SN 2005cs in M51 – I. The first month of evolution of a subluminous SN II plateau |
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| Authors: | A Pastorello D Sauer S Taubenberger P A Mazzali K Nomoto K S Kawabata S Benetti N Elias-Rosa A Harutyunyan H Navasardyan L Zampieri T Iijima M T Botticella G Di Rico M Del Principe M Dolci S Gagliardi M Ragni G Valentini |
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| Institution: | Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, 85741 Garching bei München, Germany;INAF Osservatorio Astronomico di Trieste, Via Tiepolo 11, 34131 Trieste, Italy;Department of Astronomy, School of Science, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan;Research Center for the Early Universe, School of Science, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan;Hiroshima Astrophysical Science Center, Hiroshima University, Hiroshima 739-8526, Japan;INAF Osservatorio Astronomico di Padova, Vicolo dell'Osservatorio 5, 35122 Padova, Italy;INAF Osservatorio Astronomico di Padova, Sezione di Asiago, Via dell'Osservatorio 8, 36012 Asiago (Vicenza), Italy;Universitàdegli Studi di Teramo, Viale Crucioli 122, 64100 Teramo, Italy;INAF Osservatorio Astronomico di Collurania, via M. Maggini, 64100 Teramo, Italy |
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| Abstract: | Early-time optical observations of supernova (SN) 2005cs in the Whirlpool Galaxy (M51) are reported. Photometric data suggest that SN 2005cs is a moderately underluminous Type II plateau SN (SN IIP). The SN was unusually blue at early epochs ( U ? B ≈?0.9 about three days after explosion) which indicates very high continuum temperatures. The spectra show relatively narrow P Cygni features, suggesting ejecta velocities lower than observed in more typical SNe IIP. The earliest spectra show weak absorption features in the blue wing of the He i 5876-Å absorption component and, less clearly, of Hβ and Hα. Based on spectral modelling, two different interpretations can be proposed: these features may either be due to high-velocity H and He i components, or (more likely) be produced by different ions (N ii , Si ii ). Analogies with the low-luminosity, 56Ni-poor, low-velocity SNe IIP are also discussed. While a more extended spectral coverage is necessary in order to determine accurately the properties of the progenitor star, published estimates of the progenitor mass seem not to be consistent with stellar evolution models. |
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| Keywords: | supernovae: general supernovae: individual: SN 2005cs supernovae: individual: SN 1997D supernovae: individual: SN 1999br supernovae: individual: SN 2003Z galaxies: individual: M51 |
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