276 research outputs found
Marshall University Music Department Presents the MU Guitar Ensemble
https://mds.marshall.edu/music_perf/1280/thumbnail.jp
Hubble Space Telescope Near-IR Transmission Spectroscopy of the Super-Earth HD 97658b
Recent results from the Kepler mission indicate that super-Earths (planets
with masses between 1-10 times that of the Earth) are the most common kind of
planet around nearby Sun-like stars. These planets have no direct solar system
analogue, and are currently one of the least well-understood classes of
extrasolar planets. Many super-Earths have average densities that are
consistent with a broad range of bulk compositions, including both
water-dominated worlds and rocky planets covered by a thick hydrogen and helium
atmosphere. Measurements of the transmission spectra of these planets offer the
opportunity to resolve this degeneracy by directly constraining the scale
heights and corresponding mean molecular weights of their atmospheres. We
present Hubble Space Telescope near-infrared spectroscopy of two transits of
the newly discovered transiting super-Earth HD 97658b. We use the Wide Field
Camera 3's scanning mode to measure the wavelength-dependent transit depth in
thirty individual bandpasses. Our averaged differential transmission spectrum
has a median 1 sigma uncertainty of 23 ppm in individual bins, making this the
most precise observation of an exoplanetary transmission spectrum obtained with
WFC3 to date. Our data are inconsistent with a cloud-free solar metallicity
atmosphere at the 10 sigma level. They are consistent at the 0.4 sigma level
with a flat line model, as well as effectively flat models corresponding to a
metal-rich atmosphere or a solar metallicity atmosphere with a cloud or haze
layer located at pressures of 10 mbar or higher.Comment: ApJ in press; revised version includes an updated orbital ephemeris
for the plane
An HST/STIS Optical Transmission Spectrum of Warm Neptune GJ 436b
GJ 436b is a prime target for understanding warm Neptune exoplanet
atmospheres and a target for multiple JWST GTO programs. Here, we report the
first space-based optical transmission spectrum of the planet using two
HST/STIS transit observations from 0.53-1.03 microns. We find no evidence for
alkali absorption features, nor evidence of a scattering slope longward of 0.53
microns. The spectrum is indicative of moderate to high metallicity (~100-1000x
solar) while moderate metallicity scenarios (~100x solar) require aerosol
opacity. The optical spectrum also rules out some highly scattering haze
models. We find an increase in transit depth around 0.8 microns in the
transmission spectra of 3 different sub-Jovian exoplanets (GJ 436b, HAT-P-26b,
and GJ 1214b). While most of the data come from STIS, data from three other
instruments may indicate this is not an instrumental effect. Only the transit
spectrum of GJ 1214b is well fit by a model with stellar plages on the
photosphere of the host star. Our photometric monitoring of the host star
reveals a stellar rotation rate of 44.1 days and an activity cycle of 7.4
years. Intriguingly, GJ 436 does not become redder as it gets dimmer, which is
expected if star spots were dominating the variability. These insights into the
nature of the GJ 436 system help refine our expectations for future
observations in the era of JWST, whose higher precision and broader wavelength
coverage will shed light on the composition and structure of GJ 436b's
atmosphere.Comment: 20 pages, 11 figures, 5 tables, Accepted to AJ. A full version of
table 1 is included as table1_mrt.tx
A Precise Water Abundance Measurement for the Hot Jupiter WASP-43b
The water abundance in a planetary atmosphere provides a key constraint on
the planet's primordial origins because water ice is expected to play an
important role in the core accretion model of planet formation. However, the
water content of the Solar System giant planets is not well known because water
is sequestered in clouds deep in their atmospheres. By contrast, short-period
exoplanets have such high temperatures that their atmospheres have water in the
gas phase, making it possible to measure the water abundance for these objects.
We present a precise determination of the water abundance in the atmosphere of
the 2 short-period exoplanet WASP-43b based on thermal
emission and transmission spectroscopy measurements obtained with the Hubble
Space Telescope. We find the water content is consistent with the value
expected in a solar composition gas at planetary temperatures (0.4-3.5x solar
at 1 confidence). The metallicity of WASP-43b's atmosphere suggested
by this result extends the trend observed in the Solar System of lower metal
enrichment for higher planet masses.Comment: Accepted to ApJL; this version contains three supplemental figures
that are not included in the published paper. See also our companion paper
"Thermal structure of an exoplanet atmosphere from phase-resolved emission
spectroscopy" by Stevenson et a
Fan Responses of Sponsored Environmental Sustainability Initiatives
The sport sector is advancing its efforts to be environmentally friendly. These efforts now include corporate sponsored environmental initiatives, yet fans’ responsiveness to such efforts remains unexamined. Specifically, in this study, the corporate-sponsored environmental initiatives of a college athletic department with an established history of environmental commitments were examined to evaluate the influence of a point of attachment, sport brand-sustainability fit, and receptivity to messaging on the sport organization’s desired outcomes of the campaign (i.e., sustainability behavioral, support for environmental initiative corporate partner). Data were collected from college football fans of an institution in the United States Midwest region using an internet-based survey after the 2019 football season (N = 548). We found that most of our hypotheses were supported. Specifically, attachment to athletics, athletics/sustainability fit, and ascription of responsibility to athletics explained 52.7% of the variance of receptivity to messaging from athletics. In turn, receptivity to sustainable messaging and behaviors explained 45.0% of the support for corporate partners. Our results show that sport practitioners should evaluate the ascription of responsibility their fans place on the sport organization to be environmentally responsible, increasing the receptivity of environmental messages and desired outcomes from such efforts. In addition, this study shows the versatility and applicability of the model to actual sponsored environmental sustainability campaigns of a sport organization
