A5001578554- Stellar, planetary, and galactic studies
- Astrophysics and Star Formation Studies
- Astronomy and Astrophysical Research
- Astro and Planetary Science
- Astronomical Observations and Instrumentation
- Astrophysical Phenomena and Observations
- Adaptive optics and wavefront sensing
- Molecular Spectroscopy and Structure
- Space Exploration and Technology
- Planetary Science and Exploration
- Galaxies: Formation, Evolution, Phenomena
- Atmospheric Ozone and Climate
- History and Developments in Astronomy
- Isotope Analysis in Ecology
- CCD and CMOS Imaging Sensors
- High-pressure geophysics and materials
- Gamma-ray bursts and supernovae
- Remote-Sensing Image Classification
- Spacecraft and Cryogenic Technologies
- Calibration and Measurement Techniques
- Solar and Space Plasma Dynamics
- Geochemistry and Geologic Mapping
- Origins and Evolution of Life
- Marine and environmental studies
- Atomic and Molecular Physics
European Southern Observatory
2015-2024
European Southern Observatory
2007-2019
Centre National de la Recherche Scientifique
1995-2019
Heidelberg University
2019
Aix-Marseille Université
2019
Netherlands Institute for Radio Astronomy
2019
Centro de Astrobiología
2019
Scottish Universities Physics Alliance
2019
University of Edinburgh
2019
Royal Observatory
2019
We report results from a high-resolution optical spectroscopic survey aimed to search for nearby young associations and stars among counterparts of ROSAT All-Sky Survey X-ray sources in the Southern Hemisphere. selected 1953 late-type (B-V >= 0.6), potentially young, out total 9574 1RXS follow-up observations. At least one spectrum was obtained each 1511 targets. This paper is first series presenting SACY survey. Here we describe our sample convergence method (UVW) velocity space find...
We have surveyed a sample of 165 solar-type spectroscopic binaries (SB) with periods from 1 to 30 days for higher-order multiplicity. A subsample 62 targets were observed the NACO adaptive optics system and 13 new physical tertiary companions detected. An additional 12 wide (5 still tentative) found using 2MASS all-sky survey. The belong 161 stellar systems; these 64 are triple, 11 quadruple 7 quintuple. After correction incompleteness, fraction SBs is be 63% ± 5%. find that this strong...
We present X-ray data for all entries of the Third Catalogue Nearby Stars (Gliese & Jahreiß 1991) that have been detected as sources in ROSAT all-sky survey. The catalogue contains 1252 yielding an average detection rate 32.9 percent. In addition to count rates, source parameters, hardness ratios, and fluxes we also list luminosities derived from Hipparcos parallaxes.
Nighttime polarimetric measurements are often obtained very close to the limits of instrumental capabilities. It is important be aware possible sources spurious polarization, and adopt data reduction techniques that best compensate for effects intrinsic design most common polarimeters adopted nighttime observations. We define a self-consistent framework starting from basic definitions Stokes parameters, we present an analytical description commonly used with polarimeter (consisting retarder...
A significant population of stars with ages younger than the Pleiades exists in solar neighborhood. They are grouped loose young associations, sharing similar kinematical and physical properties, but, due to their vicinity Sun, they dispersed sky, hard identify. Their strong stellar coronal activity, causing enhanced X-ray emission, allows them be identified as counterparts sources. The analysis presented here is based mainly on SACY project, aimed survey a systematic way ROSAT all-sky...
<i>Context. <i/>Our study is a follow-up of the SACY project, an extended high spectral resolution survey more than two thousand optical counterparts to X-ray sources in southern hemisphere targeted search for young nearby association. Nine associations have either been newly identified, or had their member list revised. Groups belonging Sco-Cen-Oph complex are not considered present study.<i>Aims. <i/>These nine associations, with ages between about 6 Myr and 70 Myr, form excellent sample...
