J/A+A/697/A230 Gaia DR3 with eRASS1 detection CaII IRT (Freund+, 2025)
The stellar corona-chromosphere connection.
A comprehensive study of X-ray and Ca II IRT fluxes from eROSITA and Gaia.
Freund S., Czesla S., Fuhrmeister B., Predehl P., Robrade J.,
Schneider P.C., Schmitt J.H.M.M.
<Astron. Astrophys. 697, A230 (2025)>
=2025A&A...697A.230F 2025A&A...697A.230F (SIMBAD/NED BibCode)
ADC_Keywords: X-ray sources ; Stars, late-type ; Photometry, calcium triplet
Keywords: stars: activity - stars: chromospheres - stars: coronae -
stars: late-type - X-ray: stars
Abstract:
Stellar activity can be observed at different wavelengths in a variety
of different activity indicators. We investigated the correlation
between coronal and chromospheric emissions by combining X-ray data
from stars detected in the eROSITA all-sky surveys (eRASS1 and
eRASS:5) with CaII infrared triplet (IRT) activity indices as
published in the third Gaia data release (Gaia DR3). We specifically
studied 24300 and 43200 stellar sources with reliable CaII IRT
measurement and X-ray detection in eRASS1 and eRASS:5, which is by far
the largest stellar sample available so far. The largest detection
fraction is obtained for highly active sources and stars of a late
spectral type, while F-type and less active stars (as measured in the
CaII IRT) remain mostly undetected in X-rays. Also, the correlation
is the strongest for late-type sources, while F-type stars show a
rather weak correlation between the X-ray to bolometric flux ratio and
the CaII IRT activity index. The relation between the X-ray and CaII
IRT surface fluxes changes with the fractional X-ray flux without
showing two separated branches as described in previous studies. For
fast rotators, both activity indicators saturate at a similar Rossby
number and the X-ray to bolometric flux ratio decreases faster than
the IRT index for slower rotating stars. As a consequence, the ratio
between X-ray and IRT fluxes is constant in the saturation regime and
decreases for slow rotators.
Description:
We present the list of sources with reliable CaII IRT activity
measurement from Gaia DR3 detected in eRASS1. We adopted the CaII IRT
activities from Lanzafame et al. (2023A&A...674A..30L 2023A&A...674A..30L) and consider
them as reliable if they are positive, three times larger than their
uncertainty, and with log(R'IRT)>-5.4. The eRASS1 identifications
are adopted from Freund et al. (2024A&A...684A.121F 2024A&A...684A.121F, Cat.
J/A+A/684/A121).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
catalog.dat 157 24315 List of sources with reliable CaII IRT
measurement and eRASS1 detection
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See also:
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
J/A+A/684/A121 : SRG/eROSITA all-sky survey coronal content (Freund+, 2024)
J/A+A/682/A34 : SRG/eROSITA all-sky survey catalogs (eRASS1) (Merloni+, 2024)
Byte-by-byte Description of file: catalog.dat
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Bytes Format Units Label Explanations
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1- 19 I19 --- GaiaDR3 Identifier of Gaia DR3 source (source_id)
21- 30 F10.6 deg RAdeg Right ascension (ICRS) at Ep=2016.0
of the source
32- 41 F10.6 deg DEdeg Declination (ICRS) at Ep=2016.0 of the source
43- 65 A23 --- EROName IAU name of the eRASS1 source (IAUNAME)
67- 98 A32 --- EROId Identifier of the eRASS1 source (DETUID)
100-105 F6.4 --- p-coronal Probability of the eRASS1 identification
107-112 F6.2 mas plx Parallax
114-119 F6.2 mag G0mag Extinction corrected G band magnitude
121-125 F5.2 mag (BP-RP)0 Reddening corrected BP-RP color
127-132 F6.2 Rsun Radius ? Stellar radius (radius_gspphot)
134-141 E8.3 mW/m2 FX X-ray flux in the 0.2-2.3keV band assuming
a coronal spectrum
143-150 E8.3 mW/m2 Fbol Bolometric flux
152-157 F6.2 --- logR'IRT Logarithm of the R'IRT activity index
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Acknowledgements:
Sebastian Freund, sfreund(at)mpe.mpg.de
References:
Lanzafame et al., 2023A&A...674A..30L 2023A&A...674A..30L
Gaia Data Release 3. Stellar chromospheric activity and mass accretion from
Ca II IRT observed by the Radial Velocity Spectrometer
(End) Patricia Vannier [CDS] 25-Apr-2025