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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

7.

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

《New Astronomy》2024

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

8.

A new look at the YY CrB binary system

《New Astronomy》2024

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9.

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

《New Astronomy》2022

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. 相似文献

10.

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

《New Astronomy》2022

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

11.

Finch–Skea gravastar model in f(R,T) theory

《New Astronomy》2022

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12.

First photometric and orbital period investigations of the total-eclipse contact binary V0339 Com

《New Astronomy》2022

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13.

Study of axially symmetric viscous Ricci dark energy model in Brans–Dicke theory

《New Astronomy》2022

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14.

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

《New Astronomy》2021

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15.

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

《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

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

16.

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

《New Astronomy》2021

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17.

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

《New Astronomy》2022

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18.

Re-examination of several key aspects of an earlier model analysis on cylinder hydrodynamics under self-gravity

《New Astronomy》2022

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19.

Analysis of resonant curves and phase portrait in the earth–moon system by using its unperturbed solution and earth’s equatorial ellipticity

《New Astronomy》2022

In this research article, we have investigated resonant curves due to the rate of change of earth’s equatorial ellipticity parameter

(\dot{γ})

, steady-state value of the angular velocity of the moon

({\dot{θ}}_{m o})

, and angular velocity of barycenter

(\dot{α_{0}})

in the Earth-Moon system. Equations of motion of the moon are determined in a spherical coordinate system with the help of the gravitational potential of the earth. By using the unperturbed solution, equations of motion of the moon reduced into the second-order differential equation. From the solution it is observed that resonance occurs due to the frequencies

\dot{γ}

,

{\dot{θ}}_{m 0}

, and

\dot{α_{0}}

at the resonant points

{\dot{θ}}_{m 0} = 2 \dot{γ}

,

3 {\dot{θ}}_{m 0} = 2 \dot{γ}

,

{\dot{θ}}_{m 0} = \dot{γ}

,

{\dot{θ}}_{m 0} = {\dot{α}}_{0}

. Finally, we have analyzed the phase portrait and phase space by method of Poincaré section when the system is free from forces. 相似文献

20.

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

《New Astronomy》2024

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