New Astronomy最新文献

we explored the holographic dark energy model using Hubble’s Horizon as the infrared (IR) cut-off in Locally Rotationally Symmetric (LRS) Bianchi type-I, considering the $f\left(R\right)$ gravity framework in our analysis. In order to solve the field equations, we assume a relation $F\propto a^m$ and volumetric power law expansion (where $m$ is constant). we have expressed various crucial cosmological parameters in terms of the redshift $z$ and depicted them graphically to enhance our understanding of the expansion and evolution of the universe like holographic dark energy density (${\rho }_{\Lambda }$), holographic dark energy pressure ($p_{\Lambda }$), equation of state parameter ($\omega$) , total energy density parameter ($\Omega$) etc. Also, we analyzed the stability of the universe in our model through the squared speed of sound test and its validity by energy conditions. Ultimately, our model indicates that the universe is currently in an expanding phase, exhibiting an accelerating phase, closely approaching a flat geometry, and its behavior resembles that of a quintessence dark energy model.

In attempts to resolve the neutron lifetime puzzle, there was suggested a hypothetical decay of neutrons into some unspecified dark matter (DM) particles. Later there were performed studies on how the hypothetical decay of neutrons would affect neutron stars. Recently it was shown that with the allowance for the second solution of Dirac equation for hydrogen atoms, the theoretical branching ratio (BR) for the two-body decay of neutrons (compared to their three-body decay) is amplified by a factor of 3300 from 0.000004. So, the BR becomes about 1.3% in the excellent agreement with the “experimental” BR = (1.15 ± 0.27)% required for reconciling the two distinct experimental values of the neutron lifetime: one from the beam experiments, another from the trap experiments. This meant that the two-body decay of neutrons in the beam experiments (that count only the protons) plays a much more sizable part in the overestimation of the lifetime of neutrons in these experiments than previously thought. Hydrogen atoms corresponding to the second solution of Dirac equations are called the second flavor of hydrogen atoms (SFHA) by the analogy with the flavors of quarks. The existence of the SFHA is evidenced by four different types of atomic/molecular experiments. The primary feature of the SFHA is that due to having only the s-states, they do not emit or absorb the electromagnetic radiation (except for the 21 cm line): they are practically dark. The SFHA became a candidate for a part of DM for the first time after the SFHA-based successful qualitative and quantitative explanation of the perplexing observation by Bowman et al. of the anomalous absorption in the redshifted 21 cm line from the early Universe. In the present paper we analyzed how this neutron decay into the SFHA affects neutron stars. We showed that old neutron stars could very slowly generate the new specific, described in detail baryonic DM in the form of the SFHA. Some old neutron stars would release it into their tiny atmospheres, while some other old neutron stars would release it into the interstellar medium. Besides, mergers of a neutron star with another neutron star or with a black hole, accompanied by the ejection of neutron-rich material, can also lead to the formation of SFHA as the ejecta cools down. This is another interesting aspect of the multi-messenger astronomy focused on studying these mergers through the gravitational waves they generate. These mechanisms of generating new baryonic DM in the universe should have the fundamental importance. We point out the indirect observational evidence of the continuing generation of new baryonic DM. We hope that our results will stimulate a further research in this direction.

We present the discovery of $\gamma$ Doradus-type pulsations in the eclipsing binary TIC 140736015. We obtained the physical and geometrical parameters of this detached eclipsing binary hosting a pulsating component. Based on the Transiting Exoplanet Survey Satellite (TESS) observation and Gaia DR3 data of TIC 140736015, we refined the light elements of the system using $(O-C)$ analysis and found that the eclipse times varied with a period of $\sim 2048$ days, probably linked to the multiperiodic pulsational nature. We showed that essentially, only secondary eclipse is seen in the phased light curve. The frequency analysis using the out-of-eclipse data reveals that all the pulsational frequencies are located in the region lower than $5d^{-1}$. After removing the pulsational variation from the observations we analysed the residual light curve together with the radial velocity data obtained from Gaia DR3 and find the masses and radii of the primary and secondary components as $M_1=1.429\pm 0.022$ $M_{\odot }$, $M_2=1.402\pm 0.022$ $M_{\odot }$and $R_1=1.685\pm 0.001$ $R_{\odot }$, $R_2=1.393\pm 0.001$ $R_{\odot }$, respectively. Regarding the location of the components on the Hertzsprung–Russell diagram both components can be a $\gamma$ Dor/solar-like pulsator.

