List of gravitational wave observations

This page contains a list of observed/candidate gravitational wave events.

The first measurement of a gravitational wave event

Origin and nomenclature

Direct observation of gravitational waves, which commenced with the detection of an event by LIGO in 2015,[1] plays a key role in gravitational wave astronomy. LIGO has been involved in all subsequent detections to date, with Virgo joining in August 2017.[2]

Joint observation runs of LIGO and VIRGO, designated "O1, O2, etc." span many months, with months of maintenance and upgrades in-between designed to increase the instruments sensitivity and range. Within these run periods, the instruments are capable of detecting gravitational waves.

The first run, O1, ran from September 12, 2015, to January 19, 2016, and succeeded in its first gravitational wave detection. O2 ran for a greater duration, from November 30, 2016, to August 25, 2017.[3] O3 began on April 1, 2019, which was briefly suspended on September 30, 2019, for maintenance and upgrades, thus O3a. O3b marks resuming of the run and began on November 1, 2019. Due to the COVID-19 pandemic[4] O3 was forced to end prematurely.[5] O4 is planned to begin on May 24, 2023; initially planned for March, the project needed more time to stabilize the instruments.

The O4 observing run has been extended from one year to 18 months, following plans to make further upgrades for the O5 run.[6][7] Updated observing plans are published on the official website, containing the latest information on these runs.[7]

Gravitational wave events are named starting with the prefix GW, while observations that trigger an event alert but have not (yet) been confirmed are named starting with the prefix S.[8] Six digits then indicate the final two digits of the year the event was observed, two digits for the month and two digits for the day of observation. This is similar to the systematic naming for other kinds of astronomical event observations, such as those of gamma-ray bursts.

Probable detections that are not confidently identified as gravitational wave events are designated LVT ("LIGO-Virgo trigger"). Known gravitational wave events come from the merger of two black holes (BH), two neutron stars (NS), or a black hole and a neutron star (BHNS).[9][10] Some objects are in the mass gap between the largest predicted neutron star masses (Tolman–Oppenheimer–Volkoff limit) and the smallest known black holes.

List of gravitational wave events

Events from LIGO & Virgo

O1 & O2/2015-2017 events

O3/2019 Alerts

List of binary merger events[11][12]

