J/ApJ/930/81ivo://CDS.VizieR/J/ApJ/930/81doi:10.26093/cds/vizier.19300081CDSJencson J.E.Sand D.J.Andrews J.E.Smith N.Pearson J.Strader J.,Valenti S.Beasor E.R.Rothberg B.2024-11-06T20:25:33Z2024-04-29T11:07:27ZCDS support team

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

cds-question@unistra.frgiant-starshst-photometryinfrared-sourcesWe present the discovery of an exceptional dimming event in a cool supergiant star in the Local Volume spiral M51. The star, dubbed M51-DS1, was found as part of a Hubble Space Telescope (HST) search for failed supernovae (SNe). The supergiant, which is plausibly associated with a very young (<~6Myr) stellar population, showed clear variability (amplitude {Delta}F814W~0.7mag) in numerous HST images obtained between 1995 and 2016, before suddenly dimming by >2mag in F814W sometime between late 2017 and mid-2019. In follow-up data from 2021, the star rebrightened, ruling out a failed supernova. Prior to its near-disappearance, the star was luminous and red (M_F814W_<~-7.6mag, F606W-F814W=1.9-2.2mag). Modeling of the pre-dimming spectral energy distribution of the star favors a highly reddened, very luminous (log[L/L_{sun}_]=5.4-5.7) star with Teff~3700-4700K, indicative of a cool yellow or post-red supergiant (RSG) with an initial mass of ~26-40M_{sun}_. However, the local interstellar extinction and circumstellar extinction are uncertain, and could be lower: the near-IR colors are consistent with an RSG, which would be cooler (Teff<~3700K) and slightly less luminous (log[L/L_{sun}_]=5.2-5.3), giving an inferred initial mass of ~19-22M_{sun}_. In either case, the dimming may be explained by a rare episode of enhanced mass loss that temporarily obscures the star, potentially a more extreme counterpart to the 2019-2020 "Great Dimming" of Betelgeuse. Given the emerging evidence that massive evolved stars commonly exhibit variability that can mimic a disappearing star, our work highlights a substantial challenge in identifying true failed SNe.2022ApJ...930...81Jhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/930/81CatalogResearchIsServedByTAP VizieR generic servicerelated-toB/hst : HST Archived Exposures Catalog (STScI, 2007)II/227 : The Asiago Supernova Catalogue 1999 (Barbon+, 1999)VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006)J/A+A/442/281 : Late-type giants BVRIJHKL & Teff (Kucinskas+, 2005)J/ApJ/671/781 : Red supergiants in Sct-Cru Galactic arm (Davies+, 2007)J/MNRAS/395/1409 : Type II-P SN progenitor constraints (Smartt+, 2009)J/AcA/59/239 : VI LCs of LMC long-period variables (Soszynski+, 2009)J/AJ/142/103 : Cool evolved stars in SAGE-SMC & SAGE-LMC (Boyer+, 2011)J/A+A/532/A54 : GRAMS carbon-star model grid (Srinivasan+, 2011)J/ApJ/727/53 : Red supergiant stars in the LMC. I. (Yang+, 2011)J/other/Sci/337.444 : RV curves of Galactic massive O stars (Sana+, 2012)J/ApJ/754/35 : Red supergiant stars in the SMC. II. (Yang+, 2012)J/ApJS/215/9 : PHAT X. UV-IR photometry of M31 stars (Williams+, 2014)J/ApJ/808/42 : CHemical Abundances of Spirals II. M51 (Croxall+, 2015)J/ApJ/834/107 : Follow-up phot. of M101 OT2015-1 (Blagorodnova+, 2017)J/ApJ/864/111 : HST/ACS one-year obs. of M51 stars (Conroy+, 2018)J/MNRAS/478/3138 : Cool supergiants in Magellanic Clouds (Davies+, 2018)J/ApJ/859/73 : RSGs in M31 from the iPTF survey (Soraisam+, 2018)J/ApJ/886/40 : Most luminous SPIRITS IR transients (Jencson+, 2019)J/A+A/629/A91 : A source catalog for the SMC (Yang+, 2019)J/ApJ/905/34 : 2017-2020 photometry of Betelgeuse (Harper+, 2020)J/ApJ/889/44 : UKIRT obs. of red supergiants in M31 (Neugent+, 2020)J/MNRAS/508/5757 : Synthetic sp. of red supergiants (Davies+, 2021)J/A+A/650/L17 : HERMES spectra of Betelgeuse (Kravchenko+, 2021)J/AJ/161/79 : Red supergiant stars in M31 and M33 (Massey+, 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/930/81https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/930/81http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/930/81https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/930/81https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/930/81http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/930/81GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapInfrareddefaultJ/ApJ/930/81/table1HST DOLPHOT photometryrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintObs[1995/2021] UT Year of the observationstime.epoch;obsMJD[49732.76/59371.94] Modified Julian date of observationdtime.epochdoubleInstHST instrument ("ACS/WFC", "WFC3/IR", "WFC3/UVIS" or "WFPC2")instrcharBandHST photometric bandmeta.code;instr.filtercharl_magLimit flag on mag (1)meta.code.errorcharmag[19.48/25.3] Apparent Vega magnitude in Bandmagphot.magfloate_mag[0.04/0.3]? The 1{sigma} uncertainty in magmagstat.error;phot.magfloatnullable