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 M sin i = ...5.35 + or - 0.75 M sub(+ in circle), orbital period P = 11.4433 + or - 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 + or - 0.0021 R sub(middot in circle) based on interferometry from CHARA.
Abstract
Measured spectral shifts due to intrinsic stellar variability (e.g., pulsations, granulation) and activity (e.g., spots, plages) are the largest source of error for extreme-precision ...radial-velocity (EPRV) exoplanet detection. Several methods are designed to disentangle stellar signals from true center-of-mass shifts due to planets. The Extreme-precision Spectrograph (EXPRES) Stellar Signals Project (ESSP) presents a self-consistent comparison of 22 different methods tested on the same extreme-precision spectroscopic data from EXPRES. Methods derived new activity indicators, constructed models for mapping an indicator to the needed radial-velocity (RV) correction, or separated out shape- and shift-driven RV components. Since no ground truth is known when using real data, relative method performance is assessed using the total and nightly scatter of returned RVs and agreement between the results of different methods. Nearly all submitted methods return a lower RV rms than classic linear decorrelation, but no method is yet consistently reducing the RV rms to sub-meter-per-second levels. There is a concerning lack of agreement between the RVs returned by different methods. These results suggest that continued progress in this field necessitates increased interpretability of methods, high-cadence data to capture stellar signals at all timescales, and continued tests like the ESSP using consistent data sets with more advanced metrics for method performance. Future comparisons should make use of various well-characterized data sets—such as solar data or data with known injected planetary and/or stellar signals—to better understand method performance and whether planetary signals are preserved.
We present observations of six transits and six eclipses of the transiting planet system HD 189733 taken with the Spitzer Space Telescope IRAC camera at 8 microns, as well as a re-analysis of ...previously published data. We use several novel techniques in our data analysis, the most important of which is a new correction for the detector 'ramp' variation with a double-exponential function which performs better and is a better physical model for this detector variation. Our main scientific findings are: (1) an upper limit on the variability of the day-side planet flux of 2.7% (68% confidence); (2) the most precise set of transit times measured for a transiting planet, with an average accuracy of 3 seconds; (3) a lack of transit-timing variations, excluding the presence of second planets in this system above 20% of the mass of Mars in low-order mean-motion resonance at 95% confidence; (4) a confirmation of the planet's phase variation, finding the night side is 64% as bright as the day side, as well as an upper limit on the night-side variability of 17% (68% confidence); (5) a better correction for stellar variability at 8 micron causing the phase function to peak 3.5 hours before secondary eclipse, confirming that the advection and radiation timescales are comparable at the 8 micron photosphere; (6) variation in the depth of transit, which possibly implies variations in the surface brightness of the portion of the star occulted by the planet, posing a fundamental limit on non-simultaneous multi-wavelength transit absorption measurements of planet atmospheres; (7) a measurement of the infrared limb-darkening of the star, which is in good agreement with stellar atmosphere models; (8) an offset in the times of secondary eclipse of 69 seconds, which is mostly accounted for by a 31 second light travel time delay and 33 second delay due to the shift of ingress and egress by the planet hot spot; this confirms that the phase variation is due to an offset hot spot on the planet; (9) a retraction of the claimed eccentricity of this system due to the offset of secondary eclipse, which is now just an upper limit; and (10) high precision measurements of the parameters of this system. These results were enabled by the exquisite photometric precision of the Spitzer IRAC camera; for repeat observations the scatter is less than 0.35 mmag over the 590 day time scale of our observations after decorrelating with detector parameters.
It is important to explore the diversity of characteristics of low-mass, low-density planets to understand the nature and evolution of this class of planets. We present a homogeneous analysis of 12 ...new and 9 previously published broad-band photometric observations of the Uranus-sized extrasolar planet GJ 3470b, which belongs to the growing sample of sub-Jovian bodies orbiting M dwarfs. The consistency of our analysis explains some of the discrepancies between previously published results and provides updated constraints on the planetary parameters. Our data are also consistent with previous transit observations of this system. The physical properties of the transiting system can only be constrained as well as the host star is characterized, so we provide new spectroscopic measurements of GJ 3470 from 0.33 to 2.42 μm to aid our analysis. We find R
* = 0.48 ± 0.04 R⊙, M
* = 0.51 ± 0.06 M⊙, and T
eff = 3652 ± 50K for GJ 3470, along with a rotation period of 20.70 ± 0.15 d and an R-band amplitude of 0.01 mag, which is small enough that current transit measurements should not be strongly affected by stellar variability. However, to report definitively whether stellar activity has a significant effect on the light curves, this requires future multiwavelength, multi-epoch studies of GJ 3470. We also present the most precise orbital ephemeris for this system: T
o
= 2455983.70472 ± 0.00021BJDTDB, P = 3.336 6487
$^{+0.000\,0043}_{-0.000\,0033}$
d, and we see no evidence for transit timing variations greater than 1 min. Our reported planet to star radius ratio is 0.076 42 ± 0.000 37. The physical parameters of this planet are R
p = 3.88 ± 0.32 R⊕ and M
p = 13.73 ± 1.61 M⊕. Because of our revised stellar parameters, the planetary radius we present is smaller than previously reported values. We also perform a second analysis of the transmission spectrum of the entire ensemble of transit observations to date, supporting the existence of an H2-dominated atmosphere exhibiting a strong Rayleigh scattering slope.
