58 research outputs found
The American Bar Association Joint Task Force on Reversing the School-to-Prison Pipeline Preliminary Report
In 2014, the American Bar Association (ABA) Coalition on Racial and Ethnic Justice (COREJ) turned its attention to the continuing failures in the education system where certain groups of students — for example, students of color, with disabilities, or LGBTQ — are disproportionately over- or incorrectly categorized in special education, are disciplined more harshly, including referral to law enforcement for minimal misbehavior, achieve at lower levels, and eventually drop or are pushed out of school, often into juvenile justice facilities and prisons — a pattern now commonly referred to as the School-to-Prison Pipeline. While this problem certainly is not new, it presented a convergence of several laws, policies, and practices where the legal community’s intervention is critical. Joined by the ABA Pipeline Council and Criminal Justice Section, and supported by its sister ABA entities, COREJ sponsored a series of eight Town Halls across the country to investigate the issues surrounding this pipeline. The focus of these Town Halls was to 1) explore the issues as they presented themselves for various groups and various locales; 2) gather testimony on solutions that showed success, with particular focus on interventions where the legal community could be most effective in interrupting and reversing the School-to-Prison Pipeline; and 3) draw attention to the role implicit bias plays in creating and maintaining this pipeline. This report is a result of those convenings
The MUSCLES Treasury Survey. II. Intrinsic Lyα and extreme ultraviolet spectra of K and M dwarfs with exoplanets
This work was supported by NASA grants HST-GO-12464.01 and HST-GO-13650.01 to the University of Colorado at Boulder. Sarah Rugheimer would like to acknowledge support from the Simons Foundation (339489, Rugheimer).The ultraviolet (UV) spectral energy distributions (SEDs) of low-mass (K- and M-type) stars play a critical role in the heating and chemistry of exoplanet atmospheres, but are not observationally well-constrained. Direct observations of the intrinsic flux of the Lyα line (the dominant source of UV photons from low-mass stars) are challenging, as interstellar H i absorbs the entire line core for even the closest stars. To address the existing gap in empirical constraints on the UV flux of K and M dwarfs, the MUSCLES Hubble Space Telescope Treasury Survey has obtained UV observations of 11 nearby M and K dwarfs hosting exoplanets. This paper presents the Lyα and extreme-UV spectral reconstructions for the MUSCLES targets. Most targets are optically inactive, but all exhibit significant UV activity. We use a Markov Chain Monte Carlo technique to correct the observed Lyα profiles for interstellar absorption, and we employ empirical relations to compute the extreme-UV SED from the intrinsic Lyα flux in ∼100 bins from 100-1170. The reconstructed Lyα profiles have 300 km s-1 broad cores, while >1% of the total intrinsic Lyα flux is measured in extended wings between 300 and 1200 km s-1. The Lyα surface flux positively correlates with the Mg ii surface flux and negatively correlates with the stellar rotation period. Stars with larger Lyα surface flux also tend to have larger surface flux in ions formed at higher temperatures, but these correlations remain statistically insignificant in our sample of 11 stars. We also present H i column density measurements for 10 new sightlines through the local interstellar medium.Publisher PDFPeer reviewe
Estimating the Ultraviolet Emission of M dwarfs with Exoplanets from Ca II and H
M dwarf stars are excellent candidates around which to search for exoplanets,
including temperate, Earth-sized planets. To evaluate the photochemistry of the
planetary atmosphere, it is essential to characterize the UV spectral energy
distribution of the planet's host star. This wavelength regime is important
because molecules in the planetary atmosphere such as oxygen and ozone have
highly wavelength dependent absorption cross sections that peak in the UV
(900-3200 ). We seek to provide a broadly applicable method of
estimating the UV emission of an M dwarf, without direct UV data, by
identifying a relationship between non-contemporaneous optical and UV
observations. Our work uses the largest sample of M dwarf star far- and near-UV
observations yet assembled. We evaluate three commonly-observed optical
chromospheric activity indices -- H equivalent widths and log
L/L, and the Mount Wilson Ca II H&K S and R indices
-- using optical spectra from the HARPS, UVES, and HIRES archives and new HIRES
spectra. Archival and new Hubble Space Telescope COS and STIS spectra are used
to measure line fluxes for the brightest chromospheric and transition region
emission lines between 1200-2800 . Our results show a correlation
between UV emission line luminosity normalized to the stellar bolometric
luminosity and Ca II R with standard deviations of 0.31-0.61 dex
(factors of 2-4) about the best-fit lines. We also find correlations
between normalized UV line luminosity and H log
L/L and the S index. These relationships allow one to
estimate the average UV emission from M0 to M9 dwarfs when UV data are not
available.Comment: 34 pages, 12 figures, 5 tables (one machine readable table available
online). Accepted to AAS Journal
Early Release Science of the exoplanet WASP-39b with JWST NIRCam
Measuring the metallicity and carbon-to-oxygen (C/O) ratio in exoplanet
atmospheres is a fundamental step towards constraining the dominant chemical
processes at work and, if in equilibrium, revealing planet formation histories.
