The Progenitor of Supernova 2011dh/PTF11eon In Messier 51

Creators: Van Dyk, Schuyler D.; Li, Weidong; Cenko, S. Bradley; Kasliwal, Mansi M.; Horesh, Assaf; Ofek, Eran O.; Kraus, Adam L.; Silverman, Jeffrey M.; Arcavi, Iair; Filippenko, Alexei V.; Gal-Yam, Avishay; Quimby, Robert M.; Kulkarni, Shrinivas R.; Yaron, Ofer; Polishook, David

Abstract

We have identified a luminous star at the position of supernova (SN) 2011dh/PTF11eon, in pre-SN archival, multi-band images of the nearby, nearly face-on galaxy Messier 51 (M51) obtained by the Hubble Space Telescope with the Advanced Camera for Surveys. This identification has been confirmed, to the highest available astrometric precision, using a Keck-II adaptive-optics image. The available early-time spectra and photometry indicate that the SN is a stripped-envelope, core-collapse Type IIb, with a more compact progenitor (radius ~ 10^(11) cm) than was the case for the well-studied SN IIb 1993J. We infer that the extinction to SN 2011dh and its progenitor arises from a low Galactic foreground contribution, and that the SN environment is of roughly solar metallicity. The detected object has absolute magnitude M^0_V ≈ –7.7 and effective temperature ~6000 K. The star's radius, ~10^(13) cm, is more extended than what has been inferred for the SN progenitor. We speculate that the detected star is either an unrelated star very near the position of the actual progenitor, or, more likely, the progenitor's companion in a mass-transfer binary system. The position of the detected star in a Hertzsprung-Russell diagram is consistent with an initial mass of 17-19 M_☉. The light of this star could easily conceal, even in the ultraviolet, the presence of a stripped, compact, very hot (~10^5 K), nitrogen-rich Wolf-Rayet star progenitor.

Additional Information

© 2011 The American Astronomical Society. Received 2011 June 15; accepted 2011 October 5; published 2011 October 18. This work was 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 (AURA), Inc., under NASA contract NAS 05-26555; the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA, with generous financial support from the W. M. Keck Foundation; and the Lick Observatory, operated by the University of California. KAIT and its ongoing research were made possible by donations from Sun Microsystems, Inc., the Hewlett-Packard Company, Auto-Scope Corporation, Lick Observatory, the NSF, the University of California, the Sylvia & Jim Katzman Foundation, and the TABASGO Foundation. We thank the staffs of the Lick and Keck Observatories for their assistance with the observations. We thank Peter Nugent for useful comments, and the referee for helpful suggestions which improved this manuscript. Support for this research was provided by NASA through grants GO-11575, AR-11248, and AR-12126 from the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS 5-26555. A.V.F. and his group at UC Berkeley also acknowledge generous support from Gary and Cynthia Bengier, the Richard and Rhoda Goldman Fund, NASA/Swift grant NNX10AI21G, NASA/Fermi grant NNX1OA057G, NSF grant AST–0908886, and the TABASGO Foundation. A.G. is supported by the ISF. E.O.O. is supported by an Einstein Fellowship and NASA grants. J.M.S. thanks Marc J. Staley for a graduate fellowship. Facilities: Keck:II, Keck:I, HST (ACS), Spitzer (IRAC), GALEX, KAIT

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