J/A+A/634/A18ivo://CDS.VizieR/J/A+A/634/A18doi:10.26093/cds/vizier.36340018CDSCochetti Y.R.Zorec J.Cidale L.S.Arias M.L.Aidelman Y.Torres A.F.,Fremat Y.Granada A.2020-10-02T07:05:04Z2020-06-13T10:35:52ZCDS support team

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

cds-question@unistra.frbe-starsA significant number of Be stars show a second Balmer discontinuity (sBD) attributed to an extended circumstellar envelope (CE). The fast rotational velocity of Be stars undoubtedly plays a significant role in the formation of the CE. However, Bn stars, which are also B-type rapidly rotating stars, do not all present clear evidence of being surrounded by circumstellar material. We aim to characterize the populations of Be and Bn stars, and discuss the appearance of the sBD as a function of the stellar parameters. We expect to find new indices characterizing the properties of CEs in Be stars and properties relating Be and Bn stars. We obtained low- and high-resolution spectra of a sample of Be and Bn stars, derived stellar parameters, characterized the sBD, and measured the emission in the H{alpha} line. Results. Correlations of the aspect and intensity of the sBD and the emission in the H{alpha} line with the stellar parameters and the Vsini are presented. Some Bn stars exhibit the sBD in absorption, which may indicate the presence of rather dense CEs. Six Bn stars show emission in the H{alpha} line, so they are reclassified as Be stars. The sBD in emission appears in Be stars with Vsini<=250km/s, and in absorption in both Be and Bn stars with Vsini>=50km/s Low-mass Be and Bn stars share the same region in the Hertzsprung-Russell diagram. The distributions of rotational to critical velocity ratios of Be and Bn stars corresponding to the current stellar evolutionary stage are similar, while distributions inferred for the zero-age main sequence have different skewness. We found emission in the H{alpha} line and signs of a CE in some Bn stars, which motivated us to think that Bn and Be stars probably belong to the same population. It should be noted that some of the most massive Bn stars could display the Be phenomenon at any time. The similarities found among Be and Bn stars deserve to be more deeply pursued.2020A&A...634A..18Chttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/634/A18CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toV/50 : Bright Star Catalogue, 5th Revised Ed. (Hoffleit+, 1991)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/634/A18https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/634/A18http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/634/A18https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/634/A18https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/634/A18http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/634/A18GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/634/A18/sample (Observed Be (table A1) and Bn (table A2) stars)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/634/A18/sample?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/634/A18/sample?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/634/A18/sample?GETtext/xml+votable180.050000true24.4285228333-57.23675280560.0055555555555555566/90 405 8518 12455 12659 12766 12971 12988 13017 13042 14336 16748 16989-16990 17125 17142 17158 17754 18290 18554 18856 18915 19009 19017 19402 19567 20551 20910 21110 21139 21236 21271 21313 21364 21515 21529 21893 22054 22579 22637 22803 22813 22837 22845 22906 22911 22963 22981 23007 23010 23261 23375 23451 23629 23631 23717 26672 29164 29457 29582 29732 29809 30229 30242 30298 30303 30540 30630 30655 31745 31954 32116 32145 32174 32383 32525 33930 34270 34624 34896 35801 35849 36575 36850 37105 37253 37330 37342 37360 37593 37717 37894 39679 39704 39715 39739 39853 39863 40285 40671 41171 41428 41740 41857 41866 41943 42010 42234 42298 42467 42640 44316 44502 46800 47021 47033 47179 47205 47760 47820 48072 48186 48534 48879 491383.322582951404819e-19 3.852589004194616e-19https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/634/A18?format=asciidefaultJ/A+A/634/A18/sampleObserved