100 research outputs found
Keck Interferometer V^2 science
We summarize the status of the Keck Interferometer in V^2 mode, and science results recently obtained
Standard FITS template for simulated astrophysical scenes with the WFIRST coronagraph
The science investigation teams (SITs) for the WFIRST coronagraphic
instrument have begun studying the capabilities of the instrument to directly
image reflected light off from exoplanets at contrasts down to contrasts of
~10^-9 with respect to the stellar flux. Detection of point sources at these
high contrasts requires yield estimates and detailed modeling of the image of
the planetary system as it propagates through the telescope optics. While the
SITs might generate custom astrophysical scenes, the integrated model,
propagated through the internal speckle field, is typically done at JPL. In
this white paper, we present a standard file format to ensure a single
distribution system between those who produce the raw astrophysical scenes, and
JPL modelers who incorporate those scenes into their optical modeling. At its
core, our custom file format uses FITS files, and incorporates standards on
packaging astrophysical scenes. This includes spectral and astrometric
information for planetary and stellar point sources, zodiacal light and
extragalactic sources that may appear as contaminants. Adhering to such a
uniform data distribution format is necessary, as it ensures seamless work flow
between the SITs and modelers at JPL for the goals of understanding limits of
the WFIRST coronagraphic instrument.Comment: 8 pages, white pape
Spatially Resolved Circumstellar Structure of Herbig Ae/Be Stars in the Near-Infrared
We have conducted the first systematic study of Herbig Ae/Be stars using the
technique of long baseline stellar interferometry in the near-infrared. The
principal result of this paper is that the IOTA interferometer resolves the
source of infrared excess in 11 of the 15 systems surveyed.
The visibility data for all the sources has been interpreted within the
context of four simple models which represent a range of plausible
representations for the brightness distribution of the source of excess
emission: a Gaussian, a narrow uniform ring, a flat blackbody disk with a
single temperature power law, and an infrared companion. We find that the
characteristic sizes of the near-infrared emitting regions are larger than
previously thought (0.5-5.9 AU, as given by the FWHM of the Gaussian
intensity). A further major result of this paper is that the sizes measured,
when combined with the observed spectral energy distributions, essentially rule
out accretion disk models represented by blackbody disks with the canonical
radial temperature law with exponent -3/4. We also find that, within the range
observed in this study, none of the sources (except the new binary) shows
varying visibilities as the orientation of the interferometer baseline changes.
Taken as an ensemble, with no clear evidence in favor of axi-symmetric
structure, the observations favor the interpretation that the circumstellar
dust is distributed in spherical envelopes (the Gaussian model) or thin shells
(the ring model).Comment: Accepted for publication by The Astrophysical Journa
High contrast imaging at the LBT: the LEECH exoplanet imaging survey
In Spring 2013, the LEECH (LBTI Exozodi Exoplanet Common Hunt) survey began its ~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 μm), as opposed to the shorter wavelength near-infrared bands (1-2.4 μm) of other surveys. This portion of the spectrum offers deep mass sensitivity, especially around nearby adolescent (~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 3-5μm in preparation for JWST
Control interface concepts for CHARA 6-telescope fringe tracking with CHAMP+MIRC
Cophasing six telescopes from the CHARA array, the CHARA-Michigan
Phasetracker (CHAMP) and Michigan Infrared Combiner (MIRC) are pushing the
frontiers of infrared long-baseline interferometric imaging in key scientific
areas such as star- and planet-formation. Here we review our concepts and
recent improvements on the CHAMP and MIRC control interfaces, which establish
the communication to the real-time data recording & fringe tracking code,
provide essential performance diagnostics, and assist the observer in the
alignment and flux optimization procedure. For fringe detection and tracking
with MIRC, we have developed a novel matrix approach, which provides
predictions for the fringe positions based on cross-fringe information.Comment: 6 pages, 4 figures, published in SPIE conference proceedings
(http://dx.doi.org/10.1117/12.926559
Phase Closure Nulling: results from the 2009 campaign
We present here a new observational technique, Phase Closure Nulling (PCN),
which has the potential to obtain very high contrast detection and spectroscopy
of faint companions to bright stars. PCN consists in measuring closure phases
of fully resolved objects with a baseline triplet where one of the baselines
crosses a null of the object visibility function. For scenes dominated by the
presence of a stellar disk, the correlated flux of the star around nulls is
essentially canceled out, and in these regions the signature of fainter,
unresolved, scene object(s) dominates the imaginary part of the visibility in
particular the closure phase. We present here the basics of the PCN method, the
initial proof-of-concept observation, the envisioned science cases and report
about the first observing campaign made on VLTI/AMBER and CHARA/MIRC using this
technique.Comment: To be published in the proceedings of the SPIE'2010 conference on
"Optical and Infrared Interferometry II
Planet Formation Imager (PFI): science vision and key requirements
The Planet Formation Imager (PFI) project aims to provide a strong scientific vision for ground-based optical astronomy beyond the upcoming generation of Extremely Large Telescopes. We make the case that a breakthrough in angular resolution imaging capabilities is required in order to unravel the processes involved in planet formation. PFI will be optimised to provide a complete census of the protoplanet population at all stellocentric radii and over the age range from 0.1 to ~100 Myr. Within this age period, planetary systems undergo dramatic changes and the final architecture of planetary systems is determined. Our goal is to study the planetary birth on the natural spatial scale where the material is assembled, which is the "Hill Sphere" of the forming planet, and to characterise the protoplanetary cores by measuring their masses and physical properties. Our science working group has investigated the observational characteristics of these young protoplanets as well as the migration mechanisms that might alter the system architecture. We simulated the imprints that the planets leave in the disk and study how PFI could revolutionise areas ranging from exoplanet to extragalactic science. In this contribution we outline the key science drivers of PFI and discuss the requirements that will guide the technology choices, the site selection, and potential science/technology tradeoffs
The Circumstellar Environments of Young Stars at AU Scales
We review recent advances in our understanding of the innermost regions of
the circumstellar environment around young stars, made possible by the
technique of long baseline interferometry at infrared wavelengths.
Near-infrared observations directly probe the location of the hottest dust. The
characteristic sizes found are much larger than previously thought, and
strongly correlate with the luminosity of the central young stars. This
relation has motivated in part a new class of models of the inner disk
structure. The first mid-infrared observations have probed disk emission over a
larger range of scales, and spectrally resolved interferometry has for the
first time revealed mineralogy gradients in the disk. These new measurements
provide crucial information on the structure and physical properties of young
circumstellar disks, as initial conditions for planet formation.Comment: to appear in Protostars and Planets V boo
Recent progress at the Keck Interferometer
In this paper we report on progress at the Keck Interferometer since the 2004 SPIE meeting with an emphasis on the operations improvements for visibility science
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