Astrophysics最新文献

For the perturbative model of a plane gravitational wave on a flat background of Minkowski space-time, electromagnetic radiation from a charged cloud in the field of a gravitational wave, detected by a remote observer, was found. It is shown that the charge density in the cloud does not change, and the radiation is generated by currents induced by the gravitational wave. The angular distribution of the radiation is obtained. If the refractive index of the cloud medium is greater than unity, Cherenkov-type radiation is generated.

“Dunkle Materie” (DM) came from unexpected cosmological observations. Nowadays within our solar system, diverse observations also defy conventional explanations, like the main physical process(es) underlying the heating of the different solar atmospheric layers. Streaming DM offers a viable common scenario following gravitational focusing by the solar system bodies. This fits as the underlying process behind the solar cycle, which was the first signature suggesting a planetary dependency. The challenge, since 1859, is to find a remote planetary impact, beyond the extremely feeble planetary tidal force. We stress the possible involvement of an external impact by some overlooked “streaming invisible matter”, which reconciles all investigated mysterious observations mimicking a not extant remote planetary force. Unexpected planetary relationships exist for both the dynamic Sun and Earth, reflecting multiple signatures for streaming DM. The local reasoning à la Zwicky is also suggestive for searches including puzzling biomedical phenomena. Favourite DM candidates are anti-quark-nuggets, magnetic monopoles, dark photons, or the composite “pearls”. Then, anomalies within the solar system are the manifestation of the dark Universe. The tentative streaming DM scenario enhances spatiotemporally the DM flux

We performed the first photometric study of the CSS J003106.8+313347 W Ursae Majoris (WUMa)-type system based on ground-based observations. We extracted times of minima from our observations and proposed a linear ephemeris based on the increasing incline of the orbital period using a Markov chain Monte Carlo (MCMC) approach. The PHOEBE Python code and the MCMC approach were used for the light curve analysis. This system did not need starspots for the light curve analysis. Mass ratio, fillout factor, and inclination were obtained as 0.699, 0.322, and 60°.6 respectively. We also estimated the absolute parameters of the system using the Gaia DR3 parallax. Therefore, the masses, radii, and luminosities have been determined to be M₁ = 1.675, M₂ = 1.171, R₁ = 1.292, R₂ = 1.097, L₁ = 1.348, and L₂ = 1.221. The orbital angular momentum J₀ of the CSS J003106.8+313347 illustrates that this system is located in a region of contact binaries. The positions of the primary and secondary components on the Hertzsprung-Russell (HR) diagram are depicted.

The Digitized First Byurakan Survey (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 UVX-excess (Markarian) galaxies. FBS low-resolution spectral plates have been used for a long time to search and study faint Late-Type Stars (LTS, M-type and C stars) at high Galactic latitudes. A total of 18 lists of the FBS LTS were published between 1990 and 2016. We report newly confirmed C and M giants, and also large amount of M dwarfs based on the Gaia DR3 BP/RP low-resolution spectroscopic data base. Some of the newly confirmed M dwarfs presents binary systems. Some of them are new eclipsing binaries. In our previous studies of the DFBS spectral plates, all were presented as LTS candidates. Gaia high-accuracy astrometric and photometric data and Transiting Exoplanet Survey Satellite (TESS) data are used to characterize these new confirmed LTS. TESS phase-dependent light curves show rotational modulations and flares for many new M dwarfs. This confirmations of the large number of completely new objects represents a very significant extension in the census of M giants, faint N-type Asymptotic Giant Branch C stars, CH-type C giants at high Galactic latitudes, and M dwarfs in the solar vicinity. Some objects are located more than 7 kpc from the Galactic plane. Ultimately, we aim to present value-added catalog and update the FBS LTS catalog. Note that a large amount of the blue stellar objects with UVX-excess and numerous of emission line objects were also detected.

Results are presented from an analysis of the manifestations of activity of the star WASP-193 of spectral class F9 with a super-neptune-type planet. The gaseous giant WASP-193 b with a mass 0.13 times Jupiter’s mass and almost one and a half times its radius. The planet has a low density ρ = 0.059±0.014 g/cm³ (Kepler 51 d is an analogous object; there are few other exoplanets of this type). The equilibrium temperature of the atmosphere of the planet is high at T_eq = 1254±31 K. The results of this study of the star’s activity are used to estimate the loss of matter by the atmosphere of the planet WASP-193 b using an approximation formula corresponding to a model with limited energy. Estimates of the flux of XUV-photons F_XUV were made using an analytical relationship relating F_XUV and the parameter ({text{log}}{R}_{HK}{prime}) for stars in classes F-M. Calculations showed that the loss of matter from the atmosphere of the exoplanet is quite high (even in the case of a low chromospheric activity of the parent star). The parameter (dot{M}) ranges from 1.8∙10¹⁰ g/s to 4.3∙10¹¹ g/s, depending on the assumed level of the flux of XUV-photons (high and low activity). It is probable that the planet is losing its atmosphere intensively. WASP-193 b can be regarded as a high-priority candidate for observations using the JWST space mission (the transmission spectroscopy metric TSM for this object is about 600).

