The diversity of progenitors and emission mechanisms for ultra-long bursts
Bruce Gendre, Giulia Stratta
Jean-Luc Atteia, Stéphane Basa, Michel Boër, David Coward, Sara Cutini, Valerio d'Elia, Massimilano De Pasquale, Eric Howell, Alain Klotz, Samantha Oates, Luigi Piro Progenitors of GRBs
Long GRBs are associated with supernovae • Most famous example is GRB 980425 • Most studied example is GRB 030329 • We have countless examples of such associations
SN2003dh (associated with GRB 030329) • Type Ic supernova (Stanek et al. 2003) • Comparable to other hypernovae (ultraluminous type Ib/c supernova, Iwamoto et la. 1998)
Probable progenitor of these events • Massive star with outer layers striped away • … Also named Wolf-Rayet Stars
Are all GRBs due to Wolf-Rayet stars? • Absence of observed stellar winds • Absence of SN signature in some cases • … Not sure The ultra-long GRB 111209A
Detected by Swift • Also seen by Konus-Wind • Started before trigger • Usual follow-up Gendre et al. 2013 • Redshift 0.677
Extreme long duration • T90 impossible to determine (gap in light curve) • Total time at least 25 000 seconds
FIGARO reaction • TAROT extended follow-up • XMM-Newton 50 ks ToO triggered Ultra-long bursts?
Firstly, an easy method of classification • Long GRBs : T>2s • Super long GRBs: T > 1 000 s • Ultra long GRBs: T > 10 000 s
Duration exceptional for a burst • Only event recorded in about 30 years of archives checked ! Gendre et al. 2013
However, in the fluence-duration plane: • Clear outlier from normal GRB • Well separated from shock breakout Sne • Well separated from BH/AGN wake up
And from the work of Levan et al.: • Claim for a second ultra-long like burst (GRB 101225A) • And a possible third one A gallery of progenitors
Massive star Very massive star ?
Energy Supernovae Gamma-ray burst Ultra-long gamma ray burst A gallery of progenitors
If dying stars were people:
Massive star Very massive star ?
Energy Supernovae Gamma-ray burst Ultra-long gamma ray burst
? The progenitor
Possible progenitors: • Tidal disruption of minor body. Rejected, as too energetic • Tidal disruption of star. Rejected, missing energy • Magnetar formation. Rejected, unphysical parameters needed Gendre et al. 2013
Our solution: a low metallicity blue supergiant in rapid rotation • Blue supergiant: size implied by the accretion time, i.e. by the duration of the burst • Low metallicity: required to reduce the stellar wind • Rapid rotation: required to ease the formation of the ultra relativistic jet, and its travel through the star A possible selection effect ?
Such a duration has never been observed before • 9 bursts with T90 > 1 000 s • 1 with T90 > 10 000 s : GRB 111209A • Possible selection effect or intrinsic scarcity ?
Gendre et al. 2013 Simulation of detection at various redshift • Use of Konus-Wind light curve • Detection up to z ~ 1.5 • In all cases, burst detected with duration larger than 10 000 seconds
Intrinsic scarcity in the "local" Universe and selection bias at high redshift Time lag during the prompt
During the prompt phase, one large flare • Seen at all wavelengths from Gamma- ray to optical
X-ray (hard and soft) • Incomplete observation: Earth occultation • Start of the rise compatible with gamma-rays Stratta et al. 2013
Optical • Complete TAROT observations • Time delay: 410 +/- 50 s • Very unusual, • Superlag due to the special progenitor ? Time lag during the prompt
During the prompt phase, one large flare • Seen at all wavelengths from Gamma- ray to optical
X-ray (hard and soft) • Incomplete observation: Earth occultation • Start of the rise compatible with gamma-rays Stratta et al. 2013
Optical • Complete TAROT observations • Time delay: 410 +/- 50 s • Very unusual, • Superlag due to the special progenitor ? Prompt to Afterglow transition
A B C A lesson from Swift: the steep-flat-steep • Present in a very large number of GRBs • Associated with the prompt-to afterglow transition (Willingale et al. 2007) • Usually about 1-10 ks after the start of the burst
Stratta et al. 2013 Also present in GRB 111209A • …but later: 7-9 ks after the trigger… already 5 ks after the start of the burst A B
And observed by chance by XMM-Newton • An unprecedented quality allowing slices of 500s of temporal resolution C • Presence of two component implied by the fit • One is very hard, compatible with the hard tail seen in some cases by Fermi-LAT Stratta et • Work still in progress al. 2013 A message from the Standard Model
The standard model is independent from the progenitor • Consequence of its Stratta et al. 2013 construction • The afterglow is due to the forward shock.
GRB 111209A has a very rich dataset • X-ray observation (Swift, XMM) • Optical (TAROT, GROND, VLT) • Radio (ACTA @ Australia)
Possibility to build a broadband SED • First time since 1998 • Strong constraints on the model • Data in agreement with the standard model GRB 111209A is the longest GRB ever observed With a duration of at least 25 000 seconds (7 hours)
Its properties point toward a different progenitor than a WR star We suggest a blue supergiant star for GRB 111209A
Lucky observation of the end of the steep decay, the plateau and the onset of the normal decay with XMM-Newton on a bright burst The data are very impressive, but still under analysis We however do observe two components in the spectrum
The burst has been observed from radio to X-ray at the same time Construction of the broad-band spectrum without extrapolation The data are consistent with the standard forward shock expectations