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    CCD UBV and Gaia DR3 based analysis of NGC 189, NGC 1758 and NGC 7762 open clusters
    (Elsevier Sci Ltd, 2023) Yontan, Talar; Bilir, Selcuk; Cakmak, Hikmet; Raul, Michel; Banks, Timothy; Soydugan, Esin; Canbay, Remziye
    This paper presents photometric, astrometric, and kinematic analyses of the open clusters NGC 189, NGC 1758 and NGC 7762 based on CCD UBV photometric and Gaia Data Release 3 (DR3) data. According to membership analyses, we identified 32, 57 and 106 most probable member stars with membership probabilities P >= 0:5 in NGC 189, NGC 1758 and NGC 7762, respectively. The color excesses and photometric metallicities of each cluster were determined separately using UBV two-color diagrams. The color excess E(B - V) is 0: 590 +/- 0:023 mag for NGC 189, 0:310 +/- 0:022 mag for NGC 1758 and 0:640 +/- 0:017 mag for NGC 7762. The photometric metallicity [Fe/H] is -0:08 +/- 0:03 dex for both NGC 189 and NGC 1758, and -0:12 +/- 0:02 dex for NGC 7762. Distance moduli and ages of the clusters were obtained by comparing PARSEC isochrones with the color-magnitude diagrams constructed from UBV and Gaia photometric data. During this process, we kept as constant color excess and metallicity for each cluster. The estimated isochrone distance is 1201 +/- 53 pc for NGC 189, 902 +/- 33 pc for NGC 1758 and 911 +/- 31 pc for NGC 7762. These are compatible with the values obtained from trigonometric parallax. Ages of the clusters are 500 +/- 50 Myr, 650 +/- 50 Myr and 2000 +/- 200 Myr for NGC 189, NGC 1758 and NGC 7762, respectively. Galactic orbit integration of the clusters showed that NGC 1758 completely orbits outside the solar circle, while NGC 189 and NGC 7762 enter the solar circle during their orbits. (c) 2023 COSPAR. Published by Elsevier B.V. All rights reserved.
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    Optimization applied to selected exoplanets
    (Springer, 2021) Ng, Shi Yuan; Jiadi, Zhou; Püsküllü, Çağlar; Banks, Timothy; Budding, Edwin; Rhodes, Michael D.
    Transit and radial velocity models were applied to archival data in order to examine exoplanet properties, in particular for the recently discovered super-Earth GJ357b. There is however considerable variation in estimated model parameters across the literature, and especially their uncertainty estimates. This applies even for relatively uncomplicated systems and basic parameters. Some published accuracy values thus appear highly overoptimistic. We present our reanalyses with these variations in mind and specify parameters with appropriate confidence intervals for the exoplanets Kepler-1b, -2b, -8b, -12b, -13b, -14b, -15b, -40b and -77b and 51 Peg. More sophisticated models in WINFITTER (WF), EXOFAST and DACE were applied, leading to mean planet densities for Kepler-12b, -14b, -15b and -40b as: 0:11 0:01, 4:04 0:58, 0:43 0:05 and 1:19þ0:31 0:36 g per cc respectively. We confirm a rocky mean density for the Earth-like GJ357b, although we urge caution about the modelling given the low S/N data. We cannot confidently specify parameters for the other two proposed planets in this system.