Search Publications
The mass of TOI-519 b: A close-in giant planet transiting a metal-rich mid-M dwarf
Ikuta, Kai; Tamura, Motohide; Hirano, Teruyuki +33 more
We report on the determination of the mass of TOI-519 b, a transiting substellar object around a mid-M dwarf. We carried out radial velocity measurements using Subaru/InfraRed Doppler (IRD), revealing that TOI-519 b is a planet with a mass of $0.463^{+0.082}_{-0.088}\, M_{\rm Jup}$. We also found that the host star is metal rich ([Fe/H] = 0.27 ± 0…
X-ray and optical spectroscopic study of a γ Cassiopeiae analog source π Aquarii
Tsujimoto, Masahiro; Hayashi, Takayuki; Morihana, Kumiko +1 more
γ Cas analog sources are a subset of Be stars that emit intense and hard X-ray emission. Two competing ideas for their X-ray production mechanism are (a) the magnetic activities of the Be star and its disk and (b) the accretion from the Be star to an unidentified compact object. Among such sources, π Aqr plays a pivotal role as it is one of the on…
Revisiting planetary systems in the Okayama Planet Search Program: A new long-period planet, RV astrometry joint analysis, and a multiplicity-metallicity trend around evolved stars
Izumiura, Hideyuki; Sato, Bun'ei; Yoshida, Michitoshi +15 more
In this study, we revisit 32 planetary systems around evolved stars observed within the framework of the Okayama Planet Search Program (OPSP) and its collaborative framework of the East Asian Planet Search Network to search for additional companions and investigate the properties of stars and giant planets in multiple-planet systems. With our late…
Spatial structure and dynamical state of the old open cluster Collinder 261 based on a clustering method
Gao, Xinhua
In this paper, we investigate the memberships, spatial structure, and dynamical state of the old open cluster Collinder 261 (8 Gyr) based on Gaia-DR3 data. We develop a robust clustering method to calculate membership probabilities for 24858 sample stars within 20' of the cluster center. We can identify 2619 likely cluster members (including 54 bl…
A close-in planet orbiting giant star HD 167768
Izumiura, Hideyuki; Sato, Bun'ei; Yoshida, Michitoshi +12 more
We report the detection of a giant planet orbiting the G-type giant star HD 167768 from radial velocity measurements using the High Dispersion Echelle Spectrograph (HIDES) at Okayama Astrophysical Observatory (OAO). HD 167768 has a mass of $1.08_{-0.12}^{+0.14}\, M_{\odot }$, a radius of $9.70_{-0.25}^{+0.25}\, R_{\odot }$, a metallicity of $[\mbo…
Photometric and spectroscopic properties of the eclipsing system V864 Monocerotis
Hong, Kyeongsoo; Lee, Jae Woo; Park, Jang-Ho
We present the orbital period variability and evolutionary status of the W UMa-type binary system V864 Mon from accurately measured fundamental parameters. New BV photometric observations of this system were performed in 2019 January and 2022 January, and the first high-resolution spectroscopic observations were carried out on three nights between…
Astrometric VLBI observations of H2O masers in an extreme OH/IR star candidate NSV 17351
Kurayama, Tomoharu; Honma, Mareki; Orosz, Gabor +14 more
The results of astrometric very long baseline interferometry (VLBI) observations toward an extreme OH/IR star candidate NSV 17351 are presented. Using the VERA (VLBI Exploration of Radio Astrometry) VLBI array , we observed 22 GHz H2O masers of NSV 17351 and derived an annual parallax of 0.247 ± 0.035 mas, which corresponds to a distanc…
BVRI polarization of stars in the direction of Stock 19
Topasna, Gregory A.; Mateja, Frank M.; Kaltcheva, Nadejda T.
We present BVRI polarimetric measurements of nine bright stars in a 15'-square region centered on Stock 19. Seven of them satisfy the Serkowski equation for star light polarization due to interstellar dust. This allowed us to estimate the degree of maximum polarization (pmax) and the wavelength of maximum polarization (λmax).…
Investigation of mid-infrared long-term variability of dusty AGB stars using multi-epoch scan data of AKARI and WISE
Takita, Satoshi; Ita, Yoshifusa; Tachibana, Kengo +5 more
Asymptotic giant branch (AGB) stars are one of the main sources of dust in the Universe. They form and supply dust triggered by stellar pulsations, but the details of the mechanism are still unknown. Among all AGB stars, dusty AGB stars are the most important in terms of dust supply because they contain the star with a high mass-loss rate. To inve…
Data processing pipeline for multiple-exposure photo-plate digital archives
Yu, Yong; Jia, Peng; Yang, Zhimin +2 more
Photo-plates are an invaluable historical legacy that have been used for over a hundred years to capture images of celestial objects. By digitizing these photo-plates and processing the images with digital image processing methods, scientists can study celestial objects that exhibit temporal variations. Multiple-exposure photo-plates are a unique …