2026