J/A+A/707/A193 SMGPS cross-matched with eROSITA/ROSAT and GaiaDR3 (Egbo+, 2026)
X-ray counterparts to stellar MeerKAT Galactic plane compact radio sources
Egbo O.D., Groot P.J., Buckley D.A.H., Robrade J., Schwope A.D., Freund S.,
Schneider P.C., Stelzer B.
<Astron. Astrophys. 707, A193 (2026)>
=2026A&A...707A.193E 2026A&A...707A.193E (SIMBAD/NED BibCode)
ADC_Keywords: Radio sources ; X-ray sources ; Optical ; Positional data ;
Cross identifications ; Photometry ; Spectral types ;
Galactic plane
Keywords: stars: activity - stars: coronae - stars: early-type -
stars: late-type - radio continuum: stars - X-rays: stars
Abstract:
Radio emission from magnetically active stars arises primarily from
non-thermal processes and provides information complementary to their
high-energy X-ray emission. Recent advances in sensitive, wide-field
radio and X-ray surveys have enabled the identification of larger
samples of active stars across the Galaxy.
We aim to identify and characterise radio and X-ray-emitting stars in
the Galactic plane by combining MeerKAT radio data with soft X-ray
observations, and to assess their consistency with the canonical
Guedel-Benz relation, which states that the thermal coronal emission
observed in soft X-rays is correlated with the non-thermal
gyrosynchrotron emission detected in the radio.
We cross-matched compact radio sources from the SARAO MeerKAT Galactic
Plane Survey with soft X-ray counterparts from the ROSAT All-Sky
Survey and the first release of the SRG/eROSITA all-sky survey, the
eRASS1. We investigated their radiobrightness temperatures and
computed radio and X-ray luminosities to test for consistency with the
Guedel-Benz relation.
We identify 137 stellar sources with both radio and X-ray detections.
Their radio-brightness temperatures, TB, range from 107 to
1012K, with the exception of two outliers: AXJ1600.9-5142
(TB=4.8±1.5x1012K) and HD 124831 (TB=8±1x106K). The
remaining sources are consistent with emission from incoherent
gyrosynchrotron processes. The sample generally lies below the
canonical Guedel-Benz relation, with the offset predominantly driven
by enhanced radio luminosities at 1.3GHz relative to the canonical
relation derived at 5GHz.
Our results suggest that the classical Guedel-Benz relation represents
an upper envelope rather than a tight correlation for active stars
detected at 1.3GHz. In addition, the eROSITA detections show that
early-type stars are systematically below the log(LX/Lbol)~-3
relation, which is usually seen for stars of a later spectral type.
Description:
This catalog contains radio/X-ray sources cross-matched with Gaia DR3
and includes radio, X-ray, optical, and derived luminosity parameters.
The sample includes stellar radio emitters with comprehensive
multi-wavelength characterization. The eRASS1/RASS cross-matched
sources propreties and informations are respectively presented in
erosat.dat and rosat.dat.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
erosat.dat 664 131 Radio-X-ray eRASS1 cross-matched catalog (table A1)
rosat.dat 664 47 Radio-X-ray RASS cross-matched catalog (table A1)
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See also:
J/A+A/682/A34 : SRG/eROSITA all-sky survey catalogs (eRASS1) (Merloni+, 2024)
J/A+A/588/A103 : Second ROSAT all-sky survey (2RXS) source catalog
(Boller+, 2016)
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
Byte-by-byte Description of file: erosat.dat rosat.dat
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Bytes Format Units Label Explanations
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1- 16 A16 --- SMGPS SMGPS unique source identifier (SMGPS_id)
18- 30 A13 --- FileName Name of the FITS or data file (fileName)
32- 50 F19.15 deg GLON Source galactic longitude (lon)
52- 70 F19.16 deg GLAT Source galactic latitude (lat)
72- 89 F18.14 deg RAdeg Source right ascension (ICRS) at (J2019.4)
(ra)
91-109 F19.15 deg DEdeg Source declination (ICRS) at (J2019.4)
(dec)
111-128 F18.16 arcsec e_RAdeg Uncertainty in right ascension (ra_err)
130-147 F18.16 arcsec e_DEdeg Uncertainty in declination (dec_err)
149-166 F18.16 arcsec ePos Error in both RA and Dec (radec_err)
168-187 F20.16 mJy/beam Fpeak Maximum measured flux density (peak_flux)
189-206 F18.16 mJy/beam e_Fpeak Uncertainty in peak flux (errpeakflux)
208-227 F20.16 mJy S Source integrated flux density (int_flux)
229-246 F18.16 mJy e_S Uncertainty in integrated flux
(errintflux)
248-270 A23 --- IAU IAU name ERO/2RXS of eRASS1/RASS source
(ERO/2RXS)
272-293 E22.17 mW/m2 FX X-ray flux (0.2-2.4 keV, coronal) (FX)
295-312 F18.16 uJy FXujy X-ray flux converted to uJy (FX_ujy)
314-331 F18.16 --- p ? Probability source is coronal for
ERO-eRASS1 and source is stellar for
2RXS-RASS (p-coronal/pstellar)
333-351 I19 --- GaiaDR3 Gaia DR3 source identifier (Source)
353-370 F18.14 deg RAGdeg Gaia right ascension (ICRS) at (J2016.0)
(RA_ICRS)
372-390 F19.15 deg DEGdeg Gaia declination (ICRS) at (J2016.0)
(DE_ICRS)
392-409 F18.15 mag Gmag Gaia broad-band G magnitude (Gmag)
411-429 F19.16 mag BP-RP ? Gaia colour index (BP-RP)
431-442 F12.7 pc rgeo Gaia geometric distance estimate (rgeo)
444-462 F19.16 mag GMag Absolute G magnitude (mgg)
464-486 F23.9 K Tb ? Stellar radio brightness temperature
(b_temp)
488-509 E22.17 10-7W/Hz Lrad Radio luminosity at 1.3 GHz (r_lum)
511-532 E22.17 10-7W LX X-ray luminosity (x_lum)
534-555 E22.17 10-7W Lbol Bolometric luminosity (Lerg)
557-584 A28 --- SIMBAD Main identifier from Simbad (main_id) (1)
586-597 A12 --- LType Object type label from Simbad (otype_lbl)
599-616 A18 --- OType Object type from Simbad (main_type)
618-624 A7 --- SpType Stellar spectral type Gaia DR3 (SpType-ELS)
626-645 A20 --- n_OType Additional classification notes (type_note)
647-664 F18.16 arcsec Sep SMGPS-Gaia separation (sep_arcsec)
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Note (1): Optical identifications cross-matched with Simbad database.
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Acknowledgements:
Okwudili Daniel Egbo, egbo(at)saao.ac.za
(End) Luc Trabelsi [CDS] 29-Jan-2026