491 research outputs found
Search for Rayleigh scattering in the atmosphere of GJ1214b
We investigate the atmosphere of GJ1214b, a transiting super-Earth planet
with a low mean density, by measuring its transit depth as a function of
wavelength in the blue optical portion of the spectrum. It is thought that this
planet is either a mini-Neptune, consisting of a rocky core with a thick,
hydrogen-rich atmosphere, or a planet with a composition dominated by water.
Most observations favor a water-dominated atmosphere with a small scale-height,
however, some observations indicate that GJ1214b could have an extended
atmosphere with a cloud layer muting the molecular features. In an atmosphere
with a large scale-height, Rayleigh scattering at blue wavelengths is likely to
cause a measurable increase in the apparent size of the planet towards the
blue. We observed the transit of GJ1214b in the B-band with the FOcal Reducing
Spectrograph (FORS) at the Very Large Telescope (VLT) and in the g-band with
both ACAM on the William Hershel Telescope (WHT) and the Wide Field Camera
(WFC) at the Isaac Newton Telescope (INT). We find a planet-to-star radius
ratio in the B-band of 0.1162+/-0.0017, and in the g-band 0.1180+/-0.0009 and
0.1174+/-0.0017 for the WHT & INT observations respectively. These optical data
do not show significant deviations from previous measurements at longer
wavelengths. In fact, a flat transmission spectrum across all wavelengths best
describes the combined observations. When atmospheric models are considered a
small scale-height water-dominated model fits the data best.Comment: Accepted for publication in Ap
Obesity Prevalence and Dietary Intake of Antioxidants in Native American Adolescents
Antioxidants are well known for possessing anti-inflammatory properties, which can reduce the risk of chronic disease and obesity. However, very little research has been done to examine antioxidant intake among adolescent minority populations such as Native American adolescents. Our study examined the significance of antioxidant intake among Native American adolescents at an urban residential high school in Southern California. Our study population consisted of 183 male and female Native American adolescents, 14-18 years of age, representing 43 tribes from across the United States. Students' primary source of meals was provided by the school food service. Based on the BMI calculations, the rate of obesity within our population was 38% for males and 40% for females, more than two-fold the national rate indicated by NHANESIII data. We used the Harvard School of Public Health Youth/Adolescent Questionnaire (HSPH YAQ), a semi-quantitative food frequency questionnaire, to examine antioxidant nutrient intake and evaluate the differences in the intake between normal and obese weight students. Statistical analysis of the results showed that intakes of vitamins C, E, and lycopene were the antioxidant nutrients found to be significantly different between normal and obese weight students and intakes of these nutrients were found to be higher among normal weight students (p-values = 0.02451, 0.00847, and 0.04928, respectively). These results suggest that dietary intake of antioxidants could be increased among Native American adolescents. Further research is needed to confirm our findings and identify effective ways for school food service to incorporate antioxidant rich foods into school menus
Transit Photometry with the LCOGT Network
Within a single year, we deployed and commissioned a total of seven 1m telescopes to three sites (McDonald Observatory, CTIO and SAAO). These are complemented by two existing 2m telescopes, located in the northern (Haleakala) and southern (Siding Spring Observatory) hemispheres. Before the end of 2013, one additional 1m telescope will be deployed at McDonald Observatory, and two at Siding Spring Observatory, which will complete the southern ring and enable continuous LCOGT dark time in the southern hemisphere. We present transit observations acquired at each site with currently-deployed 1m telescopes. These data demonstrate some of the network's unique capabilities, such as simultaneous transit observations from multiple sites and construction of full transits by combining partial transit light curves from two sites. Such exercises pave the path toward searching for and characterizing transits of long period exoplanets, simultaneous multi-color transit observations, as well as studying spot distributions and rotation periods of exoplanet host stars using the LCOGT network
Effects of Orbital Eccentricity on Extrasolar Planet Transit Detection and Lightcurves
It is shown herein that planets with eccentric orbits are more likely to
transit than circularly orbiting planets with the same semimajor axis by a
factor of (1-e^2)^{-1}. If the orbital parameters of discovered transiting
planets are known, as from follow-up radial velocity observations, then the
transit-detected planet population is easily debiased of this effect. The
duration of a planet's transit depends upon of its eccentricity and longitude
of periastron; transits near periastron are shorter, and those near apoastron
last longer, for a given impact parameter. If fitting for the stellar radius
with the other transit parameters, this effect causes a systematic error in the
resulting measurements. If the stellar radius is instead held fixed at a value
measured independently, then it is possible to place a lower limit on the
planet's eccentricity using photometry alone. Orbital accelerations cause a
difference in the planet's ingress and egress durations that lead to an
asymmetry in the transit lightcurve that could be used along with the transit
velocity measurement to uniquely measure the planet's eccentricity and
longitude of periapsis. However, the effect is too small to be measured with
current technology. The habitability of transiting terrestrial planets found by
Kepler depends on those planets' orbital eccentricities. While Kepler will be
able to place lower limits on those planets' orbital eccentricity, the actual
value for any given planet will likely remain unknown.Comment: 8 pages, 6 figures, to appear in PASP 2007 Septembe
A Super-Earth Transiting a Naked-Eye Star
We have detected transits of the innermost planet "e" orbiting 55 Cnc
(V=6.0), based on two weeks of nearly continuous photometric monitoring with
the MOST space telescope. The transits occur with the period (0.74 d) and phase
that had been predicted by Dawson & Fabrycky, and with the expected duration
and depth for the crossing of a Sun-like star by a hot super-Earth. Assuming
the star's mass and radius to be 0.963_{-0.029}^{+0.051} M_sun and 0.943 +/-
0.010 R_sun, the planet's mass, radius, and mean density are 8.63 +/- 0.35
Mearth, 2.00 +/- 0.14 Rearth, and 5.9_{-1.1}^{+1.5} g/cm^3. The mean density is
comparable to that of Earth, despite the greater mass and consequently greater
compression of the interior of 55 Cnc e. This suggests a rock-iron composition
supplemented by a significant mass of water, gas, or other light elements.
