6 papers
Evidence for Multiple Orbiting Hotspots in the 340 GHz Variability of Sgr A*
Kazuki Yanagisawa, Tomoharu Oka, Tatsuya Kotani +3
We analyzed 11 epochs of archival Atacama Large Millimeter/submillimeter Array (ALMA) data to investigate flux density variability of Sgr A* at 340 GHz. In one epoch, the light cur…
Detection of a Molecular Cloud toward the Heartbeating Gamma-ray Source near the Microquasar SS 433
Tomoharu Oka, Ryo Ariyama, Tatsuya Kotani
We report the detection of a molecular cloud, CO+40.05-2.40, positionally coincident with the "heartbeating" GeV source Fermi J1913+0515 at the northern boundary of the SS 433/W50…
First Determination of the Cosmic Microwave Background Radiation Temperature at Using Molecular Absorption Lines
Tatsuya Kotani, Tomoharu Oka, Rei Enokiya
We analyzed millimeter-wave data toward the quasar B0218+357 observed with the Atacama Large Millimeter/submillimeter Array and obtained absorption spectra of the =2-1 and =3…
Discovery of Multiple Ultra-Broad-Velocity Molecular Features Associated with the W44 Molecular Cloud
Momoko Makita, Tomoharu Oka, Shiho Tsujimoto +1
We report the discovery of multiple compact molecular features exhibiting extremely broad velocity widths toward the W44 molecular cloud. ALMA CO =3--2 data reveal eight ``Petit…
A New Precise Measurement of the Cosmic Microwave Background Radiation Temperature at Toward PKS1830-211
Tatsuya Kotani, Tomoharu Oka, Rei Enokiya +3
In this study, we analyzed millimeter-wave data toward the quasar PKS1830-211 observed with the Atacama Large Millimeter/submillimeter Array to obtain absorption spectra of HCN …
Signature of a Dark Ultra-compact Dwarf Galaxy Transiting the Milky Way Disk
Ken Udagawa, Tomoharu Oka, Hiroki Yokozuka +1
We report the discovery of a vertical velocity anomaly (VVA) in the stellar component of the Galactic disk, consistent with the impact of a dark, ultra-compact dwarf galaxy (UCD)-s…