Search Publications
Cloud-cloud collisions and triggered star formation
Inoue, Tsuyoshi; Tachihara, Kengo; Fukui, Yasuo +2 more
Star formation is a fundamental process for galactic evolution. One issue over the last several decades has been determining whether star formation is induced by external triggers or self-regulated in a closed system. The role of an external trigger, which can effectively collect mass in a small volume, has attracted particular attention in connec…
Time-resolved spectroscopy and photometry of M dwarf flare star YZ Canis Minoris with OISTER and TESS: Blue asymmetry in the Hα line during the non-white light flare
Notsu, Yuta; Kowalski, Adam F.; Maehara, Hiroyuki +15 more
In this paper, we present the results from spectroscopic and photometric observations of the M-type flare star YZ CMi in the framework of the Optical and Infrared Synergetic Telescopes for Education and Research (OISTER) collaborations during the Transiting Exoplanet Survey Satellite (TESS) observation period. We detected 145 white-light flares fr…
CO Multi-line Imaging of Nearby Galaxies (COMING). IX. 12CO(J = 2-1)/12CO(J = 1-0) line ratio on kiloparsec scales
Kobayashi, Masato I. N.; Kuno, Nario; Miyamoto, Yusuke +8 more
While molecular gas mass is usually derived from 12CO(J = 1-0)—the most fundamental line for exploring molecular gas—it is often derived from 12CO(J = 2-1) assuming a constant 12CO(J = 2-1) $/$ 12CO(J = 1-0) line ratio (R2/1). We present variations of R2/1 and effects of the assumpt…
ALMA CO observations of a giant molecular cloud in M 33: Evidence for high-mass star formation triggered by cloud-cloud collisions
Tokuda, Kazuki; Tachihara, Kengo; Sasaki, Manami +14 more
We report the first evidence for high-mass star formation triggered by collisions of molecular clouds in M 33. Using the Atacama Large Millimeter/submillimeter Array, we spatially resolved filamentary structures of giant molecular cloud 37 in M 33 using 12CO(J = 2-1), 13CO(J = 2-1), and C18O(J = 2-1) line emission …
The formation of young massive clusters triggered by cloud-cloud collisions in the Antennae galaxies NGC 4038/NGC 4039
Tokuda, Kazuki; Tachihara, Kengo; Ueda, Junko +5 more
The formation mechanism of super star clusters (SSCs), present-day analogs of the ancient globulars, still remains elusive. The major merger that is the Antennae galaxies is forming SSCs and is one of the primary targets to test the cluster formation mechanism. We reanalyzed the archival ALMA CO data of the Antennae and found three typical observa…
CO observations of the molecular gas in the Galactic H II region Sh2-48: Evidence for cloud-cloud collision as a trigger of high-mass star formation
Kuno, Nario; Tachihara, Kengo; Fukui, Yasuo +15 more
Sh2-48 is a Galactic H II region, 3.8 kpc distant, with an O9.5-type star identified at its center. As a part of the FOREST Unbiased Galactic plane Imaging survey using the Nobeyama 45 m telescope (FUGIN) project, we obtained a CO J = 1-0 data set for a large area of Sh2-48 at a spatial resolution of 21″ (∼0.4 pc), and used it to find a molecular …
BO Ceti: Dwarf nova showing both IW And-type and SU UMa-Type features
Monard, Berto; Tampo, Yusuke; Kato, Taichi +13 more
IW And stars are a recently recognized subgroup of dwarf novae which are characterized by (often repetitive) slowly rising standstills terminated by brightening, but the exact mechanism for this variation is not yet identified. We have identified BO Cet, which had been considered as a novalike cataclysmic variable, as a new member of IW And stars …
The formation of the young massive cluster B1 in the Antennae Galaxies (NGC 4038/NGC 4039) triggered by cloud-cloud collision
Tokuda, Kazuki; Tachihara, Kengo; Ueda, Junko +4 more
The Antennae Galaxies, one of major mergers, are a starburst. Tsuge et al. (2020, PASJ, 73, S35) showed that the five giant molecular complexes in the Antennae Galaxies have signatures of cloud-cloud collisions based on the Atacama Large Millimeter Array (ALMA) archival data with 60 pc resolution. In the present work we analyzed the new CO data to…
Tidally perturbed oblique pulsations in the hierarchical triple system V1031 Orionis
Lee, Jae Woo
We present Transiting Exoplanet Survey Satellite (TESS) photometry of the triple star system V1031 Ori (AB)C, which exhibits short-period oscillations superimposed on an eclipsing light curve.The high-quality data were analyzed in detail and combined with the published spectroscopic measurements to obtain the fundamental stellar parameters of the …
ASASSN-18aan: An eclipsing SU UMa-type cataclysmic variable with a 3.6-hr orbital period and a late G-type secondary star
Thorstensen, John R.; Nogami, Daisaku; Sasada, Mahito +41 more
We report photometric and spectroscopic observations of the eclipsing SU UMa-type dwarf nova ASASSN-18aan. We observed the 2018 superoutburst with 2.3 mag brightening and found the orbital period (Porb) to be 0.149454(3) d, or 3.59 hr. This is longward of the period gap, establishing ASASSN-18aan as one of a small number of long-Po…