Short-Duration Gamma-Ray Burst Central Engines

Brian Metzger Princeton University

In collaboration with

Eliot Quataert (Berkeley)

Todd Thompson (Ohio State)

Tony Piro (Berkeley)

Niccolo Bucciantini (Nordita)

Almudena Arcones (MPIK)

Gabriel Martinez-Pinedo (MPIK)

Chandra / Einstein Fellows Symposium Harvard CfA, October 27 2009

BATSE GRBs

Nakar 07

Gamma-Ray Bursts: Long & Short Duration

BATSE GRBs

• High Redshift, zavg ~ 2

• Large Energies (Eiso~1052-54 ergs)

• Star-Forming Host Galaxies

• Type Ic Broad-Line Supernovae

Long

Nakar 07

Gamma-Ray Bursts: Long & Short Duration

BATSE GRBs

• High Redshift, zavg ~ 2

• Large Energies (Eiso~1052-54 ergs)

• Star-Forming Host Galaxies

• Type Ic Broad-Line Supernovae

Long

Nakar 07

Gamma-Ray Bursts: Long & Short Duration

Short

Nakar 07

Merging Compact Objects (NS-NS or BH-NS) Paczynski 1986; Goodman 1986; Eichler+1989; Narayan+ 1992, …

• Target for Advanced LIGO

• Disk left behind w/ mass ~ 10-3 - 0.1 M & size ~ 10-100 km

• cooling via neutrinos: ( >>1, ~ 1 )

€

˙ M ~ 10−2 −10M• s-1

Sh

iba

ta &

Ta

nig

uc

hi 2

00

6

t = 0.7 ms

t = 3 ms

Inspiral “Chirp” Gravitational Waves

Accretion-Induced Collapse (AIC)

• Binary Accretion or WD-WD Merger

•“Failed” Type Ia SN

• Collapse of rapidly-rotating WD Disk around PNS: Mdisk ~ 10-2 - 0.3 M

Circinus X-1 (Chandra)

Neutron Star Circinus X-1 > 15 ! (Fender et al. 2004)

Similar Systems - Distinct OriginsNS-NS / BH-NS NS-NS / BH-NS

MergersMergers

Accretion-Accretion-Induced Induced CollapseCollapse

BH

NS

M ~ 0.01-0.1 MM ~ 0.01-0.1 M

R ~ 100 km

consistent with short GRB durations

KECK Bloom+06

GRB050509b

GRB050724

Berger+05

HUBBLE Fox+05

GRB050709

z = 0.225 SFR < 0.1 M yr-

1

z = 0.16 SFR = 0.2 M yr-1

z = 0.258 SFR < 0.03 M yr-1

Berger +05

Blo

om

+ 06

Short GRB Host Galaxies

KECK Bloom+06

GRB050509b

GRB050724

Berger+05

HUBBLE Fox+05

GRB050709

z = 0.225 SFR < 0.1 M yr-

1

z = 0.16 SFR = 0.2 M yr-1

z = 0.258 SFR < 0.03 M yr-1

Berger +05

Blo

om

+06

Short GRB Host Galaxies

GRB050724

No Supernova!

• Lower redshift* (z ~ 0.1-1)

• Eiso~ 1049-51 ergs*

• Older Progenitor Population (Consistent

with being drawn from field galaxies; Berger 09)

Short GRBs with Extended X-Ray Emission

BATSE Examples (Norris & Bonnell 2006)

GRB080503SEE/SGRB ~ 30

Pe

rley e

t al. 2

00

8

GRB050709~25% of Swift Bursts (2 classes?) Similarity To GRB Ongoing Engine ActivityEEE/EGRB ~ 1-30 !

Evolution of the Remnant DiskLo

cal D

isk

Mas

s

r2 (

M)

Metzger, Piro, Quataert 2008, 2009 (see also Beloborodov 2009; Lee et al. 2009)

1-D Time-Dependent Models ( viscosity; realistic -cooling)

€

J = (GM•R)1/ 2 MD

Late-Time Outflows

-Particle Formation

• Thick Disks Marginally Bound (Narayan & Yi 94; Blandford & Begelman 99)

}At t ~ 0.1-1 seconds: R ~ 500 km, M ~ 0.3 MAt t ~ 0.1-1 seconds: R ~ 500 km, M ~ 0.3 M initialinitial, T ~ 1 MeV, T ~ 1 MeV

EEBINDBIND ~ GM ~ GMBHBHmmnn/2R ~ 3 MeV nucleon/2R ~ 3 MeV nucleon-1-1

EENUCNUC ~ 7 MeV nucleon ~ 7 MeV nucleon-1-1

~20-40% of the Initial Disk is Ejected Back into Space!~20-40% of the Initial Disk is Ejected Back into Space!

BH

Powerful Winds

Blow Apart Disk

Metzger et al. 2008, 2009

???

Tidal Tails in NS-NS/NS-BH Mergers Lee

& R

amirez-R

uiz 07

Tail(s) with ~10% prompt disk mass

Late-Time Fall-Back Accretion

Rosswog 07

€

dMdt = dM

dE( ) dEdt( ) ∝ t−5 / 3

(Rosswog 07; Faber+06; Lee+09)

€

t fall−back = torb ∝ a3 / 2 ∝ E−3 / 2

+

a

r - Process Heating (not included in present simulations!)

Er ~ 1-3 MeV nucleon-1 released over theat ~ 1 second

Neutrons

Pro

ton

s

Decompressing NS Matter A ~ 100 Nuclei + Free Neutrons (Lattimer+77; Meyer 89):

+

a

r-Process Network Calculations

Metzger, Arcones, Quataert, Martinez-Pinedo 2009

Binding Energy of Merger Ejecta

Total r-Process Heating Along Fall-Back Orbits

Orbital Period

+

a

theat > 1 s theat < 1 s

+

a

torb ~ 1 s

+

a

theat > 1 s theat < 1 s

+

a

torb ~ 1 s

No Late Fall-Back

+

a

theat > 1 s theat < 1 s

+

a

torb ~ 1 s

No Late Fall-Back“Gap”

Metzger, Arcones, Quataert, Martinez-Pinedo 2009

The Effects of r-Process Heating on Fall-back Accretion

Either: Complete Suppression of Fall-Back after t ~ 1 sec

OR “Gap” of t ~ seconds opened

???

Magnetar Spin-Down

Accretion-Induced Collapse

NS-NS Merger with long-lived NS remnant

Following:

NS

Magnetar Spin-DownM

etzger, Q

ua

taert & T

ho

mp

son

08

1015 G

1016 G

3 1015 G

P0= 1 msGRB060614 Overlaid

Accretion-Induced Collapse

NS-NS Merger with long-lived NS remnant

Following:

Internal Shock Emission

~

Po

we

r (1

051 e

rgs

s-1)

NS

High Low

Conclusions

• Swift Revolution: Afterglows and Host Galaxies

long and short GRBs have distinct progenitors

• NS-NS/NS-BH Remains Promising Model

consistent w/ host galaxies, durations, energetics

– accretion disk spreads, explodes at t ~ 1 second.

~100 second X-ray Emission = Major Problem

• Oft-Discussed Explanation = Fall-Back Accretion– r-process heating must be taken into account

either: “natural” explanation or makes matters worse

• AIC = Promising Alternative Model (NS Remains!)