# List of gravitational wave observations

The first measurement of a gravitational wave event

This is a list of observed gravitational wave events. Direct observation of gravitational waves,[n 1] which commenced with the detection of an event by LIGO in 2015, constitutes part of gravitational wave astronomy. LIGO has played a role in all subsequent detections to date, with Virgo joining in August 2017.

## Nomenclature

Gravitational wave events are named starting with the prefix GW. The next two numbers indicate the year the event was observed, the middle two numbers are the month of observation and the final two numbers are the day of the month on which the event was observed. 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 black holes (BH), neutron stars (NS), or both.

## List of gravitational wave events

List of binary merger events[2][3]
GW event  Detection
time (UTC)
Date
published
Location
area
[n 2]
(deg2)
Luminosity
distance

(Mpc)
[n 3]
Energy
(c2M)
[n 4]
Chirp mass (M)[n 5] Effective spin[n 6] Primary Secondary Remnant Notes Ref
Type Mass (M) Type Mass (M) Type Mass (M) Spin[n 7]
GW150914 2015-09-14
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 [9][10][8]
GW151012 [fr] 2015-10-12
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 [11][3][2]
GW151226 2015-12-26
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
[12][13]
GW170104 2017-01-04
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
[4][14]
GW170608 2017-06-08
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 [15]
GW170729 2017-07-29
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, greatest spin and farthest event to date [3]
GW170809 2017-08-09
08:28:21
2018-11-30
340
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
[3]
GW170814 2017-08-14
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 [16][17]
GW170817 2017-08-17
12∶41:04
2017-10-16
16; NGC 4993
40+10
−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 [7][20][21]
GW170818 2017-08-18
02:25:09
2018-11-30
39
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
[3]
GW170823 2017-08-23
13:13:58
2018-11-30
1651
1850+840
−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
[3]
Gravitational Wave Transient Catalog 1. Credit:LIGO Scientific Collaboration and Virgo Collaboration/Georgia Tech/S. Ghonge & K. Jani

### Future observations from O3/2019

From the observation run O3/2019 on, observations will be published as Open Public Alerts to facilitate multi-messenger observations of events.[22][23]

• GRB 150101B, a gamma ray burst observed before GW detection was possible, with strong similarities to the neutron star merger GW170817

## Notes

1. ^ Indirect evidence for gravitational waves was obtained by 1978 from observations of orbital decay in the neutron star binary PSR B1913+16.[1]
2. ^ The area of the sky within which it was possible to localize the source.
3. ^ 1 Mpc is approximately 3.26 Mly.
4. ^ 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.
5. ^ The chirp mass, very roughly similar to the geometric mean of the binary's masses, 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.
6. ^ The dimensionless effective inspiral spin parameter is: ${\displaystyle {\frac {m_{1}a_{1}cos\theta _{LS_{1}}+m_{2}a_{2}cos\theta _{LS_{2}}}{m_{1}+m_{2}}},}$[4] where ${\displaystyle m}$ is the mass of a black hole, ${\displaystyle a}$ is its spin, and ${\displaystyle \theta _{LS}}$ is the angle between the orbital angular momentum and a black hole's spin (ranging from ${\displaystyle 0}$ when aligned to ${\displaystyle \pi }$ when antialigned). It is the mass-weighted linear combination of the components of the black holes' spins aligned with the orbital axis[4][3] 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).[5] 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.[6]
7. ^ Values of the dimensionless spin parameter ${\displaystyle a=}$ cJ/GM2 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.[7]
8. ^ Spin estimate is 0.26+0.52
−0.24
.[8]
9. ^ Spin estimate is 0.32+0.54
−0.29
.[8]
10. ^ Based on a descending spin-down chirp observed in GW post-merger, a magnetar was produced that survived at least 5 seconds.[18]
11. ^ 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.[19]

