On the detection of
gravitational waves by the Laser Interferometer Gravitational-Wave Obsevatory (LIGO)
The direct
detection of gravitational waves is one of those events long-expected by
physicists that are nevertheless a significant occurrence which excites the
world scientific community as if something unexpected has happened. The event
that happened on September 14, 2015 was not kept in utmost secrecy; however,
everybody was waiting for the press conference that took place on February 11,
2016
(the link can be found, e.g., here ) and, most importantly, the paper. Many rumors
leaked ahead of the conference, and the fact that something (that is, a signal
corresponding to gravitational waves) was discovered by LIGO (Laser
Interferometer Gravitational-Wave Observatory) was discussed on the sidelines.
The details of the observations and data analysis by the LIGO collaboration (over
1000 people) became available on the arXiv server on February 12, 2016. These papers,
including the technical ones, are listed below:
- The LIGO Scientific Collaboration, the
Virgo Collaboration. Astrophysical Implications of the Binary Black-Hole Merger
GW150914. ApJL, 818, L22, 2016. arXiv:1602.03846
- B. P. Abbott, R. Abbott, T. D. Abbott, et
al. The
Rate of Binary Black Hole Mergers Inferred from Advanced LIGO Observations
Surrounding GW150914. arXiv:1602.03842
- The LIGO Scientific Collaboration, the
Virgo Collaboration. GW150914: Implications for the stochastic gravitational wave
background from binary black holes. arXiv:1602.03847
- The LIGO Scientific Collaboration: B. P.
Abbott, et al. Calibration of the Advanced LIGO detectors for the discovery of the
binary black-hole merger GW150914. 1602.03845
- The LIGO Scientific Collaboration, the
Virgo Collaboration. Characterization of transient noise in Advanced LIGO relevant to
gravitational wave signal GW150914. arXiv:1602.03844
- The LIGO Scientific Collaboration, the
Virgo Collaboration. Observing gravitational-wave transient GW150914 with minimal
assumptions. 1602.03843
- The LIGO Scientific Collaboration, the
Virgo Collaboration. Properties of the binary black hole merger GW150914. arXiv:1602.03840
- The LIGO Scientific Collaboration, the
Virgo Collaboration. GW150914: First results from the search for binary black hole
coalescence with Advanced LIGO. arXiv:1602.03839
- The LIGO Scientific Collaboration, the
Virgo Collaboration. GW150914: The Advanced LIGO Detectors in the Era of First
Discoveries. arXiv:1602.03838
- The LIGO Scientific Collaboration, the
Virgo Collaboration. Observation of Gravitational Waves from a Binary Black Hole Merger. Physical
Review Letters 116,
061102 (2016), arXiv:1602.03837.
At the same
time, papers by authors who, apparently, expected this day knowing about the
LIGO results, appeared on arXiv:
- P.A. Evans, J.A. Kennea,
S.D. Barthelmy, et al. Swift follow-up of the
Gravitational Wave source GW150914. To
be submitted to MNRAS letters. arXiv:1602.03868
- I.Bartos, B.Kocsis,
Z.Haiman, S.Marka. Rapid and Bright Stellar-mass
Binary Black Hole Mergers in Active Galactic Nuclei. arXiv:1602.03831
- J. J. Eldridge, E. R. Stanway.
BPASS
predictions for Binary Black-Hole Mergers. Submitted
to MNRAS. arXiv:1602.03790
- T.L. Campante, I.Lopes, D.Bossini, et al. Asteroseismology of red-giant stars as a novel
approach in the search for gravitational waves. Submitted to Astronomy in
Focus, to appear in the Proc. IAU XXIX GA.
arXiv:1602.03667
- J. P. W. Verbiest,
L. Lentati, et al. The International Pulsar Timing
Array: First Data Release. Accepted for
publication in MNRAS. arXiv:1602.03640
- Maurice H.P.M. Van Putten.
Directed
searches for broadband extended gravitational-wave emission in nearby
energetic core-collapse supernovae. To
appear in ApJ. arXiv:1602.03634
- R. Ruffini, J.
A. Rueda, M. Muccino,
et al. On
the rate and on the gravitational wave emission of short and long GRBs. arXiv:1602.03545
- E.Calabrese, N.Battaglia,
D.N. Spergel. Testing Gravity with Gravitational Wave
Source Counts. (Comments:
Comments welcome, congratulations
to the LIGO team) arXiv:1602.03883
- M.A.Resco, A. de la Cruz-Dombriz, F.J. Llanes
Estrada, et al. On
neutron stars in f(R) theories: small radii, large masses and large energy
available for emission in a merger. arXiv:1602.03880
We can note
the FERMI collaboration preprint (V. Connaughton,
E. Burns, A. Goldstein, Fermi GBM Observations of LIGO
Gravitational Wave event GW150914. ) which was not posted to arXiv
at the time [ the paper appeared on arXiv on February
15, 2016: arXiv:1602.03920. ]. Also, several important popular-science
comments from physicists and astrophysicists appeared on the RuNet during the first three days, and some even earlier
(we list only a few of them here):
We should point out straight away that
the attempts to register and investigate experimentally the gravitational
waves, which were predicted in Albert Einstein's general theory of relativity,
were started in the 60's by Joseph Weber, a professor of physics at the
University of Maryland (USA). Despite the pessimistic
results of the experiments, the research was continued in many countries,
including the USSR.
We should mention that the principle of using a laser interferometer (also
employed in LIGO) to detect gravitational waves was proposed in the works of
Soviet physicists (M.E. Gertsenshtein, V.I. Pustovoit, JETP, 43, 605, 1962) back in 1962, and later also by J. Weber. Active investigations in this field are (and
have been) carried out by members of the group lead by V.B. Braginsky at the physics faculty of MSU (see the interview with Sergey Vyatchanin
and the book by Kip Thorne "Black Holes and Time Warps"), also
included in the LIGO collaboration [among the useful Russian-language links we
note also (V.M. Lipunov The gravitational wave
sky. ISSEP, V.6, No 4, p. 77 (2000); V. N. Rudenko. "The search for
gravitational waves". Chapter in a book published by "Vek 2", 2007)].
The construction of LIGO began in
the 90's (by the initiative of Rainer Weiss, Ronald Drever,
and Kip Thorne). Observations were conducted with LIGO in 2002-2010, with no
results. In September 2015, during the calibration measurements for the
modernized "Advanced LIGO" project, a signal was detected with a significance
above 5.1 sigma, corresponding to the one expected for the merger of two
massive compact objects.
Here we need to show several figures available from the LIGO website.
Fig.1. Scheme of the LIGO laser interferometer.
Fig.2. Photo of the gravitational wave detector in Hanford:
Fig.3. The signal of the event GW150914, registered by the two LIGO detectors,
interpreted as a result of a gravitational wave (which developed as a result of
a merger of two black holes) passing through the interferometer. Right: data
from the facility in Hanford