Martin Topinka

GRB 120711A: an intense INTEGRAL burst with long-lasting soft γ-ray emission and a powerful optical flash

A long and intense γ-ray burst (GRB) was detected by INTEGRAL on 11 July 2012 with a duration of ∼115 s and fluence of 2.8 × 10 −4 erg cm −2 in the 20 keV−8 MeV energy range. GRB 120711A was at z ∼ 1.405 and produced soft γ-ray emission (>20 keV) for at least ∼10 ks after the trigger. The GRB was observed by several ground-based telescopes that detected a powerful optical flash peaking at an R-band brightness of ∼11.5 mag at ∼126 s after the trigger, or ∼9th magnitude when corrected for the host galaxy extinction (AV ∼ 0.85). The X-ray afterglow was monitored by the Swift, XMM-Newton ,a ndChandra observatories from 8 ks to 7 Ms and provides evidence for a jet break at ∼0.9 Ms. We present a comprehensive temporal and spectral analysis of the long-lasting soft γ-ray emission detected in the 20−200 keV band with INTEGRAL/IBIS, the Fermi/LAT post-GRB detection above 100 MeV, the soft X-ray afterglow and the optical/near-infrared detections from Watcher, Skynet/PROMPT, GROND, and REM. The prompt emission had a very hard spectrum (Epeak ∼ 1 MeV) and yields an Eγ,iso ∼ 10 54 erg (1 keV−10 MeV rest frame), making GRB 120711A one of the most energetic GRBs detected so far. We modelled the long-lasting soft γ-ray emission using the standard afterglow scenario, which indicates a forward shock origin. The combination of data extending from the near-infrared to GeV energies suggest that the emission is produced by a broken power-law spectrum consistent with synchrotron radiation. The afterglow is well modelled using a stratified wind-like environment with a density profile k ∼ 1.2, suggesting a massive star progenitor (i.e. Wolf-Rayet) with a mass-loss – – −−

Search for Correlations Between Batse Gamma-Ray Bursts and Supernovae

We report on our statistical research of space-time correlated supernovae and CGRO-BATSE gamma-ray bursts. There exists a significantly higher abundance of core-collapse supernovae among the correlated supernovae, but the subset of all correlated objects does not seem to be physically different from the whole set. The upper limit of the fraction of possibly correlated GRBs and SNe is of order of a few percent.

Classification of gamma-ray bursts observed by INTEGRAL

Long gamma‐ray bursts (GRBs) can be divided into three classes (‘classical’ GRBs, X-ray rich bursts and X-ray flashes), based on the ratio of their fluences in a soft energy band to a hard energy band. However, the other characteristics of the X-ray rich bursts and X-ray flashes resemble those of the classical GRBs, suggesting that they are closely related phenomena. We present the classification of more than 70 GRBs triggered by the IBAS aler t on IBIS/ISGRI since the launch of INTEGRAL’s. An optimised criterion for the classification has been ca rried out, based on the 20-50 keV and 50-200 keV energy bands. A comparison between the distributions of each burst type found in the INTEGRALsample, and those identified by Swift and HETE-2, is also presented.

Spectral Cross‐Calibration of Fermi‐GBM and INTEGRAL‐ISGRI using Gamma‐Ray Bursts

We present an extended cross‐calibration study between the Fermi Gamma‐Ray Burst Monitor (GBM) and the INTEGRAL Soft Gamma‐Ray Imager ISGRI. A previous sample contained 4 GRBs; GRB081226B; GRB090107B; GRB090625B and GRB090704. A long burst detected by both instruments, GRB090817, provides us with the opportunity to further test the agreement between the previous sample and the new data. GRB090817 contains significant telemetry gaps in the ISGRI data set and methods were devised to account for these gaps. The combined datasets from both instruments for GRB090817 were fit with 3 separate spectral models—a Power Law (PL), Cut‐Off Power Law (COPL) and a Band model. The best fit joint spectral model is shown for the time averaged and time resolved joint spectral fits. As a measure of relative flux between the two instruments, a normalisation constant was calculated from the joint spectral fitting.

Observations of GRB 080723B with INTEGRAL

GRB 080723B was a long and intense gamma‐ray burst detected and localized by the INTEGRAL satellite featuring combined observations from both main instruments on‐board, IBIS and SPI. The burst was composed of several well separated peaks, allowing the time‐resolved spectral evolution to be studied. IBIS and SPI spectra and light curves for the prompt emission are presented.

Search for Correlations Between BATSE Gamma‐Ray Bursts and Supernovae

We report on our statistical research of space-time correlated supernovae and CGRO-BATSE gamma-ray bursts (GRBs). There exists a significantly higher abundance of core-collapse supernovae among the correlated supernovae, but the subset of all correlated objects does not seem to be physically different from the whole set.

Magnetic Field Dissipation in GRBs

We report on the first steps towards the three‐dimensional simulation of magnetic field dissipation in gamma‐ray burst prompt emission. The model is based on magnetically driven Poynting flux outflow.