Journal of Astrophysics and Astronomy最新文献

In this study, we considered the optical wavelength of Gaia Data Release 3 (DR3) to analyze poorly studied three newly open star clusters, namely OCSN 203, OCSN 213, and OCSN 244 clusters with ASteCA code. Here, we identified 227, 200, and 551 candidates with highly probable ((P ge 50)%) members. Fitting King’s profile within radial density profiles allows us to estimate inner stellar structures like core ((0.190 le r_{textrm{c}} mathrm{(pc)} le 1.284)) and the limiting ((0.327 le r_{textrm{cl}} mathrm{(pc)} le 1.302)) radii. Constructing color-magnitude diagrams (CMDs) fitted with suitable (log textrm{age}) (yr) between ((log t); 6.52–7.05) and metallicities (Z; 0.01308–0.01413) isochrones. Therefore, the estimated photometric parameters with CMDs reflect the heliocentric distances are (332 pm 18), (529 pm 23), and (506 pm 23) (pc) for OCSN 203, OCSN 213, and OCSN 244, respectively. Furthermore, the collective mass ((M_{C})) in solar mass units is calculated with MLR as (67 pm 8.19), (91 pm 9.54), and (353 pm 18.79). Additionally, LF determined that the mean absolute magnitudes are (9.54 pm 3.09), (8.52 pm 2.92), and (7.60 pm 2.76) for these clusters, respectively. The overall mass function reflects the slopes ((alpha )) for Salpeter within the uncertainty are ((alpha _{mathrm{OCSN 203}} = 2.41 pm 0.06)), ((alpha _{mathrm{OCSN 213}} = 2.13 pm 0.07)), and ((alpha _{mathrm{OCSN 244}} = 2.28 pm 0.07)). The results of this study, which employed a dynamical analysis over varying timescales, indicate that OCSN 203 and OCSN 244 are clusters that have undergone significant relaxation, with a dynamical evolution parameter ((tau )) that is much greater than one. In contrast, OCSN 213 exhibits characteristics of a non-relaxed cluster. A kinematic analysis of these open clusters was carried out, encompassing aspects of their apex position ((A_{textrm{o}}, D_{textrm{o}})) using the AD diagrams. Therefore, the numerical convergent point coordinates are (76^{circ }.77 pm 0^{circ }.01), (-0^{circ }.23 pm 0^{circ }.00) (OCSN 203), (85^{circ }.71 pm 0^{circ }.11), (-9^{circ }.63 pm 0^{circ }.03) (OCSN 213), and (88^{circ }.19 pm 0^{circ }.11), (-4^{circ }.04 pm 0^{circ }.01) (OCSN 244). We found that the three OCSN clusters are young stellar disc members using dynamic orbit parameters.

In this study, we present the results of the relationship between spectral type (ST) and the projected stellar rotational velocity ((vsin i)), utilizing a sample of (sim ,)50,000 single stars across a range of evolutionary stages. The STs of the stars included in this study span a broad range, from O0 to M9. We examine the stars in our data set, which has been divided into two groups according to ST and luminosity class (LC). The groups have investigated the relationship between the mean (vsin i) ((langle vsin i rangle )) and STs, as well as the dependence of (langle vsin i rangle ) on STs and LCs. The rationale for investigating the two subgroups separately is to take into account for the evolutionary status of the stars and ascertain the impact on stellar rotation. The results demonstrate a notable decline in (langle vsin i rangle ) as the spectral type progresses from early to late types. In particular, we found a significant decrease in (langle vsin i rangle ) values, amounting to (sim )100 km (hbox {s}^{-1}), between hot stars (STs O0 to F2) and cool stars (STs F2 to M9). Moreover, a reduction in (langle vsin i rangle ) is discernible as stars evolve, with this trend being most pronounced in evolutionary stages beyond the subgiant phase.

We present an analysis of bar structures in a sample of 140 strongly interacting galaxies with bridge features and 57 M51-type galaxies using high-resolution images from the Hubble Space Telescope. This study explores the influence of gravitational interactions on bar formation and stability. Our results show that the bar fraction ((f_{textrm{bar}})) is significantly low in both samples, with only 16% of galaxies exhibiting bar structures. By examining the relationship between bar fraction and key parameters such as angular separation, redshift, and surface brightness, we find that bars are more likely to form in larger, brighter galaxies with weaker interactions. Galaxies with close companions, high redshift, or fainter surface brightness show a reduced likelihood of developing or maintaining bar structures. These findings suggest that strong gravitational interactions inhibit or disrupt the formation of bars in galaxies, contributing to our understanding of galactic evolution and morphology. Our results provide valuable insights into how external forces shape galactic structures and offer important implications for studying galaxy formation and dynamics.

In the 21st century, astronomy is one of the frontier research areas, and several astronomical observatories are planned worldwide with active international collaborations. India has been actively participating in many astronomy megaprojects. The article provides the perspective of the growing interest in astronomy research across the country, the urgent need for capacity building, and its subsequent impact on human resource growth in the industry.

