483 research outputs found
The Frequency of Hot Jupiters in the Galaxy: Results from the SuperLupus Survey
We present the results of the SuperLupus Survey for transiting hot Jupiter planets, which monitored a single Galactic disk field spanning 0.66 deg2 for 108 nights over three years. Ten candidates were detected: one is a transiting planet, two remain candidates, and seven have been subsequently identified as false positives. We construct a new image quality metric, Sj , based on the behavior of 26,859 light curves, which allows us to discard poor images in an objective and quantitative manner. Furthermore, in some cases we are able to identify statistical false positives by analyzing temporal correlations between Sj and transit signatures. We use Monte Carlo simulations to measure our detection efficiency by injecting artificial transits onto real light curves and applying identical selection criteria as used in our survey. We find at 90% confidence level that 0.10+0.27- 0.08% of dwarf stars host a hot Jupiter with a period of 1-10 days. Our results are consistent with other transit surveys, but appear consistently lower than the hot Jupiter frequencies reported from radial velocity surveys, a difference we attribute, at least in part, to the difference in stellar populations probed. In light of our determination of the frequency of hot Jupiters in Galactic field stars, previous null results for transiting planets in open cluster and globular cluster surveys no longer appear anomalously low
Examining the broadband emission spectrum of WASP-19b: A new z band eclipse detection
WASP-19b is one of the most irradiated hot-Jupiters known. Its secondary
eclipse is the deepest of all transiting planets, and has been measured in
multiple optical and infrared bands. We obtained a z band eclipse observation,
with measured depth of 0.080 +/- 0.029 %, using the 2m Faulkes Telescope South,
that is consistent with the results of previous observations. We combine our
measurement of the z band eclipse with previous observations to explore
atmosphere models of WASP-19b that are consistent with the its broadband
spectrum. We use the VSTAR radiative transfer code to examine the effect of
varying pressure-temperature profiles and C/O abundance ratios on the emission
spectrum of the planet. We find models with super-solar carbon enrichment best
match the observations, consistent with previous model retrieval studies. We
also include upper atmosphere haze as another dimension in the interpretation
of exoplanet emission spectra, and find that particles <0.5 micron in size are
unlikely to be present in WASP-19b.Comment: 10 pages, 8 figures, 2 tables, accepted for publication in Ap
Measurement of the Nodal Precession of WASP-33 b via Doppler Tomography
We have analyzed new and archival time series spectra taken six years apart
during transits of the hot Jupiter WASP-33 b, and spectroscopically resolved
the line profile perturbation caused by the Rossiter-McLaughlin effect. The
motion of this line profile perturbation is determined by the path of the
planet across the stellar disk, which we show to have changed between the two
epochs due to nodal precession of the planetary orbit. We measured rates of
change of the impact parameter and the sky-projected spin-orbit misalignment of
yr and
~ yr, respectively,
corresponding to a rate of nodal precession of
~ yr. This is only the
second measurement of nodal precession for a confirmed exoplanet transiting a
single star. Finally, we used the rate of precession to set limits on the
stellar gravitational quadrupole moment of
.Comment: Published in ApJL. 5 pages, 3 figures. Corrected error in the
calculation of J_
Episodic disk accretion in the halo of the 'old' Pre-Main Sequence cluster Eta Chamaeleontis
We present multi-epoch medium-resolution observations of two M4.5 candidate
members in the halo of the ~8 Myr Eta Chamaeleontis open cluster. Over six
months of observations both stars exhibited variations in their H-alpha line
profiles on timescales of days to months, with at least one episode of
substantial activity attributable to accretion from a circumstellar disk. We
derive an accretion rate ~10^-8.7 Msun/yr for this event, with a rate of
~10^-10.6 Msun/yr in quiescence. Episodic accretion like that observed here
means existing surveys of accreting Weak-lined T-Tauri Stars in young clusters
are likely incomplete and that gas dissipation timescales calculated from the
fraction of accreting objects are underestimates.Comment: 5 pages, 5 figures, 1 table. Accepted for publication in MNRAS
Letter
SuperLupus: A Deep, Long Duration Transit Survey
SuperLupus is a deep transit survey monitoring a Galactic Plane field in the
Southern hemisphere. The project is building on the successful Lupus Survey,
and will double the number of images of the field from 1700 to 3400, making it
one of the longest duration deep transit surveys. The immediate motivation for
this expansion is to search for longer period transiting planets (5-8 days) and
smaller radii planets. It will also provide near complete recovery for the
shorter period planets (1-3 days). In March, April, and May 2008 we obtained
the new images and work is currently in progress reducing these new data.Comment: 3 pages, 2 figures, to appear in the Proceedings of IAU Symposium
253, 2008: Transiting Planet
Planets in Spin-Orbit Misalignment and the Search for Stellar Companions
The discovery of giant planets orbiting close to their host stars was one of
the most unexpected results of early exoplanetary science. Astronomers have
since found that a significant fraction of these 'Hot Jupiters' move on orbits
substantially misaligned with the rotation axis of their host star. We recently
reported the measurement of the spin-orbit misalignment for WASP-79b by using
data from the 3.9 m Anglo-Australian Telescope. Contemporary models of
planetary formation produce planets on nearly coplanar orbits with respect to
their host star's equator. We discuss the mechanisms which could drive planets
into spin-orbit misalignment. The most commonly proposed being the Kozai
mechanism, which requires the presence of a distant, massive companion to the
star-planet system. We therefore describe a volume-limited direct-imaging
survey of Hot Jupiter systems with measured spin-orbit angles, to search for
the presence of stellar companions and test the Kozai hypothesis.Comment: Accepted for publication in the peer-reviewed proceedings of the 13th
annual Australian Space Science Conferenc
An examination of the effect of the TESS extended mission on southern hemisphere monotransits
Context: NASA recently announced an extended mission for TESS. As a result it
is expected that the southern ecliptic hemisphere will be re-observed
approximately two years after the initial survey. Aims: We aim to explore how
TESS re-observing the southern ecliptic hemisphere will impact the number and
distribution of mono-transits discovered during the first year of observations.
