Search Publications
Regular radial velocity variations in nine G- and K-type giant stars: Eight planets and one planet candidate
Izumiura, Hideyuki; Sato, Bun'ei; Yoshida, Michitoshi +9 more
We report the detection of radial velocity (RV) variations in nine evolved G- and K-type giant stars. The observations were conducted at Okayama Astrophysical Observatory. Planets or planet candidates can best explain these regular variations. However, a coincidence of near 280 d variability among five of them prevents us from fully ruling out ste…
Spectral break of energetic pulsar wind nebulae detected with wideband X-ray observations
Terada, Yukikatsu; Uchida, Hiroyuki; Bamba, Aya +4 more
Pulsar wind nebulae (PWNe) are one of the most energetic galactic sources with bright emissions from radio waves to very high-energy gamma-rays. We perform wideband X-ray spectroscopy of four energetic PWNe, N 157 B, PSR J1813-1749, PSR J1400-6325, and G21.5-0.9, with the Suzaku, Chandra, NuSTAR, and Hitomi observatories. A significant spectral br…
Video observations of tiny near-Earth objects with Tomo-e Gozen
Kobayashi, Naoto; Takita, Satoshi; Usui, Fumihiko +20 more
We report the results of video observations of tiny (diameter less than 100 m) near-Earth objects (NEOs) with Tomo-e Gozen on the Kiso 105 cm Schmidt telescope. The rotational period of a tiny asteroid reflects its dynamical history and physical properties since smaller objects are sensitive to the Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effe…
Nobeyama 45 m Local Spur CO survey. I. Giant molecular filaments and cluster formation in the Vulpecula OB association
Miyamoto, Yusuke; Tokuda, Kazuki; Tachihara, Kengo +13 more
We have performed new large-scale 12CO, 13CO, and C18O J = 1-0 observations toward the Vulpecula OB association (l ~ 60°) as part of the Nobeyama 45 m Local Spur CO survey project. Molecular clouds are distributed over ~100 pc, with local peaks at the Sh 2-86, Sh 2-87, and Sh 2-88 high-mass star-forming regions in …
The soft X-ray background with Suzaku. I. Milky Way halo
Sato, Kosuke; Yamasaki, Noriko Y.; Matsushita, Kyoko +4 more
We present measurements of the soft X-ray background emission for 130 Suzaku observations at 75° < l < 285° and |b| > 15° obtained from 2005 to 2015, covering nearly one solar cycle. In addition to the standard soft X-ray background model consisting of the local hot bubble and the Milky Way Halo (MWH), we include a hot collisional-ionizat…
X-ray selected narrow-line active galactic nuclei in the COSMOS field: Nature of optically dull active galactic nuclei
Murayama, Takashi; Fitriana, Itsna K.
X-ray emission detection in a galaxy is one of the efficient tools for selecting active galactic nuclei (AGNs). However, many X-ray-selected AGNs are not easily selected as AGNs by their optical emission. These galaxies, so-called optically dull (OD) AGNs, are fascinating since their X-ray emission is bright even though the AGN signature in the op…
Relationship between gamma-ray loudness and X-ray spectra of radio galaxies
Fukazawa, Yasushi; Kayanoki, Taishu
The Fermi satellite has detected ~ 60 radio galaxies (RGs). In this study, we investigate the difference in the properties of X-ray spectra between GeV-loud RGs and GeV-quiet RGs. Our sample comprises 68 objects: 36 RGs detected with Fermi and 32 RGs not detected with gamma-rays. We analyzed the X-ray spectra of these 68 objects using data from th…
NuSTAR discovery of the hard X-ray emission and a wide-band X-ray spectrum from the Pictor A western hotspot
Katsuda, Satoru; Sato, Kosuke; Tashiro, Makoto S. +5 more
Utilizing Chandra, XMM-Newton, and NuSTAR, a wide-band X-ray spectrum from 0.2 to 20 keV is reported from the western hotspot of Pictor A. In particular, the X-ray emission is significantly detected in the 3 to 20 keV band at 30σ by NuSTAR. This is the first detection of hard X-rays with energies above 10 keV from a jet termination hotspot of acti…
Deep near-infrared imaging observation of the faint X-ray point sources constituting the Galactic bulge X-ray emission
Gandhi, Poshak; Tsujimoto, Masahiro; Ebisawa, Ken +1 more
The presence of the apparently extended hard (2-10 keV) X-ray emission along the Galactic plane has been known since the early 1980s. With a deep X-ray exposure using the Chandra X-ray Observatory of a slightly off-plane region in the Galactic bulge, most of the extended emission was resolved into faint discrete X-ray sources in the Fe K band (Rev…
Deblurring galaxy images with Tikhonov regularization on magnitude domain
Takeuchi, Tsutomu T.; Murata, Kazumi
We propose a regularization-based deblurring method that works efficiently for galaxy images. The spatial resolution of a ground-based telescope is generally limited by seeing conditions and is much worse than space-based telescopes. This circumstance has generated considerable research interest in the restoration of spatial resolution. Since imag…