First photometric study of two eclipsing binary star systems: V523 And and V543 And

Detailed photometric analysis of V523 And and V543 And from the Wide Angle Search for Planets survey is presented for the first time. It was found that while V523 And is a detached binary, V543 And is a semi-detached binary star system. The adopted masses and radii for the primary and secondary components are $M_1=0.77\pm 0.08$ M${}_{\odot }$, $R_1=0.87\pm 0.08$ R${}_{\odot }$ and $M_2=0.50\pm 0.12$ M${}_{\odot }$, $R_2=0.77\pm 0.17$ R${}_{\odot }$ for V523 And; and $M_1=1.59\pm 0.16$ M${}_{\odot }$, $R_1=1.46\pm 0.09$ R${}_{\odot }$ and $M_2=0.58\pm 0.17$ M${}_{\odot }$, $R_2=1.66\pm 0.22$ R${}_{\odot }$ for V543 And. Orbital period variations of the systems were analyzed using the O-C method. The O-C change of V523 And is discussed in terms of the magnetic activity cycle of one or both components and light travel time effect (LTTE) due to a third body in the system. Among these mechanisms, LTTE seems to be the most appropriate mechanism to explain the O-C variation of the system since the quadrupole moments of the primary and secondary components ($\Delta Q$) were found to be in the order of $10^{49}$ g cm${}^2$. The O-C diagram of V543 And shows a downward parabolic trend, which suggests a secular period decrease with a rate of $0.080\pm 0.012$ s/year. The parabolic O-C variation of V543 And was interpreted in terms of the non-conservative mass transfer mechanism. According to this scenario, the range of possible values of the mass gain rate (${\dot{M}}_1$) of the primary component of V543 And as well as the mass-loss rate ($\dot{M}$) of the system were found to be $10^{-5}$–$10^{-11}$ M${}_{\odot }$/year and $10^{-6}$–$10^{-8}$ M${}_{\odot }$/year, respectively.     

On the Sun’s distance from the center and the shape of the inner halo in the Galaxy: Gaia EDR3, HST and literature globular clusters

A statistical method is used to derive both the Sun’s distance $r_0$ from the Galactic Center (GC) and the 3D geometry of the inner ($<$ 25 kpc) halo. The spatial distribution of the 138 Gaia EDR3 globular clusters (GCs) with distances established on a combination of HST and literature data of Baumgardt and Vasiliev (2021) is explored. An estimate by using these ancient objects of the pressure-supported subsystem of the Galaxy with newly derived distances leads to the mean $r_0=7.81\pm 0.14$ kpc. The distribution of GCs within 25 kpc is almost spherically symmetric, and has the shape of an ellipsoid with a major axis of its symmetry slightly elongated toward the Sun and two minor axes of almost the same length. The obtained scale-length ratio of the major axis to the minor axis in the plane and to the vertical axis of the ellipsoid is $\approx$ 1:0.8:0.7. Based on the papers of a series, for practical use we argue to employ the following Sun’s distances from the GC and the plane: $r_0=8.15\pm 0.15$ kpc and $z_0=15\pm 5$ pc.     

Relativistic isotropic stellar model in f(R,T) gravity with Durgapal- IV metric

In this work, a new static, non-singular, spherically symmetric fluid model has been obtained in the background of $f(R,T)$ gravity. Here we consider the isotropic metric potentials of Durgapal-IV (Durgapal, 1982) solution as input to handle the Einstein field equations in $f(R,T)$ environment. For different coupling parameter values of $\chi$, graphical representations of the physical parameters have been demonstrated to describe the analytical results more clearly. It should be highlighted that the results of General Relativity (GR) are given by $\chi =0$. With the use of both analytical discussion and graphical illustrations, a thorough comparison of our results with the GR outcomes is also covered. The numerical values of the various physical attributes have been given for various coupling parameter $\chi$ values in order to discuss the impact of this parameter. Here we apply our solution by considering the compact star candidate LMC X-4 (Rawls et al., 2011) with mass $=(1.04\pm 0.09)M_{\odot }$ and radius $=8.301_{-0.2}^{+0.2}$ km. respectively, to analyze both analytically and graphically. To confirm the physical acceptance of our model, we discuss certain physical properties of our obtained solution such as energy conditions, causality, hydrostatic equilibrium through a modified Tolman–Oppenheimer–Volkoff (TOV) conservation equation, pressure–density ratio, etc. Also, our solution is well-behaved and free from any singularity at the center. From our present study, it is observed that all of our obtained results fall within the physically admissible regime, indicating the viability of our model.     

First comprehensive study of W-type W UMa eclipsing binary V1036 Her

CCD photometry of the eclipsing binary system V1036 Her was performed using Johnson V filter in Dr. Mojtahedi Observatory of the University of Birjand during July-August 2017 and July 2018. Moreover, the spectroscopy of the system was carried out by TRES during April 2018. A mass ratio of $3.07\left(27\right)$is obtained and an initial effective temperature of 5500 was suggested. For the first time, the relative and absolute parameters of the system are determined by analyzing the light curve and radial velocity data. The results indicate that V1036 Her is a W-subtype W UMa system with a degree of overcontact of 22%. The analysis of the period change shows that the period of the system changes with the rate of $\dot{P}=2.23\left(4\right)\times {10}^{-7}\text{day}/\text{year}$. With the assumption of the system mass conservation, a mass transfer rate from the primary to the secondary component of ${\dot{m}}_1=1.00\left(3\right)\times {10}^{-7}{M}_{\odot }/\mathit{year}$ is probable. Additionally, a periodic behavior with a period of about 10 years is observed in the O-C curve, which predicts the possibility of a third body with a minimum mass of $0.14\left(1\right)M_{\odot }$.     

Halo Meteors

The stellar halo contains some of the oldest stars in the Milky Way galaxy and in the universe. The detections of ‘Oumuamua, CNEOS 2014-01-08, and interstellar dust serve to calibrate the production rate of interstellar objects. We study the feasibility of a search for interstellar meteors with origins in the stellar halo. We find the mean heliocentric impact speed for halo meteors to be $\sim 270\text{km}{\mathrm{s}}^{-1},$ and the standard deviation is $\sim 90\text{km}{\mathrm{s}}^{-1},$ making the population kinematically distinct from all other meteors, which are an order-of-magnitude slower. We explore the expected abundance of halo meteors, finding that a network of all-sky cameras covering all land on Earth can take spectra and determine the orbits of a few hundred halo meteors larger than a few mm per year. The compositions of halo meteors would provide information on the characteristics of planetary system formation for the oldest stars. In addition, one could place tight constraints on baryonic dark matter objects of low masses.