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《New Astronomy》2020
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 diagram, we found for the first time that its period is increasing ( 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 K according to its spectral type, which gives us K for the secondary. The photometric mass ratio was estimated . We also compare orbital parameters of selected known Algol-type eclipsing binaries with proven mass transfer and a third body. 相似文献
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《New Astronomy》2021
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 where 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 , deceleration parameter (DP) , jerk , snap , lerk and max-out . Constraining on Hubble parameters by the observational data of we have obtained the present values of , and and by using these constrained values, we have studied other cosmological parameters. Taking the constant equation of state (EoS) 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 and discussed with CDM model. We have found the age of the present universe Gyrs, present value of DP and transition point which are compatible with several observational results. 相似文献
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《New Astronomy》2022
A statistical method is used to derive both the Sun’s distance 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 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 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: kpc and pc. 相似文献