학술논문
Spectroscopic Observations and Analysis of the Unusual Type Ia SN 1999ac
Document Type
Working Paper
Author
Project, The Supernova Cosmology; Garavini, G.; Aldering, G.; Amadon, A.; Amanullah, R.; Astier, P.; Balland, C.; Blanc, G.; Conley, A.; Dahlen, T.; Deustua, S. E.; Fabbro, R. Ellis S.; Fadeyev, V.; Fan, X.; Folatelli, G.; Frye, B.; Gates, E. L.; Gibbons, R.; Goldhaber, G.; Goldman, B.; Goobar, A.; Groom, D. E.; Haissinski, J.; Hardin, D.; Hook, I.; Howell, D. A.; Kent, S.; Kim, A. G.; Knop, R. A.; Kowalski, M.; Kuznetsova, N.; Lidman, B. C. Lee C.; Mendez, J.; Miller, G. J.; Moniez, M.; Mouchet, M.; Mourao, A.; Newberg, H.; Nobili, S.; Nugent, P. E.; Pain, R.; Perdereau, O.; Perlmutter, S.; Quimby, R.; Regnault, N.; Rich, J.; Richards, G. T.; Ruiz-Lapuente, P.; Schaefer, B. E.; Schahmaneche, K.; Smith, E.; Spadafora, A. L.; Stanishev, V.; Thomas, R. C.; Walton, N. A.; Wang, L.; Wood-Vasey, W. M.
Source
Astron.J.130:2278-2292,2005
Subject
Language
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.
Comment: 40 pages, 24 figures, accepted for publication in The Astronomical Journal
Comment: 40 pages, 24 figures, accepted for publication in The Astronomical Journal