VARIABLE SODIUM ABSORPTION IN A LOW-EXTINCTION TYPE Ia SUPERNOVA

Journal Article · Thu Sep 10 04:00:00 EDT 2009 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/702/2/1157; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA)· OSTI ID:21336026

Simon, Joshua D ^[1]; Gal-Yam, Avishay ^[2]; Gnat, Orly ^[3]; Quimby, Robert M ^[4]; Ganeshalingam, Mohan; Silverman, Jeffrey M; Weidong, Li; Filippenko, Alexei V; Peek, Kathryn M. G. ^[5]; Blondin, Stephane; Patat, Ferdinando ^[6]; Wheeler, J Craig ^[7]; Kirshner, Robert P; Foley, Ryan J ^[8]; Nugent, Peter ^[9]; Vogt, Steven S ^[10]; Butler, R Paul ^[11]; Rosolowsky, Erik ^[12]; Herczeg, Gregory J ^[13]

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1. Observatories of the Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, CA 91101 (United States)
2. Benoziyo Center for Astrophysics, Faculty of Physics, Weizmann Institute of Science, 76100 Rehovot (Israel)
3. Theoretical Astrophysics, California Institute of Technology, Mail Code 130-33, 1200 E. California Boulevard, Pasadena, CA 91125 (United States)
4. Department of Astronomy, California Institute of Technology, 1200 E. California Boulevard, MS 105-24, Pasadena, CA 91125 (United States)
5. Dept. of Astronomy, Univ. of California, Berkeley, CA 94720-3411 (United States)
6. European Southern Observatory, Karl Schwarzschild Str. 2, D-85748 Garching bei Muenchen (Germany)
7. McDonald Observatory and Dept. of Astronomy, Univ. of Texas, Austin, TX 71782 (United States)
8. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
9. Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States)
10. UCO/Lick Observatory, Univ. of California, Santa Cruz, CA 95064 (United States)
11. Dept. of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Road NW, Washington, DC 20015 (United States)
12. Dept. of Physics, Univ. of British Columbia, Okanagan, BC V1V 1V7 (Canada)
13. Max-Planck-Institut fuer Extraterrestiche Physik, Postfach 1312, 85741 Garching (Germany)

Recent observations have revealed that some Type Ia supernovae exhibit narrow, time-variable Na I D absorption features. The origin of the absorbing material is controversial, but it may suggest the presence of circumstellar gas in the progenitor system prior to the explosion, with significant implications for the nature of the supernova (SN) progenitors. We present the third detection of such variable absorption, based on six epochs of high-resolution spectroscopy of the Type Ia supernova SN 2007le from the Keck I Telescope and the Hobby-Eberly Telescope. The data span a time frame of approximately three months, from 5 days before maximum light to 90 days after maximum. We find that one component of the Na I D absorption lines strengthened significantly with time, indicating a total column density increase of {approx}2.5 x 10{sup 12} cm{sup -2}. The data limit the typical timescale for the variability to be more than 2 days but less than 10 days. The changes appear to be most prominent after maximum light rather than at earlier times when the ultraviolet flux from the SN peaks. As with SN 2006X, we detect no change in the Ca II H and K absorption lines over the same time period, rendering line-of-sight effects improbable and suggesting a circumstellar origin for the absorbing material. Unlike the previous two supernovae exhibiting variable absorption, SN 2007le is not highly reddened (E {sub B-V} = 0.27 mag), also pointing toward circumstellar rather than interstellar absorption. Photoionization calculations show that the data are consistent with a dense (10{sup 7} cm{sup -3}) cloud or clouds of gas located {approx}0.1 pc (3 x 10{sup 17} cm) from the explosion. These results broadly support the single-degenerate scenario previously proposed to explain the variable absorption, with mass loss from a nondegenerate companion star responsible for providing the circumstellar gas. We also present possible evidence for narrow H{alpha} emission associated with the SN, which will require deep imaging and spectroscopy at late times to confirm.

• OSTI ID: 21336026
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 702; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
79 ASTRONOMY AND ASTROPHYSICS
CALCIUM
EXPLOSIONS
HYDROGEN
MATTER
PHOTOIONIZATION
SODIUM
SPECTROSCOPY
SUPERNOVAE
TELESCOPES
ULTRAVIOLET RADIATION