Search Publications
Searching for hot subdwarf stars from the LAMOST Spectra. II. Pure spectroscopic identification method for hot subdwarfs
Zhao, Gang; Németh, Péter; Zhao, Jingkun +2 more
Employing a new machine-learning method, named the hierarchical extreme learning machine (HELM) algorithm, we identified 56 hot subdwarf stars in the first data release (DR1) of the Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) survey. The atmospheric parameters of the stars are obtained by fitting the profiles of hydrogen (H)…
YZ Phoenicis: a very short period K-type contact binary with variation of the O'Connell effect and orbital period change
Li, Lin-Jia; Qian, Sheng-Bang; Zhang, Jia +7 more
YZ Phe is a very short-period contact binary (Sp. = K2 V) with an orbital period of 0.2347 d near the short period limit (0.22 d). We present the complete light curves which photometric data were obtained from the 60 cm telescope of PROMPT-8 at CTIO in Chile during 2016 June to October and 2017 August. The photometric solutions were determined by …
Suzaku detection of enigmatic geocoronal solar wind charge exchange event associated with coronal mass ejection
Miyoshi, Yoshizumi; Ezoe, Yuichiro; Ishikawa, Kumi +5 more
Suzaku detected an enhancement of the soft X-ray background associated with solar eruptions on 2013 April 14-15. The solar eruptions were accompanied by an M6.5 solar flare and a coronal mass ejection with magnetic flux ropes. The enhanced soft X-ray background showed a slight variation over half a day and then a clear one in a few hours. The form…
Does AGN fraction depend on redshift or luminosity? An extinction-free test by 18-band near- to mid-infrared SED fitting in the AKARI NEP wide field
Hashimoto, Tetsuya; Goto, Tomotsugu; Kim, Seong Jin +3 more
Revealing what fraction of galaxies harbor active galactic nuclei (AGNs) is central to understanding the black hole accretion history of the universe. However, optical and soft X-ray surveys miss the most highly obscured AGNs. Infrared (IR), instead, is more robust against absorption. Previous IR photometric surveys, however, only had four or five…
An X-ray spectroscopic search for dark matter and unidentified line signatures in the Perseus cluster with Hitomi
Fabian, Andrew C.; Maeda, Yoshitomo; Gandhi, Poshak +14 more
The reported detection of a 3.5 keV emission signal in the Perseus cluster core by Bulbul et al. (2014, ApJ, 789, 13) was ruled out at high confidence in analysis conducted by Aharonian et al. (2017, ApJ, 837, L15) of X-ray spectra at 5 eV energy resolution obtained with the Hitomi observatory Soft X-ray Spectrometer (SXS). Using the same data, we…
X-ray spectra of Sagittarius A East and diffuse X-ray background near the Galactic center
Koyama, Katsuji; Nobukawa, Masayoshi; Uchiyama, Hideki +3 more
This paper reports the analysis procedure and results of simultaneous spectral fits of the Suzaku archive data for Sagittarius (Sgr) A East and the nearby Galactic center X-ray emission (GCXE). The results are that the mixed-morphology supernova remnant Sgr A East has a recombining plasma (RP) with Cr and Mn Heα lines, and a power-law component (P…
Extended star-forming regions within galaxies in a dense proto-cluster core at z = 2.53
Suzuki, Tomoko L.; Minowa, Yosuke; Koyama, Yusei +5 more
At z ∼ 2, star formation activity is thought to be high even in high-density environments such as galaxy clusters and proto-clusters. One of the critical but outstanding issues is if the structural growth of star-forming galaxies can differ depending on their surrounding environments. In order to investigate how galaxies grow their structures and …
Temporal and spectral X-ray properties of magnetar SGR 1900+14 derived from observations with NuSTAR and XMM-Newton
Enoto, Teruaki; Bamba, Aya; Odaka, Hirokazu +1 more
X-ray observations play a crucial role in understanding the emission mechanism and relevant physical phenomena of magnetars. We report on X-ray observations made in 2016 of a young magnetar, SGR 1900+14, which is famous for a giant flare in 1998 August. Simultaneous observations were conducted with XMM-Newton and NuSTAR on 2016 October 20 with 23 …
Searches for Population III pair-instability supernovae: Impact of gravitational lensing magnification
Oguri, Masamune; Koyama, Yusei; Nomoto, Ken'ichi +3 more
Superluminous supernovae have been proposed to arise from Population III progenitors that explode as pair-instability supernovae (PISNe). Population III stars are the first generation of stars in the Universe, and are thought to have formed as late as z ∼ 6. Future near-infrared imaging facilities such as ULTIMATE-Subaru will potentially be able t…
Discovery of a strong ionized-gas outflow in an AKARI-selected ultra-luminous infrared galaxy at z = 0.5
Yamamura, Issei; Noda, Hirofumi; Kokubo, Mitsuru +5 more
In order to construct a sample of ultra-luminous infrared galaxies (ULIRGs; with infrared luminosity LIR > 1012 L_{⊙}) at 0.5 < z < 1, we are conducting an optical follow-up program for bright 90 µm far-infrared sources with a faint optical (i < 20 mag) counterpart selected in the AKARI Far-Infrared Surveyor…