The 2nd international conference on particle physics and astrophysics Origin and registration of gravitational waves in space and on the Earth G.S.Bisnovatyi-Kogan, Space Research Institute of RAS, Moscow, Russia, and National Research Nuclear University “MEPhI”, Moscow, Russia The 2nd international conference on particle physics and astrophysics Moscow, October 11, 2016

Discovery of pulsars: A.Hewish, J.Bell et al., 1968, Nature, 217, 709 1973: all pulsars are single (more than 100) more than half massive stars (predesessors of pulsars) are in binaries. Possible explanations: pair disruption during explosion no possibility to form a radiopulsar in pairs 1971: X-ray satellite UHURU Discovery of X-ray pulsars in binaries. Her X-1: X ray pulsar Period of pulsations P(p)=1.24 sec, orbital P(orb)=1.7 days Neutron star mass 1.4 Solar masses Optical star mass about 2 Solar masses

This system should give birth to the binary radiopulsar Bisnovatyi-Kogan G.S. and Komberg B.V., 1974, Astron. Zh. 51,373 Reasons: 1. After 100 million years the optical star will become a white dwarf, mass transfer will be finished, and the system will be transparant to radio emission. 2. X ray pulsar is accelerating its rotation due to accretion, so after the birth of the white dwarf companion the neurton star will rotate rapidly, P(p) about 100 msec. Question: Why are the binary radiopulsars not found (1973) ? Answer (B-K, K, 1974): Because the magnetic field of the neutron star is decreasing about 100 times during the accretion, so binary radiopulsars are very faint objects, Pulsar luminosity L ~ B /P At small B luminosity L is low even at the rapid rotation Magnetic field is screened by the infalling plasma

Physics Today 1975, 28, No.11, pp. 46-54 Informal discussion at Landau Theor. Inst. Left to right: G.S.Bisnovatyi-Kogan, I.D.Novikov, Academicians V.L.Ginzburg and Ya.B.Zeldovich, and David Pines. (Photo G.Baym)

Rapid rotation and Small magnetic field The properties of the first binary pulsar coinside with our predictions: Rapid rotation and Small magnetic field The average magnetic fields of single radiopulsars is about 10 Gauss.

New class of neutron stars: recycled pulsars, more than 180 objects. All passed the stage of accreting pulsars, accelerating the rotation and decreasing the magnetic field. Ordinary pulsars Recycled pulsars P=0.033 – 8 sec P=1.5 – 50 msec B= 10 - 10 Gauss B=10 - 10 Gauss

GR Effects: NS+NS

GR is confirmed with precision ~0.01%

MERGING of COMPACT STARS in CLOSE BINARIES (LIGO-VIRGO)

Kalogera V et al. Astrophys. J. Lett. 601 L179; 614 L137 (2004) Probability density function that represents our expectation that the actual DNS binary merger rate in the Galaxy ( bottom axis) and the predicted initial LIGO rate ( top axis) take on particular values, given the observations. The solid line shows the total probability density along with those obtained for each of the three binary systems ( dashed lines). Inset: Total probability density, and corresponding 68%, 95%, and 99% confidence limits, shown in a linear scale. Kalogera V et al. Astrophys. J. Lett. 601 L179; 614 L137 (2004)

For the model of pulsar evolution, the mean galactic merging rate of BNS systems is R~83/ Myr. The 68%- and 95%-confidence level intervals are 40 ± 140 and 20 ± 290 /Myr, respectively. The expected detection rate of a gravitational-wave pulse from neighboring galaxies is 0.035 and 190 events per year for the initial (the detection limit 20 Mpc) and advanced (the detection limit 350 Mpc) LIGO interferometers, respectively. The corresponding 95%-confidence intervals are 0.007 ± 0.12 and 40 ± 660 events per year, respectively. The discovery of the double pulsar J0737-3039 increased R by 6.4 times compared to earlier calculations, because it dominates in computing the total probability, as seen in Fig. Examination of a broader class of evolutionary models of pulsars showed that in all cases, accounting for the double pulsar J0737 ± 3039 increases the BNS merging rate by 6 - 7 times, although the rates can differ by more than 50 times in individual cases

Nonspherical Gravitational Collapse (LIGO-VIRGO)

Uniform collapse without rotation 51 <~10 erg 0.109 >~ 2 10 erg for rapid rotation 45 Radiated during the collapse to maximal compression Schwarzschild radius, minimal value of large semi-axis

Maximum GW radiation is during the bounce A- the large axis, C – minimal value of C, A/C may be >> 1, K~0.01 f f The formal upper limit: Never reached

arXiv:070526755

Time evolution of the GW amplitude h and maximum density for three representative models with different rotation profiles and initial rotation rates i, at a distance d = 10 kpc .

