Stars and Galaxies, Vol. 08 （2025年）

論文リスト：

なゆた望遠鏡用に開発した補正機能付き指向コマンド pinpoint
pinpoint: Error-Correcting Pointing Command for the Nayuta Telescope
著者：高橋 隼
所属： 兵庫県立大学 天文科学センター 西はりま天文台
Author：Jun TAKAHASHI1
Affiliation： Nishi-Harima Astronomical Observatory, Center for Astronomy, University of Hyogo, 407–2 Nishigaichi, Sayo-cho, Hyogo 679–5313, Japan
著者の電子メールアドレス: takahashi@nhao.jp
Received 2025 July 1; Accepted 2025 October 6

概要：
西はりま天文台なゆた望遠鏡用に、補正機能付きの望遠鏡指向コマンド pinpoint を開発したので報 告する。 pinpoint は、経験則に基づく簡易的な指向補正の後、観測装置で取得したテスト画像を用い て、さらなる補正を行う。 観測対象天体の明るさや、視野内に写る天体の数に応じて、以下の 3 種類の方 式の中から適したものを選択する : (a) テスト画像中に検出された光源のうち最も明るいものを対象天体と 見なして補正を行う方式( self-brightest mode )、 (b) 対象天体とは別に、近傍空域にある明るい星を用いて 指向方位の誤差を測定し、その誤差を対象天体に適用して補正を行う方式( nearby-brightest mode )、 (c) 対 象天体を含む画像に付与された World Coordinate System 情報を利用して補正を行う方式( WCS mode )。 pinpoint の開発により、晴天時には、 NIC や MALLS を用いた観測の大半において、観測者による手作 業の指向補正が不要となった。 これにより、天体導入からデータ取得に至る一連の手続きをスクリプト化 できるようになり、観測の自動化が大きく前進した。

Abstract：
This document reports the development of pinpoint, an error-correcting pointing command for the Nayuta telescope at the Nishi-Harima Astronomical Observatory. The pinpoint command corrects pointing errors using test images of the target object or objects in its vicinity. Three correction modes are implemented: (a) self-brightest mode, (b) nearby-brightest mode, and (c)WCS mode. The most appropriate mode is selected based on the brightness of the target object and the number of nearby objects. With pinpoint, manual correction is no longer necessary for most observations using NIC and MALLS, provided that sky conditions are clear. The pinpoint command automates a series of procedures from pointing to data acquisition through scripting.

　Key words：telescopes — pointing correction
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Neutron capture elements in open clusters
Author：Fua SUGIMURA and Yoichi ITOH
Affiliation : Center for Astronomy, University of Hyogo, Nishi-Gaichi, Sayo, Hyogo 679-5313, Japan
著者の電子メールアドレス: yitoh@nhao.jp
Received 2025 October 8; Accepted 2025 December 3

Abstract：
Open clusters are groups of young stars that formed nearly simultaneously from the same molecular cloud. Because their member stars share a common age, distance, and initial chemical composition, open clusters serve as ideal laboratories for studying the initial mass function, stellar evolution, and chemical abundances. In recent years, spectroscopic surveys of open clusters have revealed chemical abundance gradients across the Milky Way. In particular, clusters located in the inner regions of the Galaxy tend to show higher abundances of neutron-capture elements, while those in the outer regions exhibit lower abundances of these elements. We investigated whether the abundances of neutron-capture elements differ between open clusters that have similar present-day Galactocentric distances but originated in different regions of the Galaxy. We measured the abundances of neutron-capture elements – Y, Zr, Ba, La, Ce, Pr, Nd, Sm, and Eu – in dwarfs belonging to the open clusters Pleiades, Hyades, and Praesepe. Archival high-resolution spectra obtained with the HIRES spectrograph on the Keck Telescope were used for the analysis. For each star, we determined the effective temperature, surface gravity, microturbulence velocity, and [Fe/H]. Based on these atmospheric parameters, we derived the abundances of the neutron-capture elements for a total of 32 dwarfs. There are basically no significant differences in the chemical composition among clusters, but there may be some differences. The dwarfs in the Hyades and Praesepe clusters were found to have similar abundances of neutron-capture elements. For many of these elements, the [X/Fe] in Hyades and Praesepe were 0.06 to 0.36 dex lower than those in the Pleiades. In contrast, the [X/H] were 0.03 to 0.24 dex higher in Hyades and Praesepe for the majority of the elements analyzed. The [Fe/H] of the Hyades and Praesepe clusters are higher than that of the Pleiades, suggesting a significant enrichment of iron from Type Ia supernovae at the birth sites of Hyades and Praesepe. In contrast, the higher abundances of neutron-capture elements relative to hydrogen indicate substantial contributions from neutron star mergers and/or asymptotic giant branch (AGB) stars in those regions. This chemical enrichment cannot be explained by age differences alone, as the Hyades and Praesepe are older than the Pleiades. These findings support the idea that chemical composition in the Milky Way can vary between different birth environments, even at similar Galactocentric distances.

