1,540 research outputs found
Death Penalty Without a Hearing? How the Nevada Supreme Court\u27s Decision in Bahena v. Goodyear Incorrectly Defines Discovery Sanctions and Denies Due Process to Civil Litigants
Summary of San Juan v. PSC Industrial Outsourcing, 126 Nev. Adv. Op. 35
The Supreme Court affirmed the district court’s summary judgment ruling in favor of PSC as to third party vicarious liability for the torts of an independent contractor. Specifically, the court held PSC, as hirer of independent contractor DTI, was not liable under the peculiar risk doctrine regardless of whether the independent contractor was incompetent or insolvent
A Precise Estimate of the Radius of HD 149026b
We present Spitzer 8 micron transit observations of the extrasolar planet
system HD 149026. At this wavelength, transit light curves are weakly affected
by stellar limb-darkening, allowing for a simpler and more accurate
determination of planetary parameters. We measure a planet-star radius ratio of
R_p/R_s = 0.05158 +/- 0.00077, and in combination with ground-based data and
independent constraints on the stellar mass and radius, we derive an orbital
inclination of i = 85.4 +0.9/-0.8 deg. and a planet radius of 0.755 +/- 0.040
Jupiter radii. These measurements further support models in which the planet is
greatly enriched in heavy elements.Comment: To appear in the Proceedings of the 253rd IAU Symposium: "Transiting
Planets", May 2008, Cambridge, M
Resolving the Surfaces of Extrasolar Planets With Secondary Eclipse Light Curves
We present a method that employs the secondary eclipse light curves of
transiting extrasolar planets to probe the spatial variation of their thermal
emission. This technique permits an observer to resolve the surface of the
planet without the need to spatially resolve its central star. We evaluate the
feasibility of this technique for the HD 209458 system [..]. We consider two
representations of the planetary thermal emission; a simple model parameterized
by a sinusoidal dependence on longitude and latitude, as well as the results of
a three-dimensional dynamical simulation of the planetary atmosphere previously
published by Cooper & Showman. We find that observations of the secondary
eclipse light curve are most sensitive to a longitudinal offset in the
geometric and photometric centroids of the hemisphere of the planet visible
near opposition. To quantify this signal, we define a new parameter, the
``uniform time offset,'' which measures the time lag between the observed
secondary eclipse and that predicted by a planet with a uniform surface flux
distribution. We compare the predicted amplitude of this parameter for HD
209458 with the precision with which it could be measured with IRAC. We find
that IRAC observations at 3.6um a single secondary eclipse should permit
sufficient precision to confirm or reject the Cooper & Showman model of the
surface flux distribution for this planet. We quantify the signal-to-noise
ratio for this offset in the remaining IRAC bands (4.5um, 5.8um, and 8.0um),
and find that a modest improvement in photometric precision (as might be
realized through observations of several eclipse events) should permit a
similarly robust detection.Comment: AASTeX 5.2, 24 pages, 5 figures, accepted for publication in ApJ; v2:
clarifications, updated to version accepted by ApJ; v3: try to reduce spacin
The EVIL-MC Model for Ellipsoidal Variations of Planet-Hosting Stars and Applications to the HAT-P-7 System
We present a new model for Ellipsoidal Variations Induced by a Low-Mass
Companion, the EVIL-MC model. We employ several approximations appropriate for
planetary systems to substantially increase the computational efficiency of our
model relative to more general ellipsoidal variation models and improve upon
the accuracy of simpler models. This new approach gives us a unique ability to
rapidly and accurately determine planetary system parameters. We use the
EVIL-MC model to analyze Kepler Quarter 0-2 (Q0-2) observations of the HAT-P-7
system, an F-type star orbited by a nearly Jupiter-mass companion. Our analysis
corroborates previous estimates of the planet-star mass ratio q = (1.10 +/-
0.06) x 10^(-3), and we have revised the planet's dayside brightness
temperature to 2680 +10/-20 K. We also find a large difference between the day-
and nightside planetary flux, with little nightside emission. Preliminary
dynamical+radiative modeling of the atmosphere indicates this result is
qualitatively consistent with high altitude absorption of stellar heating.
