observable signatures of the accretion-induced collapse of white dwarfs
DESCRIPTION
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. Thermal Optical Transients (Metzger, Piro & Quataert 2008,09) - PowerPoint PPT PresentationTRANSCRIPT
Observable Signatures of the Accretion-Induced Collapse of
White Dwarfs
w/ Tony Piro, Eliot Quataert, Niccolo Bucciantini (Berkeley) & Todd Thompson (Ohio State)
Brian Metzger, UC Berkeley
WD
NS
OUTLINE
1) Thermal Optical Transients(Metzger, Piro & Quataert 2008,09)
2) Connection to Short GRBs
(Metzger, Quataert & Thompson 2008)
Accretion-Induced Collapse (AIC)
Yoon+
07
• AIC Rate (Very Uncertain):~10-6-10-4 yr-1
galaxy-1
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
T = 1.7 minT = 0.86 min
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)
Collapse to a Proto-Neutron Star
Quick
Tim
e™
an
d a
TIF
F (L
ZW
) decom
pre
sso
rare
nee
de
d to
see th
is pic
ture
.
Dessart+
06
WDR ~ 103 km
Co
llapse!
NS
R ~ 30-100 km
T = 59 ms post bounce
Weak Explosion ~1050 ergs, MNi < 10-3 M (Woosley &
Baron 92; Fryer+99; Dessart+06)
But with Rapid Rotation….
1) Gravitational Wave Source? (Fryer+02; Ott 08)
2) ~ 0.1 M, ~ 30 km Disk around NS (Michel 87; Bailyn & Grindlay 90)
Disk Accretion and Viscous Spreading
NS
• Neutrino Cooled (Thin Disk)
• Degenerate Electrons
Neutron-Rich Equilibrium
€
˙ M IN
€
e− + p → ν e + n
€
e+ + n → ν e + p
R ~ 100 kmM ~ 0.1 M
T ~ 5 MeV
Initial (t = 0)
Metzger, Piro, & Quataert 2008a,b
€
n
p~ 10}
• 1D (radial) Time-Dependent Disk Evolution Solve for Disk Spreading (alpha viscosity), Heating & Cooling
Evolve Composition (n/p) via Weak Interactions
Disk Accretion and Viscous Spreading
NS
• Neutrino Cooled (Thin Disk)
• Degenerate Electrons
Neutron-Rich Equilibrium
€
˙ M INR ~ 100 km
NS
• Inefficient Cooling (Thick Disk)
• Degeneracy Lifted
• n/p “Freezes Out”
• Alpha Particles Form
• Disk Blown Apart
M ~ 0.1 MT ~ 5 MeV
Initial (t = 0)
T ~ 1 MeV
M ~ 0.03 M
R ~ 1000 kmFinal (t ~ 1 s)
Metzger, Piro, & Quataert 2008a,b
€
˙ M IN €
n
p~ 10}
• 1D (radial) Time-Dependent Disk Evolution Solve for Disk Spreading (alpha viscosity), Heating & Cooling
Evolve Composition (n/p) via Weak Interactions
€
e− + p → ν e + n
€
e+ + n → ν e + p
Disk Outflows and Nucleosynthesis -Particle Formation: ENuc > EBind
• Thick Disks only Marginally Bound (Narayan & Yi 94; Blandford & Begelman 99)
• Expansion of Hot, Dense Ejecta Heavy Element Synthesis
• Critical Quantity: Neutron-Proton Ratio in Disk @ Freeze Out
Powerful Winds}
BH1) BH Accretion (NS-NS / NS-BH Mergers)
2) NS Accretion (AIC)
Neutron-Rich Freeze Out (with n/p ~ 2-3) Rare Heavy Elements
NS
€
ν e + n → e− + p
n/p ~ 1
56Ni
Neutrino Irradiation
e.g. Se, Br, Ag
56Ni
e.g. Se, Br, Ag
56Ni
V ~ 0.1 c
V ~ 0.1 c νe
νe
νe νeνe
νe
(Metzger, Piro, & Quataert 08a,b)
Optical Transients from AIC• 56Ni 56Co + heats ejecta• Photons diffuse out as ejecta expands
1) Optical Transient SurveysPalomar Transient Factory & PanSTARRs MDS: ~1 yr-1 (RAIC/10-2 RIa)
LSST: ~ 600 yr-1 (RAIC/10-2 RIa)
€
Tpeak ~ 1 day M total
10−2 M8
⎛
⎝ ⎜
⎞
⎠ ⎟
1/ 2v
0.1 c
⎛
⎝ ⎜
⎞
⎠ ⎟−1/ 2
Metzger, Piro, & Quataert 2009
2) Beacon to Gravitational Wave Source (e.g. LIGO)
MNi ~ 10-2 M
Mtotal ~ 2 x 10-2 M
Ni / Fe-Rich Spectra
Larger Mtotal in WD-WD Merger Longer Duration Sub-Luminous Type Ia SNe? (e.g. 2008ha; Valenti +09; Foley+09)
AIC as Short GRB Progenitor
• Relativistic Jet from NS Accretion (Analogous to BH Accretion after NS-NS / NS-BH Merger)
• GRB Duration ~ Accretion Time ~ Sec
• Host Galaxies: Early & Late Type
Predict Location Inside galaxy or GC• No Bright Supernova (Hjorth+05)
(but fainter transient lasting ~ 1 day)
• Weaker / Distinct Grav. Wave Signal
050724; Berger+05
050709; Fox+05
Circinus X-1 (ATCA 1.4 GHz)
Heinz+07Tudose+06
Short GRBs with Extended Emission
GRB050709
GRB080503
BATSE SGRBEEs (Norris & Bonnell 2006)
Perley et al. 2008
I.
III.II.
SEE/SGRB ~ 30
NS
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)
€
B0,Ω(t), Lν (t),T0(t)⇒ ˙ M , ˙ E , ˙ J
Extended Emission from Magnetar Spindown (Usov 92; Thompson 94; Metzger, Thompson, & Quataert 07; Metzger, Quataert, & Thompson 08)
1015 G
1016 G
3 1015 G
P0 = 1 ms
1015 G
1016 G
3 1015 G
Metzg
er+08
1016 G3 1015 G
1015 G
LC
~
Wind Evolution Internal Shock Emission
Summary
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
WD NS