Thermodynamics under the extended uncertainty principle background: Q−ϕ criticality analysis

The study of thermodynamics in the background of the “extended uncertainty principle (EUP)” comes into interest in recent eras. In this article, we consider a charged black hole (BH) in higher dimensional space–time and present the thermodynamic parameters, based on a semiclassical framework, initially. Then we extend the same within the EUP background. We also analyze the $Q-\varphi$ criticality and find the critical points (${\varphi }_c,Q_c$ and $T_c$) when $Q-\varphi$ criticality appears. We study the effects of EUP on phase transition for higher dimensions ($d=5$) by plotting the $Q-\varphi$ diagrams. Further, we investigate the stability (thermal and global) of the BHs by employing the specific heat and the Gibbs free energy without and within EUP correction and compare the results with the Schwarzschild BHs in higher dimensions.     

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.