On August 17, 2017 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB170817A) with a time-delay of 1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of 40+-8 Mpc. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient SSS17a or. AT2017gfo in NGC4993 (at 40 Mpc) less than 11 hours after the merger. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over 10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position 9 and 16 days, respectively, after the merger. No ultra-high-energy gamma rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC4993. Multimessenger observations of the GW/GRB170817 mark the birth of multimessenger astronomy, and were listed in the first place among the Top 10 Breakthrough discoveries in 2017 by the IoP journal Physics World. In just a few months since its publication, the paper already obtained 164 citations.
COBISS.SI-ID: 4941051
This paper was published on Oct 16th 2017, in conjunction with others presented in the historic LIGO and ESO press conference on that day, announcing the first detection of an electromagnetic counterpart to a gravitational wave event. The merger of two dense stellar remnants including at least one neutron star is predicted to produce gravitational waves (GWs) and short-duration gamma ray bursts. In the process, neutron-rich material is ejected from the system and heavy elements are synthesized by r-process nucleosynthesis. The radioactive decay of these heavy elements produces additional transient radiation termed kilonova or macronova. We report measurements obtained with the Very Large Telescope in Chile and the detection of linear optical polarization, P = (0.50 ± 0.07)%,1.46 days after detection of the GWs from GW 170817—a double neutron star merger associated with an optical macronova counterpart and a short gamma ray burst. The polarization measurement was made when the macronova was still in its blue phase. The low degree of polarization is consistent with intrinsically unpolarized emission scattered by galactic dust, suggesting a symmetric geometry of the emitting region and low inclination of the merger system. Results were published in new addition to the Nature family in 2017: Nature Astronomy.
COBISS.SI-ID: 819073
We present a catalog of early-time photometry and polarimetry of all gamma-ray burst (GRB) optical afterglows observed with the RINGO2 imaging polarimeter on the Liverpool Telescope. Of the 19 optical afterglows observed, the following nine were bright enough to perform photometry and attempt polarimetry: GRB 100805A, GRB 101112A, GRB 110205A, GRB 110726A, GRB 120119A, GRB 120308A, GRB 120311A, GRB 120326A, and GRB 120327A. We present multiwavelength light curves for these 9 GRBs, together with estimates of their optical polarization degrees and/or limits. We confirm previous reports of significant polarization in GRB 110205A and 120308A, and report the new detection of P={6}-2+3% in GRB101112A.
COBISS.SI-ID: 810881