Spectroscopic Observations and Analysis of the Peculiar SN 1999aa
Abstract
We present an extensive new time-series of spectroscopic data of the peculiar SN 1999aa in NGC 2595. Our data set includes 25 optical spectra between -11 and +58 days with respect to B-band maximum light, providing an unusually complete time history. The early spectra resemble those of a SN 1991T-like object but with a relatively strong Ca H&K absorption feature. The first clear sign of Si II 6355, characteristic of Type Ia supernovae, is found at day -7 and its velocity remains constant up to at least the first month after B-band maximum light. The transition to normal-looking spectra is found to occur earlier than in SN 1991T suggesting SN 1999aa as a possible link between SN 1991T-like and Branch-normal supernovae. Comparing the observations with synthetic spectra, doubly ionized Fe, Si and Ni are identified at early epochs. These are characteristic of SN 1991T-like objects. Furthermore, in the day -11 spectrum, evidence is found for an absorption feature which could be identified as high velocity C II 6580 or H-alpha. At the same epoch C III 4648.8 at photospheric velocity is probably responsible for the absorption feature at 4500 A. High velocity Ca is found around maximum light together with Si II and Fe II confined in a narrow velocity window. Implied constraints on supernovae progenitor systems and explosion hydrodynamical models are briefly discussed.
Keywords
Cite
@article{arxiv.astro-ph/0404393,
title = {Spectroscopic Observations and Analysis of the Peculiar SN 1999aa},
author = {G. Garavini and G. Folatelli and A. Goobar and S. Nobili and G. Aldering and A. Amadon and R. Amanullah and P. Astier and C. Balland and G. Blanc and M. S. Burns and A. Conley and T. Dahlen and S. E. Deustua and R. Ellis and S. Fabbro and X. Fan and B. Frye and E. L. Gates and R. Gibbons and G. Goldhaber and B. Goldman and D. E. Groom and J. Haissinski and D. Hardin and I. M. Hook and D. A. Howell and D. Kasen and S. Kent and A. G. Kim and R. A. Knop and B. C. Lee and C. Lidman and J. Mendez and G. J. Miller and M. Moniez and A. Mourao and H. Newberg and P. E. Nugent and R. Pain and O. Perdereau and S. Perlmutter and V. Prasad and R. Quimby and J. Raux and N. Regnault and J. Rich and G. T. Richards and P. Ruiz-Lapuente and G. Sainton and B. E. Schaefer and K. Schahmaneche and E. Smith and A. L. Spadafora and V. Stanishev and N. A. Walton and L. Wang and W. M. Wood-Vasey},
journal= {arXiv preprint arXiv:astro-ph/0404393},
year = {2016}
}
Comments
46 pages including 23 figures. Accepted for publication by AJ. For full-resolution figures see http://www.physto.se/~gabri/sn99aa/