679 research outputs found
Improving Transit Predictions of Known Exoplanets with TERMS
Transiting planet discoveries have largely been restricted to the
short-period or low-periastron distance regimes due to the bias inherent in the
geometric transit probability. Through the refinement of planetary orbital
parameters, and hence reducing the size of transit windows, long-period planets
become feasible targets for photometric follow-up. Here we describe the TERMS
project that is monitoring these host stars at predicted transit times.Comment: 3 pages, 2 figures, to be published in ASP Conf. Proceedings:
"Detection and dynamics of transiting exoplanets" 2010, OHP, France (eds.: F.
Bouchy, R.F. D{\i}az, C. Moutou
The NASA-UC-UH Eta-Earth Program: IV. A Low-mass Planet Orbiting an M Dwarf 3.6 PC from Earth
We report the discovery of a low-mass planet orbiting Gl 15 A based on radial
velocities from the Eta-Earth Survey using HIRES at Keck Observatory. Gl 15 Ab
is a planet with minimum mass Msini = 5.35 0.75 M, orbital
period P = 11.4433 0.0016 days, and an orbit that is consistent with
circular. We characterize the host star using a variety of techniques.
Photometric observations at Fairborn Observatory show no evidence for
rotational modulation of spots at the orbital period to a limit of ~0.1 mmag,
thus supporting the existence of the planet. We detect a second RV signal with
a period of 44 days that we attribute to rotational modulation of stellar
surface features, as confirmed by optical photometry and the Ca II H & K
activity indicator. Using infrared spectroscopy from Palomar-TripleSpec, we
measure an M2 V spectral type and a sub-solar metallicity ([M/H] = -0.22,
[Fe/H] = -0.32). We measure a stellar radius of 0.3863 0.0021 R
based on interferometry from CHARA.Comment: ApJ accepted, 11 pages, 8 figures, 3 table
Improved Orbital Parameters and Transit Monitoring for HD 156846b
HD 156846b is a Jovian planet in a highly eccentric orbit (e = 0.85) with a
period of 359.55 days. The pericenter passage at a distance of 0.16 AU is
nearly aligned to our line of sight, offering an enhanced transit probability
of 5.4% and a potentially rich probe of the dynamics of a cool planetary
atmosphere impulsively heated during close approach to a bright star (V = 6.5).
We present new radial velocity (RV) and photometric measurements of this star
as part of the Transit Ephemeris Refinement and Monitoring Survey (TERMS). The
RV measurements from Keck-HIRES reduce the predicted transit time uncertainty
to 20 minutes, an order of magnitude improvement over the ephemeris from the
discovery paper. We photometrically monitored a predicted transit window under
relatively poor photometric conditions, from which our non-detection does not
rule out a transiting geometry. We also present photometry that demonstrates
stability at the millimag level over its rotational timescale.Comment: 7 pages, 4 figures, accepted for publication in Ap
The HD 192263 system: planetary orbital period and stellar variability disentangled
As part of the Transit Ephemeris Refinement and Monitoring Survey (TERMS), we
present new radial velocities and photometry of the HD 192263 system. Our
analysis of the already available Keck-HIRES and CORALIE radial velocity
measurements together with the five new Keck measurements we report in this
paper results in improved orbital parameters for the system. We derive
constraints on the size and phase location of the transit window for HD
192263b, a Jupiter-mass planet with a period of 24.3587 \pm 0.0022 days. We use
10 years of Automated Photoelectric Telescope (APT) photometry to analyze the
stellar variability and search for planetary transits. We find continuing
evidence of spot activity with periods near 23.4 days. The shape of the
corresponding photometric variations changes over time, giving rise to not one
but several Fourier peaks near this value. However, none of these frequencies
coincides with the planet's orbital period and thus we find no evidence of
star-planet interactions in the system. We attribute the ~23-day variability to
stellar rotation. There are also indications of spot variations on longer (8
years) timescales. Finally, we use the photometric data to exclude transits for
a planet with the predicted radius of 1.09 RJ, and as small as 0.79 RJ.Comment: 9 pages, 6 tables, 6 figures; accepted to Ap
A Comprehensive Characterization of the 70 Virgins Planetary System
An on-going effort in the characterization of exoplanetary systems is the accurate determination of host star properties. This effort extends to the relatively bright host stars of planets discovered with the radial velocity method. The Transit Ephemeris Refinement and Monitoring Survey (TERMS) is aiding in these efforts as part of its observational campaign for exoplanet host stars. One of the first known systems is that of 70 Virginis, which harbors a jovian planet in an eccentric orbit. Here we present a complete characterization of this system with a compilation of TERMS photometry, spectroscopy, and interferometry. We provide fundamental properties of the host star through direct interferometric measurements of the radius (1.5% uncertainty) and through spectroscopic analysis. We combined 59 new Keck HIRES radial velocity measurements with the 169 previously published from the ELODIE, Hamilton, and HIRES spectrographs, to calculate a refined orbital solution and construct a transit ephemeris for the planet. These newly determined system characteristics are used to describe the Habitable Zone of the system with a discussion of possible additional planets and related stability simulations. Finally, we present 19 years of precision robotic photometry that constrain stellar activity and rule out central planetary transits for a Jupiter-radius planet at the 5σ level, with reduced significance down to an impact parameter of b = 0.95
Clinical features, diagnosis, and survival analysis of dogs with glioma
Background:
Gliomas in dogs remain poorly understood.
