Signatures of supernovae powered by neutron stars and black holes

1. Signatures of supernovae powered by neutron stars and black holes Jason Dexter (with Dan Kasen) UC Berkeley

2. Super-luminous supernovae scp06f6 2005ap ptf09cnd 2006gy 2008es 2007bi Type Ia core collapse supernovae 2002bj ptf10bhp 2008ha after M. Kasliwal, D. Kasen 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 • Pair-instability explosions (Woosley 2007, Kasen+2011) • Circumsteller interaction (Blinnikov & Sorokina, Chevalier & Irwin, …) • Magnetarspindown(Kasen & Bildsten 2010) • Fallback accretion (Dexter & Kasen 2013) 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 Dexter & Kasen (2013) Wong+2013 The Structure and Signals of Neutron Stars

7. Accretion powered supernovae • Fallback accretion could power a wide range of events Dexter & 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 Time Kotera+2013 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 • Magnetarspindown 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 Kasen & Woosley (2009) • Thermal • Radioactive (56Ni) Efficiency Branch & Tammann (1992) 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 Efficiency Woosley+07 The Structure and Signals of Neutron Stars

16. MagnetarSpindown 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 The Structure and Signals of Neutron Stars