Search Publications
Astrometric VLBI observations of H2O masers in an extreme OH/IR star candidate NSV 17351
Kurayama, Tomoharu; Honma, Mareki; Orosz, Gabor +14 more
The results of astrometric very long baseline interferometry (VLBI) observations toward an extreme OH/IR star candidate NSV 17351 are presented. Using the VERA (VLBI Exploration of Radio Astrometry) VLBI array , we observed 22 GHz H2O masers of NSV 17351 and derived an annual parallax of 0.247 ± 0.035 mas, which corresponds to a distanc…
X-ray spectroscopy of the accretion disk corona source 2S 0921-630 with Suzaku archival data
Dotani, Tadayasu; Yoneyama, Tomokage
2S 0921-630 is an eclipsing low-mass X-ray binary (LMXB) with an orbital period of ~9 d. Past X-ray observations have revealed that 2S 0921-630 has an extended accretion disk corona (ADC), from which most of the X-rays from the system are emitted. We report the result of our Suzaku archival data analysis of 2S 0921-630. The average X-ray spectrum …
Cosmic-ray-driven enhancement of the C0/CO abundance ratio in W 51 C
Yamagishi, Mitsuyoshi; Kaneda, Hidehiro; Shimonishi, Takashi +5 more
We examine spatial variations of the C0$/$CO abundance ratio (XC/CO) in the vicinity of the γ-ray supernova remnant W 51 C, based on [C I] (3P1-3P0), 12CO(1-0), and 13CO(1-0) observations with the ASTE and Nobeyama 45 m telescopes. We find that XC/CO…
Twisted magnetic field in star formation processes of L1521 F revealed by submillimeter dual-band polarimetry using the James Clerk Maxwell Telescope
Shinnaga, Hiroko; Tomisaka, Kohji; Harada, Naoto +3 more
Understanding the initial conditions of star formation requires both observational studies and theoretical works taking into account the magnetic field, which plays an important role in star formation processes. Herein, we study the young nearby dense cloud core L1521 F [n(H2) ~104-6 cm-3] in the Taurus Molecular C…
BVRI polarization of stars in the direction of Stock 19
Topasna, Gregory A.; Mateja, Frank M.; Kaltcheva, Nadejda T.
We present BVRI polarimetric measurements of nine bright stars in a 15'-square region centered on Stock 19. Seven of them satisfy the Serkowski equation for star light polarization due to interstellar dust. This allowed us to estimate the degree of maximum polarization (pmax) and the wavelength of maximum polarization (λmax).…
Solar horizontal flow evaluation using neural network and numerical simulations with snapshot data
Katsukawa, Yukio; Ishikawa, Ryohtaroh T.; Masaki, Hiroyuki +1 more
We suggest a method that evaluates the horizontal velocity in the solar photosphere with easily observable values using a combination of neural network and radiative magnetohydrodynamics simulations. All three-component velocities of thermal convection on the solar surface have important roles in generating waves in the upper atmosphere. However, …
Spectral study of the Galactic ridge X-ray emission with Suzaku: Comparison of the spectral shape with point sources
Nobukawa, Masayoshi; Uchiyama, Hideki; Nobukawa, Kumiko K. +2 more
The Galactic ridge X-ray emission (GRXE) is unresolved X-ray emission located on the Galactic plane, and whether the GRXE comes from truly diffuse plasma or unresolved point sources is still debatable. We present results of spectral analysis of the GRXE with Suzaku. In order to examine the point source origin, we fitted the GRXE spectra in the 1.2…
Investigation of mid-infrared long-term variability of dusty AGB stars using multi-epoch scan data of AKARI and WISE
Takita, Satoshi; Ita, Yoshifusa; Tachibana, Kengo +5 more
Asymptotic giant branch (AGB) stars are one of the main sources of dust in the Universe. They form and supply dust triggered by stellar pulsations, but the details of the mechanism are still unknown. Among all AGB stars, dusty AGB stars are the most important in terms of dust supply because they contain the star with a high mass-loss rate. To inve…
Modeling of geocoronal solar wind charge exchange events detected with Suzaku
Miyoshi, Yoshizumi; Ezoe, Yuichiro; Ishikawa, Kumi +2 more
A model of geocoronal solar wind charge exchange (SWCX) emission was built and compared to five Suzaku detections of bright geocoronal SWCX events. An exospheric neutral hydrogen distribution model, charge exchange cross-sections, solar wind ion data taken with the ACE and WIND satellites, and magnetic field models of the Earth's magnetosphere are…
Data processing pipeline for multiple-exposure photo-plate digital archives
Yu, Yong; Jia, Peng; Yang, Zhimin +2 more
Photo-plates are an invaluable historical legacy that have been used for over a hundred years to capture images of celestial objects. By digitizing these photo-plates and processing the images with digital image processing methods, scientists can study celestial objects that exhibit temporal variations. Multiple-exposure photo-plates are a unique …