Objectives:
To characterize the clinicopathologic findings, diagnostic imaging features and survival of a large sample of dogs with glioma using the Comparative Brain Tumor Consortium diagnostic classification.
Animals:
Ninety-one dogs with histopathological diagnosis of glioma.
Methods:
Multicentric retrospective case series. Signalment, clinicopathologic findings, diagnostic imaging characteristics, treatment, and outcome were used. Tumors were reclassified according to the new canine glioma diagnostic scheme.
Results:
No associations were found between clinicopathologic findings or survival and tumor type or grade. However, definitive treatments provided significantly (P = .03) improved median survival time (84 days; 95% confidence interval [CI], 45-190) compared to palliative treatment (26 days; 95% CI, 11-54). On magnetic resonance imaging (MRI), oligodendrogliomas were associated with smooth margins and T1-weighted hypointensity compared to astrocytomas (odds ratio [OR], 42.5; 95% CI, 2.42-744.97; P = .04; OR, 45.5; 95% CI, 5.78-333.33; P < .001, respectively) and undefined gliomas (OR, 84; 95% CI, 3.43-999.99; P = .02; OR, 32.3; 95% CI, 2.51-500.00; P = .008, respectively) and were more commonly in contact with the ventricles than astrocytomas (OR, 7.47; 95% CI, 1.03-53.95; P = .049). Tumor spread to neighboring brain structures was associated with high-grade glioma (OR, 6.02; 95% CI, 1.06-34.48; P = .04).
Conclusions and Clinical Importance:
Dogs with gliomas have poor outcomes, but risk factors identified in survival analysis inform prognosis and the newly identified MRI characteristics could refine diagnosis of tumor type and grade
A Search for the Transit of HD 168443b: Improved Orbital Parameters and Photometry
The discovery of transiting planets around bright stars holds the potential
to greatly enhance our understanding of planetary atmospheres. In this work we
present the search for transits of HD 168443b, a massive planet orbiting the
bright star HD 168443 V=6.92 with a period of 58.11 days. The high eccentricity
of the planetary orbit e=0.53 significantly enhances the a-priori transit
probability beyond that expected for a circular orbit, making HD 168443 a
candidate for our ongoing Transit Ephemeris Refinement and Monitoring Survey
(TERMS). Using additional radial velocities from Keck-HIRES, we refined the
orbital parameters of this multi-planet system and derived a new transit
ephemeris for HD 168443b. The reduced uncertainties in the transit window make
a photometric transit search practicable. Photometric observations acquired
during predicted transit windows were obtained on three nights. CTIO 1.0 m
photometry acquired on 2010 September 7 had the required precision to detect a
transit but fell just outside of our final transit window. Nightly photometry
from the T8 0.8 m Automated Photometric Telescope (APT) at Fairborn
Observatory, acquired over a span of 109 nights, demonstrates that HD 168443 is
constant on a time scale of weeks. Higher-cadence photometry on 2011 April 28
and June 25 shows no evidence of a transit. We are able to rule out a
non-grazing transit of HD 168443b.Comment: Accepted in ApJ. 25 pages. 8 Figure
Limited effects of long-term daily cranberry consumption on the gut microbiome in a placebo-controlled study of women with recurrent urinary tract infections
Background: Urinary tract infections (UTIs) affect 15 million women each year in the United States, with > 20% experiencing frequent recurrent UTIs. A recent placebo-controlled clinical trial found a 39% reduction in UTI symptoms among recurrent UTI sufferers who consumed a daily cranberry beverage for 24 weeks. Using metagenomic sequencing of stool from a subset of these trial participants, we assessed the impact of cranberry consumption on the gut microbiota, a reservoir for UTI-causing pathogens such as Escherichia coli, which causes > 80% of UTIs.
Results: The overall taxonomic composition, community diversity, carriage of functional pathways and gene families, and relative abundances of the vast majority of observed bacterial taxa, including E. coli, were not changed significantly by cranberry consumption. However, one unnamed Flavonifractor species (OTU41), which represented ≤1% of the overall metagenome, was significantly less abundant in cranberry consumers compared to placebo at trial completion. Given Flavonifractor’s association with negative human health effects, we sought to determine OTU41 characteristic genes that may explain its differential abundance and/or relationship to key host functions. Using comparative genomic and metagenomic techniques, we identified genes in OTU41 related to transport and metabolism of various compounds, including tryptophan and cobalamin, which have been shown to play roles in host-microbe interactions.
Conclusion: While our results indicated that cranberry juice consumption had little impact on global measures of the microbiome, we found one unnamed Flavonifractor species differed significantly between study arms. This suggests further studies are needed to assess the role of cranberry consumption and Flavonifractor in health and wellbeing in the context of recurrent UTI.
Trial registration: Clinical trial registration number: ClinicalTrials.govNCT01776021
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