Sébastien Vievard
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View article: Dynamical Analysis of the HD 169142 Planet-forming Disk: Twelve Years of High-contrast Polarimetry
Dynamical Analysis of the HD 169142 Planet-forming Disk: Twelve Years of High-contrast Polarimetry Open
We present a dynamical analysis of the HD 169142 planet-forming disk based on high-contrast polarimetric imaging over a twelve-year observational period, offering insights into its disk evolution and planet–disk interactions. This study ex…
View article: On-sky Demonstration of Subdiffraction-limited Astronomical Measurement Using a Photonic Lantern
On-sky Demonstration of Subdiffraction-limited Astronomical Measurement Using a Photonic Lantern Open
Resolving fine details of astronomical objects provides critical insights into their underlying physical processes. This drives in part the desire to construct ever-larger telescopes and interferometer arrays and to observe at shorter wave…
View article: Multi-band Spectral and Astrometric Characterization of the HIP 99770 b Planet with SCExAO/CHARIS and Gaia<sup>∗</sup>
Multi-band Spectral and Astrometric Characterization of the HIP 99770 b Planet with SCExAO/CHARIS and Gaia<sup>∗</sup> Open
We present and analyze follow-up, higher resolution ( R ∼ 70) H and K band integral field spectroscopy of the superjovian exoplanet HIP 99770 b with SCExAO/CHARIS. Our new data recover the companion at a high SNR in both bandpasses and mor…
View article: Direct Imaging Explorations for Companions from the Subaru/IRD Strategic Program II; Discovery of a Brown-dwarf Companion around a Nearby mid-M~dwarf LSPM~J1446+4633
Direct Imaging Explorations for Companions from the Subaru/IRD Strategic Program II; Discovery of a Brown-dwarf Companion around a Nearby mid-M~dwarf LSPM~J1446+4633 Open
We report the discovery of a new directly-imaged brown dwarf companion with Keck/NIRC2+pyWFS around a nearby mid-type M~dwarf LSPM~J1446+4633 (hereafter J1446). The $L'$-band contrast ($4.5\times10^{-3}$) is consistent with a $\sim20-60\ M…
View article: Unveiling the Atmosphere of HR 7672 B from the Near-infrared High-resolution Spectrum Using REACH/Subaru
Unveiling the Atmosphere of HR 7672 B from the Near-infrared High-resolution Spectrum Using REACH/Subaru Open
Characterizing the atmospheres of exoplanets and brown dwarfs is crucial for understanding their atmospheric physics and chemistry, searching for biosignatures, and investigating their formation histories. Recent advances in observational …
View article: Unveiling the Atmosphere of HR 7672 B from the Near-Infrared High-Resolution Spectrum Using REACH/Subaru
Unveiling the Atmosphere of HR 7672 B from the Near-Infrared High-Resolution Spectrum Using REACH/Subaru Open
Characterizing the atmospheres of exoplanets and brown dwarfs is crucial for understanding their atmospheric physics and chemistry, searching for biosignatures, and investigating their formation histories. Recent advances in observational …
View article: The mass of TOI-654 b: A short-period sub-Neptune transiting a mid-M dwarf
The mass of TOI-654 b: A short-period sub-Neptune transiting a mid-M dwarf Open
Sub-Neptunes are small planets between the size of the Earth and Neptune. The orbital and bulk properties of transiting sub-Neptunes can provide clues for their formation and evolution of small planets. In this paper, we report on follow-u…
View article: The mass of TOI-654 b: A short-period sub-Neptune transiting a mid-M dwarf
The mass of TOI-654 b: A short-period sub-Neptune transiting a mid-M dwarf Open
Sub-Neptunes are small planets between the size of the Earth and Neptune. The orbital and bulk properties of transiting sub-Neptunes can provide clues for their formation and evolution of small planets. In this paper, we report on follow-u…
View article: PIRATES -- a machine-learning framework for polarized, interferometric image reconstruction
PIRATES -- a machine-learning framework for polarized, interferometric image reconstruction Open
Optical interferometric image reconstruction is a challenging, ill-posed optimization problem which usually relies on heavy regularization for convergence. Conventional algorithms regularize in the pixel domain, without cognizance of spati…
View article: Elemental abundances of 44 very metal-poor stars determined from Subaru/IRD near-infrared spectra
Elemental abundances of 44 very metal-poor stars determined from Subaru/IRD near-infrared spectra Open
The abundances of five elements, Na, Mg, Al, Si, and Sr, are investigated for 44 very metal-poor stars ($-4.0 < [{\rm Fe/H}] < -1.5$) in the Galactic halo system based on a local thermodynamic equilibrium (LTE) analysis of high-resol…
