F. Allard
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View article: THE PHYSICAL MECHANISM behind M DWARF METALLICITY INDICATORS and the ROLE of C and O ABUNDANCES
THE PHYSICAL MECHANISM behind M DWARF METALLICITY INDICATORS and the ROLE of C and O ABUNDANCES Open
We present near-infrared (NIR) synthetic spectra based on PHOENIX stellar atmosphere models of typical early and mid-M dwarfs with varied C and O abundances. We apply multiple recently published methods for determining M dwarf metallicity …
View article: A Physically Motivated and Empirically Calibrated Method to Measure the Effective Temperature, Metallicity, and Ti Abundance of M Dwarfs
A Physically Motivated and Empirically Calibrated Method to Measure the Effective Temperature, Metallicity, and Ti Abundance of M Dwarfs Open
The ability to perform detailed chemical analysis of Sun-like F-, G-, and K-type stars is a powerful tool with many applications, including studying the chemical evolution of the Galaxy and constraining planet formation theories. Unfortuna…
View article: 76 T dwarfs from the UKIDSS LAS: Benchmarks, kinematics and an updated space density
76 T dwarfs from the UKIDSS LAS: Benchmarks, kinematics and an updated space density Open
We report the discovery of 76 new T dwarfs from the UKIRT Infrared Deep Sky Survey(UKIDSS) Large Area Survey (LAS). Near-infrared broad-and narrow-band photometry and spectroscopy are presented for the new objects, along withWide-field Inf…
View article: Peering into the young planetary system AB Pic
Peering into the young planetary system AB Pic Open
Aims . We aim to revisit the formation pathway of AB Pic b, an imaged companion that straddles the exoplanet/brown-dwarf boundary. We based this study on a rich set of observations, which allows us to investigate its orbital and atmospheri…
View article: The SPHERE infrared survey for exoplanets (SHINE): II. Observations, data reduction and analysis, detection performances, and initial results
The SPHERE infrared survey for exoplanets (SHINE): II. Observations, data reduction and analysis, detection performances, and initial results Open
Context. In recent decades, direct imaging has confirmed the existence of substellar companions (exoplanets or brown dwarfs) on wide orbits (>10 au) around their host stars. In striving to understand their formation and evolution mechanism…
View article: The SPHERE infrared survey for exoplanets (SHINE)
The SPHERE infrared survey for exoplanets (SHINE) Open
Context. In recent decades, direct imaging has confirmed the existence of substellar companions (exoplanets or brown dwarfs) on wide orbits (>10 au) around their host stars. In striving to understand their formation and evolution mechanism…
View article: Medium-resolution spectrum of the exoplanet HIP 65426 b
Medium-resolution spectrum of the exoplanet HIP 65426 b Open
Medium-resolution integral-field spectrographs (IFS) coupled with adaptive-optics such as Keck/OSIRIS, VLT/MUSE, or SINFONI are appearing as a new avenue for enhancing the detection and characterization capabilities of young, gas giant exo…
View article: Detection and characterization of two VLM binaries: LP 1033-31 and LP 877-72
Detection and characterization of two VLM binaries: LP 1033-31 and LP 877-72 Open
Using the high-resolution near-infrared adaptive optics imaging from the NaCo instrument at the Very Large Telescope, we report the discovery of a new binary companion to the M-dwarf LP 1033-31 and also confirm the binarity of LP 877-72. W…
View article: VLT/SPHERE survey for exoplanets around young early-type stars, including systems with multi-belt architectures
VLT/SPHERE survey for exoplanets around young early-type stars, including systems with multi-belt architectures Open
Context. Dusty debris disks around pre- and main-sequence stars are potential signposts for the existence of planetesimals and exoplanets. Giant planet formation is therefore expected to play a key role in the evolution of the disk. This i…
View article: First results from MFOSC-P: low-resolution optical spectroscopy of a sample of M dwarfs within 100 parsecs
First results from MFOSC-P: low-resolution optical spectroscopy of a sample of M dwarfs within 100 parsecs Open