The lifetime of isolated protoplanetary disks is thought to be set by the combination viscous accretion and photoevaporation driven stellar high-energy photons. Observational evidence for magnetospheric in young Sun-like stars robust. Here we report first observational disk central star. We acquired high-resolution (R∼ 30,000) spectra [Ne ii] 12.81 μm line from seven circumstellar using VISIR on Melipal/VLT. show that three transition sample all have profiles consistent with those predicted...
Photoevaporation driven by the central star is expected to be a ubiquitous and important mechanism disperse circumstellar dust gas from which planets form. Here, we present detailed study of disk surrounding nearby TW Hya provide observational constraints its photoevaporative wind. Our new high-resolution (R ~ 30,000) mid-infrared spectroscopy in [Ne II] 12.81 {\mu}m line confirms that this diagnostic traces unbound wind component within 10AU star. From blueshift asymmetry profile, estimate...
We explore the possible connection between open cluster IC 2391 and unbound Argus association identified by SACY survey. In addition to common kinematics ages these two systems, here we their chemical abundance patterns confirm if substructures shared a origin. carry out homogenous high-resolution elemental study of eight confirmed members as well six using UVES spectra. derive spectroscopic stellar parameters abundances for Fe, Na, Mg, Al, Si, Ca, Ti, Cr, Ni Ba. All stars in were found...
Giant exoplanets on wide orbits have been directly imaged around young stars. If the thermal background in mid-infrared can be mitigated, then with lower masses also imaged. Here we present a ground-based observing approach that enables imaging low-mass temperate nearby stars, and particular within closest stellar system, α Centauri. Based 75-80% of best quality images from 100 h cumulative observations, demonstrate sensitivity to warm sub-Neptune-sized planets throughout much habitable zone...
This paper describes a systematic search for high-order multiplicity among wide visual Pre-Main Sequence (PMS) binaries. We conducted an Adaptive Optics survey of sample 58 PMS binaries from various star-forming regions, which include 52 T Tauri systems with mostly K- and M-type primaries, the NIR instrument NACO at VLT. Of these systems, 7 are found to be triple (2 new) quadruple (1 new). The new close companions most likely physically bound based on their probability chance projection and,...
Statistical analysis of the relative alignment inner and outer orbits in triple systems resulting from a dynamical decay small-N clusters () is presented compared to statistics real multiple stars. The distribution angle Φ between angular momentum vectors stars formed by shown depend on initial cluster conditions like geometry, mass function, rotational thermal energy. For realistic set conditions, modest orbital found, good agreement with latest observational data visual exhibiting an...
Context. The {\beta} Pictoris system with its debris disk and a massive giant planet orbiting at \simeq 9 AU represents an ideal laboratory to study formation evolution as well planet-disk interactions. Pic b can also help testing brightness-mass relations young ages. Other planets, yet undetected, may of course be present in the system. Aims. We aim putting direct constrains on mass searching for additional jovian planets orbits closer than typically 2 AU. Methods. use high precision Harps...
Context: Dynamically undisrupted, young populations of stars are crucial to study the role multiplicity in relation star formation. Loose nearby associations provide us with a great sample close ($
Abstract Accretion plays a central role in the physics that governs evolution and dispersal of protoplanetary disks. The primary goal this paper is to analyze stability over time mass accretion rate onto TW Hya, nearest accreting solar-mass young star. We measure veiling across optical spectrum 1169 archival high-resolution spectra obtained from 1998–2022. then converted using 26 flux-calibrated cover Balmer jump. measured excess continuum has an average 2.51 × 10 −9 M ⊙ yr −1 Gaussian...
We have imaged two bona-fide brown dwarfs with TReCS/GEMINI-S and find mid-infrared excess emission that can be explained by optically thick dust disk models. In the case of young (≈2 Myr) Cha Hα1 we measure fluxes at 10.4 μm 12.3 are fully consistent a standard flared model prominent silicate emission. For ≈10 Myr old dwarf 2MASS1207-3932 located in TW Hydrae association 8.7 respect to photosphere, confirm accretion as likely cause its strong activity. Disks around last least long their...