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2.

Quintessence compact star models under embedded class one symmetry

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3.

On the axisymmetric restricted five-body problem within the frame of variable mass: The convex case

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4.

DX Cygni: A triple system with mass transfer

《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

O - C

diagram, we found for the first time that its period is increasing (

d P / 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. 相似文献

5.

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

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

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 (27)

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 (4) \times 10^{- 7} day / 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 (3) \times 10^{- 7} M_{⊙} / 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 (1) M_{⊙}

. 相似文献

6.

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 (τ) = {[\sinh (\sqrt{2 a_{1}} τ)]}^{\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 (z)

by the observational data of

H (z)

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)

ω_{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}, ω_{d e_{0}}, ω_{0}^{(e f f)}}

and discussed with

Λ

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. 相似文献

7.

Late-time viscous cosmology in f(R,T) gravity

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8.

Interstellar polarization and extinction toward the Recurrent Nova T CrB

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9.

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 - ϕ

criticality and find the critical points (

ϕ_{c}, Q_{c}

and

T_{c}

) when

Q - ϕ

criticality appears. We study the effects of EUP on phase transition for higher dimensions (

d = 5

) by plotting the

Q - ϕ

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. 相似文献

10.

Anisotropic spheres in f(R,G)gravity with Tolman-Kuchowicz spacetime

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11.

Exact analytic solution of an unsolvable class of first Lane–Emden equation for polytropic gas sphere

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12.

A photometric study of V608 Cam: apparent period changes as a result of surface activity

Transit cosmological models coupled with zero-mass scalar field with high redshift in higher derivative theory

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13.

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14.

Gravitational wave background discovered by NANOGrav as evidence of a cyclic universe

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15.

First TESS light curve solution and orbital period analysis of V567 And

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16.

Evaluation of cosmological models in f(R,T) gravity in different dark energy scenario

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17.

Wormhole geometry and three-dimensional embedding in extended symmetric teleparallel gravity

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18.

A new look at the YY CrB binary system

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19.

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

_{⊙}

,

R_{1} = 0.87 \pm 0.08

R

_{⊙}

and

M_{2} = 0.50 \pm 0.12

M

_{⊙}

,

R_{2} = 0.77 \pm 0.17

R

_{⊙}

for V523 And; and

M_{1} = 1.59 \pm 0.16

M

_{⊙}

,

R_{1} = 1.46 \pm 0.09

R

_{⊙}

and

M_{2} = 0.58 \pm 0.17

M

_{⊙}

,

R_{2} = 1.66 \pm 0.22

R

_{⊙}

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 (

Δ Q

) were found to be in the order of

1 0^{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

1 0^{- 5}

–

1 0^{- 11}

M

_{⊙}

/year and

1 0^{- 6}

–

1 0^{- 8}

M

_{⊙}

/year, respectively. 相似文献

20.

Scaling relations for width of the power excess of stellar oscillations