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SN Hunt 248: a super-Eddington outburst from a massive cool hypergiant

Mauerhan, Jon C. and Van Dyk, Schuyler D. and Graham, Melissa L. and Zheng, WeiKang and Clubb, Kelsey I. and Filippenko, Alexei V. and Valenti, Stefano and Brown, Peter and Smith, Nathan and Howell, D. Andrew and Arcavi, Iair (2015) SN Hunt 248: a super-Eddington outburst from a massive cool hypergiant. Monthly Notices of the Royal Astronomical Society, 447 (2). pp. 1922-1934. ISSN 0035-8711.

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We present observations of SN Hunt 248, a new supernova (SN) impostor in NGC 5806, which began a multistage outburst in 2014 May. The ‘2014a’ discovery brightening exhibited an absolute magnitude of M ≈ −12 and the spectral characteristics of a cool, dense outflow, including P Cygni lines of Fe ii, H i, and Na i, and line blanketing from metals. The source rapidly climbed and peaked at M ≈ −15 mag after two additional weeks. During this bright ‘2014b’ phase the spectrum became dominated by Balmer emission and a stronger blue continuum, similar to the SN impostor SN 1997bs. Archival images from the Hubble Space Telescope between 1997 and 2005 reveal a luminous (4 × 10^5 L_⊙) variable precursor star. Its location on the Hertzsprung–Russell diagram is consistent with a massive (M_(init) ≈ 30 M_⊙) cool hypergiant having an extremely dense wind and an Eddington ratio (Γ) just below unity. At the onset of the 2014a brightening, however, the object was super-Eddington (Γ = 4–12). The subsequent boost in luminosity during the 2014b phase probably resulted from circumstellar interaction. SN Hunt 248 provides the first case of a cool hypergiant undergoing a giant eruption reminiscent of outbursts from luminous blue variable stars (LBVs). This lends support to the hypothesis that some cool hypergiants, such as ρ Cas, could be LBVs masquerading under a pseudo-photosphere created by their extremely dense winds. Moreover, SN Hunt 248 demonstrates that eruptions stemming from such stars can rival in peak luminosity the giant outbursts of much more massive systems like η Car.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Van Dyk, Schuyler D.0000-0001-9038-9950
Graham, Melissa L.0000-0002-9154-3136
Zheng, WeiKang0000-0002-2636-6508
Filippenko, Alexei V.0000-0003-3460-0103
Valenti, Stefano0000-0001-8818-0795
Howell, D. Andrew0000-0003-4253-656X
Arcavi, Iair0000-0001-7090-4898
Additional Information:© 2015 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2014 December 1. Received 2014 November 26; in original form 2014 July 17. First published online January 5, 2015. We thank the anonymous referee for a detailed review, which led to an improved paper. This work is based in part on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Data Archive at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. This work is also based on observations made with the Spitzer Space Telescope and made use of the NASA/IPAC Infrared Science Archive, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. 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. We are grateful to the staffs at the Lick and Keck Observatories for their assistance. The supernova research of AVF’s group at UC Berkeley is supported by Gary & Cynthia Bengier, the Richard & Rhoda Goldman Fund, the Christopher R. Redlich Fund, and the TABASGO Foundation. KAIT and its ongoing operation were made possible by donations from Sun Microsystems, Inc., the Hewlett-Packard Company, AutoScope Corporation, Lick Observatory, the NSF, the University of California, the Sylvia & Jim Katzman Foundation, and the TABASGO Foundation. This work is based in part on observations from the LCOGT network. We have made use of the NASA/IPAC Extragalactic Database (NED), which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA.
Funding AgencyGrant Number
NASANAS 5-26555
W. M. Keck FoundationUNSPECIFIED
Gary and Cynthia BengierUNSPECIFIED
Richard and Rhoda Goldman FundUNSPECIFIED
Christopher R. Redlich FundUNSPECIFIED
Sun Microsystems, Inc.UNSPECIFIED
Hewlett-Packard CompanyUNSPECIFIED
AutoScope CorporationUNSPECIFIED
Lick ObservatoryUNSPECIFIED
University of CaliforniaUNSPECIFIED
Sylvia and Jim Katzman FoundationUNSPECIFIED
Subject Keywords:circumstellar matter stars: evolution supernovae: general supernovae: individual: SN Hunt 248 stars: winds, outflows
Issue or Number:2
Record Number:CaltechAUTHORS:20150409-112804471
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Official Citation:Jon C. Mauerhan, Schuyler D. Van Dyk, Melissa L. Graham, WeiKang Zheng, Kelsey I. Clubb, Alexei V. Filippenko, Stefano Valenti, Peter Brown, Nathan Smith, D. Andrew Howell, and Iair Arcavi SN Hunt 248: a super-Eddington outburst from a massive cool hypergiant MNRAS (February 21, 2015) Vol. 447 1922-1934 doi:10.1093/mnras/stu2541 First published online January 5, 2015
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:56532
Deposited By: Ruth Sustaita
Deposited On:09 Apr 2015 18:49
Last Modified:22 Nov 2019 22:54

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