GW event and time (UTC)[n 1]	Date published	Location area[n 2] (deg²)	Luminosity distance (Mpc)[n 3]	Energy radiated/c² (M_☉) [n 4]	Chirp mass (M_☉) [n 5]	Effective spin[n 6]	Primary		Secondary		Remnant			Notes	Ref.
GW event and time (UTC)[n 1]	Date published	Location area[n 2] (deg²)	Luminosity distance (Mpc)[n 3]	Energy radiated/c² (M_☉) [n 4]	Chirp mass (M_☉) [n 5]	Effective spin[n 6]	Type	Mass (M_☉)	Type	Mass (M_☉)	Type	Mass (M_☉)	Spin[n 7]	Notes	Ref.
GW150914 09:50:45	2016-02-11	179; mostly to the south	430+150 −170	3.1+0.4 −0.4	28.6+1.6 −1.5	−0.01+0.12 −0.13	BH [n 8]	35.6+4.8 −3.0	BH [n 9]	30.6+3.0 −4.4	BH	63.1+3.3 −3.0	0.69+0.05 −0.04	First GW detection; first BH merger observed	[18][19][17]
GW151012 09:54:43	2016-06-15	1555	1060+540 −480	1.5+0.5 −0.5	15.2+2.0 −1.1	0.04+0.28 −0.19	BH	23.3+14.0 −5.5	BH	13.6+4.1 −4.8	BH	35.7+9.9 −3.8	0.67+0.13 −0.11	Formerly candidate LVT151012; accepted as astrophysical since February 2019	[20][12][11]
GW151226 03:38:53	2016-06-15	1033	440+180 −190	1.0+0.1 −0.2	8.9+0.3 −0.3	0.18+0.20 −0.12	BH	13.7+8.8 −3.2	BH	7.7+2.2 −2.6	BH	20.5+6.4 −1.5	0.74+0.07 −0.05		[21][22]
GW170104 10:11:58	2017-06-01	924	960+430 −410	2.2+0.5 −0.5	21.5+2.1 −1.7	−0.04+0.17 −0.20	BH	31.0+7.2 −5.6	BH	20.1+4.9 −4.5	BH	49.1+5.2 −3.5	0.66+0.08 −0.10		[13][23]
GW170608 02:01:16	2017-11-16	396; to the north	320+120 −110	0.9+0.0 −0.1	7.9+0.2 −0.2	0.03+0.19 −0.07	BH	10.9+5.3 −1.7	BH	7.6+1.3 −2.1	BH	17.8+3.2 −0.7	0.69+0.04 −0.04	Smallest BH progenitor masses to date	[24]
GW170729 18:56:29	2018-11-30	1033	2750+1350 −1320	4.8+1.7 −1.7	35.7+6.5 −4.7	0.36+0.21 −0.25	BH	50.6+16.6 −10.2	BH	34.3+9.1 −10.1	BH	80.3+14.6 −10.2	0.81+0.07 −0.13	Largest progenitor masses until GW190521	[12]
GW170809 08:28:21	2018-11-30	340; towards Cetus	990+320 −380	2.7+0.6 −0.6	25.0+2.1 −1.6	0.07+0.16 −0.16	BH	35.2+8.3 −6.0	BH	23.8+5.2 −5.1	BH	56.4+5.2 −3.7	0.70+0.08 −0.09		[12]
GW170814 10:30:43	2017-09-27	87; towards Eridanus	580+160 −210	2.7+0.4 −0.3	24.2+1.4 −1.1	0.07+0.12 −0.11	BH	30.7+5.7 −3.0	BH	25.3+2.9 −4.1	BH	53.4+3.2 −2.4	0.72+0.07 −0.05	First announced detection by three observatories; first polarization measurement	[25][26]
GW170817 12:41:04	2017-10-16	16; NGC 4993	40±10	≥ 0.04	1.186+0.001 −0.001	0.00+0.02 −0.01	NS	1.46+0.12 −0.10	NS	1.27+0.09 −0.09	NS [n 10]	≤ 2.8[n 11]	≤ 0.89	First NS merger observed in GW; first detection of EM counterpart (GRB 170817A; AT 2017gfo); nearest event to date	[16][29][30]
GW170818 02:25:09	2018-11-30	39; towards Pegasus	1020+430 −360	2.7+0.5 −0.5	26.7+2.1 −1.7	−0.09+0.18 −0.21	BH	35.5+7.5 −4.7	BH	26.8+4.3 −5.2	BH	59.8+4.8 −3.8	0.67+0.07 −0.08		[12]
GW170823 13:13:58	2018-11-30	1651	1850±840	3.3+0.9 −0.8	29.3+4.2 −3.2	0.08+0.20 −0.22	BH	39.6+10.0 −6.6	BH	29.4+6.3 −7.1	BH	65.6+9.4 −6.6	0.71+0.08 −0.10		[12]
GW190408_181802 2019-04-08	2020-10-27	140	1580+400 −590		18.3+1.4 −1.2	−0.03+0.13 −0.19	BH	24.5+5.1 −3.4	BH	18.3+3.2 −3.5	BH	41.0+3.8 −2.7	0.67+0.06 −0.07		[31]
GW190412 2019-04-12 05:30:44	2020-04-17	156; towards Virgo or Boötes	730+140 −170		13.3+0.4 −0.3	0.25+0.08 −0.11	BH	29.7+5.0 −5.3	BH	8.4+1.8 −1.0	BH	37.0+4.1 −3.9	0.67+0.05 −0.07	First possible observation of a merger of two black holes of very different masses	[32][33]
GW190413_052954 2019-04-13	2020-10-27	1400	4100+2410 −1890		24.0+5.4 −3.7	0.01+0.29 −0.33	BH	33.4+12.4 −7.4	BH	23.4+6.7 −6.3	BH	54.3+12.4 −8.4	0.69+0.12 −0.13		[31]
GW190413_134308 2019-04-13	2020-10-27	520	5150+2440 −2340		31.9+7.3 −4.6	−0.01+0.24 −0.28	BH	45.4+13.6 −9.6	BH	30.9+10.2 −9.6	BH	72.8+15.2 −10.3	0.69+0.10 −0.12		[31]
GW190421_213856 2019-04-21	2020-10-27	1000	3150+1370 −1420		30.7+5.5 −6.6	−0.05+0.23 −0.26	BH	40.6+10.4 −6.6	BH	31.4+7.5 −8.2	BH	68.6+11.7 −8.1	0.68+0.10 −0.11		[31]
GW190424_180648 2019-04-21	2020-10-27	26000	2550+1560 −1330		30.3+5.7 −4.2	0.15+0.22 −0.22	BH	39.5+10.9 −6.9	BH	31.0+7.4 −7.3	BH	67.1+12.5 −9.2	0.75+0.08 −0.09		[31]
GW190425 2019-04-25 08:18:05	2020-01-06	28; towards Hercules[34]	159+69 −72		1.44+0.02 −0.02	0.012+0.01 −0.01	NS	1.60 - 1.87	NS	1.46 - 1.69	?			Originally designated S190425z (z:26th trigger\|UTC day), this trigger was detected by a single LIGO instrument (of three LVC stations), and is considered by some scientists to have been confirmed as a binary neutron star merger.[35] It was published in 2020 that a gamma-ray burst was detected (GRB 190425) ~0.5 seconds after the LIGO trigger, lasting 6 seconds and bearing similarities to GRB170817 (such as weakness [most power in sub-100 keV, or soft X-rays) bands], elevated energetic photon background levels [signal exceeding background by less than a factor of 2], and similar differences from other transients classified as short GRBs). Confidence was established for interpretation of a set of peaks through a control interval of only 2 days prior to the LIGO-Livingston trigger in INTEGRAL Electronic anticoincidence, could not be corroborated by other instruments and wasn't initially noted as a significant event. Non-detection in other instruments may be a consequence of an Earth-occulted source as the Fermi telescope attempted follow-up.[34]	[36][37]
GW190521 2019-05-21 03:02:29	2020-09-02	765; towards Coma Berenices, Canes Venatici, or Phoenix	5300+2400 −2600	7.6+2.2 −1.9	64+13 −8	0.08+0.27 −0.36	BH	85+21 −14	BH	66+17 −18	BH	142+28 −16	0.72+0.09 −0.12	Originally designated S190521g. Largest progenitor masses to date.	[38][39]
GW190814 2019-08-14 21:11:18	2020-06-23	18.5; towards Cetus or Sculptor	241+41 −45		6.09+0.06 −0.06	−0.002+0.06 −0.061	BH	23.2+1.1 −1.0	?	2.59+0.08 −0.09	BH	25.6+1.1 −0.9	0.28+0.02 −0.02	No optical counterpart was discovered despite an extensive search of the probability region. The mass of the lighter component is estimated to be 2.6 times the mass of the Sun, placing it in the mass gap between neutron stars and black holes.[40]	[41][42][43][44][45] [46][47][48][49]
GW200105 2020-01-05 16:24:26	2021-06-29	7200	280±110		3.41+0.08 −0.07	−0.01+0.11 −0.15	BH	8.9+1.2 −1.5	NS	1.9+0.3 −0.2	BH	10.4+2.7 −2.0	0.43+0.04 −0.03	First event confirmed to be a black hole and neutron star merger. Originally designated S200105ae.	[50][51]
GW200115 2020-01-15 04:23:09	2021-06-29	600	300+150 −100		2.42+0.05 −0.07	−0.19+0.23 −0.35	BH	5.7+1.8 −2.1	NS	1.5+0.7 −0.3	BH	7.8+1.4 −1.6	0.38+0.04 −0.03	Second event confirmed to be a black hole and neutron star merger. Originally designated S200115j.	[50][52]

