676 research outputs found
A Data Cube Extraction Pipeline for a Coronagraphic Integral Field Spectrograph
Project 1640 is a high contrast near-infrared instrument probing the
vicinities of nearby stars through the unique combination of an integral field
spectrograph with a Lyot coronagraph and a high-order adaptive optics system.
The extraordinary data reduction demands, similar those which several new
exoplanet imaging instruments will face in the near future, have been met by
the novel software algorithms described herein. The Project 1640 Data Cube
Extraction Pipeline (PCXP) automates the translation of 3.8*10^4 closely
packed, coarsely sampled spectra to a data cube. We implement a robust
empirical model of the spectrograph focal plane geometry to register the
detector image at sub-pixel precision, and map the cube extraction. We
demonstrate our ability to accurately retrieve source spectra based on an
observation of Saturn's moon Titan.Comment: 35 pages, 15 figures; accepted for publication in PAS
Contested Water Governance in Myanmar/Burma : Politics, the Peace Negotiations and the Production of Scale
Along the Salween River, water is governed at multiple—at times overlapping—scales with implications for authority and claims to access. In this chapter it is argued that the scales of water governance in Myanmar are currently being contested and how this constitutes a key battleground for future decision-making not only in terms of water governance, but also with implications for the peace negotiations and the federal structure of government that it is working towards.Peer reviewe
The Solar-System-Scale Disk Around AB Aurigae
The young star AB Aurigae is surrounded by a complex combination of gas-rich
and dust dominated structures. The inner disk which has not been studied
previously at sufficient resolution and imaging dynamic range seems to contain
very little gas inside a radius of least 130 astronomical units (AU) from the
star. Using adaptive-optics coronagraphy and polarimetry we have imaged the
dust in an annulus between 43 and 302 AU from the star, a region never seen
before. An azimuthal gap in an annulus of dust at a radius of 102 AU, along
with a clearing at closer radii inside this annulus, suggests the formation of
at least one small body at an orbital distance of about 100 AU. This structure
seems consistent with crude models of mean motion resonances, or accumulation
of material at two of the Lagrange points relative to the putative object and
the star. We also report a low significance detection of a point source in this
outer annulus of dust. This source may be an overdensity in the disk due to
dust accreting onto an unseen companion. An alternate interpretation suggests
that the object's mass is between 5 and 37 times the mass of Jupiter. The
results have implications for circumstellar disk dynamics and planet formation.Comment: 11 pages, 5 figures, accepted for publication in Astrophysical
Journal, V. 680, June 10, 200
Constraining mass ratio and extinction in the FU Orionis binary system with infrared integral field spectroscopy
We report low resolution near infrared spectroscopic observations of the
eruptive star FU Orionis using the Integral Field Spectrograph Project 1640
installed at the Palomar Hale telescope. This work focuses on elucidating the
nature of the faint source, located 0.5" south of FU Ori, and identified in
2003 as FU Ori S. We first use our observations in conjunction with published
data to demonstrate that the two stars are indeed physically associated and
form a true binary pair. We then proceed to extract J and H band
spectro-photometry using the damped LOCI algorithm, a reduction method tailored
for high contrast science with IFS. This is the first communication reporting
the high accuracy of this technique, pioneered by the Project 1640 team, on a
faint astronomical source. We use our low resolution near infrared spectrum in
conjunction with 10.2 micron interferometric data to constrain the infrared
excess of FU Ori S. We then focus on estimating the bulk physical properties of
FU Ori S. Our models lead to estimates of an object heavily reddened, A_V
=8-12, with an effective temperature of ~ 4000-6500 K . Finally we put these
results in the context of the FU Ori N-S system and argue that our analysis
provides evidence that FU Ori S might be the more massive component of this
binary syste
A New High Contrast Imaging Program at Palomar Observatory
We describe a new instrument that forms the core of a long-term high contrast
imaging program at the 200-inch Hale Telescope at Palomar Observatory. The
primary scientific thrust is to obtain images and low-resolution spectroscopy
of brown dwarfs and young Jovian mass exoplanets in the vicinity of stars
within 50 parsecs of the Sun. The instrument is a microlens-based integral
field spectrograph integrated with a diffraction limited, apodized-pupil Lyot
coronagraph, mounted behind the Palomar adaptive optics system. The
spectrograph obtains imaging in 23 channels across the J and H bands (1.06 -
