Signatures of supernovae powered by neutron stars and black holes
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Transcript of Signatures of supernovae powered by neutron stars and black holes
Signatures of supernovae powered by neutron stars and black holes
Jason Dexter (with Dan Kasen)UC Berkeley
The Structure and Signals of Neutron Stars 2
Super-luminous supernovae
core collapse supernovae
after M. Kasliwal, D. Kasen
Type
Ia
2002bjptf10bhp
2008ha
2008es2007bi
2005ap scp06f6
2006gyptf09cnd
The Structure and Signals of Neutron Stars 3
Super-luminous supernovae
> 1044 ergs / s
Gal-Yam (2012)
The Structure and Signals of Neutron Stars 4
Models
• Magnetar spindown (Kasen & Bildsten 2010)
• Fallback accretion (Dexter & Kasen 2013)
• Pair-instability explosions (Woosley 2007, Kasen+2011)
• Circumsteller interaction (Blinnikov & Sorokina, Chevalier & Irwin, …)
The Structure and Signals of Neutron Stars 5
Energy from fallback accretion
• Bound material falls back after explosion, forms disk, drives outflow into ejecta, deposits energy
• Jet or wind model: > 1051 ergs / Msun
A. Tchekhovskoy
The Structure and Signals of Neutron Stars 6
Fallback accretion rate• Measure from simulated explosions• Flat at early times, asymptotically t-5/3
Wong+2013Dexter & Kasen (2013)
The Structure and Signals of Neutron Stars 7
Accretion powered supernovae• Fallback accretion could power a wide range
of eventsDexter & Kasen (2013)
The Structure and Signals of Neutron Stars 8
Evidence for a central engine?• Central engine models explain light curve shapes,
high velocities > 104 km / s• Type I: no narrow lines, need massive H-free CSM
Inserra+2013 Chatzapoulos+2012
The Structure and Signals of Neutron Stars 9
Signatures of central engines
• Central engine emission should shine through• Hard X-rays, γ-rays in nebular phase (Kotera+2013)
• Photo-ionization: UV/X-ray flash (Metzger+2014)
Kotera+2013 Metzger+2014
The Structure and Signals of Neutron Stars 10
Signatures of central engines
• Track thermalization:- Free-free (IR), lines
(optical), bound-free (UV/soft X-ray), Compton scattering (high energy)
• Sharp drops in optical light curve from ionization
Kotera+2013
Time
The Structure and Signals of Neutron Stars 11
Optical/UV colors
• Loss of thermalization potentially observable in late time colors
Inserra+2013
The Structure and Signals of Neutron Stars 12
Summary
• Central engine models promising for explaining some super-luminous supernovae– Magnetar spindown or fallback accretion
• Signatures of central engine in optical/UV and high energy emission
• Possible information about stellar collapse and/or compact object birth
The Structure and Signals of Neutron Stars 13
Open Issues• Fallback rate• As in magnetar model:
– Energy deposition in ejecta
• As in collapsar GRBs:– Disk formation– Outflow properties– Interaction of outgoing,
infalling material
The Structure and Signals of Neutron Stars 14
Powering supernova light curves• Thermal
• Radioactive (56Ni) Branch & Tammann (1992)
Kasen & Woosley (2009)Efficiency
The Structure and Signals of Neutron Stars 15
Circumstellar Interaction
• Interaction of ejecta with material at large radius resets internal energy
• Large if Rsh >> R0
Woosley+07
Efficiency
The Structure and Signals of Neutron Stars 16
Magnetar Spindown Power
Kasen & Bildsten (2010)
The Structure and Signals of Neutron Stars 17
Hard X-rays, gamma rays
• For low field strengths, can be significant high energy emission at late times
Kotera+2013
The Structure and Signals of Neutron Stars 18
Soft X-ray flash?• Pulsar could ionize ejecta near peak,
allowing X-rays to escape
Metzger+2014