Mt Abu Faint Object Spectrograph and Camera (MFOSC-P) is an in-house-developed instrument for the Physical Research Laboratory (PRL) 1.2 m telescope at Mt Abu, India, commissioned in 2019 February. Here we present the first science results…
View article: The GJ 504 system revisited: Combining interferometric, radial velocity, and high contrast imaging data
The GJ 504 system revisited: Combining interferometric, radial velocity, and high contrast imaging data Open
The G-type star GJ504A is known to host a 3 to 35 MJup companion whose temperature, mass, and projected separation all contribute to make it a test case for the planet formation theories and for atmospheric models of giant planets and ligh…
View article: Characterizing stellar parameters from high-resolution spectra of main sequence cool stars. I. The G2V–K2V stars
Characterizing stellar parameters from high-resolution spectra of main sequence cool stars. I. The G2V–K2V stars Open
The goal of the present study is to construct, test, and validate a high-resolution synthetic spectral library using PHOENIX model atmospheres and develop a reliable tool to estimate stellar parameters from high-resolution optical and/or n…
View article: Primeval very low-mass stars and brown dwarfs – VI. Population properties of metal-poor degenerate brown dwarfs
Primeval very low-mass stars and brown dwarfs – VI. Population properties of metal-poor degenerate brown dwarfs Open
We presented 15 new T dwarfs that were selected from UKIRT Infrared Deep Sky Survey, Visible and Infrared Survey Telescope for Astronomy , and Wide-field Infrared Survey Explorer surveys, and confirmed with optical to near-infrared spectra…
View article: Exploring the stellar properties of M dwarfs with high-resolution spectroscopy from the optical to the near-infrared <i>(Corrigendum)</i>
Exploring the stellar properties of M dwarfs with high-resolution spectroscopy from the optical to the near-infrared <i>(Corrigendum)</i> Open
Context. Being the most numerous and oldest stars in the galaxy, M dwarfs are\nobjects of great interest for exoplanet searches. The presence of molecules in\ntheir atmosphere complicates our understanding of their atmospheric properties.\…
View article: Exploring the stellar properties of M dwarfs with high-resolution spectroscopy from the optical to the near-infrared
Exploring the stellar properties of M dwarfs with high-resolution spectroscopy from the optical to the near-infrared Open
Context . Being the most numerous and oldest stars in the galaxy, M dwarfs are objects of great interest for exoplanet searches. The presence of molecules in their atmosphere complicates our understanding of their atmospheric properties. B…
View article: Primeval very low-mass stars and brown dwarfs – IV. New L subdwarfs, Gaia astrometry, population properties, and a blue brown dwarf binary
Primeval very low-mass stars and brown dwarfs – IV. New L subdwarfs, Gaia astrometry, population properties, and a blue brown dwarf binary Open
We present 27 new L subdwarfs and classify five of them as esdL and 22 as\nsdL. Our L subdwarf candidates were selected with the UKIRT Infrared Deep Sky\nSurvey and Sloan Digital Sky Survey. Spectroscopic follow-up was carried out\nprimari…
View article: The GJ 504 system revisited
The GJ 504 system revisited Open
Context. The G-type star GJ504A is known to host a 3–35 M Jup companion whose temperature, mass, and projected separation all contribute to making it a test case for planet formation theories and atmospheric models of giant planets and lig…
View article: Primeval very low-mass stars and brown dwarfs – III. The halo transitional brown dwarfs
Primeval very low-mass stars and brown dwarfs – III. The halo transitional brown dwarfs Open
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society. © 2018 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
View article: Simultaneous Multiwavelength Variability Characterization of the Free-floating Planetary-mass Object PSO J318.5−22
Simultaneous Multiwavelength Variability Characterization of the Free-floating Planetary-mass Object PSO J318.5−22 Open
We present simultaneous Hubble Space Telescope ( HST) WFC3+ Spitzer IRAC variability monitoring for the highly variable young (∼20 Myr) planetary-mass object PSO J318.5−22. Our simultaneous HST + Spitzer observations covered approximately …