Gravitational Wave Transient Catalog 1. Credit:LIGO Scientific Collaboration and Virgo Collaboration/Georgia Tech/S. Ghonge & K. Jani

Candidate events and marginal detections

Marginal detections from O1 and O2

In addition to well-constrained detections listed above, a number of low-significance detections of possible signals were made by LIGO and Virgo. Their characteristics are listed below:

Marginal event detections
candidate event	Detection time (UTC)	date published	Luminosity distance (Mpc)[n 12]	Detector [n 13]	False Alarm Rate (Yr)	Effective spin	Primary		Secondary		probability of terrestrial noise	Notes	Ref
candidate event	Detection time (UTC)	date published	Luminosity distance (Mpc)[n 12]	Detector [n 13]	False Alarm Rate (Yr)	Effective spin	Type	Mass (M_☉)	Type	Mass (M_☉)	probability of terrestrial noise	Notes	Ref
150928	2015-09-28 10:49:00	2018-11-05		H,L	0.042	-0.70	NS	2.53	NS	1.02	~0.9		[53]
151011	2015-10-11 19:27:49	2019-10-11	1560+1090 −740	H,L	0.12	0.09+0.29 −0.27	BH	51+18 −12	BH	31±12	0.92		[54]
151019	2015-10-19 00:23:16	2018-11-05		H,L	0.060	0.11	BH	14.93	NS	1.27	~0.9		[53]
151205	2015-12-05 19:55:25	2019-10-11	3000+2400 −1600	H,L	0.61	0.14+0.40 −0.38	BH	67+28 −17	BH	42+16 −19	0.47		[54]
151213	2015-12-13 00:12:20	2018-11-05		H,L	0.309	-0.79	BH	11.12	Mass gap	3.30	0.953		[53]
151216A	2015-12-16 09:24:16	2019-10-11	1620+1140 −910	H,L	0.10	0.51+0.21 −0.57	BH	41+15 −17	BH	14.4+7.0 −6.3	0.82		[54]
151216B	2015-12-16 18:49:30	2019-10-11	500+280 −250	H,L	0.03	−0.03+0.24 −0.49	BH	19.7+6.4 −7.4	Mass gap	3.25+1.32 −0.58	0.93	Smaller mass could be a neutron star	[54]
151217	2015-12-17 03:47:49	2019-10-11	1000+660 −440	H,L	0.15	0.70+0.15 −0.50	BH	46+13 −26	BH	8.2+5.1 −1.7	0.74		[54]
151222	2015-12-22 05:28:26	2018-11-05		H,L	0.075	-0.74	BH	6.86	Mass gap	3.26	0.988		[53]
151231	2015-12-31 00:40:30	2019-02-27		H,L							0.85		[55]
160103	2016-01-03 05:48:36	2018-11-05		H,L	0.396	0.49	BH	9.75	BH	7.29	0.939		[53]
170104	2017-01-04 21:58:40	2019-10-11	4600+4300 −3100	H,L	0.03	0.25+0.50 −0.49	BH	98+49 −40	BH	44+30 −33	0.88		[54]
170121	2017-01-21 21:25:36	2019-04-15		H,L		−0.3±0.3	BH	29+4 −3	BH		<0.01		[56]
170123	2017-01-23 20:16:42	2019-10-11	2800+2800 −1600	H,L	0.04	−0.12+0.31 −0.35	BH	44+23 −12	BH	28±13	0.92		[54]
170201	2017-02-01 11:03:12	2019-10-11	1530+1360 −770	H,L	0.16	0.44+0.28 −0.54	BH	48+13 −23	BH	13.1+8.6 −3.7	0.76		[54]
170202	2017-02-02 13:56:57	2019-10-11	1220+980 −640	H,L	0.06	−0.06+0.27 −0.32	BH	33+17 −11	BH	13.8+7.0 −4.8	0.87		[54]
170220	2017-02-20 11:36:24	2019-10-11	3600+3700 −2100	H,L	0.05	0.28+0.33 −0.37	BH	69+37 −25	BH	31+22 −14	0.90		[54]
170304	2017-03-04 16:37:53	2019-10-11	2300+1600 −1200	H,L	2.5	0.11+0.29 −0.27	BH	44.9+17.6 −9.4	BH	31.8+9.5 −11.6	0.30		[54]
170402	2017-04-02 21:51:50	2019-10-21		H,L							0.32		[57]
170403	2017-04-03 23:06:11	2019-10-11	2500+2100 −1300	H,L	0.07	−0.20+0.35 −0.37	BH	53+23 −13	BH	35+13 −15	0.97		[54]
170425	2017-04-25 05:53:34	2019-10-11	2600+2000 −1300	H,L	0.20	−0.06+0.28 −0.32	BH	45+21 −11	BH	30±11	0.79		[54]
170620	2017-06-20 01:14:02	2019-10-11	1710+1300 −850	H,L	0.04	0.05±0.25	BH	29.4+13.2 −6.8	BH	17.9+5.4 −5.5	0.98		[54]
170629	2017-06-29 04:13:55	2019-10-11	1880+1450 −940	H,L	0.06	0.73+0.15 −0.98	BH	49+20 −30	BH	7.3+4.6 −2.6	0.98		[54]
170721	2017-07-21 05:55:13	2019-10-11	1160+750 −520	H,L	0.04	−0.06+0.25 −0.29	BH	31.7+9.3 −6.1	BH	21.4+5.3 −5.6	0.94		[54]
170727	2017-07-27 01:04:30	2019-10-11	2200+1500 −1100	H,L	180	−0.05+0.25 −0.30	BH	41.6+12.8 −7.9	BH	30.4+7.9 −8.2	0.006		[54]
170801	2017-08-01 23:28:19	2019-10-11	1070+920 −580	L,V	0.04	−0.09+0.25 −0.24	BH	23.9+12.6 −6.6	BH	12.4+4.7 −4.0	0.99		[54]
170817A	2017-08-17 03:02:46	2019-10-21		H,L,V	11.5	0.5±0.2	BH	56+16 −10	BH	40+10 −11	0.14		[57]
170818	2017-08-18 09:34:45	2019-10-11	3100+1700 −1900	H,V	0.04	0.06+0.48 −0.45	BH	55+59 −28	BH	23+43 −15	0.99		[54]

