171 research outputs found
A giant planet imaged in the disk of the young star Beta Pictoris
Here we show that the ~10 Myr Beta Pictoris system hosts a massive giant
planet, Beta Pictoris b, located 8 to 15 AU from the star. This result confirms
that gas giant planets form rapidly within disks and validates the use of disk
structures as fingerprints of embedded planets. Among the few planets already
imaged, Beta Pictoris b is the closest to its parent star. Its short period
could allow recording the full orbit within 17 years.Comment: 4 pages, 2 figures. Published online 10 June 2010;
10.1126/science.1187187. To appear in Scienc
An aperture masking mode for the MICADO instrument
MICADO is a near-IR camera for the Europea ELT, featuring an extended field
(75" diameter) for imaging, and also spectrographic and high contrast imaging
capabilities. It has been chosen by ESO as one of the two first-light
instruments. Although it is ultimately aimed at being fed by the MCAO module
called MAORY, MICADO will come with an internal SCAO system that will be
complementary to it and will deliver a high performance on axis correction,
suitable for coronagraphic and pupil masking applications. The basis of the
pupil masking approach is to ensure the stability of the optical transfer
function, even in the case of residual errors after AO correction (due to non
common path errors and quasi-static aberrations). Preliminary designs of pupil
masks are presented. Trade-offs and technical choices, especially regarding
redundancy and pupil tracking, are explained.Comment: SPIE 2014 Proceeding -- Montrea
A probable giant planet imaged in the Beta Pictoris disk
Since the discovery of its dusty disk in 1984, Beta Pictoris has become the
prototype of young early-type planetary systems, and there are now various
indications that a massive Jovian planet is orbiting the star at ~ 10 AU.
However, no planets have been detected around this star so far. Our goal was to
investigate the close environment of Beta Pic, searching for planetary
companion(s). Deep adaptive-optics L'-band images of Beta Pic were recorded
using the NaCo instrument at the Very Large Telescope. A faint point-like
signal is detected at a projected distance of ~ 8 AU from the star, within the
North-East side of the dust disk. Various tests were made to rule out with a
good confidence level possible instrumental or atmospheric artifacts. The
probability of a foreground or background contaminant is extremely low, based
in addition on the analysis of previous deep Hubble Space Telescope images. The
object L'=11.2 apparent magnitude would indicate a typical temperature of ~1500
K and a mass of ~ 8 Jovian masses. If confirmed, it could explain the main
morphological and dynamical peculiarities of the Beta Pic system. The present
detection is unique among A-stars by the proximity of the resolved planet to
its parent star. Its closeness and location inside the Beta Pic disk suggest a
formation process by core accretion or disk instabilities rather than a
binary-like formation process.Comment: 5 pages, 3 figures, 1 table. A&A Letters, in pres
Constraining the orbit of the possible companion to Beta Pictoris: New deep imaging observations
We recently reported on the detection of a possible planetary-mass companion
to Beta Pictoris at a projected separation of 8 AU from the star, using data
taken in November 2003 with NaCo, the adaptive-optics system installed on the
Very Large Telescope UT4. Eventhough no second epoch detection was available,
there are strong arguments to favor a gravitationally bound companion rather
than a background object. If confirmed and located at a physical separation of
8 AU, this young, hot (~1500 K), massive Jovian companion (~8 Mjup) would be
the closest planet to its star ever imaged, could be formed via core-accretion,
and could explain the main morphological and dynamical properties of the dust
disk. Our goal was to return to Beta Pic five years later to obtain a
second-epoch observation of the companion or, in case of a non-detection,
constrain its orbit. Deep adaptive-optics L'-band direct images of Beta Pic and
Ks-band Four-Quadrant-Phase-Mask (4QPM) coronagraphic images were recorded with
NaCo in January and February 2009. We also use 4QPM data taken in November
2004. No point-like signal with the brightness of the companion candidate
(apparent magnitudes L'=11.2 or Ks ~ 12.5) is detected at projected distances
down to 6.5 AU from the star in the 2009 data. As expected, the non-detection
does not allow to rule out a background object; however, we show that it is
consistent with the orbital motion of a bound companion that got closer to the
star since first observed in 2003 and that is just emerging from behind the
star at the present epoch. We place strong constraints on the possible orbits
of the companion and discuss future observing prospects.Comment: 8 pages, 8 figures, 1 table, accepted for publication in Astronomy
and Astrophysic
Unveiling the central parsec region of an AGN: the Circinus nucleus in the near infrared with the VLT
VLT J- to M\p-band adaptive optics observations of the Circinus Galaxy on
parsec scales resolve a central bright Ks-band source with a FWHM size of 1.9
0.6 pc. This source is only visible at wavelengths longward of 1.6 m
and coincides in position with the peak of the [Si VII]~2.48 m coronal
line emission. With respect to the peak of the central optical emission, the
source is shifted by 0.15\arcsec (2.8 pc) to the south-east. Indeed, it
defines the vertex of a fairly collimated beam which extends for 10 pc,
and which is seen in both continuum light shortward of 1.6 m and in
H line emission. The source also lies at the center of a 19 pc
size [Si VII] ionization {\it bicone}.
