arXiv subjects

Talar Yontan

Publications and source records attributed to Talar Yontan.

4 recordsLinked to original sources

arXiv2026

Kings of the Milky Way: A Homogeneous Gaia DR3 Analysis of King Open Clusters and the Galactic Disc Metallicity Gradient

This study aims to establish an internally homogeneous set of structural, astrophysical, and kinematical parameters for King open clusters and to assess their role as tracers of the Galactic thin disc. We present a homogeneous structural, astrophysical, and kinematical analysis of 27 King open clusters using high-precision Gaia DR3 astrometry, photometry, and spectroscopy. Cluster reddenings, distances, metallicities, and ages are determined via a homogeneous Markov Chain Monte Carlo isochrone-fitting approach applied to Gaia colour-magnitude diagrams. The derived parameters span E(G_BP-G_RP) = 0.113-1.933 mag, metallicities of [Fe/H] = -0.40 to +0.28 dex, ages from 17 to 6166 Myr, and heliocentric distances between 739 and 6272 pc. A comparison between astrometric and isochrone-based distances yields a median parallax difference of $-13\mu$as, indicating a good level of internal consistency between the photometric and astrometric distance scales within the adopted homogeneous framework. The radial metallicity behaviour of the King clusters is also examined using three complementary Galactic distance definitions and compared with the metallicity-radius relations obtained independently from 164 spectroscopically analysed open clusters from the literature. The King-cluster gradients are close to $-0.060$ dex kpc$^{-1}$ and are broadly consistent with those of the external reference sample, indicating that the homogeneously analysed King clusters follow the negative metallicity-radius trend traced by the broader thin-disc open-cluster population. Flatter gradients are found for young clusters, suggesting more homogeneous chemical enrichment at recent epochs. When dynamical constraints are applied to reduce the effects of radial migration and orbital blurring, the inferred gradient remains close to $-0.059$ dex kpc$^{-1}$.

astro-ph.GA↗

arXiv2024

Photometric and kinematic studies of open clusters Ruprecht 1 and Ruprecht 171

This study outlines a detailed investigation using CCD {\it UBV} and {\it Gaia} DR3 data sets of the two open clusters Ruprecht 1 (Rup-1) and Ruprecht 171 (Rup-171). Fundamental astrophysical parameters such as color excesses, photometric metallicities, ages, and isochrone distances were based on {\it UBV}-data analyses, whereas membership probability calculations, structural and astrophysical parameters, as well as the kinematic analyses were based on {\it Gaia} DR3-data. We identified 74 and 596 stars as the most probable cluster members with membership probabilities over 50\% for Rup-1 and Rup-171, respectively. The color excesses $E(B-V)$ were obtained as $0.166\pm0.022$ and $0.301\pm0.027$ mag for Rup-1 and Rup-171, respectively. Photometric metallicity analyses were performed by considering F-G type main-sequence member stars and found to be [Fe/H]=$-0.09\pm 0.16$ and [Fe/H]=$-0.20\pm 0.20$ dex for Rup-1 and Rup-171, respectively. Ages and distances were based on both {\it UBV} and {\it Gaia}-data analyses; according to isochrone-fitting these values were estimated to be $t=580\pm60$ Myr, $d=1469\pm57$ pc for Rup-1 and $t=2700\pm200$ Myr, $d=1509\pm69$ pc for Rup-171. The present-day mass function slope of Rup-1 was estimated as $1.26\pm0.32$ and Rup-171 as $1.53\pm1.49$. Galactic orbit integration analyses showed that both of the clusters might be formed outside the solar circle.

astro-ph.SR↗

arXiv2022

An investigation of open clusters Berkeley 68 and Stock 20 using CCD UBV and Gaia DR3 data

We performed detailed photometric and astrometric analyses of the open star clusters Berkeley 68 and Stock 20. This was based on ground-based CCD UBV photometric data complemented by space-based Gaia Data Release 3 photometry and astrometry. 198 stars were identified as likely cluster members for Berkeley 68 and 51 for Stock 20. Two-color diagrams were used to derive the reddening and photometric metallicity for each cluster. The reddening for Berkeley 68 is $E(B-V)=0.520 \pm 0.032$ and $0.400 \pm 0.048$ mag for Stock 20. Photometric metallicity [Fe/H] is $-0.13 \pm 0.08$ dex for Berkeley 68, and $-0.01 \pm 0.06$ dex for Stock 20. Keeping as constant reddening and metallicity, we determined the distance moduli and ages of the clusters through fitting isochrones to the UBV and Gaia based color-magnitude diagrams. Photometric distances are $d=3003 \pm 165$ pc for Berkeley 69 and $2911 \pm 216$ pc for Stock 20. The cluster ages are $2.4 \pm 0.2$ Gyr and $50 \pm 10$ Myr for Berkeley 68 and Stock 20, respectively. Present-day mass function slopes were found to be $Γ= 1.38 \pm 0.71$ and $Γ= 1.53 \pm 0.39$ for Berkeley 68 and Stock 20, respectively. These values are compatible with the value of Salpeter (1955). The relaxation times were estimated as 32.55 Myr and 23.17 Myr for Berkeley 68 and Stock 20, respectively. These times are less than the estimated cluster ages, indicating that both clusters are dynamically relaxed. Orbit integration was carried out only for Berkeley 68 since radial velocity data was not available for Stock 20. Analysis indicated that Berkeley 68 was born outside the solar circle and belongs to the thin-disc component of the Milky Way.

astro-ph.GA↗

arXiv2019

Vilnius Photometry and Gaia Astrometry of Melotte 105

Archival Vilnius CCD photometric observations are presented for the heavily reddened star cluster Melotte 105, resulting in colour-magnitude diagrams and spectral class estimates. There is considerable lack of agreement between studies for reddening, age, and distance for this cluster explaining why the archival data are being made available by this paper. The derived reddening E(B-V =0.34 +/- 0.04 mag and the distance V-M =12.9 +/- 0.3 mag directly from the Vilnius photometry. The Gaia Data Release 2 (DR2) and Vilnius photometric data of the cluster were used to estimate the structural parameters of the cluster, probability of stellar membership in the cluster, the distance modulus and the cluster age. Lack of $Y$ band observations prevented determination of metal abundance. The values of the colour excess and distance module are determined by two different methods (i.e., Q and Zero Age Main Sequence, or ZAMS, methods). A distance modulus of 12.85 +/- 0.07 mag was derived by ZAMS fitting, in good agreement with the above estimate. ZAMS fitting indicates a reddening of 0.403 +/- 0.02 mag, within two sigma of the estimate above. The cluster's metallicity and age are estimated to be 0.24 dex and 240 +/-25 Myr, respectively. The derived mass function is in good agreement with the Salpeter slope. The cluster space velocity components (U, V, W) were determined as (-3.90 +/- 3.34, -13.76 +/- 5.69, +3.45 +/- 0.41) km/s. Perigalactic and apogalactic distances were obtained as R_{p} = 6.85 and R_{a} = 7.44 kpc respectively. The maximum vertical distance from the Galactic plane was calculated as Z_{max} = 84 pc and the eccentricity of the orbit was determined as e = 0.042.

astro-ph.SR↗