Observation candidates from O3/2019

From observation run O3/2019 on, observations are published as Open Public Alerts to facilitate multi-messenger observations of events.[58][59][60] Candidate event records can be directly accessed at the Gravitational-Wave Candidate Event Database (GraceDB).[61] On 1 April 2019, the start of the third observation run was announced with a circular published in the public alerts tracker.[62] The first O3/2019 binary black hole detection alert was broadcast on 8 April 2019. A significant percentage of O3 candidate events detected by LIGO are accompanied by corresponding triggers at Virgo.

False alarm rates are mixed, with more than half of events assigned false alarm rates greater than 1 per 20 years, contingent on presence of glitches around signal, foreground electromagnetic instability, seismic activity, and operational status of any one of the three LIGO-Virgo instruments. For instance, events S190421ar and S190425z weren't detected by Virgo and LIGO's Hanford site, respectively.

The LIGO/Virgo collaboration took a short break from observing during the month of October 2019 to improve performance and prepare for future plans, with no signals detected in that month as a result.[63]

The Kamioka Gravitational Wave Detector (KAGRA) in Japan became operational on 25 February 2020,[64] likely improving the detection and localization of future gravitational wave signals.[65] However, KAGRA does not report their signals in real-time on GraceDB as LIGO and Virgo do, so the results of their observation run will likely not be published until the end of O3.

The LIGO-Virgo collaboration ended the O3 run early on March 27, 2020, due to health concerns from the COVID-19 pandemic.[5][66]

Candidate detections from O3 by month
1 2 3 4 5 6 7 8 9 10 19/04 19/05 19/06 19/07 19/08 19/09 19/10 19/11 19/12 20/01 20/02 20/03 BNS mergers NS-BH mergers BBH mergers mass gap terrestrial noise false positives unidentified

O3 detections by distance
2 4 6 8 10 12 14 16 18 20 <100 Mpc 100-200 Mpc 200-500 Mpc 500-1000 Mpc 1-2 Gpc 2-5 Gpc 5+ Gpc BNS mergers NS-BH mergers BBH mergers mass gap

List of O3 event alerts[11][12]

