PHOTOMETRIC AND ASTROMETRIC ANALYSES OF NEWLY DISCOVERED AND SELECTED OPEN CLUSTERS

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Tezin Türü: Yüksek Lisans

Tezin Yürütüldüğü Kurum: İstanbul Üniversitesi, Fen Fakültesi, Astronomi Ve Uzay Bilimleri Bölümü, Türkiye

Tezin Onay Tarihi: 2024

Tezin Dili: İngilizce

Öğrenci: Zahraa AL

Danışman: Talar Yontan

Özet:

In this study, it is aimed to obtain the astrometric and fundamental astrophysical parameters of newly discovered 25 UPK open clusters located in the Solar vicinity by using photometric and astrometric data of Gaia DR3. The photometric completeness limit of 25 UPK open clusters were obtained as G=20.5 mag. Membership probabilities of each star detected in the region of clusters were calculated by using UPMASK method, a clustering algorithm. Stars with membership probabilities over than 0.5 and brighter than photometric completeness limit were selected as the most probable members of relevant clusters and these stars considered during the cluster analyzes. Vector point diagrams of the most probable cluster members with membership probability greater than 0.5 were constructed and mean proper-motion components were calculated. From these stars, trigonometric parallax histograms were also constructed and Gaussian function was fitted to the distribution and hence, mean trigonometric parallax of each studied UPK cluster was obtained. The spectroscopic metallicities of 11 of the 25 UPK open clusters were compiled from the literature, while the for the remaining 14 clusters metallicity values were derived during the estimation of astrophysical parameters. The main-sequence fitting method was used to calculate fundamental astrophysical parameters. The most probable cluster member stars were plotted on the color-magnitude diagrams and PARSEC models of different ages were fitted to these diagrams according to member stars to simultaneously determine color excess (E(G_BP-G_RP)), metallicity ([Fe/H]) (for 14 UPK open clusters with unknown metallicity), distance (d) and age (t) of 25 UPK open clusters. The analyses for the determination of astrophysical parameters resulted that the color excesses of examined clusters to be within the 0.019≤ E(G_BP-G_RP) (mag) ≤ 1.654, metallicities -0.15≤ [Fe/H] (dex) ≤ 0.60, distances 212≤ d_iso (pc) ≤ 1008 and ages 10≤ t (Myr) ≤800. In the thesis study, it was concluded that the results of astrometric and fundamental astrophysical parameters estimated from Gaia DR3 data were derived more accurately and precisely than the results obtained from Gaia DR2 data.