Vol 45, No 7 (2019)

We investigate the possibility of transferring the galaxy cluster mass scale calibrations from weak-lensing measurements to X-ray cluster mass measurements using Planck cluster mass measurements. For this purpose, we compare the mass measurements for 47 galaxy clusters that simultaneously enter the X-ray sample of clusters from Vikhlinin et al. (2009a, 2009b) and the sample of galaxy clusters from the second Planck catalogue of Sunyaev-Zeldovich sources. We show that except for a few outliers in the measurements, most of which arise from cluster projection effects in the Planck data, the scatter in the mass ratio turns out to be small, ~15%, while the accuracy of determining the mean mass ratio for this sample is about 2%. This allows the existing cluster mass measurement calibrations in the Planck survey to be transferred to Chandra X-ray mass measurements almost without any loss of accuracy. Using the derived relations and based on new cluster mass scale calibrations from weak-lensing measurements in clusters, we have obtained corrections to the constraints on cosmological parameters from Vikhlinin et al. (2009b). Given these corrections, σ₈ increases approximately by 4%, within one standard deviation of the uncertainty in the constraint on this quantity at constant Ω_m. We show that, given the systematic uncertainties, all of the currently available galaxy cluster mass function measurements yield approximately identical constraints on the parameters σ₈ and Ω_m.

An analysis of the spectra for the anomalous supernova ASASSN-15nx with a linear light curve has ruled out the emission mechanisms through radioactivity and shock interaction with circumstellar gas. An alternative mechanism for the emission of ASASSN-15nx based on the interaction of a rotating neutron star magnetosphere with gravitationally bound ejecta material is proposed. In the regime of stationary accretion the neutron star rotation frequency and the rotational energy losses decrease exponentially with time, which can explain the linearity of the light curve. Modeling of the light curve at the initial stage of the luminosity rise in combination with the expansion velocity suggest a low ejecta mass, ~1 M_⨀. The shape of the [O I] 6300, 6364 Å doublet profile points to asphericity of the oxygen distribution, which, in turn, provides evidence for a highly aspherical explosion.

For the low-amplitude Cepheid BG Cru we have constructed an O - C diagram spanning a time interval 118 years. The O - C diagram has the shape of a parabola, which has made it possible to determine for the first time the quadratic light elements and to calculate the rate of evolutionary decrease in the period, dP/dt = −0.0787 (±0.0230) s yr⁻¹. This points to the second crossing of the instability strip. The pulsation stability test proposed by Lombard and Koen (1993) confirms that the period decrease is real.

The paper is devoted to determining the parameters of the three-dimensional Ogorodnikov—Milne kinematic model based on the Gaia DR2 star catalogue (the subset of seven million stars containing radial velocities). The behavior of the parameters as a function of the distance to stars is studied. The parameters derived from the stellar proper motions and radial velocities agree well with one another. It is noted that the angular velocity of rotation retains its stability up to distances of ~3 kpc, while the parameter responsible for the translational motion along the Y axis abruptly begins to change from distances starting from 1 kpc.