　Key words：open clusters and associations: general – stars: low-mass – techniques:spectroscopy
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Detection of weather variations on the exoplanet Qatar-1 b based on multi-wavelength transit observations
Authors：Yuya HIRANO and Yoichi ITOH
Affiliation： Center for Astronomy, University of Hyogo, 407-2 Nishigaichi, Sayo, Sayo, Hyogo 679-5313, Japan
著者の電子メールアドレス: yitoh@nhao.jp
Received 2025 October 31; Accepted 2025 December 3

Abstract：
We conducted simultaneous transit observations of the exoplanet Qatar-1 b across multiple optical and near-infrared wavelengths from 2021 September 15 to 2023 October 12. The observations were carried out using the Nishi-Harima Infrared Camera (NIC) mounted on the Nayuta telescope and an optical imager on a 60 cm telescope at the Nishi-Harima Astronomical Observatory in Japan. We detected variations in radius ratios across these wavelengths and during the observational period, revealing three distinct patterns: small in the optical wavelengths and large in the near-infrared, large in the optical wavelengths and small in the near-infrared, and similar radius ratios at both wavelengths. These variations were not due to stellar spots but have been attributed to the presence of clouds or haze. Our observations indicated that Qatar-1b had a clear atmosphere on 2023 March 27, clouds or haze with a particle diameter of 0.1 μm or 0.01 μm on 2023 April 13, and clouds or haze with a particle diameter of 1.0 μm on 2023 October 12. Otherwise, the pressure at which clouds or haze exist varies between 1.0 × 10 −5 bar and 8.0 × 10 −4 bar. Observations at multiple wavelengths enable us to monitor temporal weather variations on exoplanets.

　Key words：planets and satellites: gaseous planets, – atmosphoere, techniques: photometric
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Revisiting the Near-Infrared Color of Karin Family Asteroids
Authors：Shigeru Takahashi1 Fumi Yoshida2,3, Hikaru Kubota4, Hideo Sagawa5,6, Takahiro Iino6
Affiliation： 1)Nishi-Harima Astronomical Observatory, Center for Astronomy, University of Hyogo,407–2 Nishigaichi, Sayo-cho, Hyogo 679–5313, Japan
2) University of Occupational and Environmental Health, Japan, 1-1 Iseigaoka, Yahata, Kitakyusyu, Fukuoka 807-8555, Japan
3) Planetary Exploration Research Center, Chiba Institute of Technology, 2-17-1 Tsudanuma, Narashino, Chiba 275-0016, Japan
4) Division of Science, Graduate School, Kyoto Sangyo University, Kamigamo Motoyama, Kita, Kyoto 603-8555, Japan
5) Faculty of Science, Kyoto Sangyo University, Kamigamo Motoyama, Kita-ku, Kyoto 603-8555, Japan
6) Information Technology Center, The University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-8658, Japan
著者の電子メールアドレス: shigeru@nhao.jp
Received 2025 October 28; Accepted 2025 December 19

Abstract：
We conducted a near-infrared spectrophotometric study of the Karin family asteroids; (832) Karin, (13765) Nansmith, (47640) 2000 CA30, (69880) 1998 SQ81, and a non-Karin family member (4507) Petercollins (1990 FV), using the ground-based near-infrared images taken at the UKIRT on Mauna Kea. Several previous observations have reported that (832) Karin has two distinct surface types: a red surface and a non-red surface. We detected the non-red surface. By combining our data with the previous observations, we attempted to locate the position of the red surface but could not find a clear solution that satisfies all the observational results. For the other asteroids in the Karin family, except for (47640) 2000 CA30, their colors were nearly identical to that of (832) Karin. On the other hand, (4507) Petercollins, which has been suggested to be an interloper in the Karin family, exhibited a redder surface than the other Karin family asteroids. This is consistent with the study that (4507) Petercollins is not a member of the Karin family.

　Key words：Asteroid — Near-Infrared — Spectrophotometry — (832)Karin
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