This paper presents an investigation of the X-ray emission associated with the Wolf–Rayet star, WR 48-6, using observations from the XMM-Newton and Chandra X-ray telescopes covering two epochs separated by eleven months. The X-ray spectrum of WR 48-6 is well explained by a two-temperature plasma model, with cool and hot plasma temperatures of (0.8_{-0.2}^{+0.1}) and (2.86_{-0.66}^{+1.01}) keV. No significant X-ray variability is observed during these two epochs of observations. However, an increase in the local hydrogen column density accompanied by a decrease in the intrinsic X-ray flux between two epochs of observations is seen. Additionally, the intrinsic X-ray luminosity is found to be more than (10^{33}) erg (hbox {s}^{-1}) during both epochs of observations. Based on the analysis presented, WR 48-6 is a promising colliding wind binary candidate with a possible companion of spectral type O5–O6.

This article addresses key open questions in the Milky Way and neighboring galaxies, focusing on utilizing stars and stellar populations to trace galaxy formation and evolution processes. It offers an overview of the current landscape based on community-contributed white papers and outlines emerging research avenues alongside specific observational strategies relevant to the Indian context. Recent advancements in observations, such as precision astrometry from Gaia and asteroseismology enabled by Kepler, have reinvigorated interest in stellar physics, including its role in characterizing exoplanet atmospheres and understanding planet formation and evolution. Upcoming projects like the Rubin Observatory (LSST) and future large spectroscopic surveys will significantly enhance our ability to study stellar populations across various galaxies. These efforts will improve our understanding of dark matter distribution in galaxies, galaxy formation, and their evolution. Furthermore, by studying galaxies within the local volume, researchers can delve into the history of the formation of low-mass dwarf galaxies, the most common type of galaxy in the Universe. The local volume presents an excellent opportunity to test theories of hierarchical galaxy formation and assembly, especially since high-redshift observations of these galaxies’ formation epochs are beyond the reach of current telescopes. Therefore, this article seeks to summarize the current understanding and chart a path forward for the field.

A revised catalogue of 310 Galactic supernova remnants (SNRs) and some statistics on their properties are presented. 21 SNRs have been added to the catalogue since the previously published version from 2019, and 5 entries have been removed, as they have been identified as H ii regions. Also discussed are some basic statistics of the remnants in the catalogue, the selection effects that apply to the identification of Galactic SNRs and their consequences.

We attempt to find the impact of a modified Tolman Oppenheimer Volkoff (TOV) system of equations on the luminosities of direct photons and axions for a specific axion mass in the presence of a magnetic field. We employ two different equation-of-states (EoSs), namely APR and FPS, to generate the profiles of mass and pressure for spherically symmetric and non-rotating neutron stars (NSs). We then compute the axions emission rates by the Cooper-pair-breaking and formation (PBF) process in the core using the NSCool code. We also examine the possibility of an axion-to-photon conversion in the magnetosphere of NSs. Furthermore, we investigate the impact of the magnetic field on the actual observables, such as the energy spectrum of axions and axion-converted photon flux for three different NSs. Our comparative study indicates that the axion energy spectrum and axion-converted photon flux change significantly due to an intense magnetic field.

Gas volume density is one of the critical parameters, along with dispersions in magnetic field position angles and non-thermal gas motions, for estimating the magnetic field strength using the Davis–Chandrasekhar–Fermi (DCF) relation or through its modified versions for a given region of interest. We present VolDen an novel python-based algorithm to extract the number density map from the column density map for an elongated interstellar filament. VolDen uses the workflow of RadFil to prepare the radial profiles across the spine. The user has to input the column density map and pre-computed spine along with the essential RadFil parameters (such as distance to the filament, the distance between two consecutive radial profile cuts, etc.) to extract the radial column density profiles. The thickness and volume density values are then calculated by modeling the column density profiles with a Plummer-like profile and introducing a cloud boundary condition. The cloud boundary condition was verified through an accompanying N-PDF column density analysis. In this paper, we discuss the workflow of VolDen and apply it to two filamentary clouds. We chose LDN1495 as our primary target owing to its nearby distance and elongated morphology. In addition, the distant filament RCW57A is selected as the secondary target to compare our results with the published results. Upon publication, a complete tutorial of VolDen and the codes will be available via https://github.com/aa16oaslak/volden.

A time series of high-resolution spectra in the optical wavelength region was used to examine the variability of physical parameters of the early-stage post-AGB star IRAS 22272(+)5435. Excitation balance analysis for a sample of iron (Fe), cerium (Ce), and neodymium (Nd) lines confirms effective temperature changes from about (5100pm 150) to (5750pm 100) K during the 132-day pulsation cycle. Using the method of ionization balance, we observed a minor change in surface gravity between (log g= 0.5) and (0.7pm 0.3) (cgs). The microturbulent velocity does not change within the uncertainty limits, (xi _t=4.5pm 0.5) km s(^{-1}). Large macroturbulence in the range of 20–25 km s(^{-1}) was found. We observed variable intensity of the oxygen (O) infrared triplet at 7771-5 Å  which is most likely due to changes in luminosity during the pulsation cycle.