DX Cygni: A triple system with mass transfer

A dozen of new precise times of eclipses were measured for the eclipsing binary DX Cygni as a part of our long-term observational project for studying neglected eclipsing binaries with a short orbital period. Based on a current $O-C$ diagram, we found for the first time that its period is increasing ($dP/P=1.68\times {10}^{-7}$ day/years) and that times of minima show also significant cyclical changes with a period of about 16 years, caused very probably by a third body orbiting the eclipsing pair. The minimal mass of this companion is 0.49 M_⊙. The light curve solution in Phoebe results to the typical Algol-type semidetached configuration where the secondary fills its Roche lobe. The temperature of primary component was fixed to $T_1=5300$ K according to its spectral type, which gives us $T_2=3330\pm 20$ K for the secondary. The photometric mass ratio was estimated $q=0.504\pm 0.012$. We also compare orbital parameters of selected known Algol-type eclipsing binaries with proven mass transfer and a third body.     

Tsallis holographic dark energy model with observational constraints in the higher derivative theory of gravity

The present study deals with a Tsallis holographic dark energy model in a flat Friedmann-Lamatire-Rbertson-Walker space-time geometry in the context of higher derivative theory of gravity. We have solved the field equations by applying energy conservation-law in non-interacting case and have obtained such a scale factor $a\left(\tau \right)={\left[\sinh \left(\sqrt{2a_1}\tau \right)\right]}^{\frac{1}{2}}$ where $a_1$ is called as model parameter which shows transit phase evolution of the universe (decelerating to accelerating). Using this scale factor we have obtained the various cosmological parameters viz. Hubble parameter $H$, deceleration parameter (DP) $q$, jerk $j$, snap $s$, lerk $l$ and max-out $m$. Constraining on Hubble parameters $H\left(z\right)$ by the observational data of $H\left(z\right)$ we have obtained the present values of $H_0$, $a_0$ and $a_1$ and by using these constrained values, we have studied other cosmological parameters. Taking the constant equation of state (EoS) ${\omega }_m$ for ordinary matter, we have investigated the effective behaviour of various cosmological parameters and energy conditions in our model. We have observed the present values of $\{t_0,H_0,q_0,j_0,s_0,l_0,m_0,{\omega }_{d{e}_0},{\omega }_0^{\left(eff\right)}\}$ and discussed with $\Lambda$CDM model. We have found the age of the present universe $t_0=13.05$ Gyrs, present value of DP $q_0=-0.8065$ and transition point $z_t=0.748$ which are compatible with several observational results.