In this study, new CCD photometric observations and photometric analysis of BK Vul and V699 Cep systems, which are classified as contact binaries in the literature, are presented. For the V699 Cep, the TESS light curve was also used in the photometric analysis. We determined the basic astrophysical parameters of the BK Vul and V699 Cep systems from photometric analysis using the Wilson–Devinney method. Due to the lack of spectroscopic data for both systems in the literature, these absolute parameters were approximately calculated as to be $M_2$ = 0.73 $M_{\odot }$, $R_1$ = 1.39 $R_{\odot }$ and $R_2$ = 1.09 $R_{\odot }$ for BK Vul, and $M_2$ = 0.36 $M_{\odot }$, $R_1$ = 2.40 $R_{\odot }$ and $R_2$ = 1.33 $R_{\odot }$ for V699 Cep after estimating the mass of the primary component. The period decrease rate (dP/dt) and cyclic variation period of BK Vul were determined from the $O-C$ analysis as -3.86 $\times 10^{-7}$ day yr⁻¹ and 27 yrs., respectively. The evolutionary status of components of both systems were discussed.

OPTICAM is a triple-band optical system developed for the 2.1 m telescope of the National Astronomical Observatory in the Sierra de San Pedro Mártir (OAN-SPM). Partial engineering tests were conducted in 2019, with the complete system experiencing its first light in March 2022. The system incorporates two beam splitters, enabling simultaneous observations on three channels. Users can choose three out of the five available filters from the SDSS filter set ($u^{\prime }{g}^{\prime }{r}^{\prime }{i}^{\prime }{z}^{\prime }$), covering the wavelength range from 320 to 1000 nm. It offers an effective field of view of approximately 4.7, 4.7, and 5.6 arcminutes in each of its arms, respectively. Due to its design and capabilities, OPTICAM is suitable for coordinated observations with other ground-based and space-based observatories. This document presents the final instrument design and the current system status. Some of the optical tests carried out are described. We also present the results of scientific observations conducted during its first light and first year of operations.

The future space-borne Laser Interferometer Space Antenna (LISA) is expected to detect gravitational waves (GW) from Extreme Mass Ratio Inspiral (EMRI) binaries which may live in nontrivial environments such as accretion disks. In this work, we apply the Fisher matrix Principal Component Analysis (PCA) method to assess how well LISA observations can jointly constrain the source parameters and environmental densities around EMRIs. Specifically, we calculate the Fisher matrix from the post-Newtonian parameters of an EMRI binary embedded in a fluid with a constant density profile. We determine that the most dominant measurable parameter combination is dominated by contributions from environmental effects, namely, gravitational drag, accretion, and gravitational pull (in order of contribution). The proposed reparameterization of the PN parameters can be used to improve the power and efficiency of future detection and parameter estimation methods.

We present ab initio global general-relativistic Particle-in-cell (GR-PIC) simulations of compact millisecond neutron star magnetospheres in the axisymmetric aligned rotator configuration. We investigate the role of GR and plasma supply on the polar cap particle acceleration efficiency – the precursor of coherent radio emission – employing a new module for the PIC code OSIRIS, designed to model plasma dynamics around compact objects with fully self-consistent GR effects. We provide a detailed description of the main sub-algorithms of the novel PIC algorithm, including a charge-conserving current deposit scheme for curvilinear coordinates. We demonstrate efficient particle acceleration in the polar caps of compact neutron stars with denser magnetospheres, numerically validating the spacelike current extension provided by force-free models. We show that GR relaxes the minimum required poloidal magnetospheric current for the transition of the polar cap to the accelerator regime, thus justifying the observation of weak pulsars beyond the expected death line. We denote that spin-down luminosity intermittency and radio pulse nullings for older pulsars might arise from the interplay between the polar and outer gaps. Also, narrower radio beams are expected for weaker low-obliquity pulsars.

In the present work we consider three modified Chevallier–Polarski–Linder (CPL) models with considering non-cold dark matter in the background of homogeneous and isotropic FLRW space–time model. From the observational data set ((Pantheon+)+BAO+HST) we find that all the parameters involved in the models having equation of dark energy state ${\omega }_{de}={\omega }_0+{\omega }_1\frac{a}{{(1+a)}^p}$ (Model II) and ${\omega }_{de}={\omega }_0+{\omega }_1\frac{1-a}{{(1+a)}^p}$ (Model III) do not depend on $p$. We also find that for all the models equation of state for dark matter is almost same and observe that Model I is more preferable than the other two proposed models.