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The progenitor of the supernova imposter AT 2019krl: a SN 2008S-like transient from a blue supergiant

Andrews, Jennifer E. and Jencson, Jacob E. and Van Dyk, Schuyler D. and Neustadt, Jack M. M. and Smith, Nathan and Sand, David J. and Kreckel, K. and Kochanek, C.S. and Valenti, S. and Strader, Jay and Bersten, M. C. and Blanc, Guillermo A. and Bostroem, K. Azalee and Brink, Thomas G. and Emsellem, Eric and Filippenko, Alexei V. and Folatelli, Gastón and Kasliwal, Mansi M. and Masci, Frank J. and McElroy, Rebecca and Milisavljevic, Dan and Santoro, Francesco and Szalai, Tamás (2020) The progenitor of the supernova imposter AT 2019krl: a SN 2008S-like transient from a blue supergiant. . (Unpublished)

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For a recent intermediate-luminosity transient, AT 2019krl in M74 (NGC 628) at a distance of only ~9.8 Mpc, extensive archival Hubble Space Telescope (HST), Spitzer Space Telescope, and Large Binocular Telescope (LBT) imaging reveal a bright optical and MIR progenitor star. A peak was detected in the infrared with an absolute magnitude of M_(4.5μm) = −18.4 mag, leading us to infer a visual-wavelength peak absolute magnitude of −13.5 to −14.5. The light curve from the pre-discovery archival data indicated no outbursts over the previous 16yr. The colors, magnitudes, and inferred temperatures of the progenitor best match a 13--14 M_⊙ yellow or blue supergiant, if only foreground extinction is taken into account, or a hotter and more massive star, if any additional local extinction is included. A pre-eruption spectrum of the star reveals strong Hα emission having a narrow line core with a width of about 200 km s⁻¹ (FWHM) and with wings extending to ± 2000 km s⁻¹. The post-eruption spectrum is fairly flat and featureless with only Hα, Na I D, [Ca II], and the Ca II near-infrared triplet in emission, with very little change in the shape of Hα over 120 days. As in many previous intermediate-luminosity transients, AT 2019krl shows remarkable similarities to both massive luminous blue variable (LBV) eruptions and SN 2008S-like events. However, in this case, the information about the pre-eruption star allows us to clearly rule out both a super-AGB star and an electron-capture SN as the origin of this SN 2008S-like event. Instead, the data favor either a relatively unobscured blue supergiant (likely viewed pole-on) or a highly extinguished LBV with M> 20 M_⊙, confirming that BSGs or LBVs that may undergo mergers are a viable progenitor pathway to produce SN 2008S-like events.

Item Type:Report or Paper (Discussion Paper)
Related URLs:
URLURL TypeDescription Paper
Andrews, Jennifer E.0000-0003-0123-0062
Jencson, Jacob E.0000-0001-5754-4007
Van Dyk, Schuyler D.0000-0001-9038-9950
Neustadt, Jack M. M.0000-0001-7351-2531
Sand, David J.0000-0003-4102-380X
Kreckel, K.0000-0001-6551-3091
Kochanek, C.S.0000-0001-6017-2961
Valenti, S.0000-0001-8818-0795
Strader, Jay0000-0002-1468-9668
Bersten, M. C.0000-0002-6991-0550
Blanc, Guillermo A.0000-0003-4218-3944
Bostroem, K. Azalee0000-0002-4924-444X
Brink, Thomas G.0000-0001-5955-2502
Emsellem, Eric0000-0002-6155-7166
Filippenko, Alexei V.0000-0003-3460-0103
Folatelli, Gastón0000-0001-5247-1486
Kasliwal, Mansi M.0000-0002-5619-4938
Masci, Frank J.0000-0002-8532-9395
McElroy, Rebecca0000-0003-2290-7060
Milisavljevic, Dan0000-0002-0763-3885
Santoro, Francesco0000-0002-6363-9851
Szalai, Tamás0000-0003-4610-1117
Additional Information:J.E.A. and N.S. receive support from National Science Foundation (NSF) grant AST-1515559. Research by D.J.S. is supported by NSF grants AST-1821967, 182197, 1813708, 1813466, and 1908972, as well as by the Heising-Simons Foundation under grant #2020-1864. Research by S.V. is supported by NSF grant AST-1813176. K.K. gratefully acknowledges funding from the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) in the form of an Emmy Noether Research Group (grant number KR4598/2-1). T.S. is supported by the Jnos Bolyai Research Scholarship of the Hungarian Academy of Sciences and by the GINOP-2-3-2-15-2016-00033 project (Transient Astrophysical Objects) of the National Research, Development and Innovation Office (NKFIH), Hungary, funded by the European Union. A.V.F. received funding from NASA/HST grants GO-14668, GO-15166, and AR-14295 from the Space Telescope Science Institute (STScI), as well as from the TABASGO Foundation, the Christopher J. Redlich Fund, and the Miller Institute for Basic Research in Science (U.C. Berkeley). Support for HST program GO-15151 was provided by NASA through a grant from STScI. Some of the data reported herein were obtained at the MMT Observatory, a joint facility of the University of Arizona and the Smithsonian Institution. Research at Lick Observatory is partially supported by a generous gift from Google. Based in part on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Mikulski Archive for Space Telescopes (MAST) at STScI. STScI is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS 5-26555. Support for MAST for non-HST data is provided by the NASA Office of Space Science via grant NNX13AC07G and by other grants and contracts. This work is based in part on archival data obtained with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA. Based in part on observations obtained at the Southern Astrophysical Research (SOAR) telescope, which is a joint project of the Ministério da Ciência, Tecnologia, Inovações e Comunicações (MCTIC) do Brasil, the U.S. National Optical Astronomy Observatory (NOAO), the University of North Carolina at Chapel Hill (UNC), and Michigan State University (MSU). Based in part on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programme ID 098.C-0484(A). The LBT is an international collaboration among institutions in the United States, Italy, and Germany. LBT Corporation partners are The University of Arizona on behalf of the Arizona university system; Istituto Nazionale di Astrofisica, Italy; LBT Beteiligungsgesellschaft, Germany, representing the Max-Planck Society, the Astrophysical Institute Potsdam, and Heidelberg University; The Ohio State University, and The Research Corporation, on behalf of The University of Notre Dame, University of Minnesota and University of Virginia. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA; the Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. Facilities: HST (ACS,WFC3,WFPC2), SST (IRAC), MMT (Binospec,BCH), LBT (MODS,LBC), Keck (Deimos), SOAR (Goodman) Software: astropy (Astropy Collaborationetal. 2013),
Group:Astronomy Department, Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Heising-Simons Foundation2020-1864
Deutsche Forschungsgemeinschaft (DFG)KR4598/2-1
Hungarian Academy of SciencesUNSPECIFIED
National Research, Development and Innovation Office (Hungary)GINOP-2-3-2-15-2016-00033
Christopher R. Redlich FundUNSPECIFIED
Miller Institute for Basic Research in ScienceUNSPECIFIED
NASANAS 5-26555
Ministério da Ciência, Tecnologia, Inovações e Comunicações (MCTIC)UNSPECIFIED
National Optical Astronomy Observatory (NOAO)UNSPECIFIED
University of North Carolina at Chapel HillUNSPECIFIED
Michigan State UniversityUNSPECIFIED
LBT Corporation partnersUNSPECIFIED
W. M. Keck FoundationUNSPECIFIED
Record Number:CaltechAUTHORS:20210205-093220958
Persistent URL:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:107929
Deposited By: George Porter
Deposited On:05 Feb 2021 23:03
Last Modified:05 Feb 2021 23:03

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