Using the Hα double peak emission lines of Pleione in the BeSS database from January 2009 to March 2023, we have measured the characteristic three point intensities of the line: the intensities at the blue and red emission peaks, and the intensity of the central minimum between the peaks, and calculated the radial velocities of these three points. These values are shown over a period of 14 years. The long-term variations shown are interpreted to be split into (a) the short-term variations when the companion of Pleione is close to periastron, and (b) the long-term variations in the background. For the (b) variation, we try to explain the trajectory of the central minimum intensity by the disk precession, and discuss the occurrence of the V/R phenomenon.

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The SAGI summer school 2023 (3S23) in observational astronomy is organized in the Summer 2023, at the International Center for Interdisciplinary Science and Education (ICISE) in Quy Nhon, Viet Nam. The goal of 3S23 is to promote astronomy research in Viet Nam and to teach astronomy to students. We report the activities of the school and also highlight its pedagogical approach. Using narrative and observational analysis of participants’ own words, we analyze the impacts of the school on participants and on astronomy in Viet Nam. From these results, we propose a new form of teaching, namely Learning Based on Shared Experience (LBSE). LBSE takes into account the diversities in students’ backgrounds, languages, analytical, mathematical, abilities, and experiences and create an environment where learners learn and share from each others’ experience. This approach is likely effective in teaching subjects that requires collaborations such as sciences and technologies.

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The Ellerman bombs are small-scale explosive events that occur at the base of the chromosphere and exhibit a characteristic spectral profile, showing absorption in the Hα line center and significant brightening in the wing. While magnetic reconnection is considered to be the mechanism of their occurrence, the details remain unresolved. Therefore, the aim of this study is to elucidate the temporal evolution of the three-dimensional structure of Ellerman bombs through their spectral characteristics. Using the horizontal spectrograph at the Hida Observatory, Kyoto University, in October 2022, we conducted spectroscopic observations of Ellerman bombs that occurred in the vicinity of sunspots in active regions NOAA13124 and NOAA13135, using the Hα and Ca II K lines, and obtained the temporal variations of physical quantities such as velocity, temperature, and brightness at each wavelength. As a result, we observed magnetic reconnection at the base of the chromosphere in the Hα line, and bi-directional flow resulting from it. Furthermore, we confirmed a correlation between the increase in brightness and the subsequent rise in velocity in the wing. In the Ca II K line, we considered magnetic reconnection to occur below the middle of the chromosphere, and we found a similar correlation between the velocity and brightness of the K2 component as in the Hα line wing.

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Although photometric and spectroscopic observations of Be stars (γ Cas-type variable stars) have been carried out for many years, there are many things that remain unclear, such as the mechanism of angular momentum transport to the circumstellar disk (in the case of binary systems, is there also a contribution from the companion star). Spectroscopic monitoring observations of several Be stars were performed using the Small Aperture Telescope + low-dispersion spectrograph at the school observatory starting in September 2018. As a result, we hypothesized that “the disk is ringed by tidal forces when the Be star’s companion passes through the perihelion point” (石田2022, Stars and Galaxies, 5, 10). To test this hypothesis, we performed medium-dispersion spectroscopic observations of Be stars δ Sco and π Aqr using the Nayuta Telescope at the Nishi-Harima Observatory, University of Hyogo, during and after the periastron passage of their respective companion stars. Combined with the results of the BeSS database analysis, no ring formation of the disk was observed. Combined with the observations at the School Observatory, the disk at δ Sco is expected to be expanding due to a decrease in effective temperature, and may be headed for extinction in the future. In the disk of π Aqr, the effective temperature of the disk tends to change around the perihelion. From these results, it is possible that the companion star has a significant effect on the angular momentum transport mechanism of the Be star to the disk.

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Solar activity has a cycle of ∼11 years, and its strength greatly varies depending on the cycle. I have been seeking for a formula that predicts the strength of this cycle once the beginning of the cycle is known using the old version of the relative sunspot numbers and multiple regression analysis techniques. Two multiple regression formulas have been discovered, and at least one of these pinpoints the strength of all past cycles. From these two formulas, the author concludes that while they are the byproduct of the objective of predicting the strength of the cycle, which differed from the original objective, the timing of the decline in solar activity can be identified. Furthermore, the decline in solar activity is predictable, and extremely weak declines cannot be determined merely using the relative sunspot numbers. The same two formulas exist for the new version of the relative sunspot numbers and are reported in this study.

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30%–50% of the luminous pulsating red-giant stars show light variations of a longer period than the pulsation periods. Those periods are called long secondary periods (LSP). There has been debated for many years but the origin of the LSP is still unknown. To explain the LSP variations, there have been many approaches in not only observations but also theoretical studies. However, the invariance of the length of the LSPs has been investigated little. Thus, we studied the temporal variations of the period by performing the weighted wavelet-Z-transform analysis. Using the OGLE-III database, the I-band light curves of 6904 and 1945 LSP candidates in the Large/Small Magellanic Clouds, respectively, were analyzed. Most of our sample stars indicated that the period corresponding to the LSP was constant during the observation term. However, 101 and 44 LSP stars in the LMC and SMC, respectively, showed the signature of the temporal variations of the LSPs. There were diversities of the period modulations i.e. monotonic increase or decrease, or constant until the middle and then increase, etc. The comet-like companion is one of the possible explanations for the LSP variations, but this hypothesis cannot explain the period modulations because the LSP is determined by the orbital period.

