J/other/AstL/50.780 SRG/eROSITA sources in the Pleiades (Khamitov+, 2024)
850 SRG/eROSITA sources in the Pleiades.
Khamitov I.M., Bikmaev I.F., Gilfanov M.R., Sunyaev R.A., Medvedev P.S.
<Astronomy Letters, 50, 780-795 (2024)>
=2024AstL...50..780K 2024AstL...50..780K (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, open ; X-ray sources ; Optical
Keywords: X-ray sources - stars - open clusters: the Pleiades -
instruments: SRG/eROSITA, ROSAT/PSPC
Abstract:
Using SRG/eROSITA X-ray sky survey data and the optical catalog of
2209 Pleiades cluster members constructed from Gaia data, we have
found 850 X-ray sources associated with cluster stars. More than 650
of them have been detected in X-rays for the first time. At the
distance of the Pleiades the nominal sensitivity of eROSITA in this
sky region corresponds to a 0.3-2.3keV luminosity
LX∼1.6x1028erg/s. The eROSITA sources associated with the Pleiades
radiate with a total luminosity LX,total∼1.3x1022erg/s, which
exceeds the X-ray luminosity of the quiet Sun by a million times. A
strong, more than a factor of 10, X-ray variability has been recorded
for 27 sources. Most of them are known as eruptive optical variable dM
stars. RX=log(LX/Lbol) for Pleiades stars increases with
decreasing effective stellar temperature from RX~-5 to RX~-2 . The
RX distribution of stars is bimodal. The left peak at RX~-.43 is
formed by FGK stars, while the right peak at RX~-3.1 is mostly
populated by M stars. The dependence of RX on the Rossby number Ro
is different for different spectral types. At small Rossby numbers for
K and M stars RX~-3 and depends weakly on Ro. At Ro≳0.25 a
rapid decrease in RX is observed for K stars, while there are no M
stars with large Rossby numbers in our sample. Most of the F and G
stars lie in the range of lower values, RX~-4.5, but the size of our
sample is not enough to characterize in more detail the RX-Ro
relation for them.
Description:
The catalogue of SRG/eROSITA sources accociated with Pleiades with
X-ray characteristics is presented in table 1. The list of coincidences
of ROSAT and eROSITA sources in the Pleiades is presented in table 3.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 110 888 eROSITA X-ray sources in the Pleiades
table3.dat 47 110 Pleiades coincidences of eROSITA and
ROSAT sources
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See also:
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
J/ApJS/102/75 : ROSAT observations of the Pleiades (Micela+ 1996)
J/A+A/682/A34 : SRG/eROSITA all-sky survey catalogs (eRASS1) (Merloni+, 2024)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 20 A20 --- SRGe SRGe name (SRGeJHHMMSS.s+DDMMSS)
21 A1 --- n_SRGe [*] Note on SRGe (1)
23- 41 I19 --- GaiaDR3 Gaia DR3 source_id (2)
43- 51 F9.6 deg RAdeg Gaia DR3 Right Ascension (J2000) (2)
53- 61 F9.6 deg DEdeg Gaia DR3 Declination (J2000) (2)
63- 68 F6.3 mag Gmag Gaia DR3 G-band mean magnitude (2)
70- 73 F4.1 arcsec r98 eROSITA source position error
75- 78 F4.1 arcsec sep Separation between X-ray (eROSITA) and
optical (Gaia DR3) positions of source
80 I1 --- N [1/2] Number of Pleiades stars within r98
82- 86 F5.2 10+22W LX X-ray luminosity in 0.3-2.3keV band according
to 5 eROSITA surveys (in 10+29erg/s unit)
88- 91 F4.2 10+22W e_LX 1-sigma error of X-ray luminosity in
0.3-2.3keV band according to 5 eROSITA
surveys (in 10+29erg/s unit)
93- 97 F5.2 --- logRX Log of ratio X-ray in 0.3-2.3keV to
bolometric luminosities (3)
99 I1 --- f_Xvar [0/2] Flag on Xvar (4)
101-104 F4.1 --- Xvar ? Factor of X-ray variability (5)
106-110 A5 --- SpType Spectral type (3)
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Note (1): * means that X-ray source has a few (2) optical Pleiades counterpart
which eRosita can not separate. And so kind X-ray sources will written in
catalogue a few times.
Note (2): From Gaia Collaboration, 2022yCat.1355....0G 2022yCat.1355....0G, Cat. I/355.
Note (3): The bolometric luminosities (used in RX 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,
2013 (2013ApJS..208....9P 2013ApJS..208....9P, Cat. J/ApJS/208/9).
Note (4): Flag on Xvar as follows:
0 = Xvar measured value
1 = lower limit on Xvar determination
2 = Xvar not determined
Note (5): 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 .
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- ID Identification number in Michela et al.,
1996ApJS..102...75M 1996ApJS..102...75M (1)
5- 20 A16 --- SRGe SRGe name (SRGeJHHMMSS.s+DDMMSS)
22- 26 F5.1 arcsec Delta ROSAT and eROSITA X-ray coordinates
separation
28- 31 F4.1 arcmin offaxis ROSAT off-axis value (1)
33- 37 F5.2 [10-7W] logLX-ROSAT Log of ROSAT X-ray luminosity in
0.1-2.1keV band (in log(erg/s) unit) (1)
39- 43 F5.2 [10-7W] logLX-eROSITA Log of X-ray luminosity in 0.3-2.3keV band
according to 5 eROSITA surveys
(in log(erg/s) unit)
45 I1 --- Nero [1/2] multiple eROSITA counterpart (2)
47 I1 --- Ngaia [1/2] multiple GAIA DR3 counterpart (3)
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Note (1): From Michela et al. (1996ApJS..102...75M 1996ApJS..102...75M; Cat. J/ApJS/102/75)
Note (2): indicates the number of eROSITA sources in the Pleiades that are
within the ROSAT error circle.
Note (3): indicates number of Pleiades stars within the eROSITA error circle.
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History:
From Irek Khamitov, irek_khamitov(at)hotmail.com
Acknowledgements:
This work was supported by RSF grant no. 23-12-00292.
(End) Patricia Vannier [CDS] 28-Jul-2025