On August 17, 2017 astronomers around the world were alerted to the discovery of a binary neutron star coalescence candidate 8 (later designated GW170817) observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The 9 time of merger was determined to be August 17, 2017, 12:41:04 UTC, just 1:7 s before a gamma-ray burst (GRB170817A), 10 which had been reported earlier by the Fermi Gamma-ray Burst Monitor. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of 40+8 11 8Mpc and with component masses consistent with 12 neutron stars. An extensive observing campaign was immediately launched across the electromagnetic spectrum leading to the 13 discovery of a bright optical transient (SSS17a, now with the IAU identification of AT2017gfo) in NGC 4993 (at 40Mpc) 14 by the One-Meter, Two Hemisphere (1M2H) team less than 11 hours after the merger. The optical transient was independently 15 detected by multiple teams within an hour. Subsequent observations targeted the transient and its environment. Early ultraviolet 16 observations revealed a blue transient which faded in less than 48 hours. Optical and infrared observations revealed a redward 17 evolution over about 10 days. Following early non-detections, delayed X-ray emission was discovered 9 days after the merger 18 at the position of the optical and infrared transient. This was followed by the discovery of a radio counterpart 16 days after 19 the merger. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in 20 NGC 4993 followed by a short-gamma-ray burst (GRB170817A) and radioactive decay of r-process nuclei synthesized in the 21 ejecta, known as kilonova/macronova. They also provide a unique data set with which to study this cataclysmic event from 22 100 s before merger through several weeks after.
Multi-messenger Observations of a Binary Neutron star Merger
Cattaneo P;
2017-01-01
Abstract
On August 17, 2017 astronomers around the world were alerted to the discovery of a binary neutron star coalescence candidate 8 (later designated GW170817) observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The 9 time of merger was determined to be August 17, 2017, 12:41:04 UTC, just 1:7 s before a gamma-ray burst (GRB170817A), 10 which had been reported earlier by the Fermi Gamma-ray Burst Monitor. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of 40+8 11 8Mpc and with component masses consistent with 12 neutron stars. An extensive observing campaign was immediately launched across the electromagnetic spectrum leading to the 13 discovery of a bright optical transient (SSS17a, now with the IAU identification of AT2017gfo) in NGC 4993 (at 40Mpc) 14 by the One-Meter, Two Hemisphere (1M2H) team less than 11 hours after the merger. The optical transient was independently 15 detected by multiple teams within an hour. Subsequent observations targeted the transient and its environment. Early ultraviolet 16 observations revealed a blue transient which faded in less than 48 hours. Optical and infrared observations revealed a redward 17 evolution over about 10 days. Following early non-detections, delayed X-ray emission was discovered 9 days after the merger 18 at the position of the optical and infrared transient. This was followed by the discovery of a radio counterpart 16 days after 19 the merger. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in 20 NGC 4993 followed by a short-gamma-ray burst (GRB170817A) and radioactive decay of r-process nuclei synthesized in the 21 ejecta, known as kilonova/macronova. They also provide a unique data set with which to study this cataclysmic event from 22 100 s before merger through several weeks after.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