## References

1. ^ "The Nobel Prize in Physics 1993". Nobel Foundation. Retrieved 2018-10-27. for the discovery of a new type of pulsar, a discovery that has opened up new possibilities for the study of gravitation
2. ^ a b Nitz, Alexander H. (25 February 2019). "1-OGC: The first open gravitational-wave catalog of binary mergers from analysis of public Advanced LIGO data". Astrophysical Journal. 872 (2): 195. arXiv:1811.01921v2. Bibcode:2019ApJ...872..195N. doi:10.3847/1538-4357/ab0108.
3. Farr, Will M.; et al. (30 November 2018). "GWTC-1: A Gravitational-Wave Transient Catalog of Compact Binary Mergers Observed by LIGO and Virgo during the First and Second Observing Runs" (PDF). arXiv:1811.12907. Bibcode:2018arXiv181112907T. Retrieved 1 December 2018.
4. ^ a b c Abbott, B.P.; et al. (LIGO Scientific Collaboration and Virgo Collaboration) (1 June 2017). "GW170104: Observation of a 50-Solar-Mass Binary Black Hole Coalescence at Redshift 0.2". Physical Review Letters. 118 (22): 221101. arXiv:1706.01812. Bibcode:2017PhRvL.118v1101A. doi:10.1103/PhysRevLett.118.221101. PMID 28621973.
5. ^ Farr, W. M.; Stevenson, S.; Miller, M. C.; Mandel, I.; F arr, B.; Vecchio, A. (2017). "Distinguishing spin-aligned and isotropic black hole populations with gravitational waves". Nature. 548 (7667): 426–429. arXiv:1706.01385. Bibcode:2017Natur.548..426F. doi:10.1038/nature23453. PMID 28836595.
6. ^ Vitale, S.; Lynch, R.; Raymond, V.; Sturani, R.; Veitch, J.; Graff, P. (2017). "Parameter estimation for heavy binary-black holes with networks of second-generation gravitational-wave detectors". Physical Review D. 95 (6): 064053. arXiv:1611.01122. Bibcode:2017PhRvD..95f4053V. doi:10.1103/PhysRevD.95.064053. hdl:1721.1/109575.
7. ^ a b Abbott, B.P.; et al. (LIGO Scientific Collaboration & Virgo Collaboration) (16 October 2017). "GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral". Physical Review Letters. 119 (16): 161101. arXiv:1710.05832. Bibcode:2017PhRvL.119p1101A. doi:10.1103/PhysRevLett.119.161101. PMID 29099225.
8. ^ a b c The LIGO Scientific Collaboration and The Virgo Collaboration (3 June 2016). "An improved analysis of GW150914 using a fully spin-precessing waveform model". Physical Review X. 6 (4): 041014. arXiv:1606.01210. Bibcode:2016PhRvX...6d1014A. doi:10.1103/PhysRevX.6.041014.
9. ^ Abbott, B.P.; et al. (LIGO Scientific Collaboration and Virgo Collaboration) (11 February 2016). "Observation of Gravitational Waves from a Binary Black Hole Merger". Physical Review Letters. 116 (6): 061102. arXiv:1602.03837. Bibcode:2016PhRvL.116f1102A. doi:10.1103/PhysRevLett.116.061102. PMID 26918975.
10. ^ Tushna Commissariat (11 February 2016). "LIGO detects first ever gravitational waves – from two merging black holes". Physics World.
11. ^ Abbott, B.P.; et al. (LIGO Scientific Collaboration and Virgo Collaboration) (21 October 2016). "Binary Black Hole Mergers in the first Advanced LIGO Observing Run". Physical Review X. 6 (4): 041015. arXiv:1606.04856. Bibcode:2016PhRvX...6d1015A. doi:10.1103/PhysRevX.6.041015.
12. ^ Abbott, B.P.; et al. (LIGO Scientific Collaboration and Virgo Collaboration) (15 June 2016). "GW151226: Observation of Gravitational Waves from a 22-Solar-Mass Binary Black Hole Coalescence". Physical Review Letters. 116 (24): 241103. arXiv:1606.04855. Bibcode:2016PhRvL.116x1103A. doi:10.1103/PhysRevLett.116.241103. PMID 27367379.
13. ^ Nemiroff, R.; Bonnell, J., eds. (15 June 2016). "GW151226: A Second Confirmed Source of Gravitational Radiation". Astronomy Picture of the Day. NASA.
14. ^ Overbye, Dennis (1 June 2017). "Gravitational Waves Felt From Black-Hole Merger 3 Billion Light-Years Away". New York Times. Retrieved 1 June 2017.
15. ^ Abbott, B.P.; et al. (LIGO Scientific Collaboration and Virgo Collaboration) (18 December 2017). "GW170608: Observation of a 19-solar-mass Binary Black Hole Coalescence". The Astrophysical Journal Letters. 851 (2): L35. arXiv:1711.05578. Bibcode:2017ApJ...851L..35A. doi:10.3847/2041-8213/aa9f0c.
16. ^ Abbott, B.P.; et al. (LIGO Scientific Collaboration and Virgo Collaboration) (2017-10-06). "GW170814: A three-detector observation of gravitational waves from a binary black hole coalescence". Phys. Rev. Lett. 119 (14): 141101. arXiv:1709.09660. Bibcode:2017PhRvL.119n1101A. doi:10.1103/PhysRevLett.119.141101. PMID 29053306. Lay summary (PDF).
17. ^ Overbye, Dennis (27 September 2017). "New Gravitational Wave Detection From Colliding Black Holes". The New York Times. Retrieved 28 September 2017.
18. ^ van Putten, Maurice H.P.M.; Della Valle, Massimo (January 2019). "Observational evidence for extended emission to GW170817". Monthly Notices of the Royal Astronomical Society: Letters. 482 (1): L46–L49. arXiv:1806.02165. Bibcode:2019MNRAS.482L..46V. doi:10.1093/mnrasl/sly166.
19. ^ Drout, M. R.; Piro, A. L.; Shappee, B. J.; et al. (2017-10-16). "Light curves of the neutron star merger GW170817/SSS17a: Implications for r-process nucleosynthesis". Science. 358 (6370): 1570–1574. arXiv:1710.05443. Bibcode:2017Sci...358.1570D. doi:10.1126/science.aaq0049. PMID 29038375.
20. ^ Abbott, B.P.; et al. (LIGO, Virgo and other collaborations) (October 2017). "Multi-messenger Observations of a Binary Neutron Star Merger" (PDF). The Astrophysical Journal. 848 (2): L12. arXiv:1710.05833. Bibcode:2017ApJ...848L..12A. doi:10.3847/2041-8213/aa91c9.
21. ^ Cho, Adrian (16 October 2017). "Merging neutron stars generate gravitational waves and a celestial light show". Science. Retrieved 16 October 2017.
22. ^ "Observing Plans and Public Alerts". www.ligo.org. LIGO Scientific Collaboration. October 2018. Retrieved 2018-10-28.
23. ^ Singer, Leo P. (16 March 2017). "What constitutes an open, public alert?" (PDF). LSC (LIGO Scientific Collaboration). Retrieved 30 October 2018 – via gw-astronomy.org.