NGC 4993 | |
---|---|
Observation data ( J2000 epoch) | |
Constellation | Hydra |
Right ascension | 13h 09m 47.7s [2] |
Declination | −23° 23′ 02″ [2] |
Redshift | 0.009727 [2] |
Heliocentric radial velocity | 2916 km/s [2] |
Distance | 44.1 Mpc (144 Mly) [2] |
Group or cluster | NGC 4993 Group [3] |
Apparent magnitude (V) | 13.32 [2] |
Characteristics | |
Type | (R')SAB0^-(rs) [2] |
Size | ~55,000 ly (17 kpc) (estimated) [2] |
Apparent size (V) | 1.3 x 1.1 [2] |
Notable features | Host of neutron star merger detected as gravitational wave GW170817 and gamma-ray burst GRB 170817A |
Other designations | |
NGC 4994, ESO 508-18, AM 1307-230, MCG -4-31-39, PGC 45657, WH III 766 [4] |
NGC 4993 (also catalogued as NGC 4994 in the New General Catalogue) is a lenticular galaxy [5] located about 140 million light-years away [2] in the constellation Hydra. [6] It was discovered on 26 March 1789 [7] by William Herschel [6] [7] and is a member of the NGC 4993 Group. [3]
NGC 4993 is the site of GW170817, the first astronomical event detected in both electromagnetic and gravitational radiation, the collision of two neutron stars, a discovery given the Breakthrough of the Year award for 2017 by the journal Science. [8] [9] Detecting a gravitational wave event associated with the gamma-ray burst provided direct confirmation that binary neutron star collisions produce short gamma-ray bursts. [10]
NGC 4993 has several concentric shells of stars and large dust lane with diameter of approximately a few kiloparsecs which surrounds the nucleus and is stretched out into an "s" shape. The dust lane appears to be connected to a small dust ring with a diameter of ~330 ly (0.1 kpc). [11] These features in NGC 4993 may be the result [12] of a recent merger with a gaseous late-type galaxy that occurred about 400 million years ago. [13] However, Palmese et al. suggested that the galaxy involved in the merger was a gas-poor galaxy. [14]
NGC 4993 has a dark matter halo with an estimated mass of 193.9×1010 M☉. [13]
NGC 4993 has an estimated population of 250 globular clusters. [5]
The luminosity of NGC 4993 indicates that the globular cluster system surrounding the galaxy may be dominated by metal-poor globular clusters. [15]
NGC 4993 has a supermassive black hole with an estimated mass of roughly 80 to 100 million solar masses (8×107 M☉). [16]
The presence of weak O III, NII and SII emission lines in the nucleus of NGC 4993 and the relatively high ratio of [NII]λ6583/Hα suggest that NGC 4993 is a low-luminosity AGN (LLAGN). [16] The activity may have been triggered by gas from the late-type galaxy as it merged with NGC 4993. [13]
In August 2017, rumors circulated [17] regarding a short gamma-ray burst designated GRB 170817A, of the type conjectured to be emitted in the collision of two neutron stars. [18] On 16 October 2017, the LIGO and Virgo collaborations announced that they had detected a gravitational wave event, designated GW170817. The gravitational wave signal matched prediction for the merger of two neutron stars, two seconds before the gamma-ray burst. The gravitational wave signal, which had a duration of about 100 seconds, was the first gravitational wave detection of the merger of two neutron stars. [1] [19] [20] [21] [22]
An optical transient, AT 2017gfo (also known as SSS 17a), was detected in NGC 4993 11 hours after the gravitational wave and gamma-ray signals, allowing the location of the merger to be determined. The optical emission is thought to be due to a kilonova. The discovery of AT 2017gfo was the first observation (and first localisation) of an electromagnetic counterpart to a gravitational wave source. [19] [21] [22] [23] [24]
GRB 170817A was a gamma-ray burst (GRB) detected by NASA's Fermi and ESA's INTEGRAL on 17 August 2017. [17] [25] [26] [27] Although only localized to a large area of the sky, it is believed to correspond to the other two observations, [23] in part due to its arrival time 1.7 seconds after the GW event.
