Vol 45, No 11 (2019)

The results of observations of the gravitational-wave (GW) event S190425z recorded by the LIGO/Virgo detectors with the anti-coincidence shield (ACS) of the SPI gamma-ray spectrometer onboard the INTEGRAL observatory are presented. With a high probability (>99%) it was associated with a neutron star (NS) merger in a close binary system. This is only the second event of such a type in the history of gravitational-wave observations (after GW170817). A weak gamma-ray burst, GRB190425, consisting of two pulses ∼0.5 and ∼5.9 s after the NS merger in the event S190425z with an a priori significance of 3.5 and 4.4σ (taken together 5.5σ) was detected by SPI-ACS. Analysis of the SPI-ACS count rate history recorded on these days (a total of ∼125 ks of observations) has shown that the rate of random occurrence of two close spikes with the characteristics of GRB190425 does not exceed 6.4 × 10⁻⁵ s⁻¹ (i.e., such events occur by chance, on average, every ∼4.3 hours). Note that the time profile of GRB190425 has much in common with the profile of GRB170817A accompanying the event GW170817, that both NS mergers were the nearest (≤150 Mpc) of all the events recorded by the LIGO/Virgo detectors, and that no significant excesses of the gamma-ray flux above the background were detected in any of ∼30 black hole merger events recorded to date by these detectors. No bursts of hard radiation were detected in the field of view of the SPI and IBIS/ISGRI gamma-ray telescopes onboard INTEGRAL. This, along with the absence of detection of gamma-ray emission from GRB190425 by the GBM gamma-ray burst monitor of the Fermi observatory suggesting its occultation by the Earth, allows the localization region for the source of this GWevent to be reduced significantly. The parameters E_iso and E_p for GRB190425 are estimated and compared with those for GRB170817A.

In this work, I construct a LRG sample with the redshift of 0.6 ≤ z ≤ 0.75 from the Sloan Digital Sky Survey Data Release 15 (SDSS DR15), which contains 184172 CMASS LRGs and 27158 eBOSS LRGs and examine the environmental dependence of the u–r, u–g, g–r, r–i, and i–z colors in this galaxy sample. I divide this LRG sample into subsamples with a redshift binning size of Δz = 0.01, and analyze the environmental dependence of the u–r, u–g, g–r, r–i, and i–z colors for these subsamples in each redshift bin. Overall, the u–r, u–g, g–r, and r–i colors of galaxies in LRG sample with the redshift of 0.6 ≤ z ≤ 0.75 are very weakly correlated with the local environment, which shows that minimal environmental dependence of galaxy parameters can continue to higher redshifts. It is noteworthy that i–z color of this CMASS + eBOSS LRG sample shows substantial correlation with the local environment in the redshift region 0.70 ≤ z ≤ 0.75.

We have investigated the methanol CH₃OH lines at frequencies of 19.967 GHz [2₁-3₀ E(v_t = 0) transition] and 20.971 GHz [10₁-11₂ E⁺(v_t = 1) transition] toward the massive region of active star formation G358.931-0.030 with the RT-22 (Simeiz) and RT-26 (HartRAO) radio telescopes. Two new flares have been detected. One of the flares (at 20.971 GHz) is extremely powerful in the frequency range 192-26 GHz. We present our monitoring of the flaring events detected at 19.967 and 20.971 GHz. The time dependence of the flare amplitude reflects the complex structure of the maser emission regions. The velocity structure of the flares is considered.

The high-resolution Jet Propulsion Laboratory DE431 and DE432 planetary ephemeris are used to evaluate the instantaneous eccentricity functions of the orbits of the planets of the solar system from 13 000 BC to 17 000 AD at different time scales. Spectral analyses are performed to determine the frequencies and the amplitudes of the detected perturbations from 0.1-year to 10 000-year periods. Taken as contiguous pairs (Mercury-Venus, Earth-Mars, Jupiter-Saturn, and Uranus-Neptune), we found anti-phase patterns between contiguous planets at specific time scales (30 000 years): namely, the eccentricity of one planet increases while the other decreases. Venus and Earth instead appear in phase. However, on shorter time scales the phase coupling becomes more complex and irregular. Yet, Jupiter and Saturn present a π/2 phase coupling at the 1000-year scale. Periodogram analysis of the planetary eccentricity functions shows several fast fluctuations whose magnitudes indicate the strength of their mutual interactions where the Jovian planets significantly perturb the orbits of the inner planets. Besides, the wavelet power spectrum and wavelet squared coherence spectrum analyses are adopted to examine the relationships in time-frequency space between the eccentricity functions of each couple of terrestrial and Jovian planets. The analysis reveals the complexity and the evolution of the gravitational couplings perturbing each other planetary orbits. In some cases and for specific frequencies, this analysis technique also led to the discovery that the coherence phase can rotate clockwise or anticlockwise. The eccentricity function of the orbit of Jupiter presents large oscillations with periods of about 60 and 900- 960 years, mostly due to the interaction with Saturn. These oscillations also correspond to oscillations found in several geophysical records. The eccentricity functions of Uranus and Neptune are characterized by a large 4300-year oscillation. The eccentricity function of Pluto is characterized by a large nearly 20 000-year modulation.