J/ApJ/912/81ivo://CDS.VizieR/J/ApJ/912/81doi:10.26093/cds/vizier.19120081CDSKuznetsov A.A.Kolotkov D.Y.2022-12-05T14:00:15Z2022-11-24T08:34:25ZCDS support team

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

cds-question@unistra.frstellar-flaresx-ray-sourcesinfrared-photometryvisible-astronomyWide-band photometrym-starsmetallicitystellar-massesstellar-radiiSolar and stellar flares are powerful events that produce intense radiation across the electromagnetic spectrum. Multiwavelength observations are highly important for understanding the nature of flares, because different flare-related processes reveal themselves in different spectral ranges. To study the correlation between thermal and nonthermal processes in stellar flares, we have searched the databases of Kepler (optical observations) and XMM-Newton (soft X-rays) for the flares observed simultaneously with both instruments; nine distinctive flares (with energies exceeding 10^33^erg) on three stars (of K-M spectral classes) have been found. We have analyzed and compared the flare parameters in the optical and X-ray spectral ranges; we have also compared the obtained results with similar observations of solar flares. Most of the studied stellar flares released more energy in the optical range than in X-rays. In one flare, X-ray emission strongly dominated, which could be caused either by a soft spectrum of energetic electrons or by a near-limb position of this flare. The X-ray flares were typically delayed with respect to and shorter than their optical counterparts, which is partially consistent with the Neupert effect. Using the scaling laws based on the magnetic reconnection theory, we have estimated the characteristic magnetic field strengths in the stellar active regions and the sizes of these active regions as about 25-70G and 250000-500000km, respectively. The observed stellar superflares appear to be scaled-up versions of solar flares, with a similar underlying mechanism and nearly the same characteristic magnetic field values, but with much larger active region sizes.2021ApJ...912...81Khttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/912/81CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toB/xmm : XMM-Newton Observation Log (XMM-Newton Science Operation Center, 2012)II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)V/133 : Kepler Input Catalog (Kepler Mission Team, 2009)IX/46 : XMM-Newton Serendipitous Source Catalogue 3XMM-DR5 (XMM-SSC, 2016)I/345 : Gaia DR2 (Gaia Collaboration, 2018)IV/38 : TESS Input Catalog - v8.0 (TIC-8) (Stassun+, 2019)III/284 : APOGEE-2 data from DR16 (Johnsson+, 2020)J/A+A/492/277 : Analysis of Collinder 69 stars with VOSA (Bayo+, 2008)J/ApJ/687/1264 : Age estimation for solar-type dwarfs (Mamajek+, 2008)J/ApJS/190/1 : A survey of stellar families (Raghavan+, 2010)J/AJ/142/112 : KIC photometric calibration (Brown+, 2011)J/A+A/534/A133 : Proxima Cen chromospheric em. lines (Fuhrmeister+, 2011)J/other/Nat/485.478 : Superflares on solar-type stars (Maehara+, 2012)J/ApJS/208/9 : Intrinsic colors & temperatures of PMS stars (Pecaut+, 2013)J/ApJS/209/5 : Superflares of Kepler stars. I. (Shibayama+, 2013)J/ApJ/804/64 : Empirical and model parameters of 183 M dwarfs (Mann+, 2015)J/A+A/583/A65 : Active Kepler stars differential rotation (Reinhold+, 2015)J/ApJ/829/23 : Stellar flares from Q0-Q17 Kepler LCs (Davenport, 2016)J/MNRAS/457/2877 : Kepler M dwarf stars revised properties (Gaidos+, 2016)J/ApJ/851/91 : Stat. studies of solar white-light flares (Namekata+, 2017)J/ApJS/232/26 : Catalog of Kepler flare stars (Van Doorsselaere+, 2017)J/A+A/620/A55 : Magnetic flaring from PMS stars spectra (Flaccomio+, 2018)J/ApJ/883/88 : Short-duration flares from GALEX & Kepler (Brasseur+, 2019)J/A+A/628/A41 : KIC stars in Kepler/XMM-Newton (Pizzocaro+, 2019)J/ApJ/871/174 : Kepler rapid rotators and Ks-band excesses (Simonian+, 2019)J/AJ/157/216 : Stellar mult. rate of M dwarfs within 25pc (Winters+, 2019)http://archive.stsci.edu/missions-and-data/kepler : Kepler home page on MASThttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/912/81https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/912/81http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/912/81https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/912/81https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/912/81http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/912/81GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/912/81/table1 (Parameters of the selected KIC stars)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/912/81/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/912/81/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/912/81/table1?GETtext/xml+votable180.050000true290.368657843.92933640.0055555555555555566/14772-14773 151128.650015785639275e-20 4.920466254354166e-19https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/912/81?format=asciiX-rayOpticalInfrareddefaultJ/ApJ/912/81/table1Parameters of the selected KIC starsKICKIC numbermeta.id;meta.mainintSpTSpectral type (1)src.spTypecharTeff[3357/4124] Gaia DR2 (I/345) effective temperatureKphys.temperature.effectiveintrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintb_Teff[3344/4025] Teff lower limitKphys.temperature.effective;stat.minintB_Teff[3528/4138] Teff upper limitKphys.temperature.effective;stat.maxintLum[0.05/0.12] Gaia DR2 luminositysolLumphys.luminosityfloatb_Lum[0.05/0.11] Lum lower limitsolLumphys.luminosity;stat.minfloatB_Lum[0.05/0.12] Lum upper limitsolLumphys.luminosity;stat.maxfloatDist[125/206] Gaia DR2 distancepcpos.distance;pos.heliocentricfloatb_Dist[125/199] Dist lower limitpcpos.distance;pos.heliocentric;stat.minfloatB_Dist[126/214] Dist upper limitpcpos.distance;pos.heliocentric;stat.maxfloat[Fe/H][-0.16/0.04] Metallicityphys.abund.Zfloatb_[Fe/H][-0.27/-0.05] [Fe/H] lower limitphys.abund.Fe;stat.minfloatB_[Fe/H][-0.05/0.14] [Fe/H] upper limitphys.abund.Fe;stat.maxfloatr_[Fe/H]Flag on [Fe/H] (2)meta.refcharProt[1.49/8.56] Rotational period from McQuillan+ 2014, J/ApJS/211/24dtime.periodfloatAv[0.08/0.18] Optical extinction, A_V_, from Brown+ 2011, J/AJ/142/112magphys.absorptionfloatBmag[15.34/17.3] Johnson B magnitude (3)magphot.mag;em.opt.BfloatVmag[14.08/16.01] Johnson V magnitude (3)magphot.mag;em.opt.VfloatKsmag[10.46/11.56] 2MASS (II/246) Ks-band magnitudemagphot.mag;em.IR.Kfloatb_Ksmag[10.44/11.54] Ksmag lower limitmagphot.mag;stat.minfloatB_Ksmag[10.48/11.58] Ksmag upper limitmagphot.mag;stat.maxfloatb_Gmag[13.33/14.94] Gmag lower limitmagphot.mag;stat.minfloatRPmag[12.43/13.87] Gaia DR2 RP-band magnitudemagphot.mag;em.opt.Rfloatb_RPmag[12.43/13.86] RPmag lower limitmagphot.mag;stat.minfloatB_RPmag[12.44/13.87] RPmag upper limitmagphot.mag;stat.maxfloatMass[0.4/0.6]? Estimated component mass (4)solMassphys.massfloatnullableRad[0.4/0.55]? Radius (4)solRadphys.size.radiusfloatnullablea[0.02/0.07]? Orbital separation (4)AUpos.angDistance;src.orbitalfloatnullableLCInteractive Kepler LC plotsmeta.ref.urlcharLCxInteractive XMM LC plotsmeta.ref.urlcharSimbadSimbad column added by the CDSmeta.ref.urlchar_RARight Ascension (J2000) from SIMBAD (not part of the original data)degpos.eq.ra;meta.main_DEDeclination (J2000) from SIMBAD (not part of the original data)degpos.eq.dec;meta.mainGmag[13.33/14.95] Gaia DR2 G-band magnitudemagphot.mag;em.optfloatB_Gmag[13.33/14.95] Gmag upper limitmagphot.mag;stat.maxfloatBPmag[14.18/16.1] Gaia DR2 BP-band magnitudemagphot.mag;em.opt.Bfloatb_BPmag[14.18/16.09] BPmag lower limitmagphot.mag;stat.minfloatB_BPmag[14.19/16.11] BPmag upper limitmagphot.mag;stat.maxfloatJ/ApJ/912/81/fig2Light curves of KIC 8093473recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTelTelescope; (K)epler or (X)MM/PNmeta.notecharMJD[55164.7/55830.2] Modified Julian Datedtime.epochdoubleFlux[0.0005/54963] Flux (1)phot.flux.densitydoublee_Flux[0.002/7.5] Uncertainty in Flux (2)stat.error;phot.fluxdoubleJ/ApJ/912/81/fig3Light curves of KIC 8454353recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTelTelescope; (K)epler or (X)MM/PNmeta.notecharMJD[55164.7/55830.2] Modified Julian Datedtime.epochdoubleFlux[0.0005/54963] Flux (1)phot.flux.densitydoublee_Flux[0.002/7.5] Uncertainty in Flux (2)stat.error;phot.fluxdoubleJ/ApJ/912/81/fig4Light curves of KIC 9048551MJD[55164.7/55830.2] Modified Julian Datedtime.epochdoublerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTelTelescope; (K)epler or (X)MM/PNmeta.notecharFlux[0.0005/54963] Flux (1)phot.flux.densitydoublee_Flux[0.002/7.5] Uncertainty in Flux (2)stat.error;phot.fluxdouble