Outside of transits, we detected a sinusoidal signal resembling the expected
signal due to the changing illuminated phase of the planet, but with a full
range (168 +/- 70 ppm) too large to be reflected light or thermal emission.
This signal has no straightforward interpretation and should be checked with
further observations. The host star of 55 Cnc e is brighter than that of any
other known transiting planet, which will facilitate future investigations.Comment: ApJ Letters, in press (v3) Minor changes/clarifications; (v2) Revised
after fixing an error in the data reduction pipeline; for details see
http://web.mit.edu/~jwinn/www/55cnc_response.tx
New configurations for Peruvian cinema: the rising star of Claudia Llosa
After a decade-long hiatus during which the existence of a home-grown cinema in Peru had been threatened by a lack of government and public support, a new generation
of directors broke onto the scene in the twenty-first century with a distinctive approach to both the production and circulation of their films, as well as to their relationship with the ‘national’, in terms of policy, funding and audience engagement.
This study takes one of those directors, Claudia Llosa, as the main case study, and considers the development of her profile as an internationally recognized Peruvian film-maker whose award-winning debut works (Madeinusa, 2006 and La Teta Asustada/Milk of Sorrow, 2009) sparked controversy and critical debate for their challenging portrayals of the Quechua culture of Peru. This article examines
her successes on the international festival and commercial exhibition circuits, considers some of the scholarly and critical responses to her work, and asks what impact Llosa has had on the development of cinema in Peru through her engagement with the transnational
The GROUSE project III: Ks-band observations of the thermal emission from WASP-33b
In recent years, day-side emission from about a dozen hot Jupiters has been
detected through ground-based secondary eclipse observations in the
near-infrared. These near-infrared observations are vital for determining the
energy budgets of hot Jupiters, since they probe the planet's spectral energy
distribution near its peak. The aim of this work is to measure the Ks-band
secondary eclipse depth of WASP-33b, the first planet discovered to transit an
A-type star. This planet receives the highest level of irradiation of all
transiting planets discovered to date. Furthermore, its host-star shows
pulsations and is classified as a low-amplitude delta-Scuti. As part of our
GROUnd-based Secondary Eclipse (GROUSE) project we have obtained observations
of two separate secondary eclipses of WASP-33b in the Ks-band using the LIRIS
instrument on the William Herschel Telescope (WHT). The telescope was
significantly defocused to avoid saturation of the detector for this bright
star (K~7.5). To increase the stability and the cadence of the observations,
they were performed in staring mode. We collected a total of 5100 and 6900
frames for the first and the second night respectively, both with an average
cadence of 3.3 seconds. On the second night the eclipse is detected at the
12-sigma level, with a measured eclipse depth of 0.244+0.027-0.020 %. This
eclipse depth corresponds to a brightness temperature of 3270+115-160 K. The
measured brightness temperature on the second night is consistent with the
expected equilibrium temperature for a planet with a very low albedo and a
rapid re-radiation of the absorbed stellar light. For the other night the short
out-of-eclipse baseline prevents good corrections for the stellar pulsations
and systematic effects, which makes this dataset unreliable for eclipse depth
measurements. This demonstrates the need of getting a sufficient out-of-eclipse
baseline.Comment: 12 pages, 10 figures. Accepted for publication in Astronomy and
Astrophysic
The GROUSE project II: Detection of the Ks-band secondary eclipse of exoplanet HAT-P-1b
Context: Only recently it has become possible to measure the thermal emission
from hot-Jupiters at near-Infrared wavelengths using ground-based telescopes,
by secondary eclipse observations. This allows the planet flux to be probed
around the peak of its spectral energy distribution, which is vital for the
understanding of its energy budget. Aims: The aim of the reported work is to
measure the eclipse depth of the planet HAT-P-1b at 2.2micron. This planet is
an interesting case, since the amount of stellar irradiation it receives falls
in between that of the two best studied systems (HD209458 and HD189733), and it
has been suggested to have a weak thermal inversion layer. Methods: We have
used the LIRIS instrument on the William Herschel Telescope (WHT) to observe
the secondary eclipse of HATP-1b in the Ks-band, as part of our Ground-based
secondary eclipse (GROUSE) project. The observations were done in staring mode,
while significantly defocusing the telescope to avoid saturation on the K=8.4
star. With an average cadence of 2.5 seconds, we collected 6520 frames during
one night. Results: The eclipse is detected at the 4sigma level, the measured
depth being 0.109+/-0.025%. The uncertainties are dominated by residual
systematic effects, as estimated from different reduction/analysis procedures.
The measured depth corresponds to a brightness temperature of 2136+150-170K.
This brightness temperature is significantly higher than those derived from
longer wavelengths, making it difficult to fit all available data points with a
plausible atmospheric model. However, it may be that we underestimate the true
uncertainties of our measurements, since it is notoriously difficult to assign
precise statistical significance to a result when systematic effects are
important.Comment: 7 pages, 10 figures, Accepted for publication in A&
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