Astrophysics最新文献

Here, we performed a statistical analysis of the parameters describing the transverse component of the longitudinal magnetic field gradient (∇ _⊥ B _z ) in the active regions of the AR – the AR-averaged transverse component of the longitudinal magnetic field gradient <∇ _⊥ B z >, the average transverse component of the longitudinal magnetic field gradient in the vicinity of a point with its maximum value <max∇ _⊥ B z >, the maximum value of the transverse component of the longitudinal magnetic field gradient between pairs of spots in the AR max(∇ _⊥ B _z ) _sp . For calculating the denoted parameters, magnetograms of the B _z -components of the magnetic field vector at the level of the Sun’s photosphere obtained by the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO) are used. The statistical sample contains data on 75 ARs. The values of the analyzed parameters obtained over the time of monitoring are compared with the level of flare productivity of the AR (the flare index FI). It is shown that: 1. The (langle overline{{nabla }_{perp }{{varvec{B}}}_{z}}rangle ) -FI dependence (the overhead line denotes averaging over the time of monitoring the AR) is quadratic with a correlation coefficient k = 0.54 while the spread in values of the quantity (langle overline{{nabla }_{perp }{{varvec{B}}}_{z}}rangle ) is small (lying within a a range of 0.08-0.12 G km^-1 for the overwhelming majority of the studied regions) and differs very little for regions with low and high flare productivity, which may be explained by the dependence of ∇ _⊥ B _z on the area of the AR. 2. The dependence (langle overline{{text{max}}{nabla }_{perp }{{varvec{B}}}_{z}}rangle ) -FI is quasilinear with a correlation coefficient k = 0.61. 3. The dependence (overline{{text{max}}{nabla }_{perp }{{varvec{B}}}_{z}}) -FI is linear with a correlation coefficient k = 0.63. 4. The threshold values of the analyzed parameters are found: for (langle overline{{nabla }_{perp }{{varvec{B}}}_{z}}rangle ) ≥ 0.078 G km^-1, for (langle overline{{text{max}}{nabla }_{perp }{{varvec{B}}}_{z}}rangle ) ≥ 0.983 G km^-1, and for the parameter max(∇ _⊥ B _z) _sp ≥ 0.118G km^-1. For lower values of the analyzed parameters, no x-ray flares were recorded in any of the ARs of the analyzed sample.

Photometric and spectral observations of 7 stars in the WC and WO sequences were made at the Fesenkov Astrophysical Institute in 2021-2022. These observations served as the basis of estimates of the brightness of the objects in BVRc filters and the absolute fluxes of radiation in the emission lines. Changes in the brightness of WR 121 over the limits of 0^m.1-0^m.15 were recorded. Changes in the fluxes of emission lines were detected in the spectra of several of the objects, WR 4, WR 5, WR 121, and WR 128.

Based on published data on the magnitudes of the magnetic field, models are constructed of several magnetic stars of different types of peculiarity and the parameters of the magnetic field are obtained. Among the hot objects, differences are also discovered in the physical conditions in the regions of the magnetic equators and in the region near the magnetic poles, which are not yet amenable to interpretation.

The paper deals with the investigations of the behaviour and physical acceptability of the spatially homogeneous and isotropic FLRW space-time filled with pressureless matter and Rényi holographic dark energy under the Hubble's IR-cutoff in the framework of f (T, B) gravity. We have calculated some cosmological parameters to study the astrophysical consequences of the constructed model. We discussed their behaviour during the cosmic evolution, in particular, the statefinder and EoS parameters. It is found that the constructed Rényi holographic dark energy model travels from Phantom, ΛCDM, and lastly enters & remains in Quintessence dark energy era with the increase in redshift.

Three new carbon C stars was confirmed among the sample of the Late-Type Stars candidates, selected on the Digitized First Byurakan Survey (DFBS) spectral plates. The DFBS is the digitized version of the First Byurakan Survey (FBS, or Markarian survey). The FBS was the first systematic survey of the extragalactic sky. This objective-prism survey was carried out in 1965-1980 by B.E.Markarian and his colleagues using the 1 m Schmidt telescope of the Byurakan Astrophysical Observatory and resulted in discovery of 1517 UV-excess (Markarian) galaxies. FBS spectral plates have been used long period to search and study faint LTS (C-type and M-type stars) at high Galactic latitudes. In this work we present Gaia DR3 photometric data, spectra, light curves, distances, high above/below Galactic plane, radial velocities (RV), and other important physical characteristics from the modern astronomical catalogues for three new confirmed DFBS C stars. The confirmation is based on Gaia DR3 BP/RP low-resolution spectral database. In our previous studies of the DFBS plates, these objects were presented as LTS candidates. One of the new confirmed objects is N-type C star, which is a Mira-type variable. Two remaining objects, are early CH-type giants at high Galactic latitudes. Most probably they present binary systems.

