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New candidates for AM Canum Venaticorum stars among ASAS-SN transients
Kato, Taichi; Kojiguchi, Naoto
We studied Zwicky Transient Facility (ZTF) light curves of 34 dwarf nova candidates discovered by the All-Sky Automated Survey for Supernovae (ASAS-SN) between 2020 May 12 and September 9 and found six AM CVn-type candidates. All objects showed short outbursts (post-superoutburst rebrightenings) on the fading tail. Two objects (ASASSN-20eq, ASASSN…
Hyper Suprime-Cam Legacy Archive
Takita, Satoshi; Ikeda, Hiroyuki; Koike, Michitaro +5 more
We present the launch of the Hyper Suprime-Cam Legacy Archive (HSCLA), a public archive of processed, science-ready data from the Hyper Suprime-Cam (HSC). HSC is an optical wide-field imager installed at the prime focus of the Subaru Telescope and has been in operation since 2014. While ~1/3 of the total observing time of HSC has been used for the…
An intermediate-velocity H I cloud falling to the galactic disk; Possible evidence for low-metallicity H I gas originating outside the galactic disk
Tachihara, Kengo; Sasaki, Manami; Fukui, Yasuo +6 more
We found that an intermediate-velocity cloud (IVC), IVC 86-36, in H I 21 cm emission shows a head-tail distribution toward the Galactic plane with marked parallel filamentary streamers, which is extended over 40° in the sky. The distance of IVC 86-36 is constrained to be less than ∼3 kpc from absorption of a background star as determined from opti…
A study of the accretion mechanisms of the high-mass X-ray binary IGR J00370+6122
Fukazawa, Yasushi; Makishima, Kazuo; Takahashi, Hiromitsu +1 more
IGR J00370+6122 is a high-mass X-ray binary with a B1 Ib primary star and a companion suggested to be a neutron star because of the detection of a 346 s pulsation in a one-off 4 ks observation. To better understand the nature of the compact companion, the present work performs timing and spectral studies of the X-ray data of this object, taken wit…
First star survivors as metal-rich halo stars that experienced supernova explosions in binary systems
Matsuno, Tadafumi; Saitoh, Takayuki R.; Suda, Takuma +2 more
The search for the first stars formed from metal-free gas in the universe is one of the key issues in astronomy because it relates to many fields, such as the formation of stars and galaxies, the evolution of the universe, and the origin of elements. It is not still clear if metal-free first stars can be found in the present universe. These first …
Suzaku detection of solar wind charge exchange emission from a variety of highly ionized ions in an interplanetary coronal mass ejection
Katsuda, Satoru; Ezoe, Yuichiro; Yoneyama, Tomokage +8 more
X-ray emission generated through solar-wind charge exchange (SWCX) is known to contaminate X-ray observation data, the amount of which is often significant or even dominant, particularly in the soft X-ray band, when the main target consists of comparatively weak diffuse sources, depending on the space weather during the observation. In particular,…
Spatial distribution of the X-ray-emitting plasma of U Geminorum in quiescence and outburst
Maeda, Yoshitomo; Ishida, Manabu; Hayashi, Takayuki +2 more
We present our analysis of the Suzaku data of U Geminorum (U Gem) from 2012 both in quiescence and outburst. Unlike SS Cygni (SS Cyg), the hard X-ray flux of U Gem is known to increase at times of optical outburst. A sophisticated spectral model and reliable distance estimate now reveal that this can be attributed to the fact that the mass accreti…
The nature of bright C-complex asteroids
Hasegawa, Sunao; Usui, Fumihiko; Kuroda, Daisuke +1 more
Most C-complex asteroids have albedo values less than 0.1, but there are some high-albedo (bright) C-complex asteroids with albedo values exceeding 0.1. To reveal the nature and origin of bright C-complex asteroids, we conducted spectroscopic observations of the asteroids at visible and near-infrared wavelengths. As a result, the bright B-, C-, an…
Photometric follow-up observations and transit timing analysis of HAT-P-37b
Li, Kai; Liu, Yuan; Yang, Jia-Mei +1 more
We performed follow-up photometric observations on exoplanetary system HAT-P-37 from 2011 February to 2019 September. The nine new transit light curves of the R and V bands are presented in this work. Based on the new light curves and published literature data, the physical and orbital parameters of HAT-P-37 are refined. In addition, mid-transit t…
FUGIN hot core survey. I. Survey method and initial results for l = 10°-20°
Hasegawa, Tetsuo; Saito, Hiro; Seta, Masumichi +4 more
We have developed a method to make a spectral-line-based survey of hot cores, which represent an important stage of high-mass star formation, and applied the method to the data of the FUGIN (FOREST Unbiased Galactic plane Imaging survey with the Nobeyama 45 m telescope) survey. First, we select hot core candidates by searching the FUGIN data for t…