Updated Parameters and a New Transmission Spectrum of HD 97658b
Recent years have seen increasing interest in the characterization of sub-Neptune-sized planets because of their prevalence in the Galaxy, contrasted with their absence in our solar system. HD 97658 is one of the brightest stars hosting a planet of this kind, and we present the transmission spectrum of this planet by combining four Hubble Space Telescope transits, 12 Spitzer/IRAC transits, and eight MOST transits of this system. Our transmission spectrum has a higher signal-to-noise ratio than those from previous works, and the result suggests that the slight increase in transit depth from wavelength 1.1–1.7 μm reported in previous works on the transmission spectrum of this planet is likely systematic. Nonetheless, our atmospheric modeling results are inconclusive, as no model provides an excellent match to our data. Nonetheless, we find that atmospheres with high C/O ratios (C/O ≳ 0.8) and metallicities of ≳100× solar metallicity are favored. We combine the mid-transit times from all of the new Spitzer and MOST observations and obtain an updated orbital period of P = 9.489295 ± 0.000005, with a best-fit transit time center at T₀ = 2456361.80690 ± 0.00038 (BJD). No transit timing variations are found in this system. We also present new measurements of the stellar rotation period (34 ± 2 days) and stellar activity cycle (9.6 yr) of the host star HD 97658. Finally, we calculate and rank the Transmission Spectroscopy Metric of all confirmed planets cooler than 1000 K and with sizes between 1 R⊕ and 4 R⊕. We find that at least a third of small planets cooler than 1000 K can be well characterized using James Webb Space Telescope, and of those, HD 97658b is ranked fifth, meaning that it remains a high-priority target for atmospheric characterization
The Flat Transmission Spectrum of the Super-Earth GJ1214b from Wide Field Camera 3 on the Hubble Space Telescope
Capitalizing on the observational advantage offered by its tiny M dwarf host,
we present HST/WFC3 grism measurements of the transmission spectrum of the
super-Earth exoplanet GJ1214b. These are the first published WFC3 observations
of a transiting exoplanet atmosphere. After correcting for a ramp-like
instrumental systematic, we achieve nearly photon-limited precision in these
observations, finding the transmission spectrum of GJ1214b to be flat between
1.1 and 1.7 microns. Inconsistent with a cloud-free solar composition
atmosphere at 8.2 sigma, the measured achromatic transit depth most likely
implies a large mean molecular weight for GJ1214b's outer envelope. A dense
atmosphere rules out bulk compositions for GJ1214b that explain its large
radius by the presence of a very low density gas layer surrounding the planet.
High-altitude clouds can alternatively explain the flat transmission spectrum,
but they would need to be optically thick up to 10 mbar or consist of particles
with a range of sizes approaching 1 micron in diameter.Comment: 17 pages, 12 figures, accepted for publication in Ap
Water Vapor and Clouds on the Habitable-zone Sub-Neptune Exoplanet K2-18b
Results from the Kepler mission indicate that the occurrence rate of small planets (<3 R⊕) in the habitable zone of nearby low-mass stars may be as high as 80%. Despite this abundance, probing the conditions and atmospheric properties on any habitable-zone planet is extremely difficult and has remained elusive to date. Here, we report the detection of water vapor and the likely presence of liquid and icy water clouds in the atmosphere of the 2.6 R ⊕ habitable-zone planet K2-18b. The simultaneous detection of water vapor and clouds in the mid-atmosphere of K2-18b is particularly intriguing because K2-18b receives virtually the same amount of total insolation from its host star (1368^(+114)_(-107) W m⁻²) as the Earth receives from the Sun (1361 W m⁻²), resulting in the right conditions for water vapor to condense and explain the detected clouds. In this study we observed nine transits of K2-18b using Hubble Space Telescope/WFC3 in order to achieve the necessary sensitivity to detect the water vapor, and we supplement this data set with Spitzer and K2 observations to obtain a broader wavelength coverage. While the thick hydrogen-dominated envelope we detect on K2-18b means that the planet is not a true Earth analog, our observations demonstrate that low-mass habitable-zone planets with the right conditions for liquid water are accessible with state-of-the-art telescopes
Water Vapor and Clouds on the Habitable-Zone Sub-Neptune Exoplanet K2-18b
Results from the Kepler mission indicate that the occurrence rate of small
planets ( ) in the habitable zone of nearby low-mass stars may be
as high as 80%. Despite this abundance, probing the conditions and atmospheric
properties on any habitable-zone planet is extremely difficult and has remained
elusive to date. Here, we report the detection of water vapor and the likely
presence of liquid and icy water clouds in the atmosphere of the
habitable-zone planet K2-18b. The simultaneous detection of water
vapor and clouds in the mid-atmosphere of K2-18b is particularly intriguing
because K2-18b receives virtually the same amount of total insolation from its
host star ( W m) as the Earth receives from the Sun
(1361 W m), resulting in the right conditions for water vapor to
condense and explain the detected clouds. In this study, we observed nine
transits of K2-18b using HST/WFC3 in order to achieve the necessary sensitivity
to detect the water vapor, and we supplement this data set with Spitzer and K2
observations to obtain a broader wavelength coverage. While the thick
hydrogen-dominated envelope we detect on K2-18b means that the planet is not a
true Earth analog, our observations demonstrate that low-mass habitable-zone
planets with the right conditions for liquid water are accessible with
state-of-the-art telescopes.Comment: Published in ApJL, includes important updates to stellar and planet
parameter
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