GW event	Detection time (UTC)	Location area[n 14] (deg²)	Luminosity distance (Mpc)[n 15]	Detector [n 16]	False Alarm Rate (Hz)	False Alarm chance in O3[n 17]	Classification					Notes	Ref
GW event	Detection time (UTC)	Location area[n 14] (deg²)	Luminosity distance (Mpc)[n 15]	Detector [n 16]	False Alarm Rate (Hz)	False Alarm chance in O3[n 17]	NS / NS [n 18]	NS / BH [n 19]	BH / BH [n 20]	Mass gap [n 21]	Terrestrial [n 22]	Notes	Ref
S190408an	2019-04-08 18:18:02	387; towards Pegasus or Lacerta	1473±358	H,L,V	2.8 10⁻¹⁸	8.0 10⁻¹¹	0.0	0.0	~1.0	0.0	9.8e−12		[67][68]
S190421ar	2019-04-21 21:38:56	1444	1628±535	H,L	1.5 10⁻⁸	0.348	0.0	0.0	0.967	0.0	0.033	Initially marked with 96% chance of having a terrestrial origin ["noise"], but later upgraded to 97% chance of being a binary black hole merger.	[69]
S190426c	2019-04-26 15:21:55	1131	377±100	H,L,V	1.9 10⁻⁸	0.418	0.244	0.064	0.0	0.117	0.575	Initially marked with 49% chance of being binary neutron star merger, 13% neutron star-black hole merger, 24% mass gap merger. Later marked with a 52% chance of NS-BH, 22% mass gap, 13% BNS, and 14% terrestrial, before being revised to the current solution	[70][71] [72]
S190503bf	2019-05-03 18:54:04	448; towards Columba, Pictor, or Puppis	421±105	H,L,V	1.6 10⁻⁹	0.045	0.0	0.0047	0.963	0.032	0.00012		[73]
S190510g	2019-05-10 02:59:39	1166; towards Columba or Canis Major	227±92	H,L,V	8.8 10⁻⁹	0.222	0.42	0.0	0.0	0.0	0.58	Initially reported with a 2% chance of terrestrial origin ["noise"], later downgraded to ~58% terrestrial foreground probability ["noise"].	[74]
S190512at	2019-05-12 18:07:14	252; towards Scorpius or Ophiuchus	1388±322	H,L,V	1.9 10⁻⁹	0.053	0.0	0.0	0.990	0.0	0.010		[75]
S190513bm	2019-05-13 20:54:28	691; towards Sagittarius, Capricornus, Perseus, or Camelopardalis	1987±501	H,L,V	3.7 10⁻¹³	1.1 10⁻⁵	0.0	0.0052	0.943	0.052	6.0e−8		[76]
S190517h	2019-05-17 05:51:01	939	2950±1038	H,L,V	1.8 10⁻¹²	5.1 10⁻⁵	0.0	0.00077	0.983	0.017	0.000043		[77]
S190519bj	2019-05-19 15:35:44	967	3154±791	H,L,V	5.7 10⁻⁹	0.150	0.0	0.0	0.956	0.0	0.044		[78]
S190521r	2019-05-21 07:43:59	488; towards Pegasus, Cygnus, Vulpecula, Sagitta, Hercules, Ophiuchus, or Scorpius	1136±279	H,L	3.2 10⁻¹⁰	0.009	0.0	0.0	0.9993	0.0	0.00067		[79]
S190602aq	2019-06-02 17:59:27	1172	797±238	H,L,V	1.9 10⁻⁹	0.053	0.0	0.0	0.990	0.0	0.0097		[80]
S190630ag	2019-06-30 18:52:05	1483	926±259	L,V	1.4 10⁻¹³	4.0 10⁻⁶	0.0	0.0052	0.943	0.052	1.8e−7		[81]
S190701ah	2019-07-01 20:33:45	49; towards Eridanus or Cetus	1849±446	H,L,V	1.9 10⁻⁸	0.418	0.0	0.0	0.934	0.0	0.066		[82]
S190706ai	2019-07-06 22:26:57	826	5263±1402	H,L,V	1.9 10⁻⁹	0.053	0.0	0.0	0.990	0.0	0.010		[83]
S190707q	2019-07-07 09:33:44	921	781±211	H,L	5.3 10⁻¹²	1.5 10⁻⁴	0.0	0.0	0.999989	0.0	0.000011		[84]
S190718y	2019-07-18 14:35:12	7246	227±165	H,L,V	3.6 10⁻⁸	0.642	0.022	0.0	0.0	0.0	0.979	Estimated to have a 98% chance to be terrestrial noise, despite passing data quality checks.	[85]
S190720a	2019-07-20 00:08:53	443; mostly towards Cygnus	869±283	H,L	3.8 10⁻⁹	0.103	0.0	0.0	0.989	0.0	0.011	Initially reported with a 71% chance of being terrestrial "noise" [non-cosmological in origin], upgraded to 1% after preliminary Virgo detector signal path inconsistency found to be insignificant.	[86]
S190727h	2019-07-27 06:03:51	151; towards Cassiopeia, Andromeda or Carina	2839±655	H,L,V	1.4 10⁻¹⁰	0.004	0.0	0.0018	0.922	0.028	0.048		[87]
S190728q	2019-07-28 06:45:27	104; towards Delphinus, Pegasus, or Equuleus	874±171	H,L,V	2.5 10⁻²³	7.1 10⁻¹⁶	0.0	0.144	0.340	0.516	3.6e-13	Updated from an initial estimate which gave 14.4% NS/BH, 34.0% BH/BH, 51.6% mass gap, and a later estimate which gave a virtually certain BH/BH merger.	[88]
S190828j	2019-08-28 06:34:05	228; towards Hydra, Pyxis, Antlia, Vela, Lacerta, or Cygnus	1946±388	H,L,V	8.5 10⁻²²	2.4 10⁻¹⁴	0.0	0.0	~1.0	0.0	3.8e-14		[89]
S190828l	2019-08-28 06:55:09	359; towards Pyxis, Vela, Carina, or Musca	1528±387	H,L,V	4.6 10⁻¹¹	0.001	0.0	0.0	0.9996	0.0	0.00041		[90]
