41 research outputs found
Behind Valencia: A Contemporary Play
SYNOPSIS The purpose of this play is to highlight the length that modern females go to in order to maintain a desired appearance, especially across social media. These desired appearances are influenced by the glamorous and unrealistic looks and physiques that are prevalent in the media. Essentially, the primary goal of these characters is to attract the attention of their male counterparts because of the gender roles society promotes. This shallow lifestyle can be completely consuming for impressionable, young females
G 68-34: A Double-Lined M-Dwarf Eclipsing Binary in a Hierarchical Triple System
Using high-resolution spectra from the Tillinghast Reflector Echelle
Spectrograph (TRES) and photometry from sector 56 of the Transiting Exoplanet
Survey Satellite (TESS), we report that the nearby M dwarf G 68-34 is a
double-lined eclipsing binary. The pair is spin-orbit synchronized with a
period of 0.655 days. The light curve shows significant spot modulation with a
larger photometric amplitude than that of the grazing eclipses. We perform a
joint fit to the spectroscopic and photometric data, obtaining masses of
M and M and radii of
R and R after marginalizing
over unknowns in the starspot distribution. This system adds to the small but
growing population of fully convective M dwarfs with precisely measured masses
and radii that can be used to test models of stellar structure. The pair also
has a white dwarf primary at 9" separation, with the system known to be older
than 5 Gyr from the white-dwarf cooling age. The binarity of G 68-34 confirms
our hypothesis from Pass et al. (2022): in that work, we noted that G 68-34 was
both rapidly rotating and old, highly unusual given our understanding of the
spindown of M dwarfs, and that a close binary companion may be responsible.Comment: Accepted for publication in ApJ, 10 pages, 5 figures, 3 table
Health Justice Education in the Time of Coronavirus (COVID-19): A Curriculum Review and Recommendations
Phase one of this study (Vardell & Charbonneau, 2020) sought to investigate the
intersections of health and social justice in library and information science (LIS) curriculum.
Course offerings from 60 ALA-Accredited LIS programs were extracted and comprised the study
sample. Using a thematic content analysis, a total of 220 course descriptions were analyzed to
assess the inclusion of health justice topics. Of the 220 courses identified using the health justice
search terms, only eight LIS course descriptions closely integrated health and social justice
issues. This poster will present four overarching thematic LIS course areas identified from the
212 courses that were not explicitly health justice related but nonetheless presented potential
health justice connections: 1) multicultural and diverse populations, 2) health sciences
information, 3) literacy concerns, and 4) social justice and libraries. These four thematic areas
present conceptual pathways with the potential to further incorporate health justice aspects in
LIS coursework. In phase two of the study, the focus of this work has expanded to include health
justice issues emerging during the COVID-19 public health crisis. Examples of how LIS
educators can make stronger connections in their courses between health justice issues during
public health crises, such as the COVID-19 pandemic, will be provided. Additionally, the
presenters are seeking feedback and examples from LIS educators to help shape the future of this
work and timely line of inquiry. Overall, this research initiative helps to map the curricula and
contributes the LIS educator viewpoint for advancing health justice conversations
Three Dimensional Modeling of Hot Jupiter Atmospheric Flows
We present a three dimensional hot Jupiter model, extending from 200 bar to 1
mbar, using the Intermediate General Circulation Model from the University of
Reading. Our horizontal spectral resolution is T31 (equivalent to a grid of
48x96), with 33 logarithmically spaced vertical levels. A simplified
(Newtonian) scheme is employed for the radiative forcing. We adopt a physical
set up nearly identical to the model of HD 209458b by Cooper & Showman
(2005,2006) to facilitate a direct model inter-comparison. Our results are
broadly consistent with theirs but significant differences also emerge. The
atmospheric flow is characterized by a super-rotating equatorial jet, transonic
wind speeds, and eastward advection of heat away from the dayside. We identify
a dynamically-induced temperature inversion ("stratosphere") on the planetary
dayside and find that temperatures at the planetary limb differ systematically
from local radiative equilibrium values, a potential source of bias for transit
spectroscopic interpretations. While our model atmosphere is quasi-identical to
that of Cooper & Showman (2005,2006) and we solve the same meteorological
equations, we use different algorithmic methods, spectral-implicit vs.
