Search Publications
Discovery of H2O megamasers in obscured active galactic nuclei
Terashima, Yuichi; Salak, Dragan; Nakai, Naomasa +9 more
A new method to discover obscured active galactic nuclei (AGNs) by utilizing X-ray and infrared data has recently been developed. We carried out a survey of H2O maser emission toward 10 obscured AGNs with the Nobeyama 45 m telescope. We newly detected the maser emission with a signal-noise-ratio (SNR) of above 4 from two AGNs; NGC 1402 …
Suzaku and Chandra observations of CIZA J1700.8-3144, a cluster of galaxies in the Zone of Avoidance
Maeda, Yoshitomo; Mori, Hideyuki; Nakazawa, Kazuhiro +2 more
We present the Chandra and Suzaku observations of 1RXS J170047.8-314442, located towards the Galactic bulge, to reveal a wide-band (0.3-10 keV) X-ray morphology and spectrum of this source. With the Chandra observation, no point source was found at the position of 1RXS J170047.8-314442. Instead, we revealed the presence of diffuse X-ray emission, …
X-ray study of extended emission around M 86 observed with Suzaku
Fujimoto, Ryuichi; Tanaka, Keigo; Hishi, Ukyo +4 more
We analyzed the Suzaku data of M 86 and its adjacent regions to study the extended emission around it. The M 86 core, the plume, and the tail extending toward the northwest were clearly detected, as well as the extended halo around them. From the position angle ∼ 45° to ∼ 275°, the surface brightness distribution of the core and the extended halo …
A search for a keV signature of radiatively decaying dark matter with Suzaku XIS observations of the X-ray diffuse background
Mitsuda, Kazuhisa; Yamasaki, Noriko Y.; Sekiya, Norio
We performed the deepest search for an X-ray emission line at between 0.5 and 7 keV from non-baryonic dark matter by the Suzaku XIS. Dark matter associated with the Milky Way was selected as the target to obtain the best signal-to-noise ratio. From the Suzaku archive, we selected 187 data sets of blank-sky regions that were dominated by the X-ray …
Scale heights and equivalent widths of the iron K-shell lines in the Galactic diffuse X-ray emission
Koyama, Katsuji; Nobukawa, Masayoshi; Uchiyama, Hideki +2 more
This paper reports the analysis of the X-ray spectra of the Galactic diffuse X-ray emission (GDXE) in the Suzaku archive. The fluxes of the Fe I Kα (6.4 keV), Fe XXV Heα (6.7 keV), and Fe XXVI Lyα (6.97 keV) lines are separately determined. From the latitude distributions, we confirm that the GDXE is decomposed into the Galactic center (GCXE), the…
Suzaku spectra of a Type-II supernova remnant, Kes 79
Takahashi, Tadayuki; Koyama, Katsuji; Lee, Shiu-Hang +1 more
This paper reports on results of a Suzaku observation of the supernova remnant (SNR) Kes 79 (G33.6+0.1). The X-ray spectrum is best fitted by a two-temperature model: a non-equilibrium ionization (NEI) plasma and a collisional ionization equilibrium (CIE) plasma. The NEI plasma is spatially confined within the inner radio shell with kT ∼ 0.8 keV, …
Parallax of a Mira variable R Ursae Majoris studied with astrometric VLBI
Kurayama, Tomoharu; Honma, Mareki; Nakagawa, Akiharu +5 more
We have measured an annual parallax of the Mira variable R Ursae Majoris (R UMa) with the VLBI Exploration for Radio Astronomy (VERA). From the monitoring VLBI observations over a span of about two years, we detected H2O maser spots in the LSR velocity range from 37 to 42 km s-1. We derived an annual parallax of 1.97 ± 0.05 m…
Search for gas bulk motions in eight nearby clusters of galaxies with Suzaku
Ota, Naomi; Yoshida, Hiroko
To search for bulk motions of the intracluster medium, we analyzed X-ray spectra taken with the Suzaku satellite, and measured the Doppler shift of the Fe-K line emission from eight nearby clusters of galaxies with various X-ray morphologies. In the cores of the Centaurus and Perseus clusters, the gas bulk velocity does not exceed the sound veloci…
Evidence for a 36 ks phase modulation in the hard X-ray pulses from the magnetar 1E 1547.0-5408
Enoto, Teruaki; Makishima, Kazuo; Nakazawa, Kazuhiro +4 more
The Suzaku data for the highly variable magnetar 1E 1547.0-5408, obtained during the 2009 January activity, were reanalyzed. The 2.07 s pulsation, detected in the 15-40 keV HXD data, was found to exhibit phase modulation, which can be modeled by a sinusoid with a period of 36.0^{+4.5}_{-2.5}ks and an amplitude of 0.52 ± 0.14 s. While the effect is…
Origin of the broad iron line feature and the soft X-ray variation in Seyfert galaxies
Ebisawa, Ken; Mizumoto, Misaki; Inoue, Hajime +4 more
Many Seyfert galaxies are known to exhibit significant X-ray spectral variations and seemingly broad iron K-emission line features. In this paper, we show that the "variable partial covering model," which has been successfully proposed for MCG -6-30-15 (Miyakawa et al. 2012, PASJ, 64, 140) and 1H 0707-495 (Mizumoto et al. 2014, PASJ, 66, 122), can…