We have carried out a spectral classification by the activity types for a subsample of blazars from the BZCAT v.5 Catalogue, namely the Flat Spectrum Radio Quasars (FSRQ) candidates, designated in the catalogue as BZQ subtype objects. The classification is based on the Sloan Digital Sky Survey (SDSS) homogeneous medium-resolution optical spectroscopy and along with the standard BPT-type diagnostic diagrams, we have applied our newly introduced fine classification scheme with subtypes of quasars and considering many more features. Out of 1909 BZQ objects, 618 having SDSS spectra were classified, resulting in 445 broad-line QSOs, 19 narrow-line QSOs, 138 broad-line Seyferts, 8 narrow-line Seyferts, and 2 Emission-line galaxies without a proper classification. We have calculated the absolute magnitudes and luminosities for all objects to distinguish QSOs from Seyferts, as defined by the Catalogue of QSOs and Active Galaxies, -22^m.25 separation limit. This way 148 objects changed their BZCAT subtypes between BZQ to BZG, and also 6 BZQ objects to BZU.

In this composition of plasma with negative dust charge, new classical distribution of nonthermal ions and Cairns distributed electrons, both supersonic and subsonic only rarefactive solitons are found to exist. It appears to conclude that the solitons cease to exist at the increase of c. The supersonic (M = 1.4) rarefactive solitons considerably and concavely increase from small amplitude with the increase of the ion to dust density ratio Q for various values of temperature α . The concave but increasing growth of amplitude of the rarefactive solitons for all M (>1) exhibits its distinct character. Smaller the Mach number (e.g., for M = 1.2), smaller is the amplitude of the solitons throughout the range of v₀ (ion drift). The amplitudes of the rarefactive supersonic solitons are found to increase at the increase of the nonthermal parameter β for all r ( =n_e0 /n_i0 ). The dynamical scenario of this model indicates that the mass of the dusts should decrease in the plasma to generate higher amplitude solitons.

The properties of the planetary system TOI-1422, in which two planets of a neptune type orbit around a low-activity star of solar type with an age of about 5 billion years, are examined. We have previously analyzed activity of the star TOI-1422, found indications of the existence of possible activity cycles, and considered estimates of the orbital rotation period P of the star. The inner planet TOI-1422 b belongs to the hot-neptune types; it rotates with an orbit of period about 13 days and has an equilibrium temperature of Teq,b = 867 K. Calculations using a model of atmospheric loss with an energy limit for TOI-1422 b yielded 9.4·10⁸ g/s of matter from the atmosphere. The outer planet of the system TOI-1422 c can also be regarded as a hot neptune; it has an orbital period of 29.3 days, its minimal mass, Mc sini, is 11.1M _⊕ , and the equilibrium temperature is Teq,c = 661 K. For estimating the radius of TOI-1422 c we have used an empirical M-R relation. It was found that the loss of matter from the atmosphere of the planet TOI-1422 c is 7.8·10⁷ g/s and, given the error in the parameters, it may lie within a range from 6.1·10⁷ g/s to 9.7·10⁷ g/s.

The properties of the planetary system TOI-784, in which an earth-like planet orbits a low-activity star of solar type, are examined. Archived V-band measurements of the brightness of TOI-784 in the ASAS 4 data base do not yield reliable indications about the variability of the brightness owing to rotation or about the cyclical long-term variability of this object. A possible estimate of the magnitude of the rotation period of the star is Prot/sini = 41.7 ± 11.4 days. The age of the system according to the empirical gyrochronological relations equals 7.8±3.4 billion years. The average value of the atmospheric activity parameter logR′_HK = – 4.99 which corresponds to the level of low-activity stars with analogous (B-V) color index is found and is close to that of the sun. The radius of the planet TOI-784 b is equal to 1.93 R_⊕, its mass is 9.67 M_⊕, and its average density is 7.4 g/cm³ (the planet is rocky). An estimate of the loss of matter from the atmosphere of the planet TOI-784 b was obtained from an approximate formula corresponding to a model of loss by the atmosphere with a limit on energy. Calculations have shown that the rate of loss of matter by the atmosphere of the planet is 4.7 ⋅ 10⁸ g/s. The relatively low rate of loss of matter by the planet’s atmosphere, despite a high effective temperature of the star’s atmosphere and the closeness of the planet to the star, is probably related to a low level of activity of the star.

Based on published data on the magnitudes of the magnetic field, models of the magnetic field of magnetic stars of various types of peculiarity HD57682 and HD81009 are constructed and the parameters of their magnetic fields are obtained. In HD57682, like other hot objects, differences are observed in the physical conditions in the region of the magnetic equators and in the regions near the magnetic poles, which have not yet been interpreted. In terms of its properties, the star HD81009 is a typical representative of magnetic stars of the SrCrEu-type, except for is binary character.