Bruce GendreOsservatorio di Roma / ASI Science Data Center

Recent activities from the TAROT/Zadko network

The TAROT/Zadko Network

Set of 3 robotic telescopes• France (20 cm diameter)• Chile (20 cm diameter)• Australia (1m diameter)

Aims• GRB studies• Space debris monitoring• GW source detection• Variable object survey

105 GRB observed so far• 21 during prompt phase• 35 detections

GRB 110205A

GRB 110205A• Swift trigger• Circumpolar burst, visible all night long• Redshift : 2.22

Global characteristics:• Long burst T90 = 257s• Spectral classification as X-ray Rich

Nearly perfect follow-up• Robotic telescopes (TAROT) activated during prompt phase• mid-size instruments (0.5-1m) continued the follow-up for days• large instruments (8+m) used at late time• wide spectral coverage (far IR to X-ray)

Observations

Gendre et al. 2011

Gendre et al. 2011

Jet break

At bin 11 X-ray and optical decay are:

1. identical2. asymptotic to the same value3. decay index ~ 2.3

Jet effect• Break is progressive• p = 2.3• θ = 2.1°

Optical flare

Fast rising optical flare, not seen in X-rays

• Rise slope ~ t5

• Peak time ~ 1000 sec

Interpretation : Reverse shock in thin shell• The prompt GRB and the afterglow are temporally distinct• Allows calculating the Lorentz factor Γ = 125

Optical flare

Why this burst is unique:1. low density2. Magnetized fireball3. very low Lorentz factor

Optical and Gamma-ray temporal correlation in the prompt

very good correlation between optical and gamma-ray light curves

Poor correlation between optical and X-ray light curve

Optical and gamma-ray bands are due to the same mechanism ?

An extra-component in X-ray ?

X-to-γ spectra require two breaks at few keV and 220 keV.

Optical data do not agree with this !

Optical-Gamma ray data can be fit with the Band modelBut X-ray data are clearly not in agreement

Optical and Gamma-ray prompt spectra

Internal shock

Late internal shock

Normal afterglow

Jet effect

Reverse shock

The model in image: GRB110205A

Gendre et al. 2011?????!

GRB 111209A

Gendre et al., Science in prep

Burst detected by Swift• Also observed by Konus-Wind• Duration of the gamma-ray

even : ~ 14 000 s

Followed by XRT• Sharp decay (high latitude

emission)• Tburst ~ 25 000 s

Observation by other instruments• XMM• TAROT/Zadko

Extra long bursts in past

Long bursts usually do not last longMean time is 20 s !

Only 5 cases with duration > 1 000 s• GRB 971208 (BATSE)• GRB 060814B (Konus-Wind)• GRB 060218 (Swift)• GRB 101225A (swift)• GRB 111209A (Swift)

Obvious solution:• Very high redshift burst• Not a real GRB

Golenetskii et al. 2011

Z = 1.0

Z = 10

Any other clue ?

Thermal component• GRB 060218 and GRB 101225A have strong thermal component• GRB 111209A not

However, presence of a second component in the XMM Spectrum

Any other clue ?

Stratta et al. In preparation

XMM-Newton spectra, 10 ks integration time, during steep decay

Thermal component• GRB 060218 and GRB 101225A have strong thermal component• GRB 111209A not

However, presence of a second component in the XMM Spectrum• Faint thermal component at high energy (> 7 keV)• Power law compatible with an Inverse Compton emission from the

prompt

Afterglow luminosity• Under luminous afterglow• Compatible with the idea to radiate

most of the energy in the prompt phase using only internal shocks

Any other clue ?

And so ?

With the data in hands, it is difficult to conclude…• No host galaxy info• No large follow-up despite the "Swift burst of interest" label

… but we can propose some crude hypotheses• A very high rotation of a giant star (see Swift J1644+57 case) ?• A HMXB in a common envelop stage (with the neutron star located at

the "correct" depth in the star) ?• An HMXB going into the second supernovae ?

Dear theoretician friends, please call me

Conclusion

The TAROT/Zadko network is fine• TAROT-La Silla went under refurbishment last year• Zadko will move into a new building this year with a new camera and

a low-resolution spectrometer• Bursts are still observed

GRB 110205A• This is an archetypal burst with all fireball component visible and,

actually, observed• We need more friendly burst like this to understand the model

GRB 111209A• This is the longest burst ever recorded• It is far less theoretician friendly• But far more interesting for observing dude like me !