S190901ap	2019-09-01 23:31:01	14753	241±79	L,V	7.0 10⁻⁹	0.181	0.861	0.0	0.0	0.0	0.139		[91]
S190910d	2019-09-10 01:26:19	2482	632±186	H,L	3.7 10⁻⁹	0.100	0.0	0.976	0.0	0.0	0.024		[92]
S190910h	2019-09-10 08:29:58	24264	230±88	L	3.6 10⁻⁸	0.642	0.612	0.0	0.0	0.0	0.388	Detected by only the Livingston detector, resulting in a bad sky localization.	[93]
S190915ak	2019-09-15 23:57:25	318; towards Coma Berenices, Canes Venatici, or Ursa Major	1584±381	H,L,V	9.7 10⁻¹⁰	0.027	0.0	0.0	0.995	0.0	0.0053		[94]
S190923y	2019-09-23 12:55:59	2107	438±133	H,L	4.8 10⁻⁸	0.746	0.0	0.677	0.0	0.0	0.322		[95]
S190924h	2019-09-24 02:18:46	303; towards Hydra or Cancer	548±112	H,L,V	8.9 10⁻¹⁹	2.5 10⁻¹¹	0.0	0.0	0.0	~1.0	4.7e-11	The other component of the merger has a 29.7% chance of being a neutron star, and a 70.3% chance of being either a black hole, or another object in the mass gap.	[96]
S190930s	2019-09-30 13:35:41	1748	709±191	H,L	3.0 10⁻⁹	0.082	0.0	0.0	0.0	0.951	0.049	The other component is either a black hole or another object in the mass gap.	[97]
S190930t	2019-09-30 14:34:07	24220	108±38	L	1.5 10⁻⁸	0.348	0.0	0.743	0.0	0.0	0.257	Detected by only the Livingston detector, resulting in a bad sky localization; last detection of the O3a run.	[98]
S191105e	2019-11-05 14:35:21	643	1183±281	H,L,V	2.3 10⁻⁸	0.481	0.0	0.0	0.953	0.0	0.047	First detection of the O3b run.	[99]
S191109d	2019-11-09 01:07:17	1487	1810±604	H,L	1.5 10⁻¹³	4.3 10⁻⁶	0.0	0.0	0.9999978	0.0	0.0000022		[100]
S191129u	2019-11-29 13:40:29	852	742±180	H,L	2.7 10⁻³⁵	7.7 10⁻²⁸	0.0	0.0	~1.0	0.0	1.2e-27		[101]
S191204r	2019-12-04 17:15:25	103; towards Pictor, Caelum, or Eridanus	678±149	H,L,V	3.1 10⁻²⁵	8.8 10⁻¹⁸	0.0	0.0	~1.0	0.0	8.7e-18		[102]
S191205ah	2019-12-05 21:52:08	6378	385±164	H,L,V	1.2 10⁻⁸	0.290	0.0	0.932	0.0	0.0	0.068		[103]
S191213g	2019-12-13 04:34:08	4480	201±81	H,L,V	3.5 10⁻⁸	0.631	0.768	0.0	0.0	0.0	0.232		[104]
S191215w	2019-12-15 22:30:52	361; towards Canis Major, Puppis, Vela, Carina, Equuleus, Pegasus, or Lacerta	1770±455	H,L,V	1.0 10⁻⁹	0.028	0.0	0.0	0.997	0.0	0.0028		[105]
S191216ap	2019-12-16 21:33:38	253; towards Capricornus, Aquarius, Pegasus, Vulpecula, or Cygnus	376±70	H,V	1.1 10⁻²³	3.1 10⁻¹⁶	0.0	0.0	0.9907	0.0093	8.4e-16	Initially reported to have a ~100% chance of having a component in the mass gap.	[106]
S191222n	2019-12-22 03:35:37	2324	868±265	H,L	6.5 10⁻¹²	1.9 10⁻⁴	0.0	0.0	0.999962	0.0	0.000038		[107]
S200112r	2020-01-12 15:58:38	4004	1125±289	L,V	1.3 10⁻¹¹	3.7 10⁻⁴	0.0	0.0	0.99966	0.0	0.00034		[108]
S200114f	2020-01-14 02:08:18	403; towards Gemini, Orion, or Eridanus	?	H,L,V	1.2 10⁻⁹	0.034	0.0	0.0	0.0	0.0	?	Unidentified gravitational wave "burst" lasting 0.014 seconds at a frequency of tens of Hertz.	[109]
S200128d	2020-01-28 02:20:36	2293	3702±1265	H,L	1.6 10⁻⁸	0.366	0.0	0.0	0.969	0.0	0.031		[110]
S200129m	2020-01-29 06:54:58	41; towards Equuleus, Delphinus, or Vulpecula	755±194	H,L,V	6.7 10⁻³²	1.9 10⁻²⁴	0.0	0.0	~1.0	0.0	2.0e-24		[111]
S200208q	2020-02-08 13:01:17	26; towards Pyxis or Antlia	2142±459	H,L,V	2.5 10⁻⁹	0.069	0.0	0.0	0.9936	0.0	0.0066		[112]
S200213t	2020-02-13 04:10:40	2326	201±80	H,L,V	1.8 10⁻⁸	0.401	0.629	0.0	0.0	0.0	0.371		[113]
S200219ac	2020-02-19 09:44:15	1251	1510±405	H,L,V	1.3 10⁻⁸	0.310	0.0	0.0	0.964	0.0	0.036		[114]
S200224ca	2020-02-24 22:22:34	71; towards Virgo or Crater	1585±331	H,L,V	1.6 10⁻¹¹	4.6 10⁻⁴	0.0	0.0	0.999966	0.0	0.000034		[115]
S200225q	2020-02-25 06:04:21	22; towards Ursa Minor or Cepheus	995±188	H,L	9.2 10⁻⁹	0.231	0.0	0.0	0.957	0.0	0.043		[116]
S200302c	2020-03-02 01:58:11	6704	1737±500	H,V	9.3 10⁻⁹	0.233	0.0	0.0	0.890	0.0	0.110		[117]
S200311bg	2020-03-11 11:58:53	34; towards Cetus	1115±175	H,L,V	8.9 10⁻²⁶	2.5 10⁻¹⁸	0.0	0.0	~1.0	0.0	4.0e-17		[118]
S200316bj	2020-03-16 21:57:56	1117	1222±340	H,L,V	7.1 10⁻¹¹	0.002	0.0	0.0	0.0	0.9957	0.0043	The other component is a black hole.	[119]