Characteristic GW strain spectra h_c,sp at a distance d = 10 kpc to the source for three representative models in GR with microphysical EoS and deleptonization that do not undergo centrifugal bounce. As for most other models the individual maxima f_max of their frequency spectrum is very close to fmax ≃ 718 Hz.

Zeldovich “pancakes”, and emission of very long GW (Coherent Pulsar glitches ?) 1. A simplified model of the formation of structures in dark matter and a background of very long gravitational waves Bisnovatyi-Kogan, MNRAS 347, 163 (2004) 2. Nonlinear Dynamics of self-gravitating uniform non-rotating spheroid B.-K., Tsupko Mon. Not. R. Astron. Soc. 386, 1398–1403 (2008)

Emission of very long gravitational waves Bisnovatyi-Kogan (2004) The energy emitted in GW: If all dark matter had passed through the stage of pancake formation, then very long GW have an average energy density in the Universe

Amplitude of GW:

Observation of Gravitational Waves from a Binary Black Hole Merger B. P. Abbott et al.* (LIGO Scientific Collaboration and Virgo Collaboration) On September 14, 2015 at 09:50:45 UTC the two detectors of the Laser Interferometer Gravitational-Wave Observatory simultaneously observed a transient gravitational-wave signal. The signal sweeps upwards in frequency from 35 to 250 Hz with a peak gravitational-wave strain h of 1.0 × 10−21. It matches the waveform predicted by general relativity for the inspiral and merger of a pair of black holes and the ringdown of the resulting single black hole. The signal was observed with a matched-filter signal-to-noise ratio of 24 and a false alarm rate estimated to be less than 1 event per 203 000 years, equivalent to a significance greater than 5.1σ. The source lies at a luminosity distance of 410 (+160−180 )Mpc corresponding to a redshift z=0.09(+0.03 −0.04) . In the source frame, the initial black hole masses are 36(+5 −4)M⊙ and 29(+4 −4)M⊙, and the final black hole mass is 62(+4 −4)M⊙, with 3.0(+0.5 −0.5)M⊙c2 radiated in gravitational waves. All uncertainties define 90% credible intervals.These observations demonstrate the existence of binary stellar-mass black hole systems. This is the first direct detection of gravitational waves and the first observation of a binary black hole merger. PhysRevLett.116.061102 (2016)

Individual detector reliability: This corresponds to a probability < 2 × 10−6 of observing one or more noise events as strong as GW150914 during the analysis time, equivalent to 4.6σ. In the background of this class there are four events with ηc ≥ 32.1, yielding a false alarm rate for GW150914 of 1 in 8 400 years. This corresponds to a false alarm probability of 5 × 10−6 equivalent to 4.4σ. No detection of close binary with two massive BH in the Galaxy No BH+NS (radio pulsar) binaries

GW151226: Observation of Gravitational Waves from a 22-Solar-Mass Binary Black Hole Coalescence B. P. Abbott et al. (LIGO Scientific Collaboration and Virgo Collaboration) Phys. Rev. Lett. 116, 241103 We report the observation of a gravitational-wave signal produced by the coalescence of two stellar-mass black holes. The signal, GW151226, was observed by the twin detectors of the Laser Interferometer Gravitational-Wave Observatory (LIGO) on December 26, 2015 at 03:38:53 UTC. The signal was initially identified within 70 s by an online matched-filter search targeting binary coalescences. Subsequent off-line analyses recovered GW151226 with a network signal-to-noise ratio of 13 and a significance greater than 5σ. The signal persisted in the LIGO frequency band for approximately 1 s, increasing in frequency and amplitude over about 55 cycles from 35 to 450 Hz, and reached a peak gravitational strain of 3.4(+0.7−0.9)×10−22. The inferred source-frame initial black hole masses are 14.2(+8.3−3.7)M⊙ and 7.5(+2.3−2.3)M⊙, and the final black hole mass is 20.8(+6.1−1.7)M⊙. We find that at least one of the component black holes has spin greater than 0.2. This source is located at a luminosity distance of 440(+180−190)  Mpc corresponding to a redshift of  0.09(+0.03−0.04). All uncertainties define a 90% credible interval. This second gravitational-wave observation provides improved constraints on stellar populations and on deviations from general relativity.

Conclusions 1. GW have been discovered 25 years ago in observations of binary pulsar 2. GW are radiated mainly during the first bounce in non-spherical core collapse, frequency 10-1000 Hz. 3. GW radiated during merging of NS +NS, NS+BH, BH+BH, have a chance to be registered by LIGO. The last ones are probably registered.