J/ApJ/905/34ivo://CDS.VizieR/J/ApJ/905/34doi:10.26093/cds/vizier.19050034CDSHarper G.M.Guinan E.F.Wasatonic R.Ryde N.2022-08-26T06:27:55Z2022-06-20T14:21:40ZCDS support team

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

cds-question@unistra.frsupergiant-starsm-starsinfrared-photometryvisible-astronomyeffective-temperatureThe processes that shape the extended atmospheres of red supergiants, heat their chromospheres, create molecular reservoirs, drive mass loss, and create dust remain poorly understood. Betelgeuse's V-band "Great Dimming" event of 2019 September/2020 February and its subsequent rapid brightening provides a rare opportunity to study these phenomena. Two different explanations have emerged to explain the dimming; new dust appeared in our line of sight attenuating the photospheric light, or a large portion of the photosphere had cooled. Here we present five years of Wing three-filter (A, B, and C band) TiO and near-IR photometry obtained at the Wasatonic Observatory. These reveal that parts of the photosphere had a mean effective temperature (Teff) significantly lower than that found by Levesque & Massey (2020ApJ...891L..37L). Synthetic photometry from MARCS-model photospheres and spectra reveal that the V band, TiO index, and C-band photometry, and previously reported 4000-6800{AA} spectra can be quantitatively reproduced if there are multiple photospheric components, as hinted at by Very Large Telescope (VLT)-SPHERE images in Montarges+ (2020, ESO Press Release). If the cooler component has {Delta}Teff>=250K cooler than 3650K, then no new dust is required to explain the available empirical constraints. A coincidence of the dominant short-(~430days) and long-period (~5.8yr) V-band variations occurred near the time of deep minimum (Guinan+ 2019ATel13365....1G). This is in tandem with the strong correlation of V mag and photospheric radial velocities, recently reported by Dupree+ (2020ApJ...899...68D). These suggest that the cooling of a large fraction of the visible star has a dynamic origin related to the photospheric motions, perhaps arising from pulsation or large-scale convective motions.2020ApJ...905...34Hhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/905/34CatalogResearchIsServedByTAP VizieR generic servicerelated-toIII/150 : Perkins Revised MK Types for the Cooler Stars (Keenan+ 1989)II/177 : Near IR Photometry of a Sample of IRAS Point Sources (Fouque+ 1992)J/A+A/281/817 : Model atmospheres for Vega (Castelli+ 1994)J/A+A/545/A99 : 2 supergiants and 2 hypergiants radio spectra (Teyssier+, 2012)J/ApJ/893/11 : Massive star variability in M31 from iPTF (Soraisam+, 2020)J/ApJ/902/63 : SMEI photometry of Betelgeuse (Joyce+, 2020)J/A+A/650/L17 : HERMES spectra of Betelgeuse (Kravchenko+, 2021)J/other/Nat/594.365 : Betelgeuse during its Great Dimming (Montarges+, 2021)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/905/34https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/905/34http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/905/34https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/905/34https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/905/34http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/905/34GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tap1.939888297950143e-19 3.57918122267913e-19OpticalInfrareddefaultJ/ApJ/905/34/fig1aFive years of photometry: Teff and C magnitudes, averaged into 7 day binsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintHJDHeliocentric Julian Datedtime.epochdoubleTeff[3491/3732] Calculated, 7-day binned effective temperature derived from the TiO index using Equation 2Kphys.temperature.effective;meta.modelledfloate_Teff[11/33] The 1{sigma} uncertainty in TeffKstat.error;phys.temperature.effectivefloatCmag[-2.8/-2.39] 7-day binned Wing C band (1.024um) magnitudemagphot.mag;em.IR.Jfloate_Cmag[0.017/0.04] The 1{sigma} uncertainty in Cmagmagstat.error;phot.magfloatJ/ApJ/905/34/fig1bFive years of V-band photometryrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintHJDHeliocentric Julian Datedtime.epochdoubleVmag[0.29/1.62] Unbinned V band (0.555um) magnitudemagphot.mag;em.opt.Vfloate_Vmag[0.026] Error similar to the symbol size in Figure 1 (always "0.026")magstat.error;phot.magfloat