Toward an Understanding of the Progenitors of Gamma-Ray Bursts

black hole;cosmology;gravitational waves;neutrinos;neutron stars;novae;population III;stars;Type Ic supernova

Bloom, Joshua Simon ; Kulkarni, Shrinivas R.

University:California Institute of Technology

Department:Physics, Mathematics and Astronomy

关键词: black hole;    cosmology;    gravitational waves;    neutrinos;    neutron stars;    novae;    population III;    stars;    Type Ic supernova;   

Others  :  https://thesis.library.caltech.edu/38/1/book_main_old.pdf

美国|英语

来源: Caltech THESIS

【 摘 要 】

The various possibilities for the origin ("progenitors") of gamma-ray bursts (GRBs) manifest in differing observable properties. Through deep spectroscopic and high-resolution imaging observations of some GRB hosts, I demonstrate that well-localized long-duration GRBs are connected with otherwise normal star-forming galaxies at moderate redshifts of order unity. Using high-mass binary stellar population synthesis models, I quantify the expected spatial extent around galaxies of coalescing neutron stars, one of the leading contenders for GRB progenitors. I then test this scenario by examining the offset distribution of GRBs about their apparent hosts making extensive use of ground-based optical data from Keck and Palomar and space-based imaging from the Hubble Space Telescope.The offset distribution appears to be inconsistent with the coalescing neutron star binary hypothesis (and, similarly, black-hole-neutron star coalescences); instead, the distribution is statistically consistent with a population of progenitors that closely traces the ultra-violet light of galaxies.This is naturally explained by bursts which originate from the collapse of massive stars ("collapsars").This claim is further supported by the unambiguous detections of intermediate-time (approximately three weeks after the bursts) emission "bumps" which appear substantially more red than the afterglows themselves. I claim that these bumps could originate from supernovae that occur at approximately the same time as the associated GRB; if true, GRB 980326 and GRB 011121 provide strong observational evidence connecting cosmological GRBs to high-redshift supernovae and implicate massive stars as the progenitors of at least some long-duration GRBs. Regardless of the true physical origin of these bumps, it appears that all viable alternative models of these bumps (such as dust scattering of the afterglow light) require a substantial amount of circumburst matter that is distributed as a wind-stratified medium; this too, implicates massive stars.Also suggested herein are some future observations which could further solidify or refute the supernova claim.In addition to the observational and modeling work, I also constructed the Jacobs Camera (JCAM), a dual-beam optical camera for the Palomar 200-inch Telescope designed to follow-up rapid GRB localizations.