New Astronomy最新文献

We have analyzed the light curves of three $\delta$ Scuti stars that were observed by the Kepler Space Telescope. Data collected by the Kepler space telescope, as well as analysis of the light curve of each star and the use of online databases, have been utilized to achieve the objectives of this project. Data has been collected through Kepler's main mission. We compare both data that we get from the Lightkurve package of Python and the KASOC online data centre to verify the data. We select the necessary data like flux, observation date, and the spectral type of the stars. By investigating various types of pulsating variable stars, three Delta Scuti stars have been selected due to their flux, pulsating type, etc. It is observed that most of these stars are pulsating in the p-modes. However, the selected stars pulsate in both p-modes and (possibly) g-modes. We select these stars, due to the lack of articles about them. Furthermore, some physical properties of these stars are deduced from their light curves. In summary, the results of this study indicate that the stars KIC3429637 and KIC10451090 are pulsating only in p-modes, while KIC2987660 is pulsating both in p-modes and g-modes.

We present the first combined photometric and spectroscopic solution of the bright southern contact binary S Ant based on the Transiting Exoplanet Survey Satellite (TESS) light curve and the radial velocities from the David Dunlap Observatory survey. S Ant is a W UMa type binary in deep contact, with a mass ratio of 0.34 and a relatively massive and hot F-type primary. Beside the standard modeling of the phase-binned light curve, we also perform “seasonal modeling” where we treat each of the 83 orbital cycles present in the TESS data as a separate light curve. The resulting ensemble of solutions shows evidence of quasi-periodic migration of a long-lived, dark, polar spot. The migration is confirmed independently by eclipse time variations which display remarkably strong correlation with the spot location.

In this study, we have explored the frequency separations, $\Delta \nu$ and $\delta {\nu }_{02}$, the height and width of the oscillation power excess, $H_{\mathrm{Gauss}}$ and $\delta {\nu }_{\mathrm{env}}$, as a function of the frequency of maximum power ${\nu }_{\max }$ by analyzing 187 evolved stars in six star clusters observed by the Kepler/K2 missions. We have also examined the asteroseismic relation in the Christensen-Dalsgaard diagram. Given the importance of scaling relations, the dependency of asteroseismic scaling relations on physical quantities must be verified to reduce systematic errors through the exploration of observational data obtained from various sources. In this context, the star cluster provides a valuable means to assess the age and metallicity. Focusing on evolved stars with $30\mu \mathrm{Hz}<{\nu }_{\max }<220\mu \mathrm{Hz}$, we have exploited the mass effect without the need for deriving the individual stellar mass. We have found that the considered relations appear to be associated with the age of star clusters, thereby the mass of the stars in a given evolutionary status for star clusters with different ages. By separately considering red giant branch stars and red clump stars, we have found that red clump stars appear more sensitive to the cluster age compared with red giant branch stars. It has been suggested that conclusions regarding the dependency of metallicity should be drawn with due care as outcomes are subject to how to treat metallicity. Finally, we conclude by briefly pointing out implications of our findings on asteroseismic inferences.

Following up on our initial paper (Richichi and Ohlert, 2021), we report here on 60 lunar occultation events recorded between February 2021 and March 2024 at the Michael Adrian Observatorium. An improved version of the detector was employed for the present work. The program aims mainly at the direct measurement of the angular diameter of late-type stars, and the discovery or confirmation of binary stars with small separations. Among the results, we present first time angular diameter determinations for the late-type M giants IRC +20184 and BL Tau and for the bright carbon star TU Gem. Our diameter result for RX Cnc is the first determination outside the near-IR range. We also discovered or detected directly for the first time companions around SAO 79580, BL Tau again, and SAO 78643. The lunar occultation technique at our facility is capable to reach sources as faint as $\approx$ 10 V magnitude with an angular resolution at the milliarcsecond level.

In this article, we study solutions which describe wormholes in the halos of dwarf and massive spiral galaxies with different morphologies, masses, sizes and gas fractions by taking observed flat rotation curves as input. We assume Singular Isothermal Sphere (SIS) dark matter density profile. This result confirms the possible existence of wormholes in both dwarf and massive spiral galaxies.

