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Molecular clouds toward three Spitzer bubbles S116, S117, and S118: Evidence for a cloud-cloud collision which formed the three H II regions and a 10 pc scale molecular cavity
Tachihara, Kengo; Fukui, Yasuo; Nishimura, Atsushi +6 more
We carried out a molecular-line study toward the three Spitzer bubbles S116, S117, and S118, which show active formation of high-mass stars. We found molecular gas consisting of two components with a velocity difference of ∼5 km s-1. One of them, the small cloud, has a typical velocity of -63 km s-1 and the other, the large c…
Detection of polarized gamma-ray emission from the Crab nebula with the Hitomi Soft Gamma-ray Detector
Done, Chris; Safi-Harb, Samar; Hamaguchi, Kenji +191 more
We present the results from the Hitomi Soft Gamma-ray Detector (SGD) observation of the Crab nebula. The main part of SGD is a Compton camera, which in addition to being a spectrometer, is capable of measuring polarization of gamma-ray photons. The Crab nebula is one of the brightest X-ray/gamma-ray sources on the sky, and the only source from whi…
Large-scale CO J = 1-0 observations of the giant molecular cloud associated with the infrared ring N35 with the Nobeyama 45 m telescope
Kuno, Nario; Tachihara, Kengo; Fukui, Yasuo +14 more
We report an observational study of the giant molecular cloud (GMC) associated with the Galactic infrared ring-like structure N35 and two nearby H II regions G024.392+00.072 (H II region A) and G024.510-00.060 (H II region B), using the new CO J = 1-0 data obtained as a part of the FOREST Unbiased Galactic Plane Imaging survey with the Nobeyama 45…
Suzaku and NuSTAR X-ray spectroscopy of γ Cassiopeiae and HD 110432
Tsujimoto, Masahiro; Hayashi, Takayuki; Kitaguchi, Takao +1 more
γ Cas and its dozen analogs comprise a small but distinct class of X-ray sources. They are early Be-type stars with an exceptionally hard thermal X-ray emission. The X-ray production mechanism has been under intense debate. Two competing ideas are (i) the magnetic activities in the Be star and its disk, and (ii) the mass accretion onto the unident…
Hitomi observations of the LMC SNR N 132 D: Highly redshifted X-ray emission from iron ejecta
Done, Chris; Safi-Harb, Samar; Hamaguchi, Kenji +191 more
We present Hitomi observations of N 132 D, a young, X-ray bright, O-rich core-collapse supernova remnant in the Large Magellanic Cloud (LMC). Despite a very short observation of only 3.7 ks, the Soft X-ray Spectrometer (SXS) easily detects the line complexes of highly ionized S K and Fe K with 16-17 counts in each. The Fe feature is measured for t…
Triggering the formation of the supergiant H II region NGC 604 in M 33
Tachihara, Kengo; Fukui, Yasuo; Sano, Hidetoshi +4 more
Formation mechanism of a supergiant H II region NGC 604 is discussed in terms of collision of H I clouds in M 33. An analysis of the archival H I data obtained with the Very Large Array (VLA) reveals complex velocity distributions around NGC 604. The H I clouds are composed of two velocity components separated by ∼20 km s-1 for an exten…
In-orbit performance of the soft X-ray imaging system aboard Hitomi (ASTRO-H)
Dotani, Tadayasu; Miller, Eric D.; Maeda, Yoshitomo +46 more
We describe the in-orbit performance of the soft X-ray imaging system consisting of the Soft X-ray Telescope and the Soft X-ray Imager aboard Hitomi. Verification and calibration of imaging and spectroscopic performance are carried out, making the best use of the limited data of less than three weeks. Basic performance, including a large field of …
In-flight calibration of Hitomi Soft X-ray Spectrometer. (3) Effective area
Maeda, Yoshitomo; Tsujimoto, Masahiro; Okajima, Takashi +14 more
We present the result of the in-flight calibration of the effective area of the Soft X-ray Spectrometer (SXS) on board the Hitomi X-ray satellite using an observation of the Crab nebula. We corrected for artifacts when observing high count rate sources with the X-ray microcalorimeter. We then constructed a spectrum in the 0.5-20 keV band, which we…
LAMOST J221750.59+210437.2: A new member of carbon-enhanced extremely metal-poor stars with excesses of Mg and Si
Honda, Satoshi; Li, Haining; Ishigaki, Miho N. +4 more
We report on the elemental abundances of the carbon-enhanced metal-poor (CEMP) star J2217+2104, discovered through our metal-poor star survey with LAMOST and Subaru. This object is a red giant and has extremely low Fe abundance ([Fe/H] = -4.0) and very large enhancement of C, N, and O with excesses of Na, Mg, Al, and Si. This star is a new example…
Hitomi X-ray observation of the pulsar wind nebula G21.5-0.9
Done, Chris; Safi-Harb, Samar; Hamaguchi, Kenji +194 more
We present results from the Hitomi X-ray observation of a young composite-type supernova remnant (SNR) G21.5-0.9, whose emission is dominated by the pulsar wind nebula (PWN) contribution. The X-ray spectra in the 0.8-80 keV range obtained with the Soft X-ray Spectrometer (SXS), Soft X-ray Imager, and Hard X-ray Imager (HXI) show a significant brea…