Identifying this source as the nucleus of Circinus, its size is compatible
with a putative parsec-scale torus. Its spectral energy distribution,
characterized by a prominent narrow peak, is compatible with a dust temperature
of 300 K. Hotter dust within a 1 pc radius of the center is not detected. The
AGN luminosity required to heat this dust is in the range of X-ray luminosities
that have been measured toward the central source. This in turn supports the
existence of highly obscuring material, with column densities of
cm, that must be located within 1 pc of the core.Comment: 15 pages, 4 figures; To appear in The Astrophysical Journa
The LAOG-Planet Imaging Surveys
With the development of high contrast imaging techniques and infrared
detectors, vast efforts have been devoted during the past decade to detect and
characterize lighter, cooler and closer companions to nearby stars, and
ultimately image new planetary systems. Complementary to other observing
techniques (radial velocity, transit, micro-lensing, pulsar-timing), this
approach has opened a new astrophysical window to study the physical properties
and the formation mechanisms of brown dwarfs and planets. I here will briefly
present the observing challenge, the different observing techniques, strategies
and samples of current exoplanet imaging searches that have been selected in
the context of the LAOG-Planet Imaging Surveys. I will finally describe the
most recent results that led to the discovery of giant planets probably formed
like the ones of our solar system, offering exciting and attractive
perspectives for the future generation of deep imaging instruments.Comment: 6 pages, 5 figures, Invited talk of "Exoplanets and disks: their
formation and diversity" conference, 9-12 March 200
Detection of the Sgr A* activity at 3.8 and 4.8 microns with NACO
L'-band (lambda=3.8 microns) and M'-band (lambda=4.8 microns) observations of
the Galactic Center region, performed in 2003 at VLT (ESO) with the adaptive
optics imager NACO, have lead to the detection of an infrared counterpart of
the radio source Sgr A* at both wavelengths. The measured fluxes confirm that
the Sgr A* infrared spectrum is dominated by the synchrotron emission of
nonthermal electrons. The infrared counterpart exhibits no significant short
term variability but demonstrates flux variations on daily and yearly scales.
The observed emission arises away from the position of the dynamical center of
the S2 orbit and would then not originate from the closest regions of the black
hole.Comment: 5 pages, 3 figures, accepted in Astronomy & Astrophysic
EAGLE multi-object AO concept study for the E-ELT
EAGLE is the multi-object, spatially-resolved, near-IR spectrograph
instrument concept for the E-ELT, relying on a distributed Adaptive Optics,
so-called Multi Object Adaptive Optics. This paper presents the results of a
phase A study. Using 84x84 actuator deformable mirrors, the performed analysis
demonstrates that 6 laser guide stars and up to 5 natural guide stars of
magnitude R<17, picked-up in a 7.3' diameter patrol field of view, allow us to
obtain an overall performance in terms of Ensquared Energy of 35% in a 75x75
mas^2 spaxel at H band, whatever the target direction in the centred 5' science
field for median seeing conditions. The computed sky coverage at galactic
latitudes |b|~60 is close to 90%.Comment: 6 pages, to appear in the proceedings of the AO4ELT conference, held
in Paris, 22-26 June 200
On-sky tests of the CuReD and HWR fast wavefront reconstruction algorithms with CANARY
CuReD (Cumulative Reconstructor with domain Decomposition) and HWR (Hierarchical Wavefront Reconstructor) are novel wavefront reconstruction algorithms for the Shack–Hartmann wavefront sensor, used in the single-conjugate adaptive optics. For a high-order system they are much faster than the traditional matrix–vector-multiplication method. We have developed three methods for mapping the reconstructed phase into the deformable mirror actuator commands and have tested both reconstructors with the CANARY instrument. We find out that the CuReD reconstructor runs stably only if the feedback loop is operated as a leaky integrator, whereas HWR runs stably with the conventional integrator control. Using the CANARY telescope simulator we find that the Strehl ratio (SR) obtained with CuReD is slightly higher than that of the traditional least-squares estimator (LSE). We demonstrate that this is because the CuReD algorithm has a smoothing effect on the output wavefront. The SR of HWR is slightly lower than that of LSE. We have tested both reconstructors extensively on-sky. They perform well and CuReD achieves a similar SR as LSE. We compare the CANARY results with those from a computer simulation and find good agreement between the two
Hot Very Small dust Grains in NGC 1068 seen in jet induced structures thanks to VLT/NACO adaptive optics
We present K, L and M diffraction-limited images of NGC 1068 obtained with
NAOS+CONICA at VLT/YEPUN over a 3.5" field around the central engine. Hot dust
(Tcol = 550-650 K) is found in three different regions : (a) in the true
nucleus, seen as a slightly NS elongated, core of extremely hot dust,
"resolved" in K and L with respective diameters of ~5 pc and 8.5 pc ; (b) along
the NS direction, as a "spiral arm" and a southern tongue ; (c) as a set of
parallel elongated nodules ("wave-like") bracketting the jet. Several
structures observed on radio maps, mid-IR or HST UV-visible maps are seen, so
that a precise registration can be done from UV to 6 cm. These results do
support the current interpretion that source (a) corresponds to emission from
dust near sublimation temperature delimiting the walls of the cavity in the
central obscuring torus. Structure (b) is thought to be a mixture of hot dust
and active star forming regions along a micro spiral structure that could trace
the tidal mechanism bringing matter to the central engine. Structure c)which
was not known, exhibits too high a temperature for "classical'' grains ; it is
most probably the signature of transiently heated very small dust grains (VSG)
: "nano-diamonds", which are resistant and can form in strong UV field or in
shocks, are very attractive candidates. The "waves'' can be condensations
triggered by jet induced shocks, as predicted by recent models. First
estimates, based on a simple VSG model and on a detailed radiative transfer
model, do agree with those interpretations, both qualitatively and
quantitatively.Comment: Submitted : 15 March 2003 ; accepted : 15 May 200
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