1. The nature of the longest gamma-ray bursts Andrew Levan University of Warwick

2. Burst durations Swift 1644+57 Very long bursts are often image triggers (1000+s)

3.  Correction from Swift observed rates to astrophysical rates (at Swift limits) could be a factor 10 Not as rare as you think……. For same integrated fluence, more difficult to detect long events Data courtesy J. Kennea

4. Should they be different?  Some very long bursts probably are the “tail” of the “normal” GRB distribution  Others are low luminosity GRBs (shock breakout?)  Some initially classified as GRBs are clearly different (e.g. GRB 110328A/Swift 1644+57 – Burrows talk)  Jet breakout time – longer GRBs could mean bigger stars?  Suggestion of longer lived central engines, perhaps powered by outer layers of stars (e.g. Quataert et al. 20122; Woosley & Heger 2012)  Two more recent examples discussed here (101225A, 111209A)

5. GRB 101225A Visibility from Bethlehem

6. X-ray spectrum = Powerlaw + blackbody (1 keV)

8. Optical afterglow

9. Scenario I: Galactic Tidal shredding of asteroid mass body around a NS Campana et al. 2011

10. Scenario II: Collapsar Fryer et al. 1999; Thoene et al. 2011 Supernova? He-NS merger Bang

11. Thoene et al. 2011

12. HST and late time observations Note: No proper motion in 6 months (v < 250 km/s/kpc) If host the afterglow is “on” the nucleus HST ACS/F435W (Jan)Gemini GMOS (July) g-band Significant host contribution at ~1 month, but not resolved

13. Host constraints

14. GRB 111209A 10000s

15. OIII (4959) OIII (5007)

16. X-ray afterglow

18. Supernova search HST grism spectrum J-band u-band VLT + Gemini Clear reddening, no obvious SN. Host? Chromatic afterglow?

19. HST observations WFC3/F336W WFC3/F110W Host galaxy still largely unresolved (<800pc), very compact if bright

20. Summary  Very long GRBs are more astrophysically common that we might expect. (but too long for Swift and too faint for BATSE, GBM etc).  The longest bursts appear to have distinct prompt, afterglow (and host?) properties from the majority of GRBs.  They are probably cosmological, but evidence for SN within them remains weak  Understanding the nature of the longest gamma- ray transients should remain an important task.

21. SGRs TDEs? Galactic sources (SGR, LMXB, HMXB, micro-quasar, gamma- ray pulsar) LLGRBs SGRBs LGRB unknown