943 research outputs found
Gaia: The Astrometry Revolution
The power of micro-arcsecond (as) astrometry is about to be unleashed.
ESA's Gaia mission, now headed towards the end of the first year of routine
science operations, will soon fulfil its promise for revolutionary science in
countless aspects of Galactic astronomy and astrophysics. The potential of Gaia
position measurements for important contributions to the astrophysics of
planetary systems is huge. We focus here on the expectations for detection and
improved characterization of 'young' planetary systems in the neighborhood of
the Sun using a combination of Gaia as astrometry and direct imaging
techniques.Comment: 6 pages, 3 figures, to appear in the Proceedings of IAU Symposium 314
'Young Stars & Planets Near the Sun', held on May 11-15 2015 in Atlanta (GA),
USA (J. H. Kastner, B. Stelzer, & S. A. Metchev, eds.
High resolution imaging of young M-type stars of the solar neighborhood: Probing the existence of companions down to the mass of Jupiter
Context. High contrast imaging is a powerful technique to search for gas
giant planets and brown dwarfs orbiting at separation larger than several AU.
Around solar-type stars, giant planets are expected to form by core accretion
or by gravitational instability, but since core accretion is increasingly
difficult as the primary star becomes lighter, gravitational instability would
be the a probable formation scenario for yet-to-be-found distant giant planets
around a low-mass star. A systematic survey for such planets around M dwarfs
would therefore provide a direct test of the efficiency of gravitational
instability. Aims. We search for gas giant planets orbiting around late-type
stars and brown dwarfs of the solar neighborhood. Methods. We obtained deep
high resolution images of 16 targets with the adaptive optic system of VLT-NACO
in the Lp band, using direct imaging and angular differential imaging. This is
currently the largest and deepest survey for Jupiter-mass planets around
Mdwarfs. We developed and used an integrated reduction and analysis pipeline to
reduce the images and derive our 2D detection limits for each target. The
typical contrast achieved is about 9 magnitudes at 0.5" and 11 magnitudes
beyond 1". For each target we also determine the probability of detecting a
planet of a given mass at a given separation in our images. Results. We derived
accurate detection probabilities for planetary companions, taking into account
orbital projection effects, with in average more than 50% probability to detect
a 3MJup companion at 10AU and a 1.5MJup companion at 20AU, bringing strong
constraints on the existence of Jupiter-mass planets around this sample of
young M-dwarfs.Comment: Accepted for publication in A&
High precision radial velocities with GIANO spectra
Radial velocities (RV) measured from near-infrared (NIR) spectra are a
potentially excellent tool to search for extrasolar planets around cool or
active stars. High resolution infrared (IR) spectrographs now available are
reaching the high precision of visible instruments, with a constant improvement
over time. GIANO is an infrared echelle spectrograph at the Telescopio
Nazionale Galileo (TNG) and it is a powerful tool to provide high resolution
spectra for accurate RV measurements of exoplanets and for chemical and
dynamical studies of stellar or extragalactic objects. No other high spectral
resolution IR instrument has GIANO's capability to cover the entire NIR
wavelength range (0.95-2.45 micron) in a single exposure. In this paper we
describe the ensemble of procedures that we have developed to measure high
precision RVs on GIANO spectra acquired during the Science Verification (SV)
run, using the telluric lines as wavelength reference. We used the Cross
Correlation Function (CCF) method to determine the velocity for both the star
and the telluric lines. For this purpose, we constructed two suitable digital
masks that include about 2000 stellar lines, and a similar number of telluric
lines. The method is applied to various targets with different spectral type,
from K2V to M8 stars. We reached different precisions mainly depending on the H
-magnitudes: for H ~ 5 we obtain an rms scatter of ~ 10 m s-1, while for H ~ 9
the standard deviation increases to ~ 50 - 80 m s-1. The corresponding
theoretical error expectations are ~4 m s-1 and 30 m s-1, respectively. Finally
we provide the RVs measured with our procedure for the targets observed during
GIANO Science Verification.Comment: 26 pages, 15 figures, 6 table
Family Planning Decision Making in People With Multiple Sclerosis
