Transcript Document

Part I
Properties and Origins of Long GRBs
The Origin of Long-Period GRBs
Knicole Colón
High Energy Astrophysics
March 5, 2008
Long-Period GRBs
•Standard total energy > 1051 ergs
•Bursts last for t > 2 sec (longest
known has t~2000 sec)
•Have associated X-ray, optical, and
radio afterglows
•XRFs are similar to long GRBs but
extend to softer, fainter regime
(exact connection is still uncertain)
(Aurore Simonnet SSU NASA E/PO)
Long-Period GRBs
•Located near center of
SFRs in host galaxies at
< z > = 2.3 (from Swift
observations)
•Hosts are late-type, mostly
irregular, dwarf galaxies
•Some are found to be
associated with luminous
core-collapse Type Ic SNe
(Gehrels & Cannizzo 2007)
Swift Observations
•Swift carries 3 instruments:
–Burst Alert Telescope (BAT)
–X-Ray Telescope (XRT)
–UV-Optical Telescope (UVOT)
•As of March 4, 2008, 299 GRBs
have been detected by Swift
•82 GRBs have both XRT and
UVOT detections
•18 also have radio detections
(Data from http://swift.gsfc.nasa.gov/docs/swift/swiftsc.html)
BAT Light Curves
(From http://swift.gsfc.nasa.gov/docs/swift/swiftsc.html)
Long GRB X-Ray Afterglows
(Gehrels 2008)
A Canonical X-Ray Afterglow Light Curve
(Zhang 2007)
Optical Afterglows
(Price et al. 2003)
Radio Afterglows
Radio
X-ray
(Pihlström et al. 2007)
Optical
(Willingale et al. 2004)
How do these afterglows relate to the origins
of long duration GRBs?
What else does the GRB-SNe relation tell us
about the progenitors of these GRBs?
Single Stars as Progenitors
•Long GRBs associated with core collapse of
massive Wolf-Rayet stars
•Collapse yields stellar-size BHs or rapidly
spinning, highly magnetized neutron stars
•Infalling material forms a torus around
central compact object
•Subsequent accretion of material in the torus
fuels gamma-ray jet
•Internal shocks within gamma-ray jet and
external shocks with residual wind material
result in GRBs (or XRFs) and the afterglows
(**Note: the Cannon Ball Model will not be taken into account here**)
Collapsar (or Fireball) Model
(From www.oamp.fr)
Evidence for GRB-SNe Connection
•Four direct observations of
SNe associated with GRBs
•All SNe are confirmed as
Type Ic (have no/weak H,
He, Si II lines & broad
spectral lines)
•Rebrightenings detected
during late stages of
afterglows indicate SN
contribution
•Most host galaxies have
intense SFR
GRB050525A
(Della Valle 2008)
The GRB-SNe Connection
GRB-SN/HN
XRF-SN
Non-GRB HN
Normal SN
(Nomoto et al. 2007)
Different Progenitors?
GRB-HNe
XRF-SNe
(Nomoto et al. 2007)
Non-SN GRB
Results from Numerical Models
GRB-HNe
Non-GRB
HNe/SNe
XRF-SN
Normal SN
(Nomoto et al. 2007)
A Different Single Star Model
(Yoon et al. 2008)
(Massive) Binary Progenitors
•Evolution of massive binaries
(initial mass > 20 solar masses) can
result in a long GRB
•Primary compact object formed
works to tidally spin-up core of
secondary star (allowing formation
of torus after secondary collapses)
•After the GRB, a binary compact
system of NS-NS, NS-BH, or BHBH can remain
(Davies et al. 2007)
Other Binary Models
Fryer et al. (2007) discussed the following possible progenitors:
•Classic Binary: ejection of H envelope via mass transfer
•Tidal Binary: similar to Davies et al. (2007) model
•Brown Merger: ~equal mass stars merge in second commonenvelope phase to form single massive star with ~no H/He
•Explosive Ejection: secondary accretes onto He core of
primary, spinning up the core and also producing explosions in
the core that eject He shell and H envelope
•He Merger: one star evolves into NS or BH and then merges
with companion (He-rich) star
•He case C: similar to above, but merger occurs after He burning
•Cluster: enhanced mergers that require cluster interactions?