View article: SPIRou Input Catalogue: global properties of 440 M dwarfs observed with ESPaDOnS at CFHT
SPIRou Input Catalogue: global properties of 440 M dwarfs observed with ESPaDOnS at CFHT Open
Present and future high-precision radial-velocity spectrometers dedicated to\nthe discovery of low-mass planets orbiting low-mass dwarfs need to focus on the\nbest selected stars to make an efficient use of telescope time. In the\nframewor…
View article: Photospheric properties and fundamental parameters of M dwarfs
Photospheric properties and fundamental parameters of M dwarfs Open
Context. M dwarfs are an important source of information when studying and probing the lower end of the Hertzsprung-Russell (HR) diagram, down to the hydrogen-burning limit. Being the most numerous and oldest stars in the galaxy, they carr…
View article: Science cases for a visible interferometer
Science cases for a visible interferometer Open
High spatial resolution is the key for the understanding various astrophysical phenomena. But even with the future E-ELT, single dish instruments are limited to a spatial resolution of about 4 mas in the visible. For the closest objects wi…
View article: Primeval very low-mass stars and brown dwarfs – II. The most metal-poor substellar object
Primeval very low-mass stars and brown dwarfs – II. The most metal-poor substellar object Open
SDSS J010448.46+153501.8 has previously been classified as an sdM9.5\nsubdwarf. However, its very blue $J-K$ colour ($-0.15 \\pm 0.17$) suggests a\nmuch lower metallicity compared to normal sdM9.5 subdwarfs. Here, we\nre-classify this obje…
View article: DISCOVERY OF A METAL-POOR FIELD GIANT WITH A GLOBULAR CLUSTER SECOND-GENERATION ABUNDANCE PATTERN
DISCOVERY OF A METAL-POOR FIELD GIANT WITH A GLOBULAR CLUSTER SECOND-GENERATION ABUNDANCE PATTERN Open
We report on the detection, from observations obtained with the Apache Point Observatory Galactic Evolution Experiment spectroscopic survey, of a metal-poor ([Fe/H] = −1.3 dex) field giant star with an extreme Mg–Al abundance ratio ([Mg/Fe…
View article: Physical parameters of late M-type members of Chamaeleon I and TW Hydrae Association: dust settling, age dispersion and activity
Physical parameters of late M-type members of Chamaeleon I and TW Hydrae Association: dust settling, age dispersion and activity Open
Although mid-to-late type M dwarfs are the most common stars in our stellar\nneighborhood, our knowledge of these objects is still limited. Open questions\ninclude the evolution of their angular momentum, internal structures, dust\nsettlin…
View article: Spectral energy distribution of M-subdwarfs: A study of their atmospheric properties
Spectral energy distribution of M-subdwarfs: A study of their atmospheric properties Open
Context. M-type subdwarfs are metal-poor low-mass stars and probe for the old\npopulations in our Galaxy. Accurate knowledge of their atmospheric parameters\nand especially the composition is essential for understanding the chemical\nhisto…
View article: Primeval very low-mass stars and brown dwarfs – I. Six new L subdwarfs, classification and atmospheric properties
Primeval very low-mass stars and brown dwarfs – I. Six new L subdwarfs, classification and atmospheric properties Open
We have conducted a search for L subdwarf candidates within the photometric\ncatalogues of the UKIRT Infrared Deep Sky Survey and Sloan Digital Sky Survey.\nSix of our candidates are confirmed as L subdwarfs spectroscopically at optical\na…
View article: THE PHYSICAL MECHANISM BEHIND M DWARF METALLICITY INDICATORS AND THE ROLE OF C AND O ABUNDANCES
THE PHYSICAL MECHANISM BEHIND M DWARF METALLICITY INDICATORS AND THE ROLE OF C AND O ABUNDANCES Open
We present near-infrared (NIR) synthetic spectra based on PHOENIX stellar atmosphere models of typical early and mid-M dwarfs with varied C and O abundances. We apply multiple recently published methods for determining M dwarf metallicity …
View article: Variability in A Young, L/T Transition Planetary-Mass Object
Variability in A Young, L/T Transition Planetary-Mass Object Open
As part of our ongoing NTT SoFI survey for variability in young free-floating planets and low-mass brown dwarfs, we detect significant variability in the young, free-floating planetary-mass object PSO J318.5-22, likely due to rotational mo…