NGC 4993 | |
---|---|
Observation data ( J2000 epoch) | |
Constellation | Hydra |
Right ascension | 13h 09m 47.7s [2] |
Declination | −23° 23′ 02″ [2] |
Redshift | 0.009727 [2] |
Heliocentric radial velocity | 2916 km/s [2] |
Distance | 44.1 Mpc (144 Mly) [2] |
Group or cluster | NGC 4993 Group [3] |
Apparent magnitude (V) | 13.32 [2] |
Characteristics | |
Type | (R')SAB0^-(rs) [2] |
Size | ~55,000 ly (17 kpc) (estimated) [2] |
Apparent size (V) | 1.3 x 1.1 [2] |
Notable features | Host of neutron star merger detected as gravitational wave GW170817 and gamma-ray burst GRB 170817A |
Other designations | |
NGC 4994, ESO 508-18, AM 1307-230, MCG -4-31-39, PGC 45657, WH III 766 [4] |
NGC 4993 (also catalogued as NGC 4994 in the New General Catalogue) is a lenticular galaxy [5] located about 140 million light-years away [2] in the constellation Hydra. [6] It was discovered on 26 March 1789 [7] by William Herschel [6] [7] and is a member of the NGC 4993 Group. [3]
NGC 4993 is the site of GW170817, the first astronomical event detected in both electromagnetic and gravitational radiation, the collision of two neutron stars, a discovery given the Breakthrough of the Year award for 2017 by the journal Science. [8] [9] Detecting a gravitational wave event associated with the gamma-ray burst provided direct confirmation that binary neutron star collisions produce short gamma-ray bursts. [10]
NGC 4993 has several concentric shells of stars and large dust lane with diameter of approximately a few kiloparsecs which surrounds the nucleus and is stretched out into an "s" shape. The dust lane appears to be connected to a small dust ring with a diameter of ~330 ly (0.1 kpc). [11] These features in NGC 4993 may be the result [12] of a recent merger with a gaseous late-type galaxy that occurred about 400 million years ago. [13] However, Palmese et al. suggested that the galaxy involved in the merger was a gas-poor galaxy. [14]
NGC 4993 has a dark matter halo with an estimated mass of 193.9×1010 M☉. [13]
NGC 4993 has an estimated population of 250 globular clusters. [5]
The luminosity of NGC 4993 indicates that the globular cluster system surrounding the galaxy may be dominated by metal-poor globular clusters. [15]
NGC 4993 has a supermassive black hole with an estimated mass of roughly 80 to 100 million solar masses (8×107 M☉). [16]
The presence of weak O III, NII and SII emission lines in the nucleus of NGC 4993 and the relatively high ratio of [NII]λ6583/Hα suggest that NGC 4993 is a low-luminosity AGN (LLAGN). [16] The activity may have been triggered by gas from the late-type galaxy as it merged with NGC 4993. [13]
In August 2017, rumors circulated [17] regarding a short gamma-ray burst designated GRB 170817A, of the type conjectured to be emitted in the collision of two neutron stars. [18] On 16 October 2017, the LIGO and Virgo collaborations announced that they had detected a gravitational wave event, designated GW170817. The gravitational wave signal matched prediction for the merger of two neutron stars, two seconds before the gamma-ray burst. The gravitational wave signal, which had a duration of about 100 seconds, was the first gravitational wave detection of the merger of two neutron stars. [1] [19] [20] [21] [22]
An optical transient, AT 2017gfo (also known as SSS 17a), was detected in NGC 4993 11 hours after the gravitational wave and gamma-ray signals, allowing the location of the merger to be determined. The optical emission is thought to be due to a kilonova. The discovery of AT 2017gfo was the first observation (and first localisation) of an electromagnetic counterpart to a gravitational wave source. [19] [21] [22] [23] [24]
GRB 170817A was a gamma-ray burst (GRB) detected by NASA's Fermi and ESA's INTEGRAL on 17 August 2017. [17] [25] [26] [27] Although only localized to a large area of the sky, it is believed to correspond to the other two observations, [23] in part due to its arrival time 1.7 seconds after the GW event.