Search Publications
Does the radial-tangential macroturbulence model adequately describe the spectral line broadening of solar-type stars?*
Takeda, Yoichi; UeNo, Satoru
In incorporating the effect of atmospheric turbulence in the broadening of spectral lines, the so-called radial-tangential macroturbulence (RTM) model has been widely used in the field of solar-type stars, which was devised from intuitive appearance of the granular velocity field of the Sun. Since this model assumes that turbulent motions are rest…
The mass-metallicity relation of AKARI-FMOS infrared galaxies at z ∼ 0.88 in the AKARI North Ecliptic Pole Deep Survey Field
Goto, Tomotsugu; Pearson, Chris; Matsuhara, Hideo +2 more
The mass, metallicity, and star formation rate (SFR) of a galaxy are crucial parameters in understanding galaxy formation and evolution. However, the relation between these parameters, (i.e., the fundamental relation) is still a matter of debate for luminous infrared (IR) galaxies, which carry a bulk of the SFR budget of the universe at z ∼ 1. We …
Search for the warm-hot intergalactic medium around A 2744 using Suzaku
Finoguenov, Alexis; Akamatsu, Hiroki; Ota, Naomi +2 more
We present the results from Suzaku satellite observations of the surrounding region of a galaxy cluster, A 2744, at z = 0.3. To search for oxygen emission lines from the warm-hot intergalactic medium (WHIM), we analyzed X-ray spectra from two northeastern regions 2.2-3.3 and 3.3-4.4 Mpc from the center of the cluster, which offers the first test o…
Validation of a scaling law for the coronal magnetic field strength and loop length of solar and stellar flares
Namekata, Kosuke; Shibata, Kazunari; Watanabe, Kyoko +2 more
Shibata and Yokoyama (1999, ApJ, 526, L49; 2002, ApJ, 577, 422) proposed a method of estimating the coronal magnetic field strength (B) and magnetic loop length (L) of solar and stellar flares, on the basis of magnetohydrodynamic simulations of the magnetic reconnection model. Using the scaling law provided by Shibata and Yokoyama (1999, ApJ, 526,…
A hard-to-soft state transition of Aquila X-1 observed with Suzaku
Yamaoka, Kazutaka; Makishima, Kazuo; Nakazawa, Kazuhiro +3 more
The recurrent soft X-ray transient Aquila X-1 was observed with Suzaku for a gross duration of 79.9 ks, on 2011 October 21 when the object was in a rising phase of an outburst. During the observation, the source exhibited a clear spectral transition from the hard state to the soft state, on a time scale of ∼30 ks. Across the transition, the 0.8-10…
The K2-ESPRINT project. VI. K2-105 b, a hot Neptune around a metal-rich G-dwarf
Tamura, Motohide; Hirano, Teruyuki; Sato, Bun'ei +17 more
We report on the confirmation that the candidate transits observed for the star EPIC 211525389 are due to a short-period Neptune-sized planet. The host star, located in K2 campaign field 5, is a metal-rich ([Fe/H] = 0.26 ± 0.05) G-dwarf (Teff = 5430 ± 70 K and log g = 4.48 ± 0.09), based on observations with the High Dispersion Spectrog…
Follow-up observations for the Asteroid Catalog using AKARI Spectroscopic Observations
Hasegawa, Sunao; Usui, Fumihiko; Yanagisawa, Kenshi +1 more
In the 1-2.5 µm range, spectroscopic observations are made on the AcuA-spec asteroids, the spectra of which were obtained in a continuous covered mode between 2.5-5.0 µm by AKARI. Based on the Bus-DeMeo taxonomy (DeMeo et al. 2009, Icarus, 202, 160), all the AcuA-spec asteroids are classified, using both published and our observational…
A study of the long term evolution in active region upflows
Harra, Louise K.; Ugarte-Urra, Ignacio; Baker, Deborah +5 more
Since their discovery, upflows at the edges of active regions have attracted a lot of interest, primarily as they could potentially contribute to the slow solar wind. One aspect that has not been studied yet is how the long term evolution of active regions impacts the upflows. In this work, we analyze one active region that survives three solar ro…
Suzaku Wide-band All-sky Monitor (WAM) observations of GRBs and SGRs
Yamaoka, Kazutaka; Fukazawa, Yasushi; Hanabata, Yoshitaka +29 more
We will review results for gamma-ray bursts (GRBs) and soft gamma repeaters (SGRs), obtained from the Suzaku Wide-band All-sky Monitor (WAM) which operated for about 10 years from 2005 to 2015. The WAM is a BGO (bismuth germanate: Bi4Ge3O12) lateral shield for the Hard X-ray Detector (HXD), used mainly for rejectin…
ASASSN-16eg: New candidate for a long-period WZ Sge-type dwarf nova
Nogami, Daisaku; Kato, Taichi; Isogai, Keisuke +19 more
We report on our photometric observations of the 2016 superoutburst of ASASSN-16eg. This object showed a WZ Sge-type superoutburst with prominent early superhumps with a period of 0.075478(8) d and a post-superoutburst rebrightening. During the superoutburst plateau, it showed ordinary superhumps with a period of 0.077880(3) d and a period derivat…