Sohei Kondo
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View article: Second-timescale Glints from Satellites and Space Debris Detected with Tomo-e Gozen
Second-timescale Glints from Satellites and Space Debris Detected with Tomo-e Gozen Open
A search for second-timescale optical transients is one of the frontiers of time-domain astronomy. However, it has been pointed out that reflections of sunlight from Earth-orbiting objects can also produce second-timescale “glints.” We con…
View article: Second-timescale Glints from Satellites and Space Debris Detected with Tomo-e Gozen
Second-timescale Glints from Satellites and Space Debris Detected with Tomo-e Gozen Open
A search for second-timescale optical transients is one of the frontiers of time-domain astronomy. However, it has been pointed out that reflections of sunlight from Earth-orbiting objects can also produce second-timescale ``glints.'' We c…
View article: MAGIS (Measuring Abundances of red super Giants with Infrared Spectroscopy) project
MAGIS (Measuring Abundances of red super Giants with Infrared Spectroscopy) project Open
Context . Given their high luminosities ( L ≳ 10 4 L ⊙ ), red supergiants (RSGs) are good tracers of the chemical abundances of the young stellar population in the Milky Way and nearby galaxies. However, previous abundance analyses tailore…
View article: Optical Variability of Blazars in the Tomo-e Gozen Northern Sky Transient Survey
Optical Variability of Blazars in the Tomo-e Gozen Northern Sky Transient Survey Open
We studied the optical variability of 241 BL Lacertae (BL Lacs) and 83 flat-spectrum radio quasars (FSRQs) from the 4LAC catalog using data from the Tomo-e Gozen Northern Sky Transient Survey, with ∼50 epochs per blazar on average. We excl…
View article: Optical Variability of Blazars in the Tomo-e Gozen Northern Sky Transient Survey
Optical Variability of Blazars in the Tomo-e Gozen Northern Sky Transient Survey Open
We studied the optical variability of 241 BL Lacs and 83 flat-spectrum radio quasars (FSRQ) from the 4LAC catalog using data from the Tomo-e Gozen Northern Sky Transient Survey, with $\sim$ 50 epochs per blazar on average. We excluded blaz…
View article: [N i] 10400/10410 Å Lines as Possible Disk Wind Tracers in a Young Intermediate-mass Star
[N i] 10400/10410 Å Lines as Possible Disk Wind Tracers in a Young Intermediate-mass Star Open
In this study, we performed high-resolution near-infrared (NIR) spectroscopy ( R = 28,000; λ = 0.90–1.35 μ m) with a high signal-to-noise ratio on HD 200775, a very young (∼0.1 Myr old) and massive intermediate-mass star (a binary star wit…
View article: [N I] 10400/10410 Å Lines as Possible Disk Wind Tracers in a Young Intermediate-Mass Star
[N I] 10400/10410 Å Lines as Possible Disk Wind Tracers in a Young Intermediate-Mass Star Open
In this study, we performed high-resolution near-infrared (NIR) spectroscopy (R = 28,000; $λ = 0.90$-1.35 $μ$m) with a high signal-to-noise ratio on HD 200775, a very young (${\sim}$0.1 Myr old) and massive intermediate-mass star (a binary…
View article: Intermediate-luminosity Type IIP SN 2021gmj: a low-energy explosion with signatures of circumstellar material
Intermediate-luminosity Type IIP SN 2021gmj: a low-energy explosion with signatures of circumstellar material Open
We present photometric, spectroscopic, and polarimetric observations of the intermediate-luminosity Type IIP supernova (SN) 2021gmj from 1 to 386 d after the explosion. The peak absolute V-band magnitude of SN 2021gmj is −15.5 mag, which i…
View article: Intermediate-luminosity Type IIP SN 2021gmj: a low-energy explosion with signatures of circumstellar material
Intermediate-luminosity Type IIP SN 2021gmj: a low-energy explosion with signatures of circumstellar material Open
We present photometric, spectroscopic and polarimetric observations of the intermediate-luminosity Type IIP supernova (SN) 2021gmj from 1 to 386 days after the explosion. The peak absolute V-band magnitude of SN 2021gmj is -15.5 mag, which…
View article: WARP: The Data Reduction Pipeline for the WINERED spectrograph
WARP: The Data Reduction Pipeline for the WINERED spectrograph Open
We present a data reduction pipeline written in Python for data obtained with the near-infrared cross-dispersed echelle spectrograph, WINERED, which yields a 0.91$-$1.35 $μ$m spectrum with the resolving power of $R_{\text{max}} \equiv λ/ Δ…