Observation candidates from O4/2023

On 15 June 2022, LIGO announced to start the O4 observing run in March 2023.[120] As the date got closer, engineering challenges delayed the observing run to May 2023.[121] An engineering run to assess the sensitivity of LIGO, Virgo, and KAGRA began in April, with the Hanford detector's first operations beginning on April 29,[122] and the Livingston and Virgo detectors' first operations beginning on May 5.[123]

Near the end of the engineering run on 15 May 2023, LIGO announced that O4 would be beginning on 24 May 2023, running for 20 months with up to 2 months of maintenance. The LIGO detectors failed to achieve the hoped for 160-190 mpc sensitivity for neutron star mergers, but did achieve an improved 130-150 mpc sensitivity over O3's 100-140 mpc. Virgo was found to have a damaged mirror, delaying its observing run until late June, and KAGRA achieved its planned 1 mpc neutron star merger sensitivity, with further plans to upgrade beyond 10 mpc by the end of the observing run.

On 18 May 2023, near the end of the engineering run and shortly before O4 proper, the first candidate gravitational wave event was detected.

Candidate detections from O4 by month
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 23/05 23/06 23/07 23/08 23/09 23/10 23/11 23/12 BNS mergers NS-BH mergers BBH mergers mass gap terrestrial noise false positives unidentified

O4 detections by distance
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 <100 Mpc 100-200 Mpc 200-500 Mpc 500-1000 Mpc 1-2 Gpc 2-5 Gpc 5+ Gpc BNS mergers NS-BH mergers BBH mergers mass gap

List of O4 event alerts

GW event	Detection time (UTC)	Location area[n 23] (deg²)	Luminosity distance (Mpc)[n 24]	Detector [n 25]	False Alarm Rate (Hz)	False Alarm chance in O4[n 26]	Classification					Notes	Ref
GW event	Detection time (UTC)	Location area[n 23] (deg²)	Luminosity distance (Mpc)[n 24]	Detector [n 25]	False Alarm Rate (Hz)	False Alarm chance in O4[n 26]	NS / NS [n 27]	NS / BH [n 28]	BH / BH [n 29]	Mass gap [n 30]	Terrestrial [n 31]	Notes	Ref
S230518h	2023-05-18 12:59:07	666	278±68	H,L	3.2 10^-10	0.017	0.0	0.864	0.037	0.0	0.099		[124][125]

Notes

The detection date of a GW event is indicated by its designation; i.e., event GW150914 was detected on 2015-09-14.
The relatively large and distant area of the sky within which it is claimed to be possible to localize the source.
1 Mpc is approximately 3.26 Mly.
c²M_☉ is about 1.8×10³ foe; 1.8×10⁴⁷ J; 1.8×10⁵⁴ erg; 4.3×10⁴⁶ cal; 1.7×10⁴⁴ BTU; 5.0×10⁴⁰ kWh, or 4.3×10³⁷ tonnes of TNT.
The chirp mass is the binary parameter most relevant to the evolution of the inspiral gravitational waveform, and thus is the mass that can be measured most accurately. It is related to, but less than, the geometric mean $(m_{geo})$ of the binary masses, according to $m_{geo}\left({\frac {m_{geo}}{m_{1}+m_{2}}}\right)^{1/5}$ , thus ranging from ~87% of $m_{geo}$ when the masses are the same to ~78% when they differ by an order of magnitude.
The dimensionless effective inspiral spin parameter is: ${\frac {m_{1}a_{1}cos\theta _{LS_{1}}+m_{2}a_{2}cos\theta _{LS_{2}}}{m_{1}+m_{2}}},$ [13] where $m$ is the mass of a black hole, $a$ is its spin, and $\theta _{LS}$ is the angle between the orbital angular momentum and a merging black hole's spin (ranging from $0$ when aligned to $\pi$ when antialigned). It is the mass-weighted linear combination of the components of the black holes' spins aligned with the orbital axis[13][12] and has values ranging from −1 to 1 (the extremes correspond to situations with both black hole spins exactly antialigned and aligned, respectively, with orbital angular momentum).[14] This is the spin parameter most relevant to the evolution of the inspiral gravitational waveform, and it can be measured more accurately than those of the premerger BHs.[15]
Values of the dimensionless spin parameter $a=$ c J/G M² for a black hole range from zero to a maximum of one. The macroscopic properties of an isolated astrophysical (uncharged) black hole are fully determined by its mass and spin. Values for other objects can potentially exceed one. The largest value known for a neutron star is ≤ 0.4, and commonly used equations of state would limit that value to < 0.7.[16]
Spin estimate is 0.26+0.52
−0.24.[17]
Spin estimate is 0.32+0.54
−0.29.[17]
Based on a descending spin-down chirp observed in GW post-merger, a magnetar was produced that survived at least 5 seconds.[27]
Besides the loss of mass due to GW emission that occurred during the merger, the event is thought to have ejected 0.05±0.02 M_☉ of material.[28]
1 Mpc is approximately 3.26 Mly.
Which instruments observed the event. (H = LIGO Hanford, L=LIGO Livingston, V=Virgo)
The area of the sky within which it was possible to localize the source.
1 Mpc is approximately 3.26 Mly.
Which instruments observed the event. (H = LIGO Hanford, L=LIGO Livingston, V=Virgo)
The chance a random signal of this significance would occur at any point in O3's 11-month run. Calculated by 1 - (1-false alarm rate in Hz)^28,512,000. This is not the chance of the given signal being 'real' or not: Background contamination (such as earthquakes) can cause statistically significant signals as well, and although four detections have a >50% chance to have occurred randomly in O3, there is only a 19.4% chance that none of these signals would be real.
Probability that both components have mass < 3 M_☉
Probability that one component has mass < 3 M_☉ and the other has mass > 5 M_☉
Probability that both components have mass > 5 M_☉
Probability that at least one component has a mass in the range 3-5 M_☉, between those of known neutron stars and black holes, a range sometimes identified as the "lower" mass gap
Probability that the source is terrestrial or non-cosmological (e.g. foreground noises and signals [e.g. "noise"] or a technical/systematic error ["glitch"])
The area of the sky within which it was possible to localize the source.
1 Mpc is approximately 3.26 Mly.
Which instruments observed the event. (H = LIGO Hanford, L=LIGO Livingston, V=Virgo)
The chance a random signal of this significance would occur at any point in O4's 20-month run. Calculated by 1 - (1-false alarm rate in Hz)^51,840,000. This is not the chance of the given signal being 'real' or not: Background contamination (such as earthquakes) can cause statistically significant signals as well.
Probability that both components have mass < 3 M_☉
Probability that one component has mass < 3 M_☉ and the other has mass > 5 M_☉
Probability that both components have mass > 5 M_☉
Probability that at least one component has a mass in the range 3-5 M_☉, between those of known neutron stars and black holes, a range sometimes identified as the "lower" mass gap
Probability that the source is terrestrial or non-cosmological (e.g. foreground noises and signals [e.g. "noise"] or a technical/systematic error ["glitch"])

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XML file with preliminary information

External links

"Detections". LIGO.
Video (3:10): LIGO Orrey (1 Dec 2018) on YouTube

This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.

