PI: Patrick Kelly, Stanford University, email@example.com
Address: Physics Department, 382 Via Pueblo Mall, Stanford, CA 94305, USA
CoI: Maryam Modjaz, Columbia University
CoI: David Burke, SLAC National Lab
CoI: Steve Allen, Stanford University
Title: Type IIb SN: Sensitive Probes of Pre-Explosion Stellar Evolution
Abstract: Type IIb supernovae (SN) are special among core-collapse explosions, because the masses of their progenitors' outer hydrogen envelopes must fall within a narrow range (M<~0.4M_\odot) to explain their evolving spectra. This strong constraint makes the observed SN IIb rate relative to other core-collapse species a sensitive test of stellar evolution models. In fact, recent theoretical models favor rates approximately four times smaller than the observed SN IIb rate, plausibly reflecting shortcomings in our understanding of the physics of binary evolution or wind-driven mass loss. We have separately found, from SDSS imaging, that the galactic environments near SN IIb explosion sites are dramatically bluer (~ 0.75 mag in \it u'-g') than those of even close spectroscopic cousins, SN Ib and SN II. We propose measurements of oxygen abundances, star formation rates, and stellar population ages from optical spectra at 20 SN IIb sites that will help constrain the physics of binary interaction, wind-driven mass loss rates, the binary fraction, and progenitor masses, aided by comparisons with recent measurements of SN Ib and SN Ic environments. Improved understanding of core-collapse progenitors is essential to better constrain the physics of core-collapse explosions, calibrate SN as star formation indicators, and potentially uncover any changes in the IMF.
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