Stars and Galaxies, Vol. 07 (2024)

list of papers

Long-term evolution of the Hα emission line of Pleione between Jan 2009 and Mar 2023 in the BeSS database II. Detailed profile variation during the periastron phenomenon
Author; Junichi Katahira
E-mail: atak@db3.so-net.ne.jp
Received 2024 September 28; Accepted 2024 November 13

Abstract
Using the Hα double peak emission lines of Pleione in the BeSS database from January 2009 to March 2023, the following points are discussed: 1) A comparison of the emission line profile variations observed at each periastron passage of the companion star reveals a striking similarity in the patterns of variation over the period 2015 - 2021. 2) As the periastron passage of the companion is repeated, the blue emission wing becomes stronger than the red emission wing towards the end of the Be-shell phase. 3) The mechanistic regularity whereby the red emission peak becomes earlier and stronger than the blue emission peak for a short time at each periastron passage of the companion star is interpreted qualitatively in terms of both the periastron position of the companion and the position of the disk in the celestial plane, as well as the tidal action of the companion star.

Key words; stars: Be star - stars: Pleione - stars: Be disk
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Deriving Metallicity and Atmospheric Parameters for the Fast-Rotating SB2 Binary HIP 103833: Addressing Challenges in Close Binary Spectroscopy
Author; Noriyuki KATOH
Affiliation : Graduate School of Human Development and Environment, Kobe University
E-mail: noriyuki.k@panda.kobe-u.ac.jp
Received 2024 October 31; Accepted 2024 November 21

Abstract;
The spectrum of a close binary star is a composite of the spectra of both the primary and secondary stars. Furthermore, high stellar rotational velocities lead to the blending of absorption lines, which complicates the accurate measurement of equivalent widths. In this study, we focused on the SB2 spectroscopic binary HIP 103833, for which the atmospheric parameters (effective temperature, surface gravity) and stellar parameters (mass, radius, luminosity) are already established. Utilizing spectral data obtained from the Nayuta Telescope at Nishi-Harima Observatory and MALLS, we derived atmospheric parameters and metallicities based on the equivalent widths of iron absorption lines. The parameters obtained in this research closely align with those from previous studies, thereby supporting the reliability of our equivalent width measurements. Additionally, the stellar parameters derived from our atmospheric analysis are not expected to differ significantly from those obtained from orbital motions in previous studies.

Key words; stars: abundances - binaries: close - techniques: spectroscopic
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Installation of Multi-wavelength SimultaneouS High throughput Imager and polarimeter (MuSaSHI) for Multi-color Imaging Observations on the Gunma Astronomical Observatory 150cm Telescope
Authors; Takahiro KANAI1, Yumiko OASA1,2, Hidenori TAKAHASHI3, Osamu HASHIMOTO4, Hikaru TAGUCHI5
Affiliation; 1) Graduate School of Science and Engineering, Saitama University, 255 Shimo-Okubo, Sakura, Saitama, Saitama, 338-8570, Japan
2) Faculty of Education, Saitama University, 255 Shimo-Okubo, Sakura, Saitama, Saitama, 338-8570, Japan
3) Kiso Observatory, Institute of Astronomy, School of Science, the University of Tokyo, 10762-30 Mitake, Kiso-machi, Kiso-gun, Nagano, 397-0101, Japan
4) Bisei Spaceguard Center, 1716-3 Okura, Bisei, Ibara, Okayama 714-1411, Japan
5) Gunma Astronomical Observatory, 6860-86 Nakayama, Takayama, Agatsuma, Gunma 377-0702, Japan
E-mail: s15pp223@gmail.com
Received 2024 October 31; Accepted 2024 December 5

Abstract;
We have developed a reducer and observation system for the MuSaSHI (Multi-wavelength SimultaneouS High throughput Imager and polarimeter; Oasa et al. 2020) which was originally designed for the SaCRA (Saitama university Common-use telescope for Research of Astronomy) 55 cm telescope, in order to carry out simultaneous multi-wavelength (r-, i-, and z-bands) imaging observations using the Gunma Astronomical Observatory 150 cm telescope. At the beginning of this project, we installed the MuSaSHI directly at the focal point of the 150 cm telescope (F12.2). It was successful to take the r-, i-, and z-bands simultaneously using the 150 cm telescope. There were some difficulties however in the photometric accuracy due to the small field of view (2.6' x 2.5') and the oversampling (0.147 "/pixel) against a typical seeing size. We have thus developed a new focal reducer to obtain relatively wide FoV images and the control system to handle the MuSaSHI efficiently. The new reducer is designed to reduce the focal ratio from F12.2 to F6.7 by two lenses of commercial products and to be light to reduce distortions. Some additional modifications were also introduced as the MuSaSHI and its control system to improve the operational efficiency. We have conducted 39 night multi-color simultaneous observations by the MuSaSHI on the 150 cm telescope with the new focal reducer until Oct 2024. The field of view and pixel scale were measured to be as 4.7' x 4.6', 0.27 "/pixel, respectively, as expected by the optical design. The higher photometric precisions and sensitivities (~ 1.5 mag deeper on r-band) were achieved with 150 cm/MuSaSHI than SaCRA/MuSaSHI. Future improvement could be expected by optimizing the optical designing of the reducer.

