[Show abstract][Hide abstract] ABSTRACT: In Spring 2013, the LEECH (LBTI Exozodi Exoplanet Common Hunt) survey began
its $\sim$130-night campaign from the Large Binocular Telescope (LBT) atop Mt
Graham, Arizona. This survey benefits from the many technological achievements
of the LBT, including two 8.4-meter mirrors on a single fixed mount, dual
adaptive secondary mirrors for high Strehl performance, and a cold beam
combiner to dramatically reduce the telescope's overall background emissivity.
LEECH neatly complements other high-contrast planet imaging efforts by
observing stars at L' (3.8 $\mu$m), as opposed to the shorter wavelength
near-infrared bands (1-2.4 $\mu$m) of other surveys. This portion of the
spectrum offers deep mass sensitivity, especially around nearby adolescent
($\sim$0.1-1 Gyr) stars. LEECH's contrast is competitive with other extreme
adaptive optics systems, while providing an alternative survey strategy.
Additionally, LEECH is characterizing known exoplanetary systems with
observations from 3-5$\mu$m in preparation for JWST.
[Show abstract][Hide abstract] ABSTRACT: In February 2013, the LEECH (LBTI Exozodi Exoplanet Common Hunt) survey began
its 100-night campaign from the Large Binocular Telescope atop Mount Graham in
Arizona. LEECH nearly complements other high-contrast planet imaging efforts by
observing stars in L' band (3.8 microns) as opposed to the shorter wavelength
near-infrared bands (1-2.3 microns). This part of the spectrum offers deeper
mass sensitivity for intermediate age (several hundred Myr-old) systems, since
their Jovian-mass planets radiate predominantly in the mid-infrared. In this
proceedings, we present the science goals for LEECH and a preliminary contrast
curve from some early data.
[Show abstract][Hide abstract] ABSTRACT: Ground-based long baseline interferometers have long been limited in
sensitivity by the short integration periods imposed by atmospheric turbulence.
The first observation fainter than this limit was performed on January 22, 2011
when the Keck Interferometer observed a K=11.5 target, about one magnitude
fainter than its K=10.3 limit. This observation was made possible by the Dual
Field Phase Referencing instrument of the ASTRA project: simultaneously
measuring the real-time effects of the atmosphere on a nearby bright guide
star, and correcting for it on the faint target, integration time longer than
the turbulence time scale are made possible. As a prelude to this
demonstration, we first present the implementation of Dual Field Phase
Referencing on the interferometer. We then detail its on-sky performance
focusing on the accuracy of the turbulence correction, and on the resulting
fringe contrast stability. We conclude with a presentation of early results
obtained with Laser Guide Star AO and the interferometer.
[Show abstract][Hide abstract] ABSTRACT: 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.
The Astrophysical Journal 03/2012; 752(1). · 6.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The sensitivity and astrometry upgrade ASTRA of the Keck Interferometer is introduced. After a brief overview of the underlying interferometric principles, the technology and concepts of the upgrade are presented. The interferometric dual-field technology of ASTRA will provide the KI with the means to observe two objects simultaneously, and measure the distance between them with a precision eventually better than 100 μas. This astrometric functionality of ASTRA will add a unique observing tool to fields of astrophysical research as diverse as exo-planetary kinematics, binary astrometry, and the investigation of stars accelerated by the massive black hole in the center of the Milky Way as discussed in this contribution.
New Astronomy Reviews 11/2009; · 1.82 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The formation of planets is one of the major unsolved problems in modern
astrophysics. Planets are believed to form out of the material in
circumstellar disks known to exist around young stars, and which are a
by-product of the star formation process. Therefore, the physical
conditions in these disks - structure and composition as a function of
stellocentric radius and vertical height, density and temperature
profiles of each component - represent the initial conditions under
which planets form. Clearly, a good understanding of disk structure and
its time evolution are crucial to understanding planet formation, the
evolution of young planetary systems (e.g. migration), and the recently
discovered, and unanticipated, diversity of planetary architectures.
However, the inner disk regions (interior to ~10 AU) most relevant in
the context of planet formation are very poorly known, primarily because
of observational challenges in spatially resolving this region. In this
contribution we discuss opportunities for the next decade from
spectrally and spatially resolved observations, and from direct imaging,
using infrared long baseline interferometry.
[Show abstract][Hide abstract] ABSTRACT: Recent Spitzer observations have added to the list of young stellar objects thought to possess circumstellar disks with large gaps or inner holes. The favored explanation for these large clearings is that planets are forming (or have recently formed) in these disks, and are preventing inward accretion of outer disk material. While millimeter- wavelength imaging has confirmed the existence of large holes around a few objects, substantial uncertainties remain in understanding what is going on within the cleared regions. Imaging at mid-IR wavelengths can spatially resolve the inner edges of holes and gaps, and probe small dust within the cleared regions, potentially tracing structures associated with planets in formation. We propose to use TReCS at Gemini South to spatially resolve the mid-infrared emission from protoplanetary disks suspected of harboring massive planets, and thereby directly measure the sizes and degree of clearing of the inner holes and gaps. Using a custom short-readout mode for TReCS, and the novel imaging technique of speckle interferometry, we will spatially resolve the mid- IR emission from these potentially planet-forming systems.
[Show abstract][Hide abstract] ABSTRACT: We report new near-infrared, long-baseline interferometric observations at the AU scale of the pre-main-sequence star FU Orionis with the PTI, IOTA and VLTI interferometers. This young stellar object has been observed on 42 nights over a period of 6 years from 1998 to 2003. We have obtained 287 independent measurements of the fringe visibility with 6 different baselines ranging from 20 to 110 meters in length, in the H and K bands. Our extensive (u,v)-plane coverage, coupled with the published spectral energy distribution data, allows us to test the accretion disk scenario. We find that the most probable explanation for these observations is that FU Ori hosts an active accretion disk whose temperature law is consistent with standard models. We are able to constrain the geometry of the disk, including an inclination of 55 deg and a position angle of 47 deg. In addition, a 10 percent peak-to-peak oscillation is detected in the data (at the two-sigma level) from the longest baselines, which we interpret as a possible disk hot-spot or companion. However, the oscillation in our best data set is best explained with an unresolved spot located at a projected distance of 10 AU at the 130 deg position angle and with a magnitude difference of DeltaK = 3.9 and DeltaH = 3.6 mag moving away from the center at a rate of 1.2 AU/yr. we propose to interpret this spot as the signature of a companion of the central FU Ori system on an extremely eccentric orbit. We speculate that the close encounter of this putative companion and the central star could be the explanation of the initial photometric rise of the luminosity of this object.
Astronomy and Astrophysics 03/2005; · 5.08 Impact Factor