[13] The detection date of a GW event is indicated by its designation; i.e., event GW150914 was detected on 2015-09-14.

[14] The relatively large and distant area of the sky within which it is claimed to be possible to localize the source.

[15] 1 Mpc is approximately 3.26 Mly.

[16] ²M_☉ is about 1.8×10³ foe; 1.8×10⁴⁷ J; 1.8×10⁵⁴ erg; 4.3×10⁴⁶ cal; 1.7×10⁴⁴ BTU; 5.0×10⁴⁰ kWh, or 4.3×10³⁷ tonnes of TNT.

[17] The chirp mass is the binary parameter most relevant to the evolution of the inspiral gravitational waveform, and thus is the mass that can be measured most accurately. It is related to, but less than, the geometric mean $(m_{geo})$ of the binary masses, according to $m_{geo}\left({\frac {m_{geo}}{m_{1}+m_{2}}}\right)^{1/5}$ , thus ranging from ~87% of $m_{geo}$ when the masses are the same to ~78% when they differ by an order of magnitude.

[21] The dimensionless effective inspiral spin parameter is: ${\frac {m_{1}a_{1}cos\theta _{LS_{1}}+m_{2}a_{2}cos\theta _{LS_{2}}}{m_{1}+m_{2}}},$ [13] where $m$ is the mass of a black hole, $a$ is its spin, and $\theta _{LS}$ is the angle between the orbital angular momentum and a merging black hole's spin (ranging from $0$ when aligned to $\pi$ when antialigned). It is the mass-weighted linear combination of the components of the black holes' spins aligned with the orbital axis[13][12] and has values ranging from −1 to 1 (the extremes correspond to situations with both black hole spins exactly antialigned and aligned, respectively, with orbital angular momentum).[14] This is the spin parameter most relevant to the evolution of the inspiral gravitational waveform, and it can be measured more accurately than those of the premerger BHs.[15]

[23] Values of the dimensionless spin parameter $a=$ c J/G M² for a black hole range from zero to a maximum of one. The macroscopic properties of an isolated astrophysical (uncharged) black hole are fully determined by its mass and spin. Values for other objects can potentially exceed one. The largest value known for a neutron star is ≤ 0.4, and commonly used equations of state would limit that value to < 0.7.[16]

[25] Spin estimate is 0.26+0.52
−0.24.[17]

[26] Spin estimate is 0.32+0.54
−0.29.[17]

[37] Based on a descending spin-down chirp observed in GW post-merger, a magnetar was produced that survived at least 5 seconds.[27]

[39] Besides the loss of mass due to GW emission that occurred during the merger, the event is thought to have ejected 0.05±0.02 M_☉ of material.[28]

[64] 1 Mpc is approximately 3.26 Mly.

[65] Which instruments observed the event. (H = LIGO Hanford, L=LIGO Livingston, V=Virgo)

[80] The area of the sky within which it was possible to localize the source.

[81] 1 Mpc is approximately 3.26 Mly.

[82] Which instruments observed the event. (H = LIGO Hanford, L=LIGO Livingston, V=Virgo)

[83] The chance a random signal of this significance would occur at any point in O3's 11-month run. Calculated by 1 - (1-false alarm rate in Hz)^28,512,000. This is not the chance of the given signal being 'real' or not: Background contamination (such as earthquakes) can cause statistically significant signals as well, and although four detections have a >50% chance to have occurred randomly in O3, there is only a 19.4% chance that none of these signals would be real.

[84] Probability that both components have mass < 3 M_☉

[85] Probability that one component has mass < 3 M_☉ and the other has mass > 5 M_☉

[86] Probability that both components have mass > 5 M_☉

[87] Probability that at least one component has a mass in the range 3-5 M_☉, between those of known neutron stars and black holes, a range sometimes identified as the "lower" mass gap

[88] Probability that the source is terrestrial or non-cosmological (e.g. foreground noises and signals [e.g. "noise"] or a technical/systematic error ["glitch"])

[146] The area of the sky within which it was possible to localize the source.

[147] 1 Mpc is approximately 3.26 Mly.

[148] Which instruments observed the event. (H = LIGO Hanford, L=LIGO Livingston, V=Virgo)

[149] The chance a random signal of this significance would occur at any point in O4's 20-month run. Calculated by 1 - (1-false alarm rate in Hz)^51,840,000. This is not the chance of the given signal being 'real' or not: Background contamination (such as earthquakes) can cause statistically significant signals as well.

[150] Probability that both components have mass < 3 M_☉

[151] Probability that one component has mass < 3 M_☉ and the other has mass > 5 M_☉

[152] Probability that both components have mass > 5 M_☉

[153] Probability that at least one component has a mass in the range 3-5 M_☉, between those of known neutron stars and black holes, a range sometimes identified as the "lower" mass gap

[154] Probability that the source is terrestrial or non-cosmological (e.g. foreground noises and signals [e.g. "noise"] or a technical/systematic error ["glitch"])

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[planspage-7] Ligo, Virgo and Kagra Observing Run Plans

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