33 research outputs found
GridCertLib: a Single Sign-on Solution for Grid Web Applications and Portals
This paper describes the design and implementation of GridCertLib, a Java
library leveraging a Shibboleth-based authentication infrastructure and the
SLCS online certificate signing service, to provide short-lived X.509
certificates and Grid proxies. The main use case envisioned for GridCertLib, is
to provide seamless and secure access to Grid/X.509 certificates and proxies in
web applications and portals: when a user logs in to the portal using
Shibboleth authentication, GridCertLib can automatically obtain a Grid/X.509
certificate from the SLCS service and generate a VOMS proxy from it. We give an
overview of the architecture of GridCertLib and briefly describe its
programming model. Its application to some deployment scenarios is outlined, as
well as a report on practical experience integrating GridCertLib into portals
for Bioinformatics and Computational Chemistry applications, based on the
popular P-GRADE and Django softwares.Comment: 18 pages, 1 figure; final manuscript accepted for publication by the
"Journal of Grid Computing
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
Know The Star, Know the Planet. IV. A Stellar Companion to the Host star of the Eccentric Exoplanet HD 8673b
HD 8673 hosts a massive exoplanet in a highly eccentric orbit (e=0.723).
Based on two epochs of speckle interferometry a previous publication identified
a candidate stellar companion. We observed HD 8673 multiple times with the 10 m
Keck II telescope, the 5 m Hale telescope, the 3.63 m AEOS telescope and the
1.5m Palomar telescope in a variety of filters with the aim of confirming and
characterizing the stellar companion. We did not detect the candidate
companion, which we now conclude was a false detection, but we did detect a
fainter companion. We collected astrometry and photometry of the companion on
six epochs in a variety of filters. The measured differential photometry
enabled us to determine that the companion is an early M dwarf with a mass
estimate of 0.33-0.45 M?. The companion has a projected separation of 10 AU,
which is one of the smallest projected separations of an exoplanet host binary
system. Based on the limited astrometry collected, we are able to constrain the
orbit of the stellar companion to a semi-major axis of 35{60 AU, an
eccentricity ? 0.5 and an inclination of 75{85?. The stellar companion has
likely strongly in uenced the orbit of the exoplanet and quite possibly
explains its high eccentricity.Comment: Accepted to the Astronomical Journal, 6 Pages, 5 Figure