Title: The rest-frame ultraviolet spectra of GRBs from massive rapidly rotating stellar progenitors
Authors: Robinson, Peter ×
Perna, Rosalba
Lazzati, Davide
van Marle, Allard Jan #
Issue Date: Jan-2010
Publisher: Priestley and Weale
Series Title: Monthly Notices of the Royal Astronomical Society vol:401 pages:88-98
Article number: doi:10.1111/j.1365-2966.2009.15672.x
Abstract: The properties of a massive star prior to its final explosion are imprinted in the circumstellar
medium (CSM) created by its wind and termination shock. We perform a detailed, comprehensive
calculation of the time-variable and angle-dependent transmission spectra of an
average-luminosity gamma-ray burst (GRB) which explodes in the CSM structure produced
by the collapse of a 20M, rapidly rotating, Z =0.001 progenitor star.We study both the case
in which metals are initially in the gaseous phase and the situation in which they are heavily
depleted into dust.We find that high-velocity lines from low-ionization states of silicon, carbon
and iron are initially present in the spectrum only if the metals are heavily depleted into dust
prior to the GRB explosion. However, such lines disappear on time-scales of a fraction of a
second for a burst observed on-axis, and of a few seconds for a burst seen at high latitude,
making their observation virtually impossible. Rest-frame lines produced in the termination
shock are instead clearly visible in all conditions. We conclude that time-resolved, early-time
spectroscopy is not a promising way in which the properties of the GRB progenitor wind can
be routinely studied. Previous detections of high-velocity features in GRB ultraviolet spectra
must have been either due to a superposition of a physically unrelated absorber or due to a
progenitor star with very unusual properties.
ISSN: 0035-8711
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Plasma-astrophysics Section
× corresponding author
# (joint) last author

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