1.78 microns). In addition to obtaining spectra, this wavelength resolution
allows suppression of the chromatically dependent speckle noise, which we
describe. We have recently installed a novel internal wave front calibration
system that will provide continuous updates to the AO system every 0.5 - 1.0
minutes by sensing the wave front within the coronagraph. The Palomar AO system
is undergoing an upgrade to a much higher-order AO system ("PALM-3000"): a
3388-actuator tweeter deformable mirror working together with the existing
241-actuator mirror. This system will allow correction with subapertures as
small as 8cm at the telescope pupil using natural guide stars. The coronagraph
alone has achieved an initial dynamic range in the H-band of 2 X 10^-4 at 1
arcsecond, without speckle noise suppression. We demonstrate that spectral
speckle suppression is providing a factor of 10-20 improvement over this
bringing our current contrast at an arcsecond to ~2 X 10^-5. This system is the
first of a new generation of apodized pupil coronagraphs combined with
high-order adaptive optics and integral field spectrographs (e.g. GPI, SPHERE,
HiCIAO), and we anticipate this instrument will make a lasting contribution to
high contrast imaging in the Northern Hemisphere for years.Comment: Accepted to PASP: 12 pages, 12 figure
Electric Field Conjugation with the Project 1640 coronagraph
The Project 1640 instrument on the 200-inch Hale telescope at Palomar
Observatory is a coronagraphic instrument with an integral field spectrograph
at the back end, designed to find young, self-luminous planets around nearby
stars. To reach the necessary contrast for this, the PALM-3000 adaptive optics
system corrects for fast atmospheric speckles, while CAL, a phase-shifting
interferometer in a Mach-Zehnder configuration, measures the quasistatic
components of the complex electric field in the pupil plane following the
coronagraphic stop. Two additional sensors measure and control low-order modes.
These field measurements may then be combined with a system model and data
taken separately using a white-light source internal to the AO system to
correct for both phase and amplitude aberrations. Here, we discuss and
demonstrate the procedure to maintain a half-plane dark hole in the image plane
while the spectrograph is taking data, including initial on-sky performance.Comment: 9 pages, 7 figures, in Proceedings of SPIE, 8864-19 (2013
Spectral Typing of Late Type Stellar Companions to Young Stars from Low Dispersion Near-Infrared Integral Field Unit Data
We used the Project 1640 near-infrared coronagraph and integral field
spectrograph to observe 19 young solar type stars. Five of these stars are
known binary stars and we detected the late-type secondaries and were able to
measure their JH spectra with a resolution of R\sim30. The reduced, extracted,
and calibrated spectra were compared to template spectra from the IRTF spectral
library. With this comparison we test the accuracy and consistency of spectral
type determination with the low-resolution near-infrared spectra from P1640.
Additionally, we determine effective temperature and surface gravity of the
companions by fitting synthetic spectra calculated with the PHOENIX model
atmosphere code. We also present several new epochs of astrometry of each of
the systems. Together these data increase our knowledge and understanding of
the stellar make up of these systems. In addition to the astronomical results,
the analysis presented helps validate the Project 1640 data reduction and
spectral extraction processes and the utility of low-resolution, near-infrared
spectra for characterizing late-type companions in multiple systems.Comment: Accepted to Astronomical Journal, 25 pages, 8 figure
Aperture Mask Interferometry with an Integral Field Spectrograph
A non-redundant pupil mask placed in front of a low-resolution integral field spectrograph (IFS) adds a spectral dimension to high angular resolution imaging behind adaptive optics systems. We demonstrate the first application of this technique, using the spectroscopic binary star system β CrB as our target. The mask and IFS combination enabled us to measure the first low-resolution spectrum of the F3-F5 dwarf secondary component of β CrB, at an angular separation 141 mas from its A5-A7Vp primary star. To record multi-wavelength closure phases, we collected interferograms simultaneously in 23 spectral channels spanning the J and H bands (1.1 μm-1.8 μm), using the Project 1640 IFS behind the 249-channel PalAO adaptive optics system on the Hale telescope at Palomar Observatory. In addition to providing physical information about the source, spectrally resolved mask fringes have the potential to enhance detection limits over single filter observations. While the overall dynamic range of our observation suffers from large systematic calibration errors, the information gleaned from the full channel range improves the dynamic range by a factor of 3 to 4 over the best single channel
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