The Many Facets of Cosmic Explosions
by Alicia Margarita Soderberg
- Number of Pages: 264
- ISBN-10: 1581123779
- ISBN-13: 9781581123777
- Publisher:
Dissertation.com
- Year: 2007
- Category:
Physics & Chemistry,
View First 25 Pages:
(free download) Synopsis
Over the past few years, long-duration gamma-ray bursts (GRBs),
including the subclass of X-ray flashes (XRFs), have been revealed to
be a rare variety of Type Ibc supernova (SN Ibc). While all these
events result from the death of massive stars, the electromagnetic
luminosities of GRBs and XRFs exceed those of ordinary Type Ibc SNe by
many orders of magnitude. The observed diversity of stellar death
corresponds to large variations in the energy, velocity, and geometry
of the explosion ejecta. Using multi-wavelength (radio, optical,
X-ray) observations of the nearest GRBs, XRFs, and SNe Ibc, I show
that GRBs and XRFs couple at least 1048 erg to relativistic
material while SNe Ibc typically couple less than 1048 erg to their
fastest (albeit non-relativistic) outflows. Specifically, I find that
less than 3 percent of local SNe Ibc show any evidence for association with
a GRB or XRF. Interestingly, this dichotomy is not echoed by the
properties of their optical SN emission, dominated by the radioactive
decay of Nickel-56; I find that GRBs, XRFs, and SNe Ibc show
significant overlap in their optical peak luminosity and photospheric
velocities. Recently, I identified a new class of GRBs and XRFs that
are under-luminous in comparison with the statistical sample of GRBs.
Owing to their faint high-energy emission, these sub-energetic bursts
are only detectable nearby (z < 0.1) and are likely 10 times more
common than cosmological GRBs. In comparison with local SNe Ibc and
typical GRBs/XRFs, these explosions are intermediate in terms of both
volumetric rate and energetics. Yet the essential physical process
that causes a dying star to produce a GRB, XRF, or sub-energetic
burst, and not just a SN, remains a crucial open question. Progress
requires a detailed understanding of ordinary SNe Ibc which will be
facilitated with the launch of wide-field optical surveys in the near
future.
About the Author
Alicia Margarita Soderberg received her Bachelor of
Science degree in Physics and Mathematics (double major) at Bates
College in 2000. Her senior thesis focused on detection rate
efficiency of optical supernova searches. As a National Science
Foundation Graduate Research Fellow at Churchill College, she
completed Part Three of the Mathematical Tripos at Cambridge
University (2001) and received a Certificate of Advanced Study in
Applied Mathematics. Working with Professor Shrinivas R. Kulkarni on
the observed diversity of cosmic explosions, the author received a
Ph.D. in Astrophysics at the California Institute of Technology in
2007 where she was a NASA Graduate Research Fellow. She currently
holds a Hubble Postdoctoral Fellowship with a joint appointment at
Princeton University and the Observatories of the Carnegie Institution
of Washington.