(not looked at in detail yet…)
(Fryer et al. 2007)
Conclusions
•The most likely progenitor of long-period GRBs
is…not determined!
•Problems exist with every model!
•Many factors to consider makes solving this
rather difficult (metallicity, initial mass, mass-loss
rate, rotational velocity, angular momentum, host
galaxies, properties of afterglows, etc.)
•There is no unified model for GRBs yet…
(and who knows if there will ever be one)
References
Davies, M. B., Levan, A. J., Larsson, J., King, A. R., & Fruchter, A. S. 2007, in AIP Conf. Proc. 906, Gamma-Ray
Bursts: Prospects for GLAST, ed. M. Axelsson, & F. Ryde, 69
Della Valle, M. 2008, in AIP Conf. Proc. 966, Relativistic Astrophysics – 4th Italian-Sino Workshop, ed. C. L.
Bianco, & S.-S. Xue, 31
Fryer, C. L., et al. 2007, PASP, 119, 1211
Gehrels, N. 2008, in AIP Conf. Proc. 968, Astrophysics of Compact Objects, International Conference on
Astrophysics of Compact Objects, ed. Y.-F. Yuan, X.-D. Li, & D. Lai, 3
Gehrels, N., & Cannizzo, J. K. 2007, in AIP Conf. Proc. 937, Supernova 1987A: 20 Years After, ed. S. Immler, K.
Weiler, & R. McCray, 451
Kaneko, Y., et al. 2007, ApJ, 654, 385
Lapi, A., Kawakatu, N., Bosnjak, Z., Celotti, A., Bressan, A., Granato, G. L., & Danese, L. 2008, MNRAS, in press
(astro-ph/0802.0787)
Nomoto, K., Tominaga, N., Tanaka, M., Maeda, K., Suzuki, T., Deng, J. S., & Mazzali, P. A. 2007, Il Nuovo
Cimento, in press (astro-ph/0702472)
Pihlström, Y. M., Taylor, G. B., Granot, J., & Doeleman, S. 2007, ApJ, 664, 411
Price, P. A., et al. 2003, Nature, 423, 844
Willingale, R., Osborne, J. P., O’Brien, P. T., Ward, M. J., Levan, A., & Page., K. L. 2004, MNRAS, 349, 31
Yoon, S.-C., Langer, N., Cantiello, M., Woosley, S. E., & Glatzmaier, G. A. 2008, in IAU Symp. 250, Massive
Stars as Cosmic Engines, ed. F. Bresolin, P. A. Crowther, & J. Puls, in press (astro-ph/0801.4362)
Zhang, B. 2007, CJAA, 7, 1
Part II
Optical Afterglows of Long GRBs
Optical Afterglows of Long GRBs &
The Naked-Eye GRB 080319B
Knicole Colón
High Energy Astrophysics
April 30, 2008
Image Credit: NASA, ESA, N. Tanvir (University of Leicester), and A. Fruchter
A Brief Review of Long GRBs
•Total E > 1051 ergs
•Duration > 2 sec (longest
known has t~2000 s)
•Have associated X-ray, optical,
and radio afterglows
•Located near center of SFRs in
mostly late-type, irregular,
dwarf galaxies
•Single Star Progenitors: Collapsar/Fireball Model
•Definite associations with luminous core-collapse Type Ic SNe
•Massive Binary Progenitors: Several Models!
