The Laser Interferometer Gravitational Wave Observatory (LIGO) and Virgo Collaborations Observing Run 3 has demanded the development of widely-applicable tools for gravitational wave follow-up. These tools must address the main challenges of the mult
i-messenger era, namely covering large localisation regions and quickly identifying decaying transients. To address these challenges, we present a public web interface to assist astronomers in conducting galaxy-targeted follow-up of gravitational wave events by offering a fast and public list of targets post-gravitational wave trigger. After a gravitational wave trigger, the back-end galaxy retrieval algorithm identifies and scores galaxies based on the LIGO and Virgo computed probabilities and properties of the galaxies taken from the Galaxy List for the Advanced Detector Era (GLADE) V2 galaxy catalogue. Within minutes, the user can retrieve, download, and limit ranked galaxy lists from the web application. The algorithm and website have been tested on past gravitational wave events, and execution times have been analysed. The algorithm is being triggered automatically during Observing Run 3 and its features will be extended if needed. The web application was developed using the Python based Flask web framework. The web application is freely available and publicly accessible at gwtool.watchertelescope.ie.
A long and intense gamma-ray burst (GRB) was detected by INTEGRAL on July 11 2012 with a duration of ~115s and fluence of 2.8x10^-4 erg cm^-2 in the 20 keV-8 MeV energy range. GRB 120711A was at z~1.405 and produced soft gamma-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. We present a comprehensive temporal and spectral analysis of the long-lasting soft gamma-ray emission detected in the 20-200 keV band with INTEGRAL, the Fermi/LAT post-GRB detection above 100 MeV, the soft X-ray afterglow from XMM-Newton, Chandra, and Swift and the optical/NIR detections from Watcher, Skynet, GROND, and REM. We modelled the long-lasting soft gamma-ray emission using the standard afterglow scenario, which indicates a forward shock origin. The combination of data extending from the NIR 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). The analysis of the reverse and forward shock emission reveals an initial Lorentz factor of ~120-340, a jet half-opening angle of ~2deg-5deg, and a baryon load of ~10^-5-10^-6 Msun consistent with the expectations of the fireball model when the emission is highly relativistic. Long-lasting soft gamma-ray emission from other INTEGRAL GRBs with high peak fluxes, such as GRB 041219A, was not detected, suggesting that a combination of high Lorentz factor, emission above 100 MeV, and possibly a powerful reverse shock are required. Similar long-lasting soft gamma-ray emission has recently been observed from the nearby and extremely bright Fermi/LAT burst GRB 130427A.
It is now more than 40 years since the discovery of gamma-ray bursts (GRBs) and in the last two decades there has been major progress in the observations of bursts, the afterglows and their host galaxies. This recent progress has been fueled by the a
bility of gamma-ray telescopes to quickly localise GRBs and the rapid follow-up observations with multi-wavelength instruments in space and on the ground. A total of 674 GRBs have been localised to date using the coded aperture masks of the four gamma-ray missions, BeppoSAX, HETE II, INTEGRAL and Swift. As a result there are now high quality observations of more than 100 GRBs, including afterglows and host galaxies, revealing the richness and progress in this field. The observations of GRBs cover more than 20 orders of magnitude in energy, from 10^-5 eV to 10^15 eV and also in two non-electromagnetic channels, neutrinos and gravitational waves. However the continuation of progress relies on space based instruments to detect and rapidly localise GRBs and distribute the coordinates.
INTEGRAL has two sensitive gamma-ray instruments that have detected 46 gamma-ray bursts (GRBs) up to July 2007. We present the spectral, spatial, and temporal properties of the bursts in the INTEGRAL GRB catalogue using data from the imager, IBIS, an
d spectrometer, SPI. Spectral properties of the GRBs are determined using power-law, Band model and quasithermal model fits to the prompt emission. Spectral lags, i.e. the time delay in the arrival of low-energy gamma-rays with respect to high-energy gamma-rays, are measured for 31 of the GRBs. The photon index distribution of power-law fits to the prompt emission spectra is consistent with that obtained by Swift. The peak flux distribution shows that INTEGRAL detects proportionally more weak GRBs than Swift because of its higher sensitivity in a smaller field of view. The all-sky rate of GRBs above ~0.15 ph cm^-2 s^-1 is ~1400 yr^-1 in the fully coded field of view of IBIS. Two groups are identified in the spectral lag distribution, one with short lags <0.75 s (between 25-50 keV and 50-300 keV) and one with long lags >0.75 s. Most of the long-lag GRBs are inferred to have low redshifts because of their long spectral lags, their tendency to have low peak energies and their faint optical and X-ray afterglows. They are mainly observed in the direction of the supergalactic plane with a quadrupole moment of Q=-0.225+/-0.090 and hence reflect the local large-scale structure of the Universe. The rate of long-lag GRBs with inferred low luminosity is ~25% of Type Ib/c supernovae. Some of these bursts could be produced by the collapse of a massive star without a supernova or by a different progenitor, such as the merger of two white dwarfs or a white dwarf with a neutron star or black hole, possibly in the cluster environment without a host galaxy.
The high redshift (z=0.997) blazar B2 1308+326 was observed contemporaneously at x-ray, optical and radio wavelengths in June 1996. The x-ray observations were performed with ASCA. The ASCA results were found to be consistent with reanalysed data fro
m two earlier ROSAT observations. The combined ASCA and ROSAT data reveal an x-ray spectrum that is best fit by a broken power law with absorber model. The break in the x-ray spectrum is interpreted, to be the emerging importance of inverse Compton (IC) emission which dominates the ASCA spectrum. The faint optical state reported for these observations (m_V=18.3+/-0.25) is incompatible with the high synchrotron flux previously detected by ROSAT. The IC emission detected by both ROSAT and ASCA was not significantly affected by the large change in the synchrotron component. MgII emission was detected with an equivalent width (EW) significantly different from previously reported values. Absorption at a level of in excess of the Galactic value was detected, indicating the possible presence of a foreground absorber. A gravitational microlensing scenario cannot therefore be ruled out for this blazar. B2 1308+326 could be a typical radio-selected BL Lac in terms of peak synchrotron frequency and optical and radio variability but its high bolometric luminosity, variable line emission and high Doppler boost factor make it appear more like a quasar than a BL Lac. It is suggested that B2 1308+326 be considered as the prototype of this class of composite source.