Be (table A1) and Bn (table A2) starsBtypesrc.classcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameNamemeta.id;meta.maincharRAICRSRight ascension (ICRS, J2000.0)pos.eq.ra;meta.mainDEICRSDeclination (ICRS, J2000.0)pos.eq.dec;meta.mainVmagV magnitudemagphot.mag;em.opt.VfloatObs.datel1Low-resolution observation datestime.epochnullableObs.datel2Low-resolution observation datestime.epochnullableObs.dateh1High-resolution observation datestime.epochnullablen_Obs.dateh1[ab] Note on Obs.dateh1 (1)meta.notecharObs.dateh2High-resolution observation datestime.epochnullablen_Obs.dateh2[ab] Note on Obs.dateh2 (1)meta.notecharFlag[*] Flag for Bn stars reclassified as Be starsmeta.code.errorcharSimbadSimbad column added by the CDSmeta.ref.urlcharJ/A+A/634/A18/tablea56Derived apparent fundamental parameters of Be (table A5) and Bn (table A6) starsNameNamemeta.id;meta.maincharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintBtypesrc.classcharMassStellar masssolMassphys.massfloate_Massrms uncertainty on MasssolMassstat.error;phys.massfloatloggSurface gravitylog(cm.s**-2)phys.gravityfloate_loggrms uncertainty on logglog(cm.s**-2)stat.errorfloatRStellar radiussolRadphys.size.radiusfloate_Rrms uncertainty on RadiussolRadstat.errorfloatVcEquatorial critical velocitykm/sphys.veloc;pos.eqinte_Vcrms uncertainty on Vckm/sstat.error;pos.cartesian.yintt/tMSStellar age in terms of the fractional age tMStime.age;arith.ratiofloate_t/tMSrms uncertainty on t/tMSstat.errorfloatJ/A+A/634/A18/tablea89Parent nonrotating counterpart (pnrc) fundamental parameters of Be (table A5) and Bn (table A6) starsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintBtypesrc.classcharNameNamemeta.id;meta.maincharTeffEffective temperatureKphys.temperature.effectiveinte_Teffrms uncertainty on TeffKstat.error;phys.temperature.effectiveintlogLStellar luminositylog(solLum)phys.luminosityfloate_logLrms uncertainty on logLlog(solLum)stat.errorfloatloggSurface gravitylog(cm.s**-2)phys.gravityfloate_loggrms uncertainty on logglog(cm.s**-2)stat.errorfloatMassStellar masssolMassphys.massfloate_Massrms uncertainty on MasssolMassstat.error;phys.massfloatvsini? Rotational velocitykm/sphys.veloc.rotatintnullablee_vsini? rms uncertainty on vsinikm/sstat.error;phys.veloc.rotatintnullableVcEquatorial critical velocitykm/sphys.veloc;pos.eqinte_Vcrms uncertainty on Vckm/sstat.error;pos.cartesian.yintt/tMSStellar age in terms of the fractional age tMStime.age;arith.ratiofloate_t/tMSrms uncertainty on t/tMSstat.errorfloatJ/A+A/634/A18/tablea23Observed BCD and apparent parameters of Be (table A3) and Bn (table A4) starsn_d2[ea] Note on d2 (2)meta.notecharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintBtypesrc.classcharNameNamemeta.id;meta.maincharD*BCD quantity D* (1)stat.fit.paramfloatlambda1BCD quantity {lambda}1em.wlintSpTypeSpectral typesrc.spTypechard1? BCD quantity d (1)stat.fit.paramfloatnullablen_d1[ea] Note on d1 (2)meta.notechard2? Second measurement of BCD quantity d (1)stat.fit.paramfloatnullableE(B-V)Reddeningmagphot.color.excessfloatVMAGAbsolute V magnitudemagphys.magAbs;em.opt.Vfloate_VMAGrms uncertainty on VMAGmagstat.errorfloatTeffEffective temperature, Teff(lambda1,D*)Kphys.temperature.effectiveinte_Teffrms uncertainty on TeffKstat.error;phys.temperature.effectiveintlogLLuminositylog(solLum)phys.luminosityfloate_logLrms uncertainty on logLlog(solLum)stat.errorfloatvsini? Rotational velocitykm/sphys.veloc.rotatintnullablee_vsini? rms uncertainty on vsinikm/sstat.error;phys.veloc.rotatintnullabler_vsiniReference for vsini (3)meta.refintJ/A+A/634/A18/tablea7Halpha line emission equivalent widths and fluxes of Be starsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintBtypesrc.classcharNameNamemeta.id;meta.maincharWeEquivalent width of the emission superimposed to the underlying photospheric absorption line profile0.1nmspect.line.eqWidthfloatWTotal equivalent width0.1nmspect.line.eqWidthfloatFHaFlux in the Halpha line emission (10^9^erg/cm^2^/s)1e+12W.m**-2phot.flux;em.line.Halpha;spect.linefloatdBCD quantity dstat.fit.paramfloat