Similar analyses of Kepler and CoRoT photometry of other planets using EVIL-MC
will play a key role in providing constraints on the properties of many
extrasolar systems, especially given the limited resources for follow-up and
characterization of these systems. However, as we highlight, there are
important degeneracies between the contributions from ellipsoidal variations
and planetary emission and reflection. Consequently, for many of the hottest
and brightest Kepler and CoRoT planets, accurate estimates of the planetary
emission and reflection, diagnostic of atmospheric heat budgets, will require
accurate modeling of the photometric contribution from the stellar ellipsoidal
variation.Comment: Accepted to ApJ; minor revisions to original submission; An IDL
version of the EVIL-MC model is publicly available at
http://www.lpl.arizona.edu/~bjackson/idl_code/index.htm
Near-Infrared Thermal Emission from TrES-3b: A Ks-band detection and an H-band upper limit on the depth of the secondary eclipse
We present H and Ks-band photometry bracketing the secondary eclipse of the
hot Jupiter TrES-3b using the Wide-field Infrared Camera on the
Canada-France-Hawaii Telescope. We detect the secondary eclipse of TrES-3b with
a depth of 0.133+/-0.017% in Ks-band (8-sigma) - a result in sharp contrast to
the eclipse depth reported by de Mooij & Snellen. We do not detect its thermal
emission in H-band, but place a 3-sigma limit on the depth of the secondary
eclipse in this band of 0.051%. A secondary eclipse of this depth in Ks
requires very efficient day-to-nightside redistribution of heat and nearly
isotropic reradiation, conclusion that is in agreement with longer wavelength,
mid-infrared Spitzer observations. Our 3-sigma upper-limit on the depth of our
H-band secondary eclipse also argues for very efficient redistribution of heat
and suggests that the atmospheric layer probed by these observations may be
well homogenized. However, our H-band upper limit is so constraining that it
suggests the possibility of a temperature inversion at depth, or an absorbing
molecule, such as methane, that further depresses the emitted flux at this
wavelength. The combination of our near-infrared measurements and those
obtained with Spitzer suggest that TrES-3b displays a near isothermal dayside
atmospheric temperature structure, whose spectrum is well approximated by a
blackbody. We emphasize that our strict H-band limit is in stark disagreement
with the best-fit atmospheric model that results from longer wavelength
observations only, thus highlighting the importance of near-infrared
observations at multiple wavelengths in addition to those returned by Spitzer
in the mid-infrared to facilitate a comprehensive understanding of the energy
budgets of transiting exoplanets.Comment: ApJ accepted, 8 pages, 7 figures, in EmulateApJ forma
Worlds Beyond: A Strategy for the Detection and Characterization of Exoplanets Executive Summary of a Report of the ExoPlanet Task Force Astronomy and Astrophysics Advisory Committee Washington, DC June 23, 2008
[No abstract
NLTT 41135: a field M-dwarf + brown dwarf eclipsing binary in a triple system, discovered by the MEarth observatory
We report the discovery of an eclipsing companion to NLTT 41135, a nearby M5
dwarf that was already known to have a wider, slightly more massive common
proper motion companion, NLTT 41136, at 2.4 arcsec separation. Analysis of
combined-light and radial velocity curves of the system indicates that NLTT
41135B is a 31-34 +/- 3 MJup brown dwarf (where the range depends on the
unknown metallicity of the host star) on a circular orbit. The visual M-dwarf
pair appears to be physically bound, so the system forms a hierarchical triple,
with masses approximately in the ratio 8:6:1. The eclipses are grazing,
preventing an unambiguous measurement of the secondary radius, but follow-up
observations of the secondary eclipse (e.g. with the James Webb Space
Telescope) could permit measurements of the surface brightness ratio between
the two objects, and thus place constraints on models of brown dwarfs.Comment: 15 pages, 6 figures, 10 tables, emulateapj format. Accepted for
publication in Ap
A Spitzer Transmission Spectrum for the Exoplanet GJ 436b, Evidence for Stellar Variability, and Constraints on Dayside Flux Variations
In this paper we describe a uniform analysis of eight transits and eleven
secondary eclipses of the extrasolar planet GJ 436b obtained in the 3.6, 4.5,
and 8.0 micron bands using the IRAC instrument on the Spitzer Space Telescope
between UT 2007 June 29 and UT 2009 Feb 4. We find that the best-fit transit
depths for visits in the same bandpass can vary by as much as 8% of the total
(4.7 sigma significance) from one epoch to the next. Although we cannot
entirely rule out residual detector effects or a time-varying, high-altitude
cloud layer in the planet's atmosphere as the cause of these variations, we
consider the occultation of active regions on the star in a subset of the
transit observations to be the most likely explanation. We reconcile the
presence of magnetically active regions with the lack of significant visible or
infrared flux variations from the star by proposing that the star's spin axis
is tilted with respect to our line of sight, and that the planet's orbit is
therefore likely to be misaligned. These observations serve to illustrate the
challenges associated with transmission spectroscopy of planets orbiting
late-type stars; we expect that other systems, such as GJ 1214, may display
comparably variable transit depths. Our measured 8 micron secondary eclipse
depths are consistent with a constant value, and we place a 1 sigma upper limit
of 17% on changes in the planet's dayside flux in this band. Averaging over the
eleven visits gives us an improved estimate of 0.0452% +/- 0.0027% for the
secondary eclipse depth. We combine timing information from our observations
with previously published data to produce a refined orbital ephemeris, and
determine that the best-fit transit and eclipse times are consistent with a
constant orbital period. [ABRIDGED]Comment: 26 pages, 18 figures, 7 tables in emulateapj format. Accepted for
publication in Ap
Secondary Eclipse Photometry of WASP-4b with Warm Spitzer
We present photometry of the giant extrasolar planet WASP-4b at 3.6 and 4.5
micron taken with the Infrared Array Camera on board the Spitzer Space
Telescope as part of Spitzer's extended warm mission. We find secondary eclipse
depths of 0.319+/-0.031% and 0.343+/-0.027% for the 3.6 and 4.5 micron bands,
respectively and show model emission spectra and pressure-temperature profiles
for the planetary atmosphere. These eclipse depths are well fit by model
emission spectra with water and other molecules in absorption, similar to those
used for TrES-3 and HD 189733b. Depending on our choice of model, these results
indicate that this planet has either a weak dayside temperature inversion or no
inversion at all. The absence of a strong thermal inversion on this highly
irradiated planet is contrary to the idea that highly irradiated planets are
expected to have inversions, perhaps due the presence of an unknown absorber in
the upper atmosphere. This result might be explained by the modestly enhanced
activity level of WASP-4b's G7V host star, which could increase the amount of
UV flux received by the planet, therefore reducing the abundance of the unknown
stratospheric absorber in the planetary atmosphere as suggested in Knutson et
al. (2010). We also find no evidence for an offset in the timing of the
secondary eclipse and place a 2 sigma upper limit on |ecos(omega)| of 0.0024,
which constrains the range of tidal heating models that could explain this
planet's inflated radius.Comment: 8 pages, 7 figures (some in color), accepted for publication in Ap
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