•No other conclusions…
(Gehrels & Cannizzo 2007)
Optical Afterglows
•Synchrotron emission resulting
from a relativistic expanding jet
colliding with ambient medium
•Continuous transfer of energy to
swept-up medium and shock front
physics (reverse/forward) yield
power-law decaying curves
•Two components:
GRB050525A
–counterpart emission tracks
prompt gamma-rays
–afterglow emission starts during
prompt phase or shortly after and
dims progressively for hours to days
•Light curves contaminated by host
galaxy light, SN bumps
(Della Valle 2008)
“Early” Afterglows
•At early times (30-104 s after trigger), behavior is different in different bursts
•Angular structure of relativistic outflow and variations in observer location
may account for diversity manifested by early light curves
(Panaitescu & Vestrand 2008)
“Late” Afterglows
Late time behavior includes:
1. Jet Breaks (sudden increase
of the fading rate due to jet
geometry, typically few
days after initial GRB)
3. SN bumps
2. Flares
(Dai et al. 2008)
Overall Afterglow Behavior
•Narrow/Clustered bimodal
distribution of optical
afterglow luminosity
–Intrinsic?
–60% of bursts are
absorbed by large amount
(> 1.5 mag) of gray dust?
–Clear separation between
luminous and subluminous families
(Nardini et al. 2008)
Knowing all of this about optical afterglows…
where does GRB 080319B fit in?
The Naked-Eye GRB 080319B
Swift’s XRT & UVOT Images
•GRB duration ~ 60 sec
•Gamma-Ray E ~ 1054 erg
•V ~ 5.6 mag (Mpeak ~ -38.0)
•z = 0.937 (relatively nearby)
•At 10 kpc, would peak at V ~ -28.5
Image Credit: NASA/Swift/Stefan Immler, et al.
•Highest-fluence event & isotropicequivalent energy release ever recorded
(Bloom et al. 2008)
Animation Credit: Pi of the Sky
Brightest Optical Afterglow Ever!
•Fast-rising afterglow
•“Early” afterglow
decays extremely rapidly
(drops from 5th to 21st
mag in < 1 day)
•2 short-timescale flares
•Smooth AG overall
(note that many GRBs
show significant
jaggedness)
(Bloom et al. 2008)
•Rather unremarkable at late times
•Similar to 3 other “ultra-luminous”
GRBs
•“Late” time afterglow
•No jet break seen
– Occurred extremely early (within
first 100 sec)?
– Early rapid decay reverse-shock
dominated, & jet break hidden in
transition region around 103 sec?
•Second scenario: brought on by
extreme level of collimation
(Bloom et al. 2008)
Fits “Cannon Ball” Model…?
•Ordinary GRB
produced by jet of
highly relativistic
plasmoids (CBs)
ejected in corecollapse SN
•Viewed very near
axis of CB-emission
•Generated by
“typical” GRB SNe,
SN1998bw? Or mostluminous one
detected, SN2006gy?
(Dado et al. 2008)
Results (?)
•Bloom et al. (2008) conclude the extreme brightness is
related to macroscopic parameters of central engine
(primarily collimation angle… maybe also Mejecta, initial
Lorentz factor, circumburst medium?) rather than extrema in
shock parameters
•Similarly, Dado et al. (2008) claim “cannon ball” model
fits… (but this model is not as widely accepted by GRB
community – “fire ball” model dominates)
•Also claim AG properties fit those of other AG/GRBs
associated with “typical” SN (remains to be seen…)
•Final Fun Fact: disregarding absorption, this GRB would be
observable even if placed at the epoch of reionization!
References
Bloom, J.S., et al. 2008, astro-ph/0803.3215
Dado, S., Dar, A., & De Rujula, A. 2008, astro-ph/0804.0621
Dai, X., et al. 2007, astro-ph/0712.2239
Della Valle, M. 2008, in AIP Conf. Proc. 966, Relativistic Astrophysics – 4th ItalianSino Workshop, ed. C. L. Bianco, & S.-S. Xue, 31
Gehrels, N., & Cannizzo, J. K. 2007, in AIP Conf. Proc. 937, Supernova 1987A: 20
Years After, ed. S. Immler, K. Weiler, & R. McCray, 451
Nardini, M., Ghisellini, G., & Ghirlanda, G. 2008, MNRAS, 386, L87
Panaitescu, A., & Vestrand, W. T. 2008, submitted to MNRAS, astro-ph/0803.1872
Uemura, M., et al. 2003, astro-ph/0306396