Abstract
To accurately characterize the planets a star may be hosting, stellar parameters must first be well determined.
τ
Ceti is a nearby solar analog and often a target for exoplanet searches. ...Uncertainties in the observed rotational velocities have made constraining
τ
Ceti’s inclination difficult. For planet candidates from radial velocity (RV) observations, this leads to substantial uncertainties in the planetary masses, as only the minimum mass (
m
sin
i
) can be constrained with RV. In this paper, we used new long-baseline optical interferometric data from the CHARA Array with the MIRC-X beam combiner and extreme precision spectroscopic data from the Lowell Discovery Telescope with EXPRES to improve constraints on the stellar parameters of
τ
Ceti. Additional archival data were obtained from a Tennessee State University Automatic Photometric Telescope and the Mount Wilson Observatory HK project. These new and archival data sets led to improved stellar parameter determinations, including a limb-darkened angular diameter of 2.019 ± 0.012 mas and rotation period of 46 ± 4 days. By combining parameters from our data sets, we obtained an estimate for the stellar inclination of 7° ± 7°. This nearly pole-on orientation has implications for the previously reported exoplanets. An analysis of the system dynamics suggests that the planetary architecture described by Feng et al. may not retain long-term stability for low orbital inclinations. Additionally, the inclination of
τ
Ceti reveals a misalignment between the inclinations of the stellar rotation axis and the previously measured debris disk rotation axis (
i
disk
= 35° ± 10°).
IMPORTANCE In 2003, the first phase of duty hour requirements for US residency programs recommended by the Accreditation Council for Graduate Medical Education (ACGME) was implemented. Evidence ...suggests that this first phase of duty hour requirements resulted in a modest improvement in resident well-being and patient safety. To build on these initial changes, the ACGME recommended a new set of duty hour requirements that took effect in July 2011. OBJECTIVE To determine the effects of the 2011 duty hour reforms on first-year residents (interns) and their patients. DESIGN As part of the Intern Health Study, we conducted a longitudinal cohort study comparing interns serving before (2009 and 2010) and interns serving after (2011) the implementation of the new duty hour requirements. SETTING Fifty-one residency programs at 14 university and community-based GME institutions. PARTICIPANTS A total of 2323 medical interns. MAIN OUTCOME MEASURES Self-reported duty hours, hours of sleep, depressive symptoms, well-being, and medical errors at 3, 6, 9, and 12 months of the internship year. RESULTS Fifty-eight percent of invited interns chose to participate in the study. Reported duty hours decreased from an average of 67.0 hours per week before the new rules to 64.3 hours per week after the new rules were instituted (P < .001). Despite the decrease in duty hours, there were no significant changes in hours slept (6.8 → 7.0; P = .17), depressive symptoms (5.8 → 5.7; P = .55) or well-being score (48.5 → 48.4; P = .86) reported by interns. With the new duty hour rules, the percentage of interns who reported concern about making a serious medical error increased from 19.9% to 23.3% (P = .007). CONCLUSIONS AND RELEVANCE Although interns report working fewer hours under the new duty hour restrictions, this decrease has not been accompanied by an increase in hours of sleep or an improvement in depressive symptoms or well-being but has been accompanied by an unanticipated increase in self-reported medical errors.
Abstract
We present a new optical transmission spectrum of the hot Jupiter WASP-79b. We observed three transits with the STIS instrument mounted on the Hubble Space Telescope (HST), spanning 0.3–1.0
...μ
m. Combining these transits with previous observations, we construct a complete 0.3–5.0
μ
m transmission spectrum of WASP-79b. Both HST