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Title: HIGH-VELOCITY LINE FORMING REGIONS IN THE TYPE Ia SUPERNOVA 2009ig

We report measurements and analysis of high-velocity (HVF) (>20,000 km s{sup –1}) and photospheric absorption features in a series of spectra of the Type Ia supernova (SN) 2009ig obtained between –14 days and +13 days with respect to the time of maximum B-band luminosity (B-max). We identify lines of Si II, Si III, S II, Ca II, and Fe II that produce both HVF and photospheric-velocity (PVF) absorption features. SN 2009ig is unusual for the large number of lines with detectable HVF in the spectra, but the light-curve parameters correspond to a slightly overluminous but unexceptional SN Ia (M{sub B} = –19.46 mag and Δm{sub 15}(B) = 0.90 mag). Similarly, the Si II λ6355 velocity at the time of B-max is greater than 'normal' for an SN Ia, but it is not extreme (v{sub Si} = 13,400 km s{sup –1}). The –14 days and –13 days spectra clearly resolve HVF from Si II λ6355 as separate absorptions from a detached line forming region. At these very early phases, detached HVF are prevalent in all lines. From –12 days to –6 days, HVF and PVF are detected simultaneously, and the two line forming regions maintain a constant separation of about 8000more » km s{sup –1}. After –6 days all absorption features are PVF. The observations of SN 2009ig provide a complete picture of the transition from HVF to PVF. Most SNe Ia show evidence for HVF from multiple lines in spectra obtained before –10 days, and we compare the spectra of SN 2009ig to observations of other SNe. We show that each of the unusual line profiles for Si II λ6355 found in early-time spectra of SNe Ia correlate to a specific phase in a common development sequence from HVF to PVF.« less
Authors:
; ; ;  [1] ; ; ;  [2] ;  [3] ;  [4] ;  [5] ;  [6] ;  [7] ;  [8] ; ;  [9] ;  [10]
  1. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
  2. University of Texas at Austin, 1 University Station C1400, Austin, TX 78712-0259 (United States)
  3. Carnegie Observatories, Las Campanas Observatory, Colina El Pino, Casilla 601 (Chile)
  4. George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy, Department of Physics and Astronomy, Texas A and M University, 4242 AMU, College Station, TX 77843 (United States)
  5. Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States)
  6. Department of Physics, University of Notre Dame, 225 Nieuwland Science Hall, Notre Dame, IN 46556 (United States)
  7. Adnet Systems, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)
  8. Las Cumbres Observatory Global Telescope Network, Goleta, CA 93117 (United States)
  9. Department of Astronomy and Astrophysics, Penn State University, 525 Davey Lab, University Park, PA 16802 (United States)
  10. Physics Department and Tsinghua Center for Astrophysics (THCA), Tsinghua University, Beijing 1,00084 (China)
Publication Date:
OSTI Identifier:
22270680
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 777; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABSORPTION SPECTRA; ASTRONOMY; ASTROPHYSICS; COMPARATIVE EVALUATIONS; LUMINOSITY; PHOTOSPHERE; SILICON IONS; SUPERNOVAE; VELOCITY; VISIBLE RADIATION