Abstract
Long duration γ-ray bursts are a rare subclass of
stripped-envelope core-collapse supernovae (SNe) that launch collimated
relativistic outflows (jets). All γ-ray-burst-associated SNe are
spectroscopically Type Ic, with broad-lines, but the fraction of
broad-lined SNe Ic harboring low-luminosity γ-ray bursts remains
largely unconstrained. Some SNe should be accompanied by off-axis
γ-ray burst jets that initially remain invisible, but then emerge
as strong radio sources (as the jets decelerate). However, this critical
prediction of the jet model for γ-ray bursts has yet to be
verified observationally. Here, we present K. G. Jansky Very Large Array
observations of 15 broad-lined SNe of Type Ic discovered by the Palomar
Transient Factory in an untargeted manner. Most of the SNe in our sample
exclude radio emission observationally similar to that of the
radio-loud, relativistic SN 1998bw. We constrain the fraction of
1998bw-like broad-lined SNe Ic to be ≲ 41 % (99.865% confidence).
Most of the events in our sample also exclude off-axis jets similar to
GRB 031203 and GRB 030329, but we cannot rule out off-axis γ-ray
bursts expanding in a low-density wind environment. Three SNe in our
sample are detected in the radio. PTF11qcj and PTF14dby show late-time
radio emission with average ejecta speeds of ≈0.3–0.4 c, on the
dividing line between relativistic and “ordinary” SNe. The
speed of PTF11cmh radio ejecta is poorly constrained. We estimate that
≲ 85 % (99.865% confidence) of the broad-lined SNe Ic in our
sample may harbor off-axis γ-ray bursts expanding in media with
densities in the range probed by this study.
Original language | English |
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Article number | 42 |
Number of pages | 18 |
Journal | The Astrophysical Journal |
Volume | 830 |
Issue number | 1 |
DOIs | |
Publication status | Published - 01 Oct 2016 |
Keywords
- gamma-ray burst: general
- radiation mechanisms: non-thermal
- supernovae: general