View article: Experimental and on-sky demonstration of spectrally dispersed wavefront sensing using a photonic lantern
Experimental and on-sky demonstration of spectrally dispersed wavefront sensing using a photonic lantern Open
Adaptive optics (AO) systems are critical in any application where highly resolved imaging or beam control must be performed through a dynamic medium. Such applications include astronomy and free-space optical communications, where light p…
View article: Dynamical and Atmospheric Characterization of the Substellar Companion HD 33632 Ab from Direct Imaging, Astrometry, and Radial-velocity Data*
Dynamical and Atmospheric Characterization of the Substellar Companion HD 33632 Ab from Direct Imaging, Astrometry, and Radial-velocity Data* Open
We present follow-up SCExAO/CHARIS H- and K -band ( R ∼ 70) high-contrast integral field spectroscopy and Keck/NIRC2 photometry of directly imaged brown dwarf companion HD 33632 Ab and new radial-velocity data for the system from the SOPHI…
View article: Weighing Single-lined Spectroscopic Binaries Using Tidal Effects on Radial Velocities: The Case of V723 Monocerotis
Weighing Single-lined Spectroscopic Binaries Using Tidal Effects on Radial Velocities: The Case of V723 Monocerotis Open
In single-lined spectroscopic binaries (SB1s) where flux variations due to tidal deformation of the primary star (ellipsoidal variations, EVs) are detected, the binary mass can be determined by combining EVs with the primary's radial veloc…
View article: SCExAO/CHARIS Near-infrared Scattered-light Imaging and Integral Field Spectropolarimetry of the AB Aurigae Protoplanetary System
SCExAO/CHARIS Near-infrared Scattered-light Imaging and Integral Field Spectropolarimetry of the AB Aurigae Protoplanetary System Open
We analyze near-infrared integral field spectropolarimetry of the AB Aurigae protoplanetary disk and protoplanet (AB Aur b), obtained with SCExAO/CHARIS in 22 wavelength channels covering the J , H , and K passbands ( λ 0 = 1.1–2.4 μ m) ov…
View article: Spectral characterization of a 3-port photonic lantern for application to spectroastrometry
Spectral characterization of a 3-port photonic lantern for application to spectroastrometry Open
Spectroastrometry, which measures wavelength-dependent shifts in the center of light, is well-suited for studying objects whose morphology changes with wavelength at very high angular resolutions. Photonic lantern (PL)-fed spectrometers ha…
View article: Visible-light High-contrast Imaging and Polarimetry with SCExAO/VAMPIRES
Visible-light High-contrast Imaging and Polarimetry with SCExAO/VAMPIRES Open
We present significant upgrades to the Visible Aperture-Masking Polarimetric Imager/Interferometer for Resolving Exoplanetary Signatures (VAMPIRES) instrument, a visible-light (600–800 nm) high-contrast imaging polarimeter integrated withi…
View article: Weighing Single-lined Spectroscopic Binaries Using Tidal Effects on Radial Velocities: The Case of V723 Monocerotis
Weighing Single-lined Spectroscopic Binaries Using Tidal Effects on Radial Velocities: The Case of V723 Monocerotis Open
In single-lined spectroscopic binaries (SB1s) where flux variations due to tidal deformation of the primary star (ellipsoidal variations, EVs) are detected, the binary mass can be determined by combining EVs with the primary's radial veloc…
View article: Visible-Light High-Contrast Imaging and Polarimetry with SCExAO/VAMPIRES
Visible-Light High-Contrast Imaging and Polarimetry with SCExAO/VAMPIRES Open
We present significant upgrades to the VAMPIRES instrument, a visible-light (600 nm to 800 nm) high-contrast imaging polarimeter integrated within SCExAO on the Subaru telescope. Key enhancements include new qCMOS detectors, coronagraphs, …
View article: Spectroscopy using a visible photonic lantern at the Subaru Telescope: Laboratory characterization and the first on-sky demonstration on Ikiiki (<i>α</i> Leo) and ‘Aua (<i>α</i> Ori)
Spectroscopy using a visible photonic lantern at the Subaru Telescope: Laboratory characterization and the first on-sky demonstration on Ikiiki (<i>α</i> Leo) and ‘Aua (<i>α</i> Ori) Open
Context. Photonic lanterns (PLs) are waveguide devices enabling high-throughput single-mode spectroscopy and high angular resolution. Aims. We aim to present the first on-sky demonstration of a PL operating in visible light, to measure its…
View article: Spectroscopy using a visible photonic lantern at the Subaru telescope: Laboratory characterization and first on-sky demonstration on Ikiiki (α Leo) and `Aua (α Ori)
Spectroscopy using a visible photonic lantern at the Subaru telescope: Laboratory characterization and first on-sky demonstration on Ikiiki (α Leo) and `Aua (α Ori) Open
