The merger of two dense stellar remnants including at least one neutron star is predicted to produce gravitational waves and shortduration gamma ray bursts. In the process, heavy chemical elements are produced and their radioactive decay produces additional transient radiation termed kilonova or macronova. Here we reported the detection of linear optical polarization, P = (0.50 ± 0.07)%, 1.46 days after detection of the GWs from GW 170817—a double neutron star merger associated with an optical macronova counterpart and a short gamma ray burst. The low degree of polarization is consistent with intrinsically unpolarized emission scattered by galactic dust, suggesting a symmetric geometry of the emitting region and low inclination of the merger system.
COBISS.SI-ID: 819073
We used the LSST simulation framework and defined tidal disruption events (TDE) catalogs on 20 fields of 20.25 deg2 size. Observations of TDEs over 10 years of LSST operation were simulated with the simulated observing strategy database minion_1016. Based on the results of our simulations, we estimate that the LSST should discover between 35,000 and 80,000 TDEs in 10 years of operation, depending on the assumed super-massive black hole mass distribution. We also find that probing the super-massive black hole mass distribution with TDE observations will not be straightforward, due to the fact that TDEs caused by low-mass black holes (10^5M_Sun) are expected to be less luminous and shorter than TDEs by heavier SMBHs () 10^6M_Sun).
COBISS.SI-ID: 5565947
We studied the dynamical behaviour of tidal disruption events produced by an Sgr A*-like massive black hole by changing different initial orbital parameters, taking into account the observed orbits of S stars near our Galactic Center Sgr A*. We performed smoothed particle hydrodynamics simulations, using a polytrope model with ? = 5/3 for the star and a generalised post-Newtonian potential for the black hole, which takes into account the relativistic effects of the Schwarzschild space-time. We find that mass return rate distributions of Solar-like stars and S-like stars with the same eccentricities have similar durations, but S-like stars have higher mass return rate distributions, as expected due to their larger masses. Regarding debris circularisation, we identify four types of evolution related to the mechanisms and processes involved during circularisation.
COBISS.SI-ID: 35712771
We report multicolor optical imaging and polarimetry observations of the afterglow of the first TeV-detected gamma-ray burst (GRB), GRB 190114C, using the RINGO3 and MASTER II polarimeters. Observations begin 31 s after the onset of the GRB and continue until ~7000 s postburst. We model the light curves as a combination of reverse and forward shock components with magnetization parameter RB ~ 70. The observed polarization degree decreases from 7.7% ± 1.1% to 2%–4% 52–109 s postburst and remains steady at this level for the subsequent ~2000 s at a constant position angle. We interpret the measured afterglow polarization as intrinsically low and dominated by dust —in contrast to the P ) 10% measured previously for other GRB reverse shocks.
COBISS.SI-ID: 5602555