Kawaguchi, Toshihiro, Kawasaki, Masahiro, Takayama, Tsutomu, Yamaguchi, Masahide, Yokoyama, Jun'ichi
Formation of primordial black holes (PBHs) on astrophysical mass scales is a natural consequence of inflationary cosmology if the primordial perturbation spectrum has a large and negative running of...
A Stellar-mass Black Hole in the Ultra-luminous X-ray Source M82 X-1? (2006)
Okajima, Takashi, Ebisawa, Ken, Kawaguchi, Toshihiro
We have analyzed the archival XMM-Newton data of the bright Ultra-Luminous X-ray Source (ULX) M82 X-1 with an 105 ksec exposure when the source was in the steady state. Thanks to the high photon...
Do Ultraluminous X-ray Sources Really Contain Intermediate-mass Black Holes? (2006)
Vierdayanti, Kiki, Mineshige, Shin, Ebisawa, Ken, Kawaguchi, Toshihiro
An open question remains whether Ultraluminous X-ray Sources (ULXs) really contain intermediate-mass black holes (IMBHs). We carefully investigated the XMM-Newton EPIC spectra of the four ULXs that...
Collin, Suzy, Kawaguchi, Toshihiro, Peterson, Brad, Vestergaard, Marianne
We try to identify the sources and systematics of the uncertainty of the masses of the central black holes in active galactic nuclei (AGNs) which have been obtained by reverberation-mapping methods....
The Largest Blueshifts of [O III] emission line in Two Narrow-Line Quasars (2004)
Aoki, Kentaro, Kawaguchi, Toshihiro, Ohta, Kouji
We have obtained optical intermediate resolution spectra (R = 3000) of the narrow-line quasars DMS 0059-0055 and PG 1543+489. The [O III] emission line in DMS 0059-0055 is blueshifted by 880 km/s...
Super-Eddington accretion rates in Narrow Line Seyfert 1 galaxies (2004)
Collin, S., Kawaguchi, Toshihiro
Using the BH masses deduced from the empirical relation of Kaspi et al. (2000) and assuming that the optical luminosity is provided by the accretion disc, we show that Narrow Line Seyfert Galaxies 1...
Super-Eddington accretion onto black holes (BHs) may occur at ultraluminous compact X-ray sources in nearby galaxies, Galactic microquasars and narrow-line Seyfert 1 galaxies (NLS1s). Effects of...
A Chandra Observation of the Luminous NLS1 1H 0707-495 (2002)
Leighly, Karen M., Zdziarski, Andrzej A., Kawaguchi, Toshihiro, Matsumoto, Chiho
We present preliminary results from a long Chandra HETG observation of the luminous Narrow-line Seyfert 1 galaxy 1H 0707-495. We find a complex X-ray spectrum comprised of a two-component continuum...
Kawaguchi, Toshihiro, Shimura, Toshiya, Mineshige, Shin
We construct a disk-corona model which accounts for the optical-to-X-ray spectral properties of Seyfert nuclei and QSOs. We study emission spectrum emerging from a vertical disk-corona structure...
Slim Disk Model for Soft X-Ray Excess and Variability of Narrow-Line Seyfert 1 Galaxies (2000)
Mineshige, Shin, Kawaguchi, Toshihiro, Takeuchi, Mitsuru, Hayashida, Kiyoshi
Narrow-line Seyfert 1 galaxies (NLS1s) exhibit extreme soft X-ray excess and large variability. We argue that both features can be basically accounted for by the slim disk model. We assume that a...