NOAO >   Observing Info >   Approved Programs >   2014A-0215

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Proposal Information for 2014A-0215


PI: Melissa L. Graham, UC Berkeley, mgraham@lcogt.net
Address: Astronomy Department, B-20 Hearst Field Annex #3411, University of California at Berkeley, Berkeley, CA, 94720-3411, USA

CoI: David Sand, Texas Tech
CoI: Jerod Parrent, Dartmouth/LCOGT
CoI: D. Andrew Howell, UCSB/LCOGT
CoI: Stefano Valenti, UCSB/LCOGT
CoI: Paolo Mazzali, LJMU

Title: Understanding the Power Source in Type Ia Supernovae with Nebular Phase Spectroscopy

Abstract: Type Ia supernovae (SNeIa) will not be above suspicion as standard candles until their progenitor scenario and explosion mechanism are well understood. Nebular phase spectra, taken once the ejecta is optically thin, provide several unique diagnostics and are the only way to directly observe the power source in SNeIa: radioactive nickel-56. We propose to obtain 1-2 epochs of nebular phase spectroscopy for 4 bright SNeIa with GMOS. Our science goals are threefold: 1) identify the binary companion star type in the progenitor system by constraining the amount of hydrogen in the circumstellar medium, 2) explore the physical cause of the width-luminosity relation (through which SNeIa are standardized) by investigating the discrepancy between nickel mass estimates from peak luminosity and nebular spectra, and 3) evaluate the asymmetric explosion model by comparing the silicon line velocity at early times with shifts of the iron lines in nebular spectra. This proposal leverages both the wide-field low-z discovery power of recent surveys, and the new robotic capabilities of the Las Cumbres Observatory Global Telescope Network with which requisite early-time spectroscopic and photometric monitoring is done or underway. Every rare nebular spectrum provides unique constraints on SNIa explosion models; these data will advance our understanding of SNeIa and help improve their use as cosmological probes.


National Optical Astronomy Observatory, 950 North Cherry Avenue, P.O. Box 26732, Tucson, Arizona 85726, Phone: (520) 318-8000, Fax: (520) 318-8360



NOAO >   Observing Info >   Approved Programs >   2014A-0215

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