grid-explicit, which are known to yield fully consistent results in the Earth
modeling context. The model discrepancies identified here indicate that one or
both numerical methods do not faithfully capture all of the atmospheric
dynamics at work in the hot Jupiter context. We highlight the emergence of a
shock-like feature in our model, much like that reported recently by Showman et
al. (2009), and suggest that improved representations of energy conservation
may be needed in hot Jupiter atmospheric models, as emphasized by Goodman
(2009).Comment: 25 pages, 6 figures, minor revisions, ApJ accepted, version with
hi-res figures:
http://www.astro.columbia.edu/~kristen/Hires/hotjup.3d.deep.ps.g
Radiation-Hydrodynamics of Hot Jupiter Atmospheres
Radiative transfer in planetary atmospheres is usually treated in the static
limit, i.e., neglecting atmospheric motions. We argue that hot Jupiter
atmospheres, with possibly fast (sonic) wind speeds, may require a more
strongly coupled treatment, formally in the regime of radiation-hydrodynamics.
To lowest order in v/c, relativistic Doppler shifts distort line profiles along
optical paths with finite wind velocity gradients. This leads to flow-dependent
deviations in the effective emission and absorption properties of the
atmospheric medium. Evaluating the overall impact of these distortions on the
radiative structure of a dynamic atmosphere is non-trivial. We present
transmissivity and systematic equivalent width excess calculations which
suggest possibly important consequences for radiation transport in hot Jupiter
atmospheres. If winds are fast and bulk Doppler shifts are indeed important for
the global radiative balance, accurate modeling and reliable data
interpretation for hot Jupiter atmospheres may prove challenging: it would
involve anisotropic and dynamic radiative transfer in a coupled
radiation-hydrodynamical flow. On the bright side, it would also imply that the
emergent properties of hot Jupiter atmospheres are more direct tracers of their
atmospheric flows than is the case for Solar System planets.
Radiation-hydrodynamics may also influence radiative transfer in other classes
of hot exoplanetary atmospheres with fast winds.Comment: 25 pages, 4 figures, accepted for publication in ApJ (minor
revisions
Atmospheric Circulation of Hot Jupiters: A Shallow Three-Dimensional Model
Remote observing of exoplanetary atmospheres is now possible, offering us
access to circulation regimes unlike any of the familiar Solar System cases.
Atmospheric circulation models are being developed to study these new regimes
but model validations and intercomparisons are needed to establish their
consistency and accuracy. To this end, we present a simple Earth-like
validation of the pseudo-spectral solver of meteorological equations called
IGCM (Intermediate General Circulation Model), based on Newtonian relaxation to
a prescribed latitudinal profile of equilibrium temperatures. We then describe
a straightforward and idealized model extension to the atmospheric flow on a
hot Jupiter with the same IGCM solver. This shallow, three-dimensional hot
Jupiter model is based on Newtonian relaxation to a permanent day-night pattern
of equilibrium temperatures and the absence of surface drag. The baroclinic
regime of the Earth's lower atmosphere is contrasted with the more barotropic
regime of the simulated hot Jupiter flow. For plausible conditions at the 0.1-1
bar pressure level on HD 209458b, the simulated flow is characterized by
unsteadiness, subsonic wind speeds, a zonally-perturbed superrotating
equatorial jet and large scale polar vortices. Violation of the Rayleigh-Kuo
inflexion point criterion on the flanks of the accelerating equatorial jet
indicates that barotropic (horizontal shear) instabilities may be important
dynamical features of the simulated flow. Similarities and differences with
previously published simulated hot Jupiter flows are briefly noted.Comment: 31 pages, 9 figures, accepted for publication in ApJ. Version with
hi-res figures:
http://www.astro.columbia.edu/~kristen/Hires/hotjup.3d.shallow.ps.g
Ohmic Dissipation in the Atmospheres of Hot Jupiters
Hot Jupiter atmospheres exhibit fast, weakly-ionized winds. The interaction
of these winds with the planetary magnetic field generates drag on the winds
and leads to ohmic dissipation of the induced electric currents. We study the
magnitude of ohmic dissipation in representative, three-dimensional atmospheric
circulation models of the hot Jupiter HD 209458b. We find that ohmic
dissipation can reach or exceed 1% of the stellar insolation power in the
deepest atmospheric layers, in models with and without dragged winds. Such
power, dissipated in the deep atmosphere, appears sufficient to slow down
planetary contraction and explain the typically inflated radii of hot Jupiters.