View article: Shock Excitation in Narrow-line Regions Powered by AGN Outflows
Shock Excitation in Narrow-line Regions Powered by AGN Outflows Open
Outflows in an active galactic nucleus (AGN) are considered to play a key role in the evolution of the host galaxy through transfer of a large amount of energy. A narrow-line region (NLR) in the AGN is composed of ionized gas extending fro…
View article: Shock Excitation in Narrow Line Regions Powered by AGN Outflows
Shock Excitation in Narrow Line Regions Powered by AGN Outflows Open
Outflows in the Active Galactic Nucleus (AGN) are considered to play a key role in the host galaxy evolution through transfer of a large amount of energy. A Narrow Line Region (NLR) in the AGN is composed of ionized gas extending from pc-s…
View article: A search for extragalactic fast optical transients in the Tomo-e Gozen high-cadence survey
A search for extragalactic fast optical transients in the Tomo-e Gozen high-cadence survey Open
The population of optical transients evolving within a time-scale of a few hours or a day (so-called fast optical transients, FOTs) has recently been debated extensively. In particular, our understanding of extragalactic FOTs and their rat…
View article: A search for extragalactic fast optical transients in the Tomo-e Gozen high-cadence survey
A search for extragalactic fast optical transients in the Tomo-e Gozen high-cadence survey Open
The population of optical transients evolving within a time-scale of a few hours or a day (so-called fast optical transients, FOTs) has recently been debated extensively. In particular, our understanding of extragalactic FOTs and their rat…
View article: Survey of Near-infrared Diffuse Interstellar Bands in Y and J Bands. I. Newly Identified Bands
Survey of Near-infrared Diffuse Interstellar Bands in Y and J Bands. I. Newly Identified Bands Open
We searched for diffuse interstellar bands (DIBs) in the 0.91 < λ < 1.33 μ m region by analyzing the near-infrared (NIR) high-resolution ( R = 20,000 and 28,000) spectra of 31 reddened early-type stars (0.04 < E ( B − V ) < 4.58) and an un…
View article: Fast optical flares from M dwarfs detected by a one-second-cadence survey with Tomo-e Gozen
Fast optical flares from M dwarfs detected by a one-second-cadence survey with Tomo-e Gozen Open
We report on a one-second-cadence wide-field survey for M-dwarf flares using the Tomo-e Gozen camera mounted on the Kiso Schmidt telescope. We detect 22 flares from M3–M5 dwarfs with a rise time of 5 s ≲ trise ≲ 100 s and an amplitude of 0…
View article: Video observations of tiny near-Earth objects with Tomo-e Gozen
Video observations of tiny near-Earth objects with Tomo-e Gozen Open
We report the results of video observations of tiny (diameter less than 100 m) near-Earth objects (NEOs) with Tomo-e Gozen on the Kiso 105 cm Schmidt telescope. The rotational period of a tiny asteroid reflects its dynamical history and ph…
View article: Survey of near-infrared diffuse interstellar bands in $Y$ and $J$ bands. I. Newly identified bands
Survey of near-infrared diffuse interstellar bands in $Y$ and $J$ bands. I. Newly identified bands Open
We searched for diffuse interstellar bands (DIBs) in the 0.91$<λ<$1.33 $μ$m region by analyzing the near-infrared (NIR) high-resolution ($R=20,000$ and 28,000) spectra of 31 reddened early-type stars ($0.04
View article: Deep Simultaneous Limits on Optical Emission from FRB 20190520B by 24.4 fps Observations with Tomo-e Gozen
Deep Simultaneous Limits on Optical Emission from FRB 20190520B by 24.4 fps Observations with Tomo-e Gozen Open
We conduct 24.4 fps optical observations of repeating fast radio burst (FRB) 20190520B using Tomo-e Gozen, a high-speed CMOS camera mounted on the Kiso 105 cm Schmidt telescope, simultaneously with radio observations carried out using the …
View article: A Very Metal-poor RR Lyrae Star with a Disk Orbit Found in the Solar Neighborhood
A Very Metal-poor RR Lyrae Star with a Disk Orbit Found in the Solar Neighborhood Open
Metal-deficient stars are important tracers for understanding the early formation of the Galaxy. Recent large-scale surveys with both photometric and spectroscopic data have reported an increasing number of metal-deficient stars whose kine…
