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Transcript
GRB Progenitors and their
environments
Chris Fryer (LANL, UA &
UNM)
 The Wide World of GRB Progenitors
 Understanding Massive Star Environments
 Examples from Supernovae
The Wide World of
GRB progenitors
• Because GRBs and
Hypernovae are
relatively rare, exotic
scenarios for
progenitors remain
viable.
• Although this talk is
focused on Black Hole
Accretion Disk
progenitors, many of
the characteristics of
NS progenitors are
similar.
Short Duration Bursts:
• Merger of 2 compact objects: NS/NS (do they form BHs?), BH/NS
(many do not produce disk), BH/WD, NS/WD (disk too wide to produce
short bursts?).
• The distribution of the debris from the merger will play a role in timing.
But the compact merger likely travels beyond the star formation site
(stellar mass ejection unimportant in observed properties).
Long Duration Bursts:
• Collapsar Models: Can be produced in single and binary stars. Single
star models require high rotation with minimal angular momentum loss
in winds (perhaps rotationally-induced mixing can help?). Binary
systems are used to i) remove the hydrogen envelope without losing
angular momentum, ii) spinning up the stellar core (through a merger or
orbital coupling)
• Helium-merger models (the merger of a star with a compact object –
who named these?): inspiral of compact object both ejects outer layers
and spins up the soon-to-be accreting material.
• Environments surrounding both models tightly tied to stellar
winds/binary mass ejection.
There are a wide
set of
progenitors for
each of these
models. Let’s
review the Hemerger
progenitors as
an example:
Scenario 1 – CE
evolution.
Kick Collision: Fryer,
Woosley & Hartmann
(1998) argued this
progenitor is rare.
In both cases, mass
ejection from both
common envelope
phases and wind
phases are important,
but they have very
different
characteristics.
Mass
ejection
from
Common
Envelope
Phase:
We are now
able to model
common
envelope
evolution,
producing
detailed
density
structures
Diehl, Passey, et al.
These
calculations will
also constrain
progenitors by
helping us
understand the
inspiral in a
common
envelope
calculation.
Mass ejection
from winds,
and more
importantly,
luminous
blue variable
outbursts.
Mass loss is
far from
constant!
Putting it all together: providing detailed
density profiles to model GRB jets.
Putting the time variable wind
profiles will produce noisy
density profiles, presumably
with clumps.
Multi-dimensional profiles are
ultimately necessary, but are doable.
SN 2008D/XRO 08019
• While observing SN
2007uy, Swift discovered an
X-ray outburst lasting ~600s.
• Subsequent observations
classify this supernova as a
type Ib.
• Many models of initial X-ray
outburst, most focusing on
shock breakout.
• Frey et al., modeling shock
breakout, could match the
duration/shape with binary
CE ejection, but not the
luminosity – is it a shock
hitting an LBV outburst?
Cassiopeia A: A well constrained core-collapse SN
• Cas A is a well studied remnant,
with constraints on yield,
explosion energy, and ejecta
mass. Recently, an integrated
spectrum has been observed
through light echoes. More data
expected (NuSTAR will map the
44Ti production).
• Progenitor likely to be from a
binary – CE needed to eject most
of the hydrogen in a 16 solar
mass star.
• Dwek & Arendt (2008) argued
that a burst of X-ray photons was
required to explain the IR
hotspots. Fryer et al. (2010)
argue that LBV shells are
required to match this data.
Summary
• For compact mergers, detailed predictions
of the accretion rate onto the disk might be
doable – timing in the engine.
• For massive star long-duration burst
progenitors, engine perturbations will be
difficult to predict. But we can differentiate
the surrounding environment – ongoing
work on both CE and wind/LBV phases.
Supernovae may provide hints.
Understanding
progenitors:
observing
massive star
binaries:
Kiminki et al.
(2007),
Kobulnicky &
Fryer (2007)