Transcript A Model for Short Gamma-Ray Bursts with Extended Emission

Observable Signatures of the
Accretion-Induced Collapse of
White Dwarfs
Brian Metzger, UC Berkeley
w/ Tony Piro, Eliot Quataert, Niccolo Bucciantini (Berkeley)
& Todd Thompson (Ohio State)
OUTLINE
WD
1) Thermal Optical Transients
(Metzger, Piro & Quataert 2008,09)
2) Connection to Short GRBs
NS
(Metzger, Quataert & Thompson 2008)
Accretion-Induced Collapse (AIC)
e.g. Miyaji+80, Nomoto & Kondo 91; Canal+92; Gutierrez+05
• “Failed” Thermonuclear Explosion (otherwise Type Ia SN)
• Paths to AIC:
T = 0.21 min
Yoon+07
1) Non-Degenerate Binary
Accretion: electron captures
faster than nuclear burning
(e.g. O-Ne WDs)
2) Double White Dwarf Merger:
 Super-Chandrasekhar
WD + Remnant Torus
(Candidates: SPY Survey;
Napiwotzki+02)
•
AIC Rate (Very Uncertain):
~10-6-10-4 yr-1 galaxy-1
T = 0.86 min
T = 1.7 min

Collapse to a Proto-Neutron Star
Weak Explosion ~1050 ergs, MNi < 10-3 M
(Woosley & Baron 92; Fryer+99; Dessart+06)
WD
But with Rapid Rotation….
R ~ 103 km
1) Gravitational Wave Source?
(Fryer+02; Ott 08)
2) ~ 0.1 M, ~ 30 km Disk around NS
(Michel 87; Bailyn & Grindlay 90)
T = 59 ms post bounce
NS
Dessart+06
R ~ 30-100 km
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
Disk Accretion and Viscous Spreading
Metzger, Piro, & Quataert 2008a,b
• 1D (radial) Time-Dependent Disk Evolution
 Solve for Disk Spreading (alpha viscosity), Heating & Cooling
 Evolve Composition (n/p) via Weak Interactions
• Neutrino Cooled (Thin Disk)
Initial (t = 0)
ÝIN
M
NS
• Degenerate Electrons 
R ~ 100 km
M ~ 0.1 M
T ~ 5 MeV
Neutron-Rich Equilibrium
e  p   e  n
e   n  e  p




n
} p ~ 10
Disk Accretion and Viscous Spreading
Metzger, Piro, & Quataert 2008a,b
• 1D (radial) Time-Dependent Disk Evolution
 Solve for Disk Spreading (alpha viscosity), Heating & Cooling
 Evolve Composition (n/p) via Weak Interactions
• Neutrino Cooled (Thin Disk)
Initial (t = 0)
ÝIN
M
NS
R ~ 100 km
M ~ 0.1 M
T ~ 5 MeV
• Degenerate Electrons 
Neutron-Rich Equilibrium
e  p   e  n
e   n  e  p

Final (t ~ 1 s)
ÝIN
M

R ~ 1000km
M ~ 0.03 M
NS
n
} p ~ 10
• Inefficient Cooling (Thick Disk)
 Lifted
• Degeneracy
• n/p “Freezes Out”
T ~ 1 MeV

• Alpha Particles Form
• Disk Blown Apart
Disk Outflows and Nucleosynthesis
• -Particle Formation: ENuc > EBind
• Thick Disks only Marginally Bound
}  Powerful Winds
(Narayan & Yi 94; Blandford & Begelman 99)
• Expansion of Hot, Dense Ejecta  Heavy Element Synthesis
•
Critical Quantity:
Neutron-Proton Ratio in Disk @ Freeze Out
e.g. Se, Br, Ag
e.g. Se, Br, Ag
1) BH Accretion
Neutron-Rich Freeze Out
(with n/p ~ 2-3)
 Rare Heavy Elements
BH
(NS-NS / NS-BH Mergers)
56Ni
e
e
(Metzger, Piro, & Quataert 08a,b)
e
V ~ 0.1 c
2) NS Accretion
 e  n  e  p
(AIC)
NS
V ~ 0.1 c
e

Neutrino Irradiation
e

56Ni
 n/p ~ 1
 56Ni
Optical Transients from AIC
Metzger, Piro, & Quataert 2009
• 56Ni  56Co +  heats ejecta
• Photons diffuse out as ejecta expands
 M total 1/ 2 v 1/ 2
Tpeak ~ 1 day  2

 
10 M  0.1 c

MNi ~ 10-2 M
Mtotal ~ 2 x
-2 M
Ni /10
Fe-Rich
Spectra

1) Optical Transient Surveys

Palomar Transient Factory &
PanSTARRs MDS: ~1 yr-1 (RAIC/10-2 RIa)
LSST: ~ 600 yr-1 (RAIC/10-2 RIa)
Larger Mtotal in WD-WD Merger
 Longer Duration
 Sub-Luminous Type Ia SNe?
2008ha; Valenti +09; Foley+09)
(e.g.
2) Beacon to Gravitational
Wave Source (e.g. LIGO)
Circinus X-1
(ATCA 1.4 GHz)
AIC as Short GRB Progenitor
• Relativistic Jet from NS Accretion
(Analogous to BH Accretion after NS-NS / NS-BH Merger)Tudose+06
• GRB Duration ~ Accretion Time ~ Sec
• Host Galaxies: Early & Late Type
Predict Location Inside galaxy or GC
• No Bright Supernova (Hjorth+05)
Heinz+07
050724; Berger+05
(but fainter transient lasting ~ 1 day)
• Weaker / Distinct Grav. Wave Signal
050709; Fox+05
Short GRBs with Extended Emission
GRB050709
I.
II.
III.
Perley et al. 2008
GRB080503
SEE/SGRB ~ 30
BATSE SGRBEEs (Norris & Bonnell 2006)
Extended Emission from Magnetar Spindown
(Usov 92; Thompson 94; Metzger, Thompson, & Quataert 07; Metzger, Quataert, & Thompson 08)

ERot ~5 1052 erg, SD ~100 s for P ~ 1 ms & B ~ 1015 G

Emission Delay: Neutron Star Cooling Time (~10 s)
“Proto-Magnetar” Winds (Metzger+07)
Ý, EÝ, JÝ
B0,(t), L (t),T0 (t)  M
Wind Evolution
3 1015 G
1016 G

Internal Shock
Emission
1016 G 1016 G
1015 G
3 1015 G
1015 G
3 1015 G
P0 = 1 ms
1015 G
Metzger+08
LC ~ 
NS

WD
Summary
NS
 AIC + Rapid Rotation  Proto-Neutron Star + Accretion Disk
 Disk Viscously Spreads, Neutrino Irradiation Drives n/p to ~ 1
 Thermal/Nuclear-Driven Winds blow disk apart at t ~ 1 second
 ~ 10-2 M in 56Ni Synthesized in Outflow
 Optical Transient with LV ~ 1041 erg s-1 for ~ 1 day
(Longer Duration Possible in WD-WD Merger Case)
- Detectable w/ Transient Surveys or as Beacon to G-Wave Source
 NS Accretion may also Produce a Short GRB
 Extended Emission from S-GRBs Hard to Explain w/ Accretion
 If NS is Strongly Magnetized, EE may be Rotation Powered
 Proto-Magnetar Wind + Internal Shock Emission Model Fits Data