The whole article deals with the analysis of the cosmic model of Ruban’s space-time in the context of a bulk viscosity impact in the form of Ricci dark energy within the framework Brans-Dicke theory. We believe that outer space is filled with dark matter and viscous Ricci dark energy (VRDE) under the pressureless situation. The velocity and rate at which the Universe is expanding are presumed to be proportional to the coefficient of total bulk viscosity, is in the form, ({upxi }_{0}+{upxi }_{1}dot{a}/a+{upxi }_{2}ddot{a}/a,) where ({upxi }_{0},{upxi }_{1}) and ({upxi }_{2}) are the constants. To solve the RDE model's field equations, we utilize the relation among the metric potentials and also the power-law relation among the average scale factor a(t) and scalar field ϕ. To examine the evolutionary dynamics of the Universe, we investigate the deceleration parameter q, jerk parameter j, EoS parameter ({upomega }_{de},) Om(z) , stability of the obtained models through the square speed of the sound ({v}_{s}^{2},{upomega }_{de}-{omega }_{de}{prime}) plane, statefinder parameter planes (r, s) and (q, r) and presented via graphical representation. By the end of the discussion, VRDE model was found to be compatible with the present accelerated expansion of the Universe.

The magnetic field of the star HD133880 is modeled assuming a magnetic field structure that is described by two theoretical magnetic dipoles. A comparison of this result with what was found previously using a representation of the phase dependence Be(Φ) employing a dipole+quadrupole+octupole expansion for the structure shows that this scheme leads only to a formal description of the phase dependence, while the terms in the expansion lack physical significance.

Data from the TESS orbital observatory are used to study the most active flare stars indicating 100 or more flares during the period from July 2018 through October 2020. The main objectives of this study were: (a) analysis of the light curves, determination of the axial rotation periods, and identification of physical features in individual stars, (b) determination of the parameters of the periodic/cyclical variability of the flare frequencies of flare stars owing to axial/orbital rotations. The corresponding periods of the flare frequency functions were obtained and compared with the axial rotation periods of the stars. The periods of the frequency functions of the flares turned out to be close to the axial rotation periods of the stars. Theoretical phase distributions of the flares are constructed and compared with analogous observations of the flares for the given period. For all the stars without exception, a comparison with the aid of the χ² criterion confirms the periodicity of the flare frequency. It is proposed that the distribution of spots over the longitude of flare stars can be represented by an angular von Mises distribution, for which the parameters are determined by the corresponding parameters of the flare frequency function. The binarity of the star CD-56 1032 is discussed in detail.

Photometric and spectral observations of 11 Wolf-Rayet stars of the WN sequence were made at the AFIF during 2021-2022. Estimates of the brightness of objects in BVRc filters and the absolute fluxes of radiation in emission lines in this group are obtained on the basis of these observations. Changes in the brightness over a range of 0^m.1-0^m.15 are recorded for the stars WR 120, WR 151, and WR 152 in the WR I stars. Changes in the emission fluxes are detected in the spectra of several objects: WR 120, WR 128, and WR 145.

This paper is a study of the dynamics of the parameters describing the transverse component of the gradient of the longitudinal magnetic field ∇_⊥ B_z in active regions (AR) with different levels of flare productivity. Data obtained by the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO) has been used to analyze 75 ARs in the 24-th cycle of solar activity. ∇_⊥ B_z has been calculated using two approaches, modern and classical. In each case the parameters describing the quantity ∇_⊥ B_z in the AR are determined. For the modern approach, this includes the average of ∇_⊥ B_z over the AR, <∇_⊥ B_z> and the average value of ∇_⊥ B_z in the neighborhood of the point with its maximum value, <max ∇_⊥ B_z>; for the classical approach, the maximum value of ∇_⊥ B_z between pairs of spots in the AR, <max ∇_⊥ B_z>. The dynamics of the chosen parameters are studied over the time of monitoring each of the regions of the analyzed sample. It is shown that: 1. the spread in values of ∇_⊥ B_z is small (for the overwhelming majority of studied regions it lies within a range of 0.08-0.12 G·km^-1) and differs little for regions with low and high flare activity. 2. The numerical values of the parameter max(∇_⊥ B_z) and its dynamics in the overwhelming majority of examined cases are greater in regions with a higher level of flare activity. 3. The numerical values of the parameter max(∇_⊥ B_z) and its dynamics are greater in regions with higher levels of flare activity. 4. In the AR NOAA 11283 a stable rise in the magnitude of max (∇_⊥ B_z)_sp was detected for approximately 19 h before the development of the first of a series of flares in high x-ray classes.