71 research outputs found
BIGRE: a low cross-talk integral field unit tailored for extrasolar planets imaging spectroscopy
Integral field spectroscopy (IFS) represents a powerful technique for the
detection and characterization of extrasolar planets through high contrast
imaging, since it allows to obtain simultaneously a large number of
monochromatic images. These can be used to calibrate and then to reduce the
impact of speckles, once their chromatic dependence is taken into account. The
main concern in designing integral field spectrographs for high contrast
imaging is the impact of the diffraction effects and the non-common path
aberrations together with an efficient use of the detector pixels. We focus our
attention on integral field spectrographs based on lenslet-arrays, discussing
the main features of these designs: the conditions of appropriate spatial and
spectral sampling of the resulting spectrograph's slit functions and their
related cross-talk terms when the system works at the diffraction limit. We
present a new scheme for the integral field unit (IFU) based on a dual-lenslet
device (BIGRE), that solves some of the problems related to the classical TIGER
design when used for such applications. We show that BIGRE provides much lower
cross-talk signals than TIGER, allowing a more efficient use of the detector
pixels and a considerable saving of the overall cost of a lenslet-based
integral field spectrograph.Comment: 17 pages, 18 figures, accepted for publication in Ap
Basaltic asteroids observed with ESO/XShooter
We present new spectroscopic observations of 17 putative basaltic asteroids, in the 0.3-2.5 micron spectral band, with the ESO/XShooter facility. The observed spectral range encompasses the two pyroxene bands centred at 0.9 and 2.0 micron, typical of the basaltic asteroids. The data allowed to taxonomically classify the observed asteroids, and in some cases to confirm their basaltic nature
Exoplanet detection with the SCAO mode of MAORY-MICADO: preliminary results from end-to-end simulations
The SCAO mode of MAORY-MICADO provides us with a very intriguing opportunity as for detection and characterization of extrasolar planets. Deep observations of the innermost regions (below 100 mas) of nearby stars will be possible thanks to the unprecedented resolution of the E-ELT. In this article, we present the results of a simulation campaign aimed at investigating the instrument performances in terms of exoplanet detectability. For this purpose, we developed an end-to-end simulator in IDL language. We simulated the AO correction as expected from the SCAO system using the end-to-end platform COMPASS. We also included the contribution of NCPA, whose dynamical evolution has been modeled on the instrument rotation. Optical aberrations are propagated through the foreseen MICADO coronagraphs, following the Fraunhofer propagation scheme. A sequence of image is generated, in order to apply post-processing algorithms to derive the corresponding detection limits.
We applied this study to some benchmark exoplanetary systems and compared the expected performances with those of current 8-meter high-contrast imagers. Our goal is to investigate which kind of contribution MAORYMICADO can offer to the science of extrasolar planets
On the characterization of GJ 504: a magnetically active planet-host star observed by the Transiting Exoplanet Survey Satellite (TESS)
We present the results of the analysis of the photometric data collected in
long and short-cadence mode by the Transiting Exoplanet Survey Satellite (TESS)
for GJ 504, a well studied planet-hosting solar-like star, whose fundamental
parameters have been largely debated during the last decade. Several attempts
have been made by the present authors to isolate the oscillatory properties
expected on this main-sequence star, but we did not find any presence of
solar-like pulsations. The suppression of the amplitude of the acoustic modes
can be explained by the high level of magnetic activity revealed for this
target, not only by the study of the photometric light-curve, but also by the
analysis of three decades available of Mount Wilson spectroscopic data. In
particular, our measurements of the stellar rotational period Prot=3.4 d and of
the main principal magnetic cycle of 12 a confirm previous findings and allow
us to locate this star in the early main sequence phase of its evolution during
which the chromospheric activity is dominated by the superposition of several