View article: Highly Sensitive, Non-cryogenic NIR High-resolution Spectrograph, WINERED
Highly Sensitive, Non-cryogenic NIR High-resolution Spectrograph, WINERED Open
WINERED is a novel near-infrared (NIR) high-resolution spectrograph (HRS) that pursues the highest possible sensitivity to realize high-precision spectroscopy in the NIR as in the optical wavelength range. WINERED covers 0.9–1.35 μ m ( z ,…
View article: Discovery of the Fastest Early Optical Emission from Overluminous SN Ia 2020hvf: A Thermonuclear Explosion within a Dense Circumstellar Environment
Discovery of the Fastest Early Optical Emission from Overluminous SN Ia 2020hvf: A Thermonuclear Explosion within a Dense Circumstellar Environment Open
In this Letter we report a discovery of a prominent flash of a peculiar overluminous Type Ia supernova, SN 2020hvf, in about 5 hr of the supernova explosion by the first wide-field mosaic CMOS sensor imager, the Tomo-e Gozen Camera. The fa…
View article: Mg II and Fe II fluxes of luminous quasars at z ~ 2.7 and the Baldwin effect in flux-to-abundance conversion for chemical evolution of quasars at high redshifts
Mg II and Fe II fluxes of luminous quasars at z ~ 2.7 and the Baldwin effect in flux-to-abundance conversion for chemical evolution of quasars at high redshifts Open
To investigate the chemical abundance of broad-line region clouds in quasars at high redshifts, we performed near-infrared spectroscopy of six luminous quasars at z ~ 2.7 with the WINERED spectrograph mounted on the New Technology Telescop…
View article: The effect of surface gravity on line-depth ratios in the wavelength range 0.97–1.32 µm
The effect of surface gravity on line-depth ratios in the wavelength range 0.97–1.32 µm Open
A line-depth ratio (LDR) of two spectral lines with different excitation potentials is expected to be correlated with the effective temperature (Teff). It is possible to determine Teff of a star with a precision of tens of Kelvin if dozens…
View article: Effective temperatures of red supergiants estimated from line-depth ratios of iron lines in the <i>YJ</i> bands, 0.97-1.32μm
Effective temperatures of red supergiants estimated from line-depth ratios of iron lines in the <i>YJ</i> bands, 0.97-1.32μm Open
Determining the effective temperatures (Teff) of red supergiants (RSGs) observationally is important in many fields of stellar physics and galactic astronomy, yet some significant difficulties remain as a result of the model uncertainty, w…
View article: Identification of Absorption Lines of Heavy Metals in the Wavelength Range 0.97–1.32 μm
Identification of Absorption Lines of Heavy Metals in the Wavelength Range 0.97–1.32 μm Open
Stellar absorption lines of heavy elements can give us various insights into the chemical evolution of our Galaxy and other nearby galaxies. Recently developed spectrographs for the near-infrared wavelengths are becoming more and more powe…
View article: WINERED High-resolution Near-infrared Line Catalog: A-type Star
WINERED High-resolution Near-infrared Line Catalog: A-type Star Open
We present a catalog of absorption lines in the z', Y, and J bands that we identified in 21 Lyn, a slowly rotating A0.5 V star. We detected 155 absorption features in the high-resolution (0.90–1.35 μm, R = 28,000) spectrum obtained with th…
View article: Optical and Near-infrared High-resolution Spectroscopic Observations of Nova V2659 Cyg: Structure of Nova Ejecta and Origin of Two-distinct Velocity Systems
Optical and Near-infrared High-resolution Spectroscopic Observations of Nova V2659 Cyg: Structure of Nova Ejecta and Origin of Two-distinct Velocity Systems Open
Two distinct absorption-line systems distinguished by radial velocities have often been observed in the optical high-resolution spectra of classical novae during their early decline phase. The origin of these absorption-line systems is und…
View article: A newly identified emission-line region around P Cygni
A newly identified emission-line region around P Cygni Open
We present a high-resolution ($R \\simeq 20,000$) near-infrared (9,100-13,500\n$\\AA$) long-slit spectrum of P Cygni obtained with the newly commissioned\nWINERED spectrograph in Japan. In the obtained spectrum, we have found that the\nvel…