Search Publications
Annual parallax measurement of the Mira variable star BX Camelopardalis with VERA
Kurayama, Tomoharu; Honma, Mareki; Nakagawa, Akiharu +8 more
We report the results of astrometric VLBI observations toward the Mira variable star BX Cam using the VERA VLBI array. The observation was performed from 2012 February to 2014 November. The parallax obtained is 1.73 ± 0.03 mas corresponding to a distance of 0.58 ± 0.01 kpc. The parallax of this source was reported in Gaia DR2 as 4.13 ± 0.25 mas, a…
Distribution of physical parameters for 380 contact binaries in the Kepler field
Zhu, Li-Ying; Liu, Liang; Li, Xu-Zhi
We present the physical parameters (p, T, q, i, f) of 380 Kepler contact binary systems (hereafter called CBs). A statistical study on the CBs is carried out based on a Kepler photometric database. Our samples were selected from the Kepler Eclipsing Binary Catalogue of EW-type eclipsing binaries with periods around 0.2-1 d and amplitudes greater t…
First detection of two superoutbursts during the rebrightening phase of a WZ Sge-type dwarf nova: TCP J21040470+4631129
Ruiz, Javier; Nogami, Daisaku; Tamura, Motohide +51 more
We report on photometric and spectroscopic observations and analysis of the 2019 superoutburst of TCP J21040470+4631129. This object showed a 9 mag superoutburst with early superhumps and ordinary superhumps, which are the features of WZ Sge-type dwarf novae. Five rebrightenings were observed after the main superoutburst. The spectra during the po…
Comprehensive photometric investigation of an active early K-type contact system—IL Cancri
Sarotsakulchai, Thawicharat; Liu, Nian-Ping; Rattanasoon, Somsawat +1 more
Comprehensive photometric investigation of the early K-type contact binary IL Cnc was carried out. A few light curves from both ground-based telescopes and the Kepler space telescope were obtained (or downloaded) and then analyzed in detail. They are mostly found to be asymmetric and there are even continuously changing O'Connell effects in the li…
TESS photometry of the eclipsing δ Scuti star AI Hydrae
Kristiansen, Martti H.; Hong, Kyeongsoo; Lee, Jae Woo
AI Hya has been known as an eclipsing binary with a monoperiodic $\delta$ Sct pulsator. We present the results from its TESS (Transiting Exoplanet Survey Satellite) photometry observed during Sector 7. Including our five minimum epochs, the eclipse timing diagram displays the apsidal motion with a rate of $\dot{\omega } = 0.075 \pm 0.031\:$ deg $\…
Trigonometric parallax of O-rich Mira variable star OZ Gem (IRAS 07308+3037): A confirmation of the difference between the P-L relations of the Large Magellanic Cloud and the Milky Way
Kawabata, Koji; Fujimoto, Masayuki Y.; Yamanaka, Masayuki +11 more
OZ Geminorum (OZ Gem) is a galactic Mira variable in the Milky Way (MW). We measured its annual parallax with VLBI Exploration of Radio Astrometry to be π = 0.806 ± 0.039 mas, corresponding to a distance of D = 1.24 ± 0.06 kpc. Based on multi-epoch infrared observations with the Kagoshima University 1 m telescope, we also derived the mean J-, H-, …
ALMA twenty-six arcmin2 survey of GOODS-S at one millimeter (ASAGAO): Millimeter properties of stellar mass selected galaxies
Ouchi, Masami; Fujimoto, Seiji; Tamura, Yoichi +19 more
We make use of the ALMA twenty-Six Arcmin2 survey of GOODS-S At One-millimeter (ASAGAO), deep 1.2 mm continuum observations of a 26-arcmin2 region in the Great Observatories Origins Deep Survey-South (GOODS-S) obtained with Atacama Large Millimeter/sub-millimeter Array (ALMA), to probe dust-enshrouded star formation in K-band…
Measurements of the Ca II infrared triplet emission lines of pre-main-sequence stars
Itoh, Yoichi; Takagi, Yuhei; Yamashita, Mai
We investigated the chromospheric activity of 60 pre-main-sequence (PMS) stars in four molecular clouds and five moving groups. It is considered that strong chromospheric activity is driven by the dynamo processes generated by stellar rotation. In contrast, several researchers have pointed out that the chromospheres of PMS stars are activated by m…
Investigation of contact binaries in the field of NGC 6811
Liu, Liang; Li, Xu-Zhi; Zhang, Xu-Dong
Contact binary systems are very important for studying physical processes such as strong interactions between stars, mass transfer, and stellar merger. Further, the members of an open cluster have the same age, metal abundance, and interstellar extinction conditions. Therefore, we can conduct a comparative study on the different binary systems of …
Performance of VERA in 10 micro-arcsecond astrometry
Hirota, Tomoya; Honma, Mareki; Nakagawa, Akiharu +9 more
Very Long Baseline Interferometry (VLBI) astrometry using the phase-referencing technique remains an open issue for the quantitative characterization of the observing conditions to achieve a feasible parallax precision of 10 micro-arcseconds (µas). To address this issue, we evaluated the astrometric performance of the VLBI Exploration of Rad…