In 2012, Brazil began the studies to send its first deep space exploration mission, ASTER, which would be the first mission to orbit a triple asteroid system, 2001 SN263. We aim to contribute to the ASTER mission by defining the parameters of a multispectral camera system that will be used to study the asteroid system 2001 SN263, through software simulations that should help planning the data collection. We inserted the shape model of the objects in the software POV-Ray and modeled two cameras, a Wide Angle (WAC) and a Narrow Angle (NAC). We inserted the asteroid's parameters and simulated the satellite position. We created various scenes so we could obtain a good view of the asteroid. Alpha is entirely visible only in the WAC images, while the NAC is expected to reveal surface details. Beta seems relatively small in the WAC images, whereas we obtain a broad view from the NAC at 100 km distance. Gamma, smaller than Beta, should provide more detailed images through the NAC, whereas the WAC images should be able to show its inclined orbit around Alpha. To see Gamma behind Alpha in its revolution movement, we would have to elevate the camera's orbit. The method employed to simulate images generated by satellite cameras can be applied to other scenarios where the target requires imaging, extending beyond the field of planetary geology.

In this paper, we study the curved Krori–Barua spacetime geometry to describe compact stars with two components: dark and ordinary matter, using a two-fluid model approach. We choose the equation of state derived from the rotational curves of galaxies for dark matter and the polytropic equation of state for ordinary matter. The physical requirements for a realistic compact star are satisfied using specific parameters. For the polytropic index $\eta =2$, we find the values of observed masses, reported in our previous investigation (Mafa et al., 2020).

Recent observational evidence confirms the weak-collision dynamics of hot optically thin accretion flows around Sgr A${}^{\ast }$ and other nearby galactic nuclei. As a result, thermal conduction as a diffusion process can transfer the heat by electrons in a collisionless magnetized plasma. While most of the previous analytical studies consider the azimuthal viscosity, the recent studies indicated that the radial viscosity strongly affects the properties of the advection dominated accretion discs. So, in this paper, we explore the roles of two parts of anisotropic thermal conduction (parallel and perpendicular) and radial viscosity in the hot accretion disc by considering axisymmetric and steady state assumptions in the presence of outflows that can transport energy from accretion disc outward. We use the set of self-similar solutions to solve the basic equations in our present model. Our solutions reveal that transverse thermal conduction as a cooling mechanism, leads to reductions in gas temperature, disc thickness, and accretion velocity of the disc, whereas the disc rotates at a fast rate. Moreover Our solutions indicate that the perpendicular thermal conduction and the radial viscosity have opposite behavior in the physical variables of the disc. Also, our results have indicated that the anisotropic thermal conduction is significant in the parameter space of radial viscosity, outflow in the regions that the physical constraints $t_{in}\ge t_{\perp ,con}$ and $q_{\parallel ,con}⩽q_{\perp ,con}$ are satisfied.

We present spectroscopic observations of Nova Cas 2020 (V1391 Cas) obtained using the Russian Turkish Telescope during different stages of its 2020 outburst. We followed the spectral evolution of the nova until it entered the nebular phase. The expansion velocity of the ejecta reached $\sim 780{\mathrm{km\; s}}^{-1}$. The fluxes of the neutral [O I] lines at wavelengths 6300, 6364, and 5577 $\text{̊A}$ were used to calculate the electron temperature and the mass of neutral oxygen in the ejecta. We found average values $T_e=\mathrm{4890}K$, $M_{\mathrm{OI}}=\mathrm{2.54}\times {\mathrm{10}}^{\mathrm{-5}}{M}_{\odot }$ which are consistent with the values calculated for other novae. We modeled the nova’s ejected envelope 515 days after its discovery and found that the log elemental abundances by number relative to Hydrogen of the envelope are He = −0.7, C = −5.5, O = −2.5, N = −2.0 and Ne = −4.0.