PS1-10bzj: A Fast, Hydrogen-Poor Superluminous Supernova in a Metal Poor
  Host Galaxy
  We present observations and analysis of PS1-10bzj, a superluminous supernova
(SLSN) discovered in the Pan-STARRS Medium Deep Survey at a redshift z = 0.650.
Spectroscopically, PS1-10bzj is similar to the hydrogen-poor SLSNe 2005ap and
SCP 06F6, though with a steeper rise and lower peak luminosity (M_bol = -21.4
mag) than previous events. We construct a bolometric light curve, and show that
while PS1-10bzj's energetics were less extreme than previous events, its
luminosity still cannot be explained by radioactive nickel decay alone. We
explore both a magnetar spin-down and circumstellar interaction scenario and
find that either can fit the data. PS1-10bzj is located in the Extended Chandra
Deep Field South and the host galaxy is imaged in a number of surveys,
including with the Hubble Space Telescope. The host is a compact dwarf galaxy
(M_B ~ -18 mag, diameter < 800 pc), with a low stellar mass (M_* ~ 2.4 * 10^7
M_sun), young stellar population (\tau_* ~ 5 Myr), and a star formation rate of
~ 2-3 M_sun/yr. The specific star formation rate is the highest seen in a SLSN
host so far (~ 100 Gyr^{-1}). We detect the [O III]\lambda 4363 line, and find
a low metallicity: 12+(O/H) = 7.8 +/- 0.2 (~ 0.1 Z_sun). Together, this
indicates that at least some of the progenitors of SLSNe come from young,
low-metallicity populations.
