The Blue Supergiant Progenitor of the Supernova Imposter AT 2019krl

Creators: Andrews, Jennifer E.; Jencson, Jacob E.; Van Dyk, Schuyler D.; Smith, Nathan; Neustadt, Jack M. M.; Sand, David J.; Kreckel, K.; Kochanek, C. S.; Valenti, S.; Strader, Jay; Bersten, M. C.; Blanc, Guillermo A.; Bostroem, K. Azalee; Brink, Thomas G.; Emsellem, Eric; Filippenko, Alexei V.; Folatelli, Gastón; Kasliwal, Mansi M.; Masci, Frank J.; McElroy, Rebecca; Milisavljevic, Dan; Santoro, Francesco; Szalai, Tamás

Abstract

Extensive archival Hubble Space Telescope, Spitzer Space Telescope, and Large Binocular Telescope imaging of the recent intermediate-luminosity transient, AT 2019krl in M74, reveal a bright optical and mid-infrared progenitor star. While the optical peak of the event was missed, a peak was detected in the infrared with an absolute magnitude of M_(4.5 μm) = −18.4 mag, leading us to infer a visual-wavelength peak absolute magnitude of −13.5 to −14.5. The pre-discovery light curve indicated no outbursts over the previous 16 yr. The colors, magnitudes, and inferred temperatures of the progenitor best match a 13–14 M_⊙ yellow or blue supergiant (BSG) 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 and [N ii] emission 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 triplet in emission. As in many previous intermediate-luminosity transients, AT 2019krl shows remarkable observational similarities to luminous blue variable (LBV) giant eruptions, SN 2008S-like events, and massive-star mergers. However, the information about the pre-eruption star favors either a relatively unobscured BSG or a more extinguished LBV with M > 20 M_⊙ likely viewed pole-on.

Additional Information

© 2021. The American Astronomical Society. Received 2020 September 26; revised 2021 May 25; accepted 2021 June 8; published 2021 August 17. We thank the referees for comments that helped us improve this paper, as well as the staffs of the observatories where data were obtained. 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). TS is supported by the János Bolyai Research Scholarship of the Hungarian Academy of Sciences, by the New National Excellence Program (UNKP-20-5) of the Ministry of Technology and Innovation of Hungary, by the GINOP-2-3-2-15-2016-00033 project of the National Research, Development and Innovation Office of Hungary (NKFIH) funded by the European Union, and by NKFIH/OTKA FK-134432 grant. A.V.F.'s group 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; A.V.F. is a Miller Senior Fellow). 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 MAST at STScI. STScI is operated by the Association of Universities for Research in Astronomy, Inc. under © 2021. The American Astronomical Society. Received 2020 September 26; revised 2021 May 25; accepted 2021 June 8; published 2021 August 17. We thank the referees for comments that helped us improve this paper, as well as the staffs of the observatories where data were obtained. 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). TS is supported by the János Bolyai Research Scholarship of the Hungarian Academy of Sciences, by the New National Excellence Program (UNKP-20-5) of the Ministry of Technology and Innovation of Hungary, by the GINOP-2-3-2-15-2016-00033 project of the National Research, Development and Innovation Office of Hungary (NKFIH) funded by the European Union, and by NKFIH/OTKA FK-134432 grant. A.V.F.'s group 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; A.V.F. is a Miller Senior Fellow). 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 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 program 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) - , Lick (Kast) - , LBT (MODS - , LBC) - , Keck (Deimos) - , SOAR (Goodman). - Software: astropy (Astropy Collaboration et al. 2013).

Attached Files

Published - Andrews_2021_ApJ_917_63.pdf

Submitted - 2009.13541.pdf

Files

Andrews_2021_ApJ_917_63.pdf

Files (11.1 MB)

Name	Size	Download all
Andrews_2021_ApJ_917_63.pdf md5:958ae55f86d273706dec3cfb14acb622	2.9 MB	Preview Download
2009.13541.pdf md5:22c42e5797a6dec350eb4384eb9fef51	8.1 MB	Preview Download

Additional details

	All versions	This version
Views	0	0
Downloads	0	0
Data volume	0 Bytes	0 Bytes