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In this paper, we report the results obtained from the first observations of exoplanet transit conducted with the 600 mm telescope at Quy Nhon Observatory (QNO) in Vietnam. The object of our observation is the exoplanet WASP- 3b, transiting its host starWASP-3 with a period of approximately 1.8468 Earth days. Through our observations and modeling, we obtained a magnitude depth of 0.0121 ± 0.007 mag and a planet radius of 1.42 ± 0.05 RJupiter for WASP-3b. This result is consistent with the previous published results and it implies that QNO 600 mm telescope is capable of monitoring short-period exoplanet transits, even at the atmospheric conditions of Quy Nhon city.

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This paper aims to investigate the the fundamental knowledge, comprehension, awareness, and interest in the realm of astronomy among university students aspiring to become teachers. We have conducted questionnaire surveys from 2013 to 2023 among 3432 students in the Faculty of Education, a teacher-training department, in order to assess their interest in science and astronomy and their understanding of astronomical concepts studied during elementary/junior-high school. As a result, there has been a consistent interest around 80-90% in science among education and science major students over the past decade. There appears to be no clear trend of “decline in students’ positive attitude toward science” during this period. While there was a relatively high retention of knowledge regarding diurnal/annual motions and the classification of the Sun and Moon, there was a lower comprehension of astrophysical characteristics. From comparisons of the percentage of correct responses, interest in science/astronomy, direct experiences in astronomical observations using telescopes and/or gazing our Milky Way, and learning “earth science” in high school, it was found that there existed a discernible gap in understanding astrophysical characteristics, while there were no significant differences in understanding diurnal/annual motions and the classification of the Sun/Moon. The logistic regression analyses on the students’ interests, experiences, and understanding of astronomy indicated that direct experiences, interests, and/or curiosity in astronomy, as well as studying “earth science” in high school, could have a impact on knowledge and understanding of astronomy. Furthermore, a comparison between first-year and subsequent years’ surveys for science major students aspiring to become science teachers at elementary, junior high, and high schools revealed a progressive improvement in understanding. The results suggest that studying astronomy during university, often considered the final opportunity to learn astronomy, could significantly contribute to nurturing essential knowledge and scientific literacy for teachers. In summary, in order to enhance and retain the fundamental understanding of astronomy among university students in teacher training programs, it is recommended to implement the following strategies: （1） observational experiences and hands-on learning utilizing telescopes, （2） studying “earth science （basic）” in high school, and （3） educational practices involving astronomical observations at the university level.

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Klinkerfues comet (1853) was observed at Tsuchimikado in Kyoto and Hazama in Osaka in Japan. Their daily observational records were found to give us numerical data of apparent positions of the comet and permit us to get equatorial coordinates of daily positions of the comet. By mutual comparison of observational accuracies , we found that (1) there are error of +4◦ in azimuth and −2◦ in altitude in Tsuchimikado’s measureing device setting and that after the correction of device setting error, the orbit of the comet well fit the western observational result with a random error of 2◦. (2) The orbit derived from Hazama measurement is less well fit the western observational result than Tsuchimikado’s measurements, with a random error of 5◦.

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Bisei town, located in the west part of Japan, is known as a place where the local community protects its beautiful night sky from light pollution through its unique ordinances and the efforts of the local residents. It is also important to monitor in the quantity and quality of light pollution for precise measurement of astronomical observations. The fluorescent lamps in the city were gradually replaced with light emitting diode (LED) lamps. In order to investigate how much light pollution is affecting astronomical observation, we analyzed the archival photometric and spectroscopic data taken by the 101 cm telescope that has been installed at Bisei Astronomical Observatory (BAO) since 2006. As a result, we found that there is no significant variability in sky brightness in optical bands, but from spectroscopic observation, we observed a blue humps around 4500 ˚A originating from LED lights from 2017 to 2023. The brightness of light pollution observed at BAO is not varied but the origin of light has gradually changed from fluorescent lamps toLED lamps.

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Ultra-Long-Period Cepheids (Periods longer than 80 days) are examined using linear nonadiabatic pulsation models. We found models with ultra-long-periods even with Z = 0.02 models, so such a Cepheid may exist in our Galaxy, which has not been discovered yet. We seem to need a survey of the far side of our Galaxy or a survey in the other galaxy with a similar chemical composition to discover such an object. It is also shown that the models with periods longer than 200 days need to be more massive than the Cepheid upper mass limit, inferred from the stellar evolution theory. It is pointed out that the Cepheid’s nature of HV 1956 in SMC, which has over-200 days period, needs careful confirmation.

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