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Spectroscopic Observations and Analysis of the Unusual Type Ia SN 1999ac | | The Supernova Cosmology Project: G. Garavini
; G. Aldering
; A. Amadon
; R. Amanullah
; P. Astier
; C. Balland
; G. Blanc
; A. Conley
; T. Dahlen
; S. E. Deustua
; R. Ellis S. Fabbro
; V. Fadeyev
; X. Fan
; G. Folatelli
; B. Frye
; E. L. Gates
; R. Gibbons
; G. Goldhaber
; B. Goldman
; A. Goobar
; D. E. Groom
; J. Haissinski
; D. Hardin
; I. Hook
; D. A. Howell
; S. Kent
; A. G. Kim
; R. A. Knop
; M. Kowalski
; N. Kuznetsova
; B. C. Lee C. Lidman
; J. Mendez
; G. J. Miller
; M. Moniez
; M. Mouchet
; A. Mourao
; H. Newberg
; S. Nobili
; P. E. Nugent
; R. Pain
; O. Perdereau
; S. Perlmutter
; R. Quimby
; N. Regnault
; J. Rich
; G. T. Richards
; P. Ruiz-Lapuente
; B. E. Schaefer
; K. Schahmaneche
; E. Smith
; A. L. Spadafora
; V. Stanishev
; R. C. Thomas
; N. A. Walton
; L. Wang
; W. M. Wood-Vasey
; | | Date: |
12 Jul 2005 | | Subject: | astro-ph | | Abstract: | We present optical spectra of the peculiar Type Ia supernova (SN Ia) 1999ac. The data extend from -15 to +42 days with respect to B-band maximum and reveal an event that is unusual in several respects. Prior to B-band maximum, the spectra resemble those of SN 1999aa, a slowly declining event, but possess stronger SiII and CaII signatures (more characteristic of a spectroscopically normal SN). Spectra after B-band maximum appear more normal. The expansion velocities inferred from the Iron lines appear to be lower than average; whereas, the expansion velocity inferred from Calcium H and K are higher than average. The expansion velocities inferred from SiII are among the slowest ever observed, though SN 1999ac is not particularly dim. The analysis of the parameters v_10, R(SiII), dv(SiII)/dt, and d_m15 further underlines the unique characteristics of SN 1999ac. We find convincing evidence of CII 6580 in the day -15 spectrum with ejection velocity v > 16,000 km/s, but this signature disappears by day -9. This rapid evolution at early times highlights the importance of extremely early-time spectroscopy. | | Source: | arXiv, astro-ph/0507288 | | Services: | Forum | Review | PDF | Favorites | |
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