THE BROAD-LINED Type Ic SN 2012ap AND THE NATURE OF RELATIVISTIC SUPERNOVAE LACKING A GAMMA-RAY BURST DETECTION
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
- Department of Physics and Astronomy, Dartmouth College, 6127 Wilder Laboratory, Hanover, NH 03755 (United States)
- Astrophysics Research Institute, Liverpool John Moores University, Liverpool L3 5RF (United Kingdom)
- Department of Astronomy, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502 (Japan)
- Astrophysics Science Division, NASA Goddard Space Flight Center, Mail Code 661, Greenbelt, MD 20771 (United States)
- University of Texas at Austin, 1 University Station C1400, Austin, TX 78712-0259 (United States)
- Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States)
- Southern African Large Telescope, P.O. Box 9, Observatory 7935, Cape Town (South Africa)
- Hiroshima Astrophysical Science Center, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8526 (Japan)
- Subaru Telescope, National Astronomical Observatory of Japan, Hilo, HI 96720 (United States)
- Carnegie Observatories, Las Campanas Observatory, Colina El Pino, Casilla 601 (Chile)
We present ultraviolet, optical, and near-infrared observations of SN 2012ap, a broad-lined Type Ic supernova in the galaxy NGC 1729 that produced a relativistic and rapidly decelerating outflow without a gamma-ray burst signature. Photometry and spectroscopy follow the flux evolution from –13 to +272 days past the B-band maximum of –17.4 ± 0.5 mag. The spectra are dominated by Fe II, O I, and Ca II absorption lines at ejecta velocities of v ≈ 20,000 km s{sup –1} that change slowly over time. Other spectral absorption lines are consistent with contributions from photospheric He I, and hydrogen may also be present at higher velocities (v ≳ 27,000 km s{sup –1}). We use these observations to estimate explosion properties and derive a total ejecta mass of ∼2.7 M {sub ☉}, a kinetic energy of ∼1.0 × 10{sup 52} erg, and a {sup 56}Ni mass of 0.1-0.2 M {sub ☉}. Nebular spectra (t > 200 days) exhibit an asymmetric double-peaked [O I] λλ6300, 6364 emission profile that we associate with absorption in the supernova interior, although toroidal ejecta geometry is an alternative explanation. SN 2012ap joins SN 2009bb as another exceptional supernova that shows evidence for a central engine (e.g., black hole accretion or magnetar) capable of launching a non-negligible portion of ejecta to relativistic velocities without a coincident gamma-ray burst detection. Defining attributes of their progenitor systems may be related to notable observed properties including environmental metallicities of Z ≳ Z {sub ☉}, moderate to high levels of host galaxy extinction (E(B – V) > 0.4 mag), detection of high-velocity helium at early epochs, and a high relative flux ratio of [Ca II]/[O I] >1 at nebular epochs. These events support the notion that jet activity at various energy scales may be present in a wide range of supernovae.
- OSTI ID:
- 22364468
- Journal Information:
- Astrophysical Journal, Vol. 799, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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