J/A+A/620/A32ivo://CDS.VizieR/J/A+A/620/A32doi:10.26093/cds/vizier.36200032CDSSiebenmorgen R.Scicluna P.Krelowski J.2020-01-29T09:12:52Z2018-11-23T10:33:45ZCDS support team

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

cds-question@unistra.fro-starsinfrared-astronomyspectroscopyWe present results of the analysis of a sample of 22 stars of spectral types from O7 to B5 and luminosity classes I-V for which spectra from the Infrared Spectrograph (IRS) of Spitzer are available. The IRS spectra of these stars are examined for signs of excess infrared (IR) emission by comparison with stellar atmospheric spectra. We find that the spectra of half of the studied stars are dominated by excess emission in the far-IR, including all six super- and bright giants. In order to examine the origin of the far-IR excess, we supplement the Spitzer data with optical high-resolution echelle spectroscopy ({lambda}{Delta}{lambda}~10^5^), near-IR high-contrast coronagraphic imaging taken with the SPHERE instrument at VLT with a spatial resolution of 0.05", and WISE and Herschel photometry. In the optical region, we detect various absorption and emission lines (H{alpha}, CIII, and NIII) irrespective of the far-IR excess. Pfund{alpha} and Humphrey{alpha} lines are observed at the same time as the far-IR excess. These lines are stronger in stars with far-IR excess than in stars without excess. A scattered-light disk in the central r<2.5" region of the far-IR excess stars HD149404, HD151804, and HD154368 can be excluded from H band imaging down to a 1{sigma} contrast of F(r)/F*~10^-6^. The far-IR excess is fit either by a free-free component from ionized gas as for the winds of hot stars or a large (1pc) circumstellar dust shell. The putative dust envelopes required to explain the excess have a visual extinction as low as a few hundred micro-mag.2018A&A...620A..32Shttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/620/A32CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/620/A32https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/620/A32http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/620/A32https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/620/A32https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/620/A32http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/620/A32GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/620/A32/table2 (Spectral lines for stars with and without far-IR excess)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/620/A32/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/620/A32/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/620/A32/table2?GETtext/xml+votable180.050000true59.741259435.79103140.0055555555555555566/1558 13557 14630 14643 14824 15631 21233 21646 22855 23637 23717 30818 39209 39334 42408 42416 42470 42994 47648https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/620/A32?format=asciiInfrareddefaultJ/A+A/620/A32/table2Spectral lines for stars with and without far-IR excessn_Ha[c] Note on Ha (1)meta.notecharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintspShow the spectrummeta.ref.urlcharIRexcessIR excess (Excess or No excess)meta.codecharNameStar namemeta.id;meta.maincharInstInstrumentmeta.id;instrcharObs.dateObservation datetime.epoch;obsnullableDistP? Distance estimate from GAIA parallaxespcpos.distance;pos.heliocentricintnullableDistCaII? Distance estimate from CaIIpcpos.distance;pos.heliocentricintnullableDistsp? Distance estimate from spectral and luminosity classpcpos.distance;pos.heliocentricintnullableHaPresence of H{alpha} 6563{AA}meta.codecharCIIIPresence of CIII 5596{AA}meta.codecharNIIIPresence of NIII 4641{AA}meta.codecharl_FPfaLimit flag on FPfameta.code.errorcharFPfaPfund {alpha} (n=6->5) 7.5um hydrogen transition continuum subtracted line flux1e-17W.m**-2phot.fluxfloate_FPfa? rms uncertainty on FPfa1e-17W.m**-2stat.errorfloatnullableEWPfa? Pfund {alpha} (n=6->5) 7.5um hydrogen transition equivalent width0.1nmspect.line.eqWidth;em.IR.4-8um;phys.atmol.transitionintnullablel_FHuaLimit flag on FHuameta.code.errorcharFHuaHumphrey {alpha} (n=7->6) 12.3um hydrogen transition continuum subtracted line flux1e-17W.m**-2phot.fluxfloate_FHua? rms uncertainty on FHua1e-17W.m**-2stat.errorfloatnullableEWHua? Humphrey {alpha} (n=7->6) 12.3um hydrogen transition equivalent width0.1nmspect.line.eqWidth;em.IR.8-15um;phys.atmol.transitionintnullableFileNameName of the spectrum file in subdirectory spmeta.id;meta.filecharSimbadSimbad 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.main