Transmission spectroscopy provides the necessary means by constraining the
abundances of oxygen- and carbon-bearing species; however, this requires broad
wavelength coverage, moderate spectral resolution, and high precision that,
together, are not achievable with previous observatories. Now that JWST has
commenced science operations, we are able to observe exoplanets at previously
uncharted wavelengths and spectral resolutions. Here we report time-series
observations of the transiting exoplanet WASP-39b using JWST's Near InfraRed
Camera (NIRCam). The long-wavelength spectroscopic and short-wavelength
photometric light curves span 2.0 - 4.0 m, exhibit minimal systematics,
and reveal well-defined molecular absorption features in the planet's spectrum.
Specifically, we detect gaseous HO in the atmosphere and place an upper
limit on the abundance of CH. The otherwise prominent CO feature at 2.8
m is largely masked by HO. The best-fit chemical equilibrium models
favour an atmospheric metallicity of 1-100 solar (i.e., an enrichment
of elements heavier than helium relative to the Sun) and a sub-stellar
carbon-to-oxygen (C/O) ratio. The inferred high metallicity and low C/O ratio
may indicate significant accretion of solid materials during planet formation
or disequilibrium processes in the upper atmosphere.Comment: 35 pages, 13 figures, 3 tables, Nature, accepte
Early Release Science of the exoplanet WASP-39b with JWST NIRISS
Transmission spectroscopy provides insight into the atmospheric properties
and consequently the formation history, physics, and chemistry of transiting
exoplanets. However, obtaining precise inferences of atmospheric properties
from transmission spectra requires simultaneously measuring the strength and
shape of multiple spectral absorption features from a wide range of chemical
species. This has been challenging given the precision and wavelength coverage
of previous observatories. Here, we present the transmission spectrum of the
Saturn-mass exoplanet WASP-39b obtained using the SOSS mode of the NIRISS
instrument on the JWST. This spectrum spans m in wavelength and
reveals multiple water absorption bands, the potassium resonance doublet, as
well as signatures of clouds. The precision and broad wavelength coverage of
NIRISS-SOSS allows us to break model degeneracies between cloud properties and
the atmospheric composition of WASP-39b, favoring a heavy element enhancement
("metallicity") of the solar value, a sub-solar
carbon-to-oxygen (C/O) ratio, and a solar-to-super-solar potassium-to-oxygen
(K/O) ratio. The observations are best explained by wavelength-dependent,
non-gray clouds with inhomogeneous coverage of the planet's terminator.Comment: 48 pages, 12 figures, 2 tables. Under review at Natur
A broadband thermal emission spectrum of the ultra-hot Jupiter WASP-18b
Close-in giant exoplanets with temperatures greater than 2,000 K (''ultra-hot
Jupiters'') have been the subject of extensive efforts to determine their
atmospheric properties using thermal emission measurements from the Hubble and
Spitzer Space Telescopes. However, previous studies have yielded inconsistent
results because the small sizes of the spectral features and the limited
information content of the data resulted in high sensitivity to the varying
assumptions made in the treatment of instrument systematics and the atmospheric
retrieval analysis. Here we present a dayside thermal emission spectrum of the
ultra-hot Jupiter WASP-18b obtained with the NIRISS instrument on JWST. The
data span 0.85 to 2.85 m in wavelength at an average resolving power of
400 and exhibit minimal systematics. The spectrum shows three water emission
features (at 6 confidence) and evidence for optical opacity,
possibly due to H, TiO, and VO (combined significance of 3.8).
Models that fit the data require a thermal inversion, molecular dissociation as
predicted by chemical equilibrium, a solar heavy element abundance
(''metallicity'', M/H = 1.03 solar), and a
carbon-to-oxygen (C/O) ratio less than unity. The data also yield a dayside
brightness temperature map, which shows a peak in temperature near the
sub-stellar point that decreases steeply and symmetrically with longitude
toward the terminators.Comment: JWST ERS bright star observations. Uploaded to inform JWST Cycle 2
proposals. Manuscript under review. 50 pages, 14 figures, 2 table
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