Introduction: The majority of people diagnosed with MS are of childbearing or child fathering age, therefore family planning is an important issue for both women and men with MS. Fertility and the course of pregnancy are not affected by MS; however, people with MS (pwMS) may have concerns that there will be a greater risk of complications to the mother and/or adverse pregnancy outcomes either due to the disease or to ongoing medication. This survey aimed to understand family planning decision making in pwMS and related unmet educational needs. Methods: A total of 332 pwMS across the USA, UK, France, Germany, Italy, and Spain were recruited from a specialist patient panel agency to participate in a smartphone-enabled standing panel. The 80-question survey focussed on decision making and information sources for pwMS regarding family planning, as well as behavior during and after pregnancy. Male patients with MS did not respond to specific questions on pregnancy. Survey results were directly compared with the 2016 US and 2010 UN census data. Results: pwMS were more likely to have no children than the general population, particularly in the subgroup of patients aged 36–45 years. A total of 56% of pwMS reported that the disease affected, with different degrees of impact, their family planning decision making. Of these, 21% significantly changed their plans for timing of pregnancy and the number of children, and 14% decided against having children. Participants indicated that healthcare professionals were the primary source of information on family planning (81% of responses). The timing of planned pregnancy was not considered when selecting treatment by 78% of participants. Conclusion: MS was found to significantly impact family planning decision making, with pwMS significantly less likely to have children in comparison with the general population
A survey of young, nearby, and dusty stars to understand the formation of wide-orbit giant planets
Direct imaging has confirmed the existence of substellar companions on wide
orbits. To understand the formation and evolution mechanisms of these
companions, the full population properties must be characterized. We aim at
detecting giant planet and/or brown dwarf companions around young, nearby, and
dusty stars. Our goal is also to provide statistics on the population of giant
planets at wide-orbits and discuss planet formation models. We report a deep
survey of 59 stars, members of young stellar associations. The observations
were conducted with VLT/NaCo at L'-band (3.8 micron). We used angular
differential imaging to reach optimal detection performance. A statistical
analysis of about 60 % of the young and southern A-F stars closer than 65 pc
allows us to derive the fraction of giant planets on wide orbits. We use
gravitational instability models and planet population synthesis models
following the core-accretion scenario to discuss the occurrence of these
companions. We resolve and characterize new visual binaries and do not detect
any new substellar companion. The survey's median detection performance reaches
contrasts of 10 mag at 0.5as and 11.5 mag at 1as. We find the occurrence of
planets to be between 10.8-24.8 % at 68 % confidence level assuming a uniform
distribution of planets in the interval 1-13 Mj and 1-1000 AU. Considering the
predictions of formation models, we set important constraints on the occurrence
of massive planets and brown dwarf companions that would have formed by GI. We
show that this mechanism favors the formation of rather massive clump (Mclump >
30 Mj) at wide (a > 40 AU) orbits which might evolve dynamically and/or
fragment. For the population of close-in giant planets that would have formed
by CA, our survey marginally explore physical separations (<20 AU) and cannot
constrain this population
Deep imaging survey of young, nearby austral stars: VLT/NACO near-infrared Lyot-coronographic observations
Context. High contrast and high angular resolution imaging is the optimal search technique for substellar companions to nearby stars at physical separations larger than typically 10 AU. Two distinct populations of substellar companions, brown dwarfs and planets, can be probed and characterized. As a result, fossile traces of processes of formation and evolution can be revealed by physical and orbital properties, both for individual systems and as an ensemble.
Aims. Since November 2002, we have conducted a large, deep imaging, survey of young, nearby associations of the southern hemisphere. Our goal is detection and characterization of substellar companions with projected separations in the range 10–500 AU. We have observed a sample of 88 stars, primarily G to M dwarfs, younger than 100 Myr, and within 100 pc of Earth.
Methods. The VLT/NACO adaptive optics instrument of the ESO Paranal Observatory was used to explore the faint circumstellar environment between typically 0.1 and 10". Diffraction-limited observations in H and K_s-band combined with Lyot-coronagraphy enabled us to reach primary star-companion brightness ratios as small as 10^(-6). The existence of planetary mass companions could therefore be probed. We used a standardized observing sequence to precisely measure the position and flux of all detected sources relative to their visual primary star. Repeated observations at several epochs enabled us to discriminate comoving companions from background objects.
