Taubenberger, S. and Valenti, S. and Benetti, S. and Cappellaro, E. and Della Valle, M. and Elias-Rosa, N. and Hachinger, S. and Hillebrandt, W. and Maeda, K. and Mazzali, P. A. and Pastorello, A. and Patat, F. and Sim, S. A. and Turatto, M. (2009) Nebular emission-line profiles of Type Ib/c supernovae – probing the ejecta asphericity. Monthly Notices of the Royal Astronomical Society, 397 (2). pp. 677-694. ISSN 0035-8711 http://resolver.caltech.edu/CaltechAUTHORS:20090917-195911539
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In order to assess qualitatively the ejecta geometry of stripped-envelope core-collapse supernovae (SNe), we investigate 98 late-time spectra of 39 objects, many of them previously unpublished. We perform a Gauss-fitting of the [O i] λλ6300, 6364 feature in all spectra, with the position, full width at half maximum and intensity of the λ6300 Gaussian as free parameters, and the λ6364 Gaussian added appropriately to account for the doublet nature of the [O i] feature. On the basis of the best-fitting parameters, the objects are organized into morphological classes, and we conclude that at least half of all Type Ib/c SNe must be aspherical. Bipolar jet models do not seem to be universally applicable, as we find too few symmetric double-peaked [O i] profiles. In some objects, the [O i] line exhibits a variety of shifted secondary peaks or shoulders, interpreted as blobs of matter ejected at high velocity and possibly accompanied by neutron-star kicks to assure momentum conservation. At phases earlier than ∼200 d, a systematic blueshift of the [O i] λλ6300, 6364 line centroids can be discerned. Residual opacity provides the most convincing explanation of this phenomenon, photons emitted on the rear side of the SN being scattered or absorbed on their way through the ejecta. Once modified to account for the doublet nature of the oxygen feature, the profile of Mg i] λ4571 at sufficiently late phases generally resembles that of [O i] λλ6300, 6364 , suggesting negligible contamination from other lines and confirming that O and Mg are similarly distributed within the ejecta.
|Additional Information:||© 2009 The Authors. Journal compilation © 2009 Royal Astronomical Society (RAS). Accepted 2009 April 29. Received 2009 April 21; in original form 2008 October 1. ST is grateful to Marilena Salvo for kindly agreeing to the use of a previously unpublished spectrum of SN 2002ap obtained at Siding Spring Observatory. He also wants to thank Bruno Leibundgut, Daniel Sauer, Luca Zampieri and Maryam Modjaz for stimulating discussions and helpful comments. SB, EC and MT are supported by the Italian Ministry of Education via the PRIN 2006 n.2006022731 002 andASI/INAF grant n. I/088/06/0. KM acknowledges the support by World Premier International Research Center Initiative, MEXT. This work is based on data collected with the 3.6-m, 2.2-m, 1.5- m and Danish Telescopes at ESO–La Silla (programme numbers 145.4-0004, 057.D-0534, 058.D-0307, 059.D-0332, 060.D-0415, 061.D-0630, 065.H-0292 and 066.D-0683), the 8.2-m VLT-U1 at ESO–Paranal (programme numbers 075.D-0662, 078.D-0246 and 079.D-0716), the 2.3-m Telescope at Siding Spring Observatory and the 2.56-m Nordic Optical Telescope at Roque de los Muchachos Observatory. The authors made use of the Asiago Supernova Catalogue, the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration; the Lyon-Meudon Extragalactic Database (LEDA), supplied by the LEDA team at the Centre de Recherche Astronomique de Lyon, Observatoire de Lyon; the NIST Atomic Spectra Database, provided by the National Institute of Standards and Technology, Gaithersburg; the Online Supernova Spectrum Archive (SUSPECT), initiated and maintained at theHomer L.Dodge Department of Physics and Astronomy, University of Oklahoma; and the Bright Supernova web pages, maintained by David Bishop as part of the International Supernovae Network (http://www.supernovae.net).|
|Subject Keywords:||line: profiles; techniques: spectroscopic; supernovae: general|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Joy Painter|
|Deposited On:||28 Sep 2009 20:51|
|Last Modified:||26 Dec 2012 11:24|
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