2,412 research outputs found
A brown dwarf companion to the intermediate-mass star HR6037
In the course of an imaging survey we have detected a visual companion to the
intermediate-mass star HR 6037. In this letter, we present two epoch
observations of the binary with NACO/VLT, and near-IR spectroscopy of the
secondary with ISAAC/VLT. The NACO observations allow us to confirm HR 6037B as
a co-moving companion. Its J and H band ISAAC spectra suggest the object has an
spectral type of M9+-1, with a surface gravity intermediate between that of 10
Myr dwarfs and field dwarfs with identical spectral type. The comparison of its
Ks-band photometry with evolutionary tracks allows us to derive a mass,
effective temperature, and surface gravity of 62+-20 MJup, Teff = 2330+-200 K,
and log g = 5.1+-0.2, respectively. The small mass ratio of the binary, -0.03,
and its long orbital period, -5000 yr, makes HR 6037 a rare and uncommon binary
system.Comment: (5 pages, 4 figures, accepted for publication in A&A Letters
The near-infrared spectral energy distribution of {\beta} Pictoris b
A gas giant planet has previously been directly seen orbiting at 8-10 AU
within the debris disk of the ~12 Myr old star {\beta} Pictoris. The {\beta}
Pictoris system offers the rare opportunity to study the physical and
atmospheric properties of an exoplanet placed on a wide orbit and to establish
its formation scenario. We obtained J (1.265 {\mu}m), H (1.66 {\mu}m), and M'
(4.78 {\mu}m) band angular differential imaging of the system between 2011 and
2012. We detect the planetary companion in our four-epoch observations. We
estimate J = 14.0 +- 0.3, H = 13.5 +- 0.2, and M' = 11.0 +- 0.3 mag. Our new
astrometry consolidates previous semi-major axis (sma=8-10 AU) and excentricity
(e <= 0.15) estimates of the planet. These constraints, and those derived from
radial velocities of the star provides independent upper limits on the mass of
{\beta} Pictoris b of 12 and 15.5 MJup for semi-major axis of 9 and 10 AU. The
location of {\beta} Pictoris b in color-magnitude diagrams suggests it has
spectroscopic properties similar to L0-L4 dwarfs. This enables to derive
Log10(L/Lsun) = -3.87 +- 0.08 for the companion. The analysis with 7
PHOENIX-based atmospheric models reveals the planet has a dusty atmosphere with
Teff = 1700 +- 100 K and log g = 4.0+- 0.5. "Hot-start" evolutionary models
give a new mass of 10+3-2 MJup from Teff and 9+3-2 MJup from luminosity.
Predictions of "cold-start" models are inconsistent with independent
constraints on the planet mass. "Warm-start" models constrain the mass to M >=
6MJup and the initial entropies to values (Sinit >= 9.3Kb/baryon), intermediate
between those considered for cold/hot-start models, but likely closer to those
of hot-start models.Comment: 19 pages, accepted in Astronomy and Astrophysic
Planetary Science Virtual Observatory architecture
In the framework of the Europlanet-RI program, a prototype of Virtual
Observatory dedicated to Planetary Science was defined. Most of the activity
was dedicated to the elaboration of standards to retrieve and visualize data in
this field, and to provide light procedures to teams who wish to contribute
with on-line data services. The architecture of this VO system and selected
solutions are presented here, together with existing demonstrators
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
OTS44: Disk and accretion at the planetary border
We discover that the very low-mass brown dwarf OTS44 (M9.5, ~12 M_Jup) has
significant accretion and a substantial disk, which demonstrates that the
processes that accompany canonical star formation occur down to a central mass
of a few Jupiter masses. We discover in VLT/SINFONI spectra that OTS44 has
strong, broad, and variable Paschen beta emission that is evidence for active
accretion at the planetary border. We also detect strong Halpha emission of
OTS44 in a literature spectrum and determine an Halpha EW (-141 A) that is
indicative of active accretion. Both the Pa beta and Halpha emission lines have
broad profiles with wings extending to velocities of about +/-200 km/s. We
determine the mass accretion rate of OTS44 based on Halpha to 7.6x10^{-12}
Msun/yr, which shows that OTS44 has a relatively high mass-accretion rate
considering its small central mass. This mass rate is nevertheless consistent
with the general decreasing trend found for stars of several solar masses down
to brown dwarfs. Furthermore, we determine the properties of the disk
surrounding OTS44 through radiative transfer modeling of flux measurement from
the optical to the far-IR (Herschel) by applying a Bayesian analysis. We find
that OTS44 has a highly flared disk (beta >1.2) with a mass of 9.1x10^{-5}
M_Sun, i.e. about 0.1 M_Jup or 30 M_Earth. We show that the ratio of
disk-to-central-mass of about 10^{-2} found for objects between 0.03 Msun and
14 Msun is also valid for OTS44 at a mass of ~0.01 M_Sun. Our observations are
in line with an isolated star-like mode of the formation of brown dwarfs down
to 0.01 M_Sun.Comment: Accepted for publication in Astronomy and Astrophysics Lette
Searching for sub-stellar companion into the LkCa15 proto-planetary disk
Recent sub-millimetric observations at the Plateau de Bure interferometer
evidenced a cavity at ~ 46 AU in radius into the proto-planetary disk around
the T Tauri star LkCa15 (V1079 Tau), located in the Taurus molecular cloud.
Additional Spitzer observations have corroborated this result possibly
explained by the presence of a massive (>= 5 MJup) planetary mass, a brown
dwarf or a low mass star companion at about 30 AU from the star. We used the
most recent developments of high angular resolution and high contrast imaging
to search directly for the existence of this putative companion, and to bring
new constraints on its physical and orbital properties. The NACO adaptive
optics instrument at VLT was used to observe LkCa15 using a four quadrant phase
mask coronagraph to access small angular separations at relatively high
contrast. A reference star at the same parallactic angle was carefully observed
to optimize the quasi-static speckles subtraction (limiting our sensitivity at
less than 1.0). Although we do not report any positive detection of a faint
companion that would be responsible for the observed gap in LkCa15's disk
(25-30 AU), our detection limits start constraining its probable mass,
semi-major axis and eccentricity. Using evolutionary model predictions, Monte
Carlo simulations exclude the presence of low eccentric companions with masses
M >= 6 M Jup and orbiting at a >= 100 AU with significant level of confidence.
For closer orbits, brown dwarf companions can be rejected with a detection
probability of 90% down to 80 AU (at 80% down to 60 AU). Our detection limits
do not access the star environment close enough to fully exclude the presence
of a brown dwarf or a massive planet within the disk inner activity (i.e at
less than 30 AU). Only, further and higher contrast observations should unveil
the existence of this putative companion inside the LkCa15 disk.Comment: 6 pages, 4 figures, accepted for publication in A&
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