Results. We report the discovery of 17 new close (0.1–5.0") multiple systems. HIP 108195 AB and C (F1 III-M6), HIP 84642 AB (a~14 AU, K0-M5) and TWA22 AB (a~1.8 AU; M6-M6) are confirmed comoving systems. TWA22 AB is likely to be a rare astrometric calibrator that can be used to test evolutionary model predictions. Among our complete sample, a total of 65 targets were observed with deep coronagraphic imaging. About 240 faint companion candidates were detected around 36 stars. Follow-up observations with VLT or HST for 83% of these stars enabled us to identify a large fraction of background contaminants. Our latest results that pertain to the substellar companions to GSC 08047-00232, AB Pic and 2M1207 (confirmed during this survey and published earlier), are reviewed. Finally, a statistical analysis of our complete set of coronagraphic detection limits enables us to place constraints on the physical and orbital properties of giant planets between typically 20 and 150 AU
MESS (Multi-purpose Exoplanet Simulation System): A Monte Carlo tool for the statistical analysis and prediction of exoplanets search results
The high number of planet discoveries made in the last years provides a good
sample for statistical analysis, leading to some clues on the distributions of
planet parameters, like masses and periods, at least in close proximity to the
host star. We likely need to wait for the extremely large telescopes (ELTs) to
have an overall view of the extrasolar planetary systems. In this context it
would be useful to have a tool that can be used for the interpretation of the
present results,and also to predict what the outcomes would be of the future
instruments. For this reason we built MESS: a Monte Carlo simulation code which
uses either the results of the statistical analysis of the properties of
discovered planets, or the results of the planet formation theories, to build
synthetic planet populations fully described in terms of frequency, orbital
elements and physical properties. They can then be used to either test the
consistency of their properties with the observed population of planets given
different detection techniques or to actually predict the expected number of
planets for future surveys. In addition to the code description, we present
here some of its applications to actually probe the physical and orbital
properties of a putative companion within the circumstellar disk of a given
star and to test constrain the orbital distribution properties of a potential
planet population around the members of the TW Hydrae association. Finally,
using in its predictive mode, the synergy of future space and ground-based
telescopes instrumentation has been investigated to identify the mass-period
parameter space that will be probed in future surveys for giant and rocky
planetsComment: 14 pages, 16 figure
Discovery of a probable 4-5 Jupiter-mass exoplanet to HD 95086 by direct-imaging
Direct imaging has just started the inventory of the population of gas giant
planets on wide-orbits around young stars in the solar neighborhood. Following
this approach, we carried out a deep imaging survey in the near-infrared using
VLT/NaCo to search for substellar companions. We report here the discovery in
L' (3.8 microns) images of a probable companion orbiting at 56 AU the young
(10-17 Myr), dusty, and early-type (A8) star HD 95086. This discovery is based
on observations with more than a year-time-lapse. Our first epoch clearly
revealed the source at 10 sigma while our second epoch lacked good observing
conditions hence yielding a 3 sigma detection. Various tests were thus made to
rule out possible artifacts. This recovery is consistent with the signal at the
first epoch but requires cleaner confirmation. Nevertheless, our astrometric
precision suggests the companion to be comoving with the star, with a 3 sigma
confidence level. The planetary nature of the source is reinforced by a
non-detection in Ks-band (2.18 microns) images according to its possible
extremely red Ks - L' color. Conversely, background contamination is rejected
with good confidence level. The luminosity yields a predicted mass of about
4-5MJup (at 10-17 Myr) using "hot-start" evolutionary models, making HD 95086 b
the exoplanet with the lowest mass ever imaged around a star.Comment: accepted for publication to APJ
AF Lep b: the lowest mass planet detected coupling astrometric and direct imaging data
Aims. Using the direct imaging technique we searched for low mass companions
around the star AF Lep that presents a significant proper motion anomaly (PMa)
signal obtained from the comparison of Hipparcos and Gaia eDR3 catalogs.
Methods. We observed AF Lep in two epochs with VLT/SPHERE using its subsystems
IFS and IRDIS in the near-infrared (NIR) covering wavelengths ranging from the
Y to the K spectral bands (between 0.95 and 2.3 {\mu}m). The data were then
reduced using the high-contrast imaging techniques angular differential imaging
(ADI) and spectral differential imaging (SDI) to be able to retrieve the signal
from low mass companions of the star. Results. A faint companion was retrieved
at a separation of ~0.335" from the star and with a position angle of ~70.5 deg
in the first epoch and with a similar position in the second epoch. This
corresponds to a projected separation of ~9 au. The extracted photometry
allowed us to estimate for the companion a mass between 2 and 5 MJup. This mass
is in good agreement with what is expected for the dynamic mass of the
companion deduced using astrometric measures (5.2-5.5 MJup). This is the first
companion with a mass well below the deuterium burning limit discovered
coupling direct imaging with PMa measures. Orbit fitting done using the orvara
tool allowed to further confirm the companion mass and to define its main
orbital parameters.Comment: 10 pages, 8 Figures, accepted for publication on A&
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