Key words; instrumentation - optical - multi-color photometry
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Optical and Near-Infrared Transit Observations of the Exoplanet TrES-3 b
Authors; Yuya HIRANO, Yoichi ITOH
Affiliation; Nishi-Harima Astronomical Observatory, Center for Astronomy, University of Hyogo, 407-2 Nishigaichi, Sayo-cho, Hyogo 679-5313, Japan
E-mail: hirano@nhao.jp, yitoh@nhao.jp
Received 2024 October 31; Accepted 2024 December 6

Abstract：
We conducted simultaneous transit observations of the exoplanet TrES-3 b in multiple optical and near-infrared wavelengths from March 19, 2023 to August 7, 2024. Observations were carried out using the 2 m Nayuta telescope equipped with the Nishiharima Infrared Camera (NIC) and a 60 cm telescope at the Nishi-Harima Astronomical Observatory. The observed planet-to-star radius ratios ranged from 0.152 to 0.161 in the V band, 0.151 to 0.162 in the J band, 0.155 to 0.159 in the H band, and 0.134 to 0.157 in the K s band. Throughout the observation period, no significant wavelength-dependent variations were detected in the radius ratio, suggesting uniformity in the radius ratio across all wavelengths. This indicates that the atmosphere of TrES-3 b is not significantly expanded and can be explained by both clear and cloudy atmospheric models. Additionally, no prominent Rayleigh scattering feature was detected, supporting the findings of Mackebrandt et al. (2017).

Key words; planets and satellites: atmospheres - techniques: photometric - astrochemistry
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Installation and initial performance of MALLS echelle mode
Authors; Satoshi HONDA1, Kurumi FURUTSUKA1,2 Yoichi ITOH1
Affiliation; 1) Nishi-Harima Astronomical Observatory, Center for Astronomy, University of Hyogo, 407-2 Nishigaichi, Sayo-cho, Hyogo 679-5313, Japan
2) Graduate School of Science, University of Hyogo E-mail: honda@nhao.jp
Received 2024 November 6; Accepted 2024 December 6

Abstract;
MALLS is a spectrograph on the 2m Nayuta telescope at Nishi-Harima Astronomical Observatory in the University of Hyogo. The instrument can perform spectroscopy in the low to medium dispersion mode by switching between three gratings, but in 2018 an echelle and a cross-disperser were installed. Investigations of the performance in the initial echelle mode showed a wavelength resolution (R) of about 35,000, spectral coverage of 4960-6800 A, and an efficiency of about one-third of that in the medium dispersion mode (1800 mm-1 grating). The performance is sufficient for studying the chemical composition and other properties of relatively bright stars (V < 8).

Key words; Instrumentation:spectrograph - Nayuta - MALLS Echelle
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Astrometric Search for Open Clusters and Associations around Binaries with Early Type Primaries
Author; Yoichi ITOH
Affiliation; Nishi-Harima Astronomical Observatory, Center for Astronomy, University of Hyogo,407-2 Nishigaichi, Sayo-cho, Hyogo 679-5313, Japan
E-mail: yitoh@nhao.jp Received 2024 October 31; Accepted 2024 December 10

Abstract;
In this study, we present result of astrometric search for open clusters and associations around an early-type primary star in a binary or multiple star system. Based on the position, parallax, and proper motion measured by Gaia satellite, 98 open clusters and 110 associations were identified. Among them, 109 clusters and associations are newly discovered. The number of the membership ranged from 8 to 1526. The ages of the open clusters and associations were estimated to be between 10 6.3 yr and 10 8.9 yr. It is indicated that most of early-type stars are born in a stellar cluster with a number of low-mass stars. The low-mass stars in the open clusters and associations are candidates of post T Tauri stars.

Key words; open clusters and associations: general - parallaxes - proper motions
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table 2

Study of spectral variability by spectroscopic observation of recurrent nova / symbiotic stars T CrB
Author: Kazuko Ando1, Toshimitsu Toda1, Shuichi Nakagawa1 , Syoki Muraoka1, Tomohito Oshima2, Kenta Taguchi3,4, Naoya Fukuda1
Affiliation;
1) Okayama University of Science, 1-1 Ridaicho, Kita-ku, Okayama-shi 700-0005, Japan
2) Nishi-Harima Astronomical Observatory, Center for Astronomy, University of Hyogo, 407-2 Nishigaichi, Sayo-cho, Hyogo 679-5313, Japan
3) Okayama Observatory, Kyoto University, 3037-5 Honjo, Kamogata-cho, Asakuchi, Okayama 719-0232, Japan
4) Department of Astronomy,KyotoUniversity, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan
E-mail: Kazuko.ando02@gmail.jp
Received 2024 October 31; Accepted 2024 December 11

Abstract;
T CrB is a recurrent nova that has attracted attention because of several nova explosions in the past. This object is a binary of a white dwarf and a red giant (M3III), and it is also known that semi-regular variability is observed because the apparent size of the photosphere changes due to the orbital motion (P = 227.55 d) of the binary star. This object was reported to have been in active-state from 2015 to 2023, and began to fade from March 2023. Since T CrB showed the temporary dimming just before previous nova eruption, it might be a sign of the nova eruption, but the nature of this phenomenon is still under discussion. We have performed 14 nights low- resolution spectroscopic observations from April 2016 to May 2019, when it was just in the active-state, and 4 nights spectroscopic observations (including 1 night medium-resolution spectroscopic observations) from February 2023 to July 2024, when it was in the temporary-dimming phase. In this paper, we compare our previous observations with the photometric results of the Kamogata Kiso Kyoto Wide-field survey (KWS) and summarize the spectral variations by different phase.

Key words; nova - symbiotic stars - cataclysmic stars
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