This simulation will be able to be scaled to any future TESS re-observations.
Methods: We carry out an updated simulation of TESS detections in the southern
ecliptic hemisphere. This simulation includes realistic Sector window-functions
based on the first 11 sectors of SPOC 2 min SAP lightcurves. We then extend
this simulation to cover the expected Year 4 of the mission when TESS will
re-observed the southern ecliptic fields. For recovered monotransits we also
look at the possibility of predicting the period based on the coverage in the
TESS data. Results: We find an updated prediction of 339 monotransits from the
TESS Year 1 southern ecliptic hemisphere, and that approximately 80% of these
systems (266/339) will transit again in the Year 4 observations. The Year 4
observations will also contribute new monotransits not seen in Year 1,
resulting in a total of 149 monotransits from the combined Year 1 and Year 4
data sets. We find that 75% (189/266) of recovered Year 1 monotransits will
only transit once in the Year 4 data set. For these systems we will be able to
constrain possible periods, but period aliasing due to the large time gap
between Year 1 and Year 4 observations means that the true period will remain
unknown with further spectroscopic or photometric follow-up.Comment: 6 pages, 6 figures. Version to be published Astronomy and
Astrophysic
The occurrence rate of giant planets orbiting low-mass stars with TESS
We present a systematic search for transiting giant planets () orbiting nearby low-mass stars (). The formation of giant planets around low-mass stars is
predicted to be rare by the core-accretion planet formation theory. We search
91,306 low-mass stars in the TESS 30 minute cadence photometry detecting
fifteen giant planet candidates, including seven new planet candidates which
were not known planets or identified as TOIs prior to our search. Our
candidates present an exciting opportunity to improve our knowledge of the
giant planet population around the lowest mass stars. We perform planet
injection-recovery simulations and find that our pipeline has a high detection
efficiency across the majority of our targeted parameter space. We measure the
occurrence rates of giant planets with host stars in different stellar mass
ranges spanning our full sample. We find occurrence rates of %
(0.088 - 0.26 ), % (0.26 - 0.42 ), and
% (0.42 - 0.71 ). For our full sample (0.088 - 0.71
) we find a giant planet occurrence rate of %. We
have measured for the first time the occurrence rate for giant planets orbiting
stars with and we demonstrate this occurrence rate
to be non-zero. This result contradicts currently accepted planet formation
models and we discuss some possibilities for how these planets could have
formed.Comment: 20 pages, 14 figures. Accepted for publication in MNRA
A 3- and 6- Month Follow-Up to a Student-Led Approach to Patient Safety in Pre-Clinical Curriculum
Introduction: Preventable medical errors are currently the third leading cause of death in the United States following heart disease and cancer. In light of this, integration of formal patient safety education into undergraduate medical education has been encouraged by the World Health Organization. This study aimed to assess the change in patient safety knowledge, attitudes, and beliefs in students after early exposure to patient safety during pre-clinical years.
Methods: First and second-year medical students participated in the training and responses were assessed through a pre-test, immediate post-test, 3-month post-test, and 6-month post-test. The survey assessed student knowledge on aspects of patient safety, course of action in patient safety scenarios, and Likert scale questions on patient safety interest.
Results: Of the original 23 medical students, 12 and 7 students completed the 3-month and 6-month post-tests, respectively. Data showed improvement in students considering themselves to be well-versed in different aspects of patient safety in the 3-month post-test (33.3%; p-value=1.00) compared to the pre-test training (11.8%) but declined in the 6-month post-test (14.3%; p-value=1.00). The percent of students that agreed they plan to incorporate patient safety techniques into their future practice was 83% in the 3-month post-test (pre-test: 94.1%; p-value=1.00) and 100% in the 6-month post-test (p-value=1.00).
Conclusion: The improvement in students who considered themselves to be knowledgeable about patient safety and the high agreement to incorporate patient safety techniques is promising. This indicates the long-term influence that patient safety training can have in preclinical years and potentially in clerkship years
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