Search Publications
Poisson vs. Gaussian statistics for sparse X-ray data: Application to the soft X-ray spectrometer
Eckart, Megan E.; Kelley, Richard L.; Kilbourne, Caroline A. +8 more
Reliable results when fitting X-ray data require proper consideration of the statistics involved. We probe the impact of Gaussian versus Poisson statistics at low count levels using both the standard χ2 method and maximum likelihood based on Poisson (C) statistics. The difference is studied and quantified through simulated spectra with …
Third-nearest WZ Sge-Type dwarf nova candidate ASASSN-14dx classified on the basis of Gaia Data Release 2
Nogami, Daisaku; Monard, Berto; Ohshima, Tomohito +8 more
ASASSN-14dx showed an extraordinary outburst whose features are a small outburst amplitude (∼2.3 mag) and long duration (>4 yr). Because we found a long observational gap of 123 d before the outburst detection, we propose that the main outburst plateau was missed and that this outburst is just a "fading tail" often seen after the WZ Sge-type su…
Revised wavelength and spectral response calibrations for AKARI near-infrared grism spectroscopy: Post-cryogenic phase
Nakagawa, Takao; Baba, Shunsuke; Onaka, Takashi +2 more
We present a new calibration for the second-order light contamination in the near-infrared grism spectroscopy with the Infrared Camera aboard AKARI, specifically for the post-cryogenic phase of the satellite (Phase 3). Following our previous work on the cryogenic phase (Phases 1 and 2), the wavelength and spectral response calibrations were revise…
Active galactic nucleus selection in the AKARI NEP-Deep field with the fuzzy support vector machine algorithm
Goto, Tomotsugu; Matsuhara, Hideo; Poliszczuk, Artem +15 more
The aim of this work is to create a new catalog of reliable active galactic nucleus (AGN) candidates selected from the AKARI NEP-Deep field. Selection of the AGN candidates was done by applying a fuzzy support vector machine algorithm, which allows the incorporation of measurement uncertainties into the classification process. The training dataset…
Spectral properties of gamma-ray bursts observed by the Suzaku wide-band all-sky monitor
Yamaoka, Kazutaka; Fukazawa, Yasushi; Kokubun, Motohide +17 more
We have systematically studied the spectral properties of 302 localized gamma-ray bursts (GRBs) observed by the Suzaku wide-band all-sky monitor (WAM) from 2005 August to 2010 December. The energy spectra in the 100-5000 keV range integrated over the entire emission and the 1 s peak were fitted by three models: a single power law, a power law with…
AKARI mid-infrared slit-less spectroscopic catalogue
Baba, Shunsuke; Onaka, Takashi; Yamamura, Issei +4 more
AKARI/IRC is capable of conducting slit-less spectroscopy in the mid-infrared (5-13 µm) over a 10' × 10' area with a spectral resolution of 50, which is suitable for serendipitous surveys. The data reduction is, however, rather complicated by the confusion of nearby sources after dispersing the spectra. To achieve efficient and reliable data…
On surface brightness and flux calibration for point and compact extended sources in the AKARI Far-IR All-Sky Survey (AFASS) maps
Takita, Satoshi; Ueta, Toshiya; Szczerba, Ryszard +1 more
The AKARI infrared astronomical satellite produced all-sky survey (AFASS) maps in the far-infrared at roughly arcminute spatial resolution, enabling us to investigate the whole sky in the far-infrared for objects having surface brightnesses greater than a few to a couple of dozen MJy sr-1. While the AFASS maps are absolutely calibrated …
LAMOST J011939.222-012150.45: The most barium-enhanced CEMP-s turnoff star
Zhao, Gang; Li, Haining; Matsuno, Tadafumi +2 more
We have performed chemical abundance analyses for a newly discovered metal-poor turn-off star (Teff = 6276 K, log g = 3.93, [Fe/H] = -2.93), LAMOST J011939.222-012150.45, based on high-resolution and high signal-to-noise ratio spectra in both optical and near-UV obtained by Subaru. Abundances have been derived for 20 elements, including…
The interplay between active galactic nuclei and star formation activities of type 1 active galactic nuclei probed by polycyclic aromatic hydrocarbon 3.3 µm emission feature with AKARI
Nakagawa, Takao; Oyabu, Shinki; Ohyama, Youichi +11 more
We investigate the connection between active galactic nucleus (AGN) and star formation activities of AGN host galaxies by studying the 3.3 µm polycyclic aromatic hydrocarbon (PAH) emission feature of 79 type 1 AGNs using the AKARI space telescope. Utilizing the slitless spectroscopic capability of the AKARI Infrared Camera, we obtained the s…
Membership and fundamental parameters of the intermediate-age open clusters NGC 2281 and NGC 2539 based on Gaia-DR2
Gao, Xin-Hua
This paper presents an investigation on the two intermediate-age open clusters NGC 2281 and NGC 2539 based on Gaia Data Release 2 (Gaia-DR2). A combined machine-learning method is used to identify likely cluster members of the two clusters, taking into account the astrometric and photometric data of Gaia-DR2. It is found that NGC 2281 and NGC 2539…