GRB Coordinates Network Research Articles

DETECTION OF GAMMA-RAY INDUCED MUONS WITH ANTARES

This paper presents a gamma-ray down-going induced muon analysis combining the Gamma-ray bursts Coordinates Network (which announces a possible GRB event) with a blind strategy. The goal of this analysis is to find an astrophysical source through the ability of distinguishing between a real alert (signal) and a fake one (background), through comparisons between the position of an Antares event and the position of the alert, leading us to a better understanding of gamma-ray bursts.

A GRB Follow-up System at the Xinglong Observatory and Detection of the High-Redshift GRB 060927

A gamma-ray burst (GRB) optical photometric follow-up system at the Xinglong Observatory of National Astronomical Observatories of China (NAOC) has been constructed. It uses the 0.8-m Tsinghua-NAOC Telescope (TNT) and the 1-m EST telescope, and can automatically respond to GRB Coordinates Network (GCN) alerts. Both telescopes slew relatively fast, being able to point to a new target field within ∼1 min upon a request. Whenever available, the 2.16-m NAOC telescope is also used. In 2006 the system responded to 15 GRBs and detected seven early afterglows. In 2007 six GRBs have been detected among 18 follow-up observations. TNT observations of the second most distant GRB 060927 (z = 5.5) are shown, which started as early as 91 s after the GRB trigger. The afterglow was detected in the combined image of the first 19×20 s unfiltered exposures. This GRB follow-up system has joined the East-Asia GRB Follow-up Observation Network (EAFON).

SWIFT OBSERVATIONS OF GAMMA-RAY BURSTS

The Swift mission, launched on 20 November 2004, is detecting ~ 100 gamma-ray bursts (GRBs) each year, and immediately (within ~ 90 s) starting X-ray and UV/optical observations of the afterglow. It has already collected an impressive database including prompt emission to higher sensitivities than BATSE, uniform monitoring of afterglows, and rapid follow-up by other observatories notified through the Gamma-ray bursts Coordinates Network (GCN). The X-ray afterglows have been found to have complex temporal shapes including tails emission from the prompt phase and bright flares. X-ray and optical afterglow detections from short bursts have led to accurate localizations. It is found that they can occur in non-star forming galaxies or regions, whereas long GRBs are strongly concentrated within star forming regions. This is consistent with the NS merger model. Swift has greatly increased the redshift range of GRB detection. The highest redshift GRBs, at z ~ 5-6, are approaching the era of reionization. Ground-based deep optical spectroscopy of high redshift bursts is giving metallicity measurements and other information on the source environment to much greater distance than other techniques. The localization of GRB 060218 in a nearby galaxy, and association with SN 2006aj, added a valuable member to the class of GRBs with detected supernova. The prospects for future progress are excellent given the > 10 year orbital lifetime of the Swift satellite.

Gamma-ray observations with Swift and their impact

The Swift gamma-ray burst explorer was launched on Nov. 20, 2004 from Cape Canaveral, Florida. The .rst instrument onboard became fully operational less than a month later. Since that time the Burst Alert Telescope (BAT) on Swift has detected more than 180 gamma-ray bursts (GRBs), most of which have also been observed within two minutes by the Swift narrow-.eld instruments: the X-Ray Telescope (XRT) and the Ultra-Violet and Optical Telescope (UVOT). Swift trigger notices are distributed worldwide within seconds of the trigger through the Gamma-ray burst Coordinates Network (GCN) and a substantial fraction of GRBs have been followed up by ground and space-based telescopes, ranging in wavelength from radio to TeV. Correlations of Swift bursts with neutrino and gravity wave detectors have promise of finding the .rst non-electromagnetic signature of a GRB. Swift is also a sensitive X-ray observatory with capabilities to monitor galactic and extragalactic transients on a daily basis, carry out the .rst all-sky hard X-ray survey since HEAO-1, and study in detail the spectra of X-ray transients as part of coordinated multi-wavelength observing campaigns.

HETE-2 Localization and Observations of the Gamma-Ray Burst GRB 020813

Abstract A bright, long gamma-ray burst (GRB) was detected and localized by the instruments on board the High Energy Transient Explorer 2 satellite (HETE-2) at 02:44:19.17 UTC (9859.17 s UT) on 2002 August 13. The location was reported to the GRB Coordinates Network (GCN) about 4 min after the burst. In the prompt emission, the burst had a duration of approximately 125 s, and more than four peaks. We analyzed the time-resolved 2–400 keV energy spectra of the prompt emission of GRB 020813 using the Wide Field X-Ray Monitor (WXM) and the French Gamma Telescope (FREGATE) in detail. We found that the early part of the burst (17–52 s after the burst trigger) shows a depletion of low-energy photons below about 50 keV. It is difficult to explain the depletion by either synchrotron self-absorption or Comptonization. One possibility is that the low-energy depletion may be understood as a mixture of “jitter” radiation with the usual synchrotron radiation component.

Super‐LOTIS (Livermore Optical Transient Imaging System)

AbstractThe 0.6‐m Super‐LOTIS telescope is a fully robotic system dedicated to the search for prompt optical emission from gamma‐ray bursts (GRBs). The telescope began routine operations from its Steward Observatory site atop Kitt Peak (KPNO) in April 2000. This system is capable of responding to the Gamma‐ray burst Coordinate Network (GCN) triggers within seconds. Together with LOTIS, these systems have been monitoring the GCN real‐time data for automatic HETE2 GRB triggers. We will summarize the current capabilities of the system and present recent scientific results. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

A Spectrograph for Prompt Observations of Gamma-Ray Bursts with a 1-m Telescope

AbstractWe are developing a new slit-less spectrograph for gamma-ray bursts (GRBs) at Bisei Astronomical Observatory. We can quickly point the 1-m telescope to the GRB coordinates provided by HETE-2 via the GRB Coordinates Network. The pointing is readjusted when the position is refined to 5” accuracy by the small optical telescope RIBOTS using the optical image of the GRB, and we then take an exposure immediately with the slit-less spectrograph.

Rapid Optical Follow‐up Observations of SGR Events with ROTSE‐I

In order to observe nearly simultaneous emission from gamma-ray bursts (GRBs), the Robotic Optical Transient Search Experiment (ROTSE) receives triggers via the GRB Coordinates Network (GCN). Since beginning operations in 1998 March, ROTSE has also taken useful data for 10 SGR events: eight from SGR 1900+14 and two from SGR 1806-20. We have searched for new or variable sources in the error regions of these SGRs, and no optical counterparts were observed. Limits are in the range mROTSE ≈ 12.5-15.5 during the period 20 s to 1 hr after the observed SGR events.