Search Publications
Starspots, chromospheric emission lines, and flares of zero-age main-sequence stars
Itoh, Yoichi; Oasa, Yumiko; Yamashita, Mai
Zero-age main-sequence (ZAMS) stars are considered to have enormous starspots and show strong chromospheric emission lines because of their strong surface magnetic field. We discuss the dynamo activities of ZAMS stars with respect to their periodic light variation caused by a starspot and with respect to the strength of the chromospheric emission …
High-resolution X-ray study of supernova remnant J0453.6-6829 with unusually high forbidden-to-resonance ratio
Uchida, Hiroyuki; Tsuru, Takeshi Go; Tanaka, Takaaki +3 more
Recent high-resolution X-ray spectroscopy has revealed that several supernova remnants (SNRs) in the Large Magellanic Cloud (LMC) show unusually high forbidden-to-resonance (f/r) line ratios. While their origin is still uncertain and debated, most of these SNRs have asymmetric morphology and/or show evidence of interaction with dense material, whi…
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…