This atmospheric scenario does not require a top insulating layer or radial
currents that penetrate deep in the planetary interior. Circulation in the
deepest atmospheric layers may actually be driven by spatially non-uniform
ohmic dissipation. A consistent treatment of magnetic drag and ohmic
dissipation is required to further elucidate the consequences of magnetic
effects for the atmospheres and the contracting interiors of hot Jupiters.Comment: Accepted to the Astrophysical Journa
Active Stars in the Spectroscopic Survey of Mid-to-Late M Dwarfs Within 15pc
We present results from the volume-complete spectroscopic survey of
0.1-0.3M M dwarfs within 15pc. This work discusses the active sample
without close binary companions, providing a comprehensive picture of these 123
stars with H emission stronger than -1\unicode{xC5}. Our analysis
includes rotation periods (including 31 new measurements), H
equivalent widths, rotational broadening, inclinations, and radial velocities,
determined using high-resolution, multi-epoch spectroscopic data from the TRES
and CHIRON spectrographs supplemented by photometry from TESS and MEarth. Using
this volume-complete sample, we establish that the majority of active, low-mass
M dwarfs are very rapid rotators: specifically, 744% have rotation periods
shorter than 2 days, while 194% have intermediate rotation periods of 2-20
days, and the remaining 83% have periods longer than 20 days. Among the
latter group, we identify a population of stars with very high H
emission, which we suggest is indicative of dramatic spindown as these stars
transition from the rapidly to slowly rotating modes. We are unable to
determine rotation periods for six stars and suggest that some of the stars
without measured rotation periods may be viewed pole-on, as such stars are
absent from the distribution of inclinations we measure; this lack
notwithstanding, we recover the expected isotropic distribution of spin axes.
Our spectroscopic and photometric data sets also allow us to investigate
activity-induced radial-velocity variability, which we show can be estimated as
the product of rotational broadening and the photometric amplitude of spot
modulation.Comment: Accepted for publication in AJ; 18 pages, 12 figures, 3 table
A General Circulation Model for Gaseous Exoplanets with Double-Gray Radiative Transfer
We present a new version of our code for modeling the atmospheric circulation
on gaseous exoplanets, now employing a "double-gray" radiative transfer scheme,
which self-consistently solves for fluxes and heating throughout the
atmosphere, including the emerging (observable) infrared flux. We separate the
radiation into infrared and optical components, each with its own absorption
coefficient, and solve standard two-stream radiative transfer equations. We use
a constant optical absorption coefficient, while the infrared coefficient can
scale as a powerlaw with pressure. Here we describe our new code in detail and
demonstrate its utility by presenting a generic hot Jupiter model. We discuss
issues related to modeling the deepest pressures of the atmosphere and describe
our use of the diffusion approximation for radiative fluxes at high optical
depths. In addition, we present new models using a simple form for magnetic
drag on the atmosphere. We calculate emitted thermal phase curves and find that
our drag-free model has the brightest region of the atmosphere offset by ~12
degrees from the substellar point and a minimum flux that is 17% of the
maximum, while the model with the strongest magnetic drag has an offset of only
~2 degrees and a ratio of 13%. Finally, we calculate rates of numerical loss of
kinetic energy at ~15% for every model except for our strong-drag model, where
there is no measurable loss; we speculate that this is due to the much
decreased wind speeds in that model.Comment: 29 pages, 12 figures, 2 tables, submitted to Ap
HST/WFC3 Light Curve Confirms the Closest Exoplanet to Transit an M Dwarf is Terrestrial
Previous studies of the exoplanet LTT 1445Ac concluded that the light curve
from the Transiting Exoplanet Survey Satellite (TESS) was consistent with both
grazing and non-grazing geometries. As a result, the radius and hence density
of the planet remained unknown. To resolve this ambiguity, we observed the LTT
1445 system for six spacecraft orbits of the Hubble Space Telescope (HST) using
WFC3/UVIS imaging in spatial scan mode, including one partial transit of LTT
1445Ac. This imaging produces resolved light curves of each of the three stars
in the LTT 1445 system. We confirm that the planet transits LTT 1445A and that
LTT 1445C is the source of the rotational modulation seen in the TESS light
curve, and we refine the estimate of the dilution factor for the TESS data. We
perform a joint fit to the TESS and HST observations, finding that the transit
of LTT 1445Ac is not grazing with 97% confidence. We measure a planetary radius
of 1.10 R. Combined with previous radial velocity
observations, our analysis yields a planetary mass of M
and a planetary density of 5.6 g cm. LTT 1445Ac is an
Earth analog with respect to its mass and radius, albeit with a higher
instellation, and is therefore an exciting target for future atmospheric
studies.Comment: Submitted to AJ. 9 pages, 7 figures, 3 table