Photonic lanterns are waveguide devices enabling high throughput single mode spectroscopy and high angular resolution. We aim to present the first on-sky demonstration of a photonic lantern (PL) operating in visible light, to measure its t…
View article: Coronagraphy robust to segmented aberrations: low-wind effect mitigation on Subaru/SCExAO
Coronagraphy robust to segmented aberrations: low-wind effect mitigation on Subaru/SCExAO Open
International audience
View article: AO3k at Subaru: First on-sky results of the facility extreme-AO
AO3k at Subaru: First on-sky results of the facility extreme-AO Open
The facility adaptive optics of the Subaru Telescope AO188 recently received some long-awaited upgrades: a new 3224-actuator deformable mirror (DM) from ALPAO (hence the name change to AO3000 or AO3k), an upgraded GPU-based real-time compu…
View article: Visible Photonic Lantern integration, characterization and on-sky testing on Subaru/SCExAO
Visible Photonic Lantern integration, characterization and on-sky testing on Subaru/SCExAO Open
A Photonic Lantern (PL) is a novel device that efficiently converts a multi-mode fiber into several single-mode fibers. When coupled with an extreme adaptive optics (ExAO) system and a spectrograph, PLs enable high throughput spectroscopy …
View article: SCExAO/CHARIS Multiwavelength High-contrast Imaging of the BD+45<sup>°</sup>598 Debris Disk
SCExAO/CHARIS Multiwavelength High-contrast Imaging of the BD+45<sup>°</sup>598 Debris Disk Open
We present a multiwavelength (1.16–2.37 μ m) view of the debris disk around BD+45 ° 598, using the Subaru Coronagraphic Extreme Adaptive Optics system paired with the Coronagraphic High Angular Resolution Imaging Spectrograph. With an assu…
View article: Transit spectroscopy of K2-33b with subaru/IRD: Spin-Orbit alignment and tentative atmospheric helium
Transit spectroscopy of K2-33b with subaru/IRD: Spin-Orbit alignment and tentative atmospheric helium Open
Exoplanets in their infancy are ideal targets to probe the formation and evolution history of planetary systems, including the planet migration and atmospheric evolution and dissipation. In this paper, we present spectroscopic observations…
View article: Transit Spectroscopy of K2-33b with Subaru/IRD: Spin-Orbit Alignment and Tentative Atmospheric Helium
Transit Spectroscopy of K2-33b with Subaru/IRD: Spin-Orbit Alignment and Tentative Atmospheric Helium Open
Exoplanets in their infancy are ideal targets to probe the formation and evolution history of planetary systems, including the planet migration and atmospheric evolution and dissipation. In this paper, we present spectroscopic observations…
View article: Direct-imaging Discovery of a Substellar Companion Orbiting the Accelerating Variable Star HIP 39017
Direct-imaging Discovery of a Substellar Companion Orbiting the Accelerating Variable Star HIP 39017 Open
We present the direct-imaging discovery of a substellar companion (a massive planet or low-mass brown dwarf) to the young, γ Doradus ( γ Dor)-type variable star HIP 39017 (HD 65526). The companion’s SCExAO/CHARIS JHK (1.1–2.4 μ m) spectrum…
View article: Testing Magnetospheric Accretion as an Hα Emission Mechanism of Embedded Giant Planets: The Case Study for the Disk Exhibiting Meridional Flow Around HD 163296
Testing Magnetospheric Accretion as an Hα Emission Mechanism of Embedded Giant Planets: The Case Study for the Disk Exhibiting Meridional Flow Around HD 163296 Open
Recent high-sensitivity observations reveal that accreting giant planets embedded in their parental circumstellar disks can emit H α at their final formation stages. While the origin of this emission is not yet determined, magnetospheric a…
View article: Testing magnetospheric accretion as an H$α$ emission mechanism of embedded giant planets: The case study for the disk exhibiting meridional flow around HD 163296
Testing magnetospheric accretion as an H$α$ emission mechanism of embedded giant planets: The case study for the disk exhibiting meridional flow around HD 163296 Open
Recent high-sensitivity observations reveal that accreting giant planets embedded in their parental circumstellar disks can emit H$α$ at their final formation stages. While the origin of such emission is not determined yet, magnetospheric …
View article: Real-time experimental demonstrations of a photonic lantern wavefront sensor
Real-time experimental demonstrations of a photonic lantern wavefront sensor Open
The direct imaging of an Earth-like exoplanet will require sub-nanometric wavefront control across large light-collecting apertures, to reject host starlight and detect the faint planetary signal. Current adaptive optics (AO) systems, whic…