Gezari, S. and Halpern, J. P. and Grupe, D. and Yuan, F. and Quimby, R. and McKay, T. and Chamarro, D. and Sisson, M. D. and Akerlof, C. and Wheeler, J. C. and Brown, P. J. and Cenko, S. B. and Rau, A. and Djordjevic, J. O. and Terndrup, D. M. (2009) Discovery of the Ultra-Bright Type II-L Supernova 2008es. Astrophysical Journal, 690 (2). pp. 1313-1321. ISSN 0004-637X http://resolver.caltech.edu/CaltechAUTHORS:GEZapj09
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We report the discovery by the Robotic Optical Transient Search Experiment (ROTSE-IIIb) telescope of SN 2008es, an overluminous supernova (SN) at z = 0.205 with a peak visual magnitude of –22.2. We present multiwavelength follow-up observations with the Swift satellite and several ground-based optical telescopes. The ROTSE-IIIb observations constrain the time of explosion to be 23 ± 1 rest-frame days before maximum. The linear decay of the optical light curve, and the combination of a symmetric, broad Hα emission line profile with broad P Cygni Hβ and Na I λ5892 profiles, are properties reminiscent of the bright Type II-L SNe 1979C and 1980K, although SN 2008es is greater than 10 times more luminous. The host galaxy is undetected in pre-supernova Sloan Digital Sky Survey images, and similar to Type II-L SN 2005ap (the most luminous SN ever observed), the host is most likely a dwarf galaxy with Mr > – 17. Swift Ultraviolet/Optical Telescope observations in combination with Palomar 60 inch photometry measure the spectral energy distribution of the SN from 200 to 800 nm to be a blackbody that cools from 14000 K at the time of the optical peak to 6400 K 65 days later. The inferred blackbody radius is in good agreement with the radius expected for the expansion speed measured from the broad lines (10000 km s^–1). The bolometric luminosity at the optical peak is 2.8 × 10^44 erg s^–1, with a total energy radiated over the next 65 days of 5.6 × 10^50 erg. The exceptional luminosity of SN 2008es requires an efficient conversion of kinetic energy produced from the core-collapse explosion into radiation. We favor a model in which the large peak luminosity is a consequence of the core collapse of a progenitor star with a low-mass extended hydrogen envelope and a stellar wind with a density close to the upper limit on the mass-loss rate measured from the lack of an X-ray detection by the Swift X-Ray Telescope.
|Additional Information:||© 2009 The American Astronomical Society. Received 2008 August 20, accepted for publication 2008 September 4. Published 2008 December 12. Print publication: Issue 2 (2009 January 10). We thank the Swift P.I. Neil Gehrels for approving our various ToO monitoring requests for SN 2008es, the Swift Science Operating Center team for performing the observations, Don Schneider for approving our HET ToO request, and the HET resident astronomers for performing our HET spectroscopic follow-up observations. The Hobby-Eberly Telescope (HET) is a joint project of the University of Texas at Austin, the Pennsylvania State University (PSU), Stanford University, Ludwig-Maximilians-Universität München, and Georg-August-Universität Göttingen. The HET is named in honor of its principal benefactors, William P. Hobby and Robert E. Eberly. Swift is supported at PSU by NASA contract NAS5-00136. ROTSE-III has been supported by NASA grant NNG-04WC41G, the Australian Research Council, the University of New South Wales, the University of Texas, and the University of Michigan. P60 operations are funded in part by NASA through the Swift Guest Investigator Program (grant NNG06GH61G). F.Y. is supported by NASA grants NNX-07AF02G and NNX-08AN25G. J.C.W. is supported in part by NSF grant AST 0707769.|
|Subject Keywords:||supernovae: general; supernovae: individual (SN 2008es); ultraviolet: ISM|
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|Deposited By:||Archive Administrator|
|Deposited On:||22 Dec 2008 22:09|
|Last Modified:||26 Dec 2012 10:39|
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