J/A+A/709/A275ivo://CDS.VizieR/J/A+A/709/A275CDSZheng X.Ponti G.Locatelli N.Stelzer B.Magaudda E.Dennerl K.,Freyberg M.Sanders J.Caramazza M.Sasaki M.Merloni A.Robrade J.,Liu T.Zhang H.-S.Mayer M.G.F.Zhang Y.Yeung M.C.H.Becker W.2026-05-27T06:22:36Z2026-05-27T07:19:36ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frx-ray-sourcesdwarf-starslate-type-starsm-starsThe F, G, K and M type stars are the most abundant stellar population in the Milky Way and are expected to contribute to its diffuse X-ray emission. Yet their intrinsic average X-ray spectrum remains poorly constrained due to their faint X-ray luminosities, leaving their collective role in the X-ray background of the Milky Way uncertain. We aim to derive a distance-normalised average X-ray spectrum for nearby M dwarfs and F, G, and K stars and to characterise their ensemble spectral properties. We analysed the volume-complete sample of M- (M0-M6) and FGK-type stars within 10 pc of the Sun using data from eROSITA all-sky survey aboard the Spectrum-Roentgen-Gamma (SRG) mission (eRASS:4). Individual spectra were normalized by exposure and distance and stacked to produce representative averages. The distance-normalized emission measures yield an average X-ray luminosity of (2.6+/-0.1)x10^27^erg/s for M-type stars, and (15+/-3)x10^27^erg/s for F, G and K-type stars in 0.2-2.0keV. The average spectra could be well described by a sum of three and two thermal models. Fitted temperatures and abundances remain consistent across M-star subgroups, while early-M stars are surprisingly on average less luminous than mid/late-M types. These results offer new insights into the collective X-ray properties of nearby stars, and provide motivation to explore the link with the unresolved soft X-ray background of the Galaxy.2026A&A...709A.275Zhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/709/A275CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toI/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)J/A+A/650/A201 : 10 parsec sample in the Gaia era first update (Reyle+, 2021)J/A+A/682/A34 : SRG/eROSITA all-sky survey catalogs (eRASS1) (Merloni+, 2024)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/709/A275https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/709/A275http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/709/A275https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/709/A275https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/709/A275http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/709/A275GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/709/A275/fgk (FGK stars)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/709/A275/fgk?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/709/A275/fgk?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/709/A275/fgk?GETtext/xml+votable180.050000true224.3731-21.42550.005555555555555556Cone search capability for table J/A+A/709/A275/m (M stars)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/709/A275/m?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/709/A275/m?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/709/A275/m?GETtext/xml+votable180.050000true139.28973889-77.827856110.0055555555555555566/4158 4444 4462 4693 5333 5377 5420 6672 16391 20507 20896 21060 21136 21149 21151 21925 21953 22014 22040 22148 22289 22300 22309 22325 22645 22708 22807 22818 23047 23369 23564 23735 23867 23910 23997 24151 24227 24362 24616 24713 24924 25009 26279 26327 26487 26538 26560 26583 26972 27201 27289 27392 27459 27462 27731 27762 28343 28548 28605 29196 33281 33425 33533 33964 34181 34446 34448 34817 34896 35247 35670 36511 36614 36693 36697 36971 37122 37257 37332 37377 37379 38238 38456 38551 39331 39499 40250 40430 40496 40505 40801 41591 41763 42054 42255 42285 42290 42314 42459 42528 42652 42784 43187 43411 43413 43580 43723 44284 44437 44921 44937 45322 45485 45564 45669 46632 47347 474141.9867573869263685e-19 3.916500758235022e-19https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/709/A275?format=asciiX-raydefaultJ/A+A/709/A275/fgkFGK starsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintIDInternal source identifiermeta.idintNameObject namemeta.id;meta.maincharRA_ICRSMean right ascension (ICRS) at Ep=2016.0degpos.eq.ra;meta.mainDE_ICRSMean declination (ICRS) at Ep=2016.0degpos.eq.dec;meta.mainDistDistancepcpos.distancefloate_Dist? Uncertainty on distancepcstat.errorfloatnullableSpTypeSpectral typesrc.spTypecharGmag? Gaia G-band magnitudemagphot.mag;em.optdoublenullableeRASS1F[FALSE/TRUE ] Whether source is in eRASS1 cataloguemeta.codecharGNameGliese namemeta.idcharFlagComments (1)meta.code.errorcharCR1? eRASS1 count rate (Rate_erass1)ct/sphot.count;em.X-rayfloatnullablee_CR1? Uncertainty on eRASS1 count ratect/sstat.errorfloatnullableSimbadNameSimbad column added by the CDSmeta.idcharnullableJ/A+A/709/A275/mM starsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintIDInternal source identifiermeta.idintNameObject namemeta.id;meta.maincharRA_ICRSMean right ascension (ICRS) at Ep=2016.0degpos.eq.ra;meta.mainDE_ICRSMean declination (ICRS) at Ep=2016.0degpos.eq.dec;meta.mainDistDistancepcpos.distancefloate_Dist? Uncertainty on distancepcstat.errorfloatnullableSpTypeSpectral typesrc.spTypecharGmag? Gaia G-band magnitudemagphot.mag;em.optdoublenullableeRASS1F[FALSE/TRUE ] Whether source is in eRASS1 cataloguemeta.codecharGNameGliese namemeta.idcharFlagComments (1)meta.code.errorcharSimbadNameSimbad column added by the CDSmeta.idcharnullableCR1? eRASS1 count rate (Rate_erass1)ct/sphot.count;em.X-rayfloatnullablee_CR1? Uncertainty on eRASS1 count ratect/sstat.errorfloatnullable