Seamus Meehan

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 – – −−

Photometry and spectroscopy of GRB 060526: a detailed study of the afterglow and host galaxy of a z = 3.2 gamma-ray burst

Aims. With this paper we want to investigate the highly variable afterglow light curve and environment of gamma-ray burst (GRB) 060526 at z = 3: 221. Methods. We present one of the largest photometric datasets ever obtained for a GRB afterglow, consisting of multi-color photometric data from the ultraviolet to the near infrared. The data set contains 4 12 data points in total to which we add additional data from the literature. Furthermore, we present low-resolution high signal-to-noise spectra of the afterglow. The afterglow light curve is modeled with both an analytical model using broken power law fits and with a broad-band numerical model wh ich includes energy injections. The absorption lines detec ted in the spectra are used to derive column densities using a multi-ion single-component curve-of-growth analysis from which we derive the metallicity of the host of GRB 060526. Results. The temporal behaviour of the afterglow follows a double broken power law with breaks at t = 0: 090�0: 005 and t = 2: 401�0: 061 days. It shows deviations from the smooth set of power laws that can be modeled by additional energy injections from the central engine, although some significant microvariability remains. The broadband spect ral-energy distribution of the afterglow shows no significa nt extinction along the line of sight. The metallicity derived from S II and Fe II of [S/H] = ‐0.57� 0.25 and [Fe/H] = ‐1.09� 0.24 is relatively high for a galaxy at that redshift but comparable to the metallicity of other GRB hosts at similar redshifts. At the position of the afterglow, no host is detect ed to F775W(AB)= 28.5 mag with the HST, implying an absolute magnitude of the host M(1500 A)>‐18.3 mag which is fainter than most long-duration hosts, although the GRB may be associated with a faint galaxy at a distance of 11 kpc.

Integration of the Watcher Telescope into the Sierra Stars Observatory Network – Lessons Learned for GLORIA

The UCD Watcher robotic telescope is planning to participate in the Sierra Stars Observatory Network (SSON), a US-based organisation that provides astronomical images upon request to subscribing users, who are typically either amateurs or university/college students. Implementing the tasks required for the integration of Watcher to SSON, such as remote scheduling, file transfer, image quality validation and the provision of meteorological information, have provided useful experience for the GLORIA project. It has also become apparent that managing user expectations will be important for GLORIA.

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.

Photometry and spectroscopy of GRB 060526: A detailed study of the afterglow and host galaxy of a z = 3.2 gamma-ray burst

Aims. With this paper we want to investigate the highly variable afterglow light curve and environment of gamma-ray burst (GRB) 060526 at z = 3: 221. Methods. We present one of the largest photometric datasets ever obtained for a GRB afterglow, consisting of multi-color photometric data from the ultraviolet to the near infrared. The data set contains 4 12 data points in total to which we add additional data from the literature. Furthermore, we present low-resolution high signal-to-noise spectra of the afterglow. The afterglow light curve is modeled with both an analytical model using broken power law fits and with a broad-band numerical model wh ich includes energy injections. The absorption lines detec ted in the spectra are used to derive column densities using a multi-ion single-component curve-of-growth analysis from which we derive the metallicity of the host of GRB 060526. Results. The temporal behaviour of the afterglow follows a double broken power law with breaks at t = 0: 090�0: 005 and t = 2: 401�0: 061 days. It shows deviations from the smooth set of power laws that can be modeled by additional energy injections from the central engine, although some significant microvariability remains. The broadband spect ral-energy distribution of the afterglow shows no significa nt extinction along the line of sight. The metallicity derived from S II and Fe II of [S/H] = ‐0.57� 0.25 and [Fe/H] = ‐1.09� 0.24 is relatively high for a galaxy at that redshift but comparable to the metallicity of other GRB hosts at similar redshifts. At the position of the afterglow, no host is detect ed to F775W(AB)= 28.5 mag with the HST, implying an absolute magnitude of the host M(1500 A)>‐18.3 mag which is fainter than most long-duration hosts, although the GRB may be associated with a faint galaxy at a distance of 11 kpc.

Operating a global network of autonomous observatories

We discuss our experiences operating a heterogeneous global network of autonomous observatories. The observatories are presently situated on four continents, with a fifth expected during the summer of 2010. The network nodes are small to intermediate diameter telescopes (<= 150 cm) owned by different institutions but running the same observatory control software. We report on the experience gained during construction, commissioning and operation of the observatories, as well as future plans. Problems encountered in the construction and operation of the nodes are summarised. Operational statistics as well as scientific results from the observatories are also presented.

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.