cycles before the transition to the phase of the magnetic-braking shutdown with
the subsequent decrease of the magnetic activity
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Jupiter-like planets might be common in a low-density environment
Radial velocity surveys suggest that the Solar System may be unusual and that Jupiter-like planets have a frequency < 20% around solar-type stars. However, they may be much more common in one of the closest associations in the solar neighbourhood. Young moving stellar groups are the best targets for direct imaging of exoplanets and four massive Jupiter-like planets have been already discovered in the nearby young β Pic Moving Group (BPMG) via high-contrast imaging, and four others were suggested via high precision astrometry by the European Space Agency’s Gaia satellite. Here we analyze 30 stars in BPMG and show that 20 of them might potentially host a Jupiter-like planet as their orbits would be stable. Considering incompleteness in observations, our results suggest that Jupiter-like planets may be more common than previously found. The next Gaia data release will likely confirm our prediction
Characterization of V-type asteroids orbiting in the middle and outer main belt
We present new spectral observations using ground-based telescopes of 23 putative V-type asteroids, selected according to colour surveys in the visible from the Moving Objects Catalogue of the Sloan Digital Sky Survey and near-infrared from the Moving Objects VISTA catalogue. 10 asteroids are orbiting in the middle main belt, while five in the outer part of the main asteroid belt. For the observed asteroids, we assign a taxonomical classification and confirm the basaltic nature for 16 of them. The high-quality spectra in the UV range, obtained with the X-Shooter spectrograph at ESO, allowed the identification of the Fe2+ forbidden transition of pyroxene for 10 asteroids. This band is centred at 506.5 nm, and it is diagnostic of the Ca-content in the pyroxene form. We determined a low Fe-content composition for asteroids (2452) Lyot, (5758) Brunini, (7675) Gorizia, (9197) Endo, (22308) 1990 UO4, (36118) 1999 RE135, (66905) 1999 VC160, and (189597) 2000 WG119, and a composition more rich in Fe for asteroids (75661) 2000 AB79 and (93620) 2000 UQ70. We also present a dynamical investigation of V-type asteroids in the middle and outer main belt. The principal finding of these simulations is that the middle and outer V-types are more likely to be associated with some families, which were considered as possibly originated from the break up of a partially or totally differentiated parent body by diverse studies. This reinforces the hypothesis that the identified V-type in the region were not originated from (4) Vesta and that the number of differentiated objects in the middle and outer main belt must have been much larger than previously assumed
The Gray Needle: Large Grains in the HD 15115 Debris Disk from LBT/PISCES/Ks and LBTI/LMIRcam/L' Adaptive Optics Imaging
We present diffraction-limited \ks band and \lprime adaptive optics images of
the edge-on debris disk around the nearby F2 star HD 15115, obtained with a
single 8.4 m primary mirror at the Large Binocular Telescope. At \ks band the
disk is detected at signal-to-noise per resolution element (SNRE) \about 3-8
from \about 1-2\fasec 5 (45-113 AU) on the western side, and from \about
1.2-2\fasec 1 (63-90 AU) on the east. At \lprime the disk is detected at SNRE
\about 2.5 from \about 1-1\fasec 45 (45-90 AU) on both sides, implying more
symmetric disk structure at 3.8 \microns . At both wavelengths the disk has a
bow-like shape and is offset from the star to the north by a few AU. A surface
brightness asymmetry exists between the two sides of the disk at \ks band, but
not at \lprime . The surface brightness at \ks band declines inside 1\asec
(\about 45 AU), which may be indicative of a gap in the disk near 1\asec. The
\ks - \lprime disk color, after removal of the stellar color, is mostly grey
for both sides of the disk. This suggests that scattered light is coming from
large dust grains, with 3-10 \microns -sized grains on the east side and 1-10
\microns dust grains on the west. This may suggest that the west side is
composed of smaller dust grains than the east side, which would support the
interpretation that the disk is being dynamically affected by interactions with
the local interstellar medium.Comment: Apj-accepted March 27 2012; minor correction
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