NOAO >   Observing Info >   Approved Programs >   2010A-0415

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Proposal Information for 2010A-0415


PI: Nathan Smith, UC Berkeley, nathans@astro.berkeley.edu
Address: Astronomy Department, 610 Campbell Hall, Berkeley, CA 94720, United States

CoI: Weidong Li, UC Berkeley
CoI: Alex Filippenko, UC Berkeley

Title: Late-time Photometry of Recent Optical Transients

Abstract: Two extragalactic transient sources discovered in 2008 (named SN 2008S and NGC 300-OT) stirred interest and controversy in the late evolution of stars with initial masses of 8-10 M_\odot, near the boundary between supernovae (SNe) and white dwarf progenitors. While the outbursts resembled known eruptions of luminous blue variables (LBVs), the progenitors were dust-obscured and had low luminosity compared to objects like Eta Carinae. Moreover, they had peculiar spectral properties. The two leading hypothesis are (1) non-terminal eruptions similar to LBVs, but occurring at lower initial masses than previously recognized (10-20 M_\odot), or (2) electron capture SNe from stars with initial mass 8-10 M_\odot. Two more transients discovered in 2009 (named SN 2009ip and UCG 2773-OT) added to the mystery because they have LBV-like variability over the last 5-10 years before the peaks of their outburst, but they share some spectral similarity with the mysterious 2008 transients. The LBV eruption hypothesis predicts that the star survives, whereas the electron capture SN hypothesis predicts a luminosity and fading rate consistent with a low mass of ^56Ni at late times 1-2 yr after explosion. We aim to choose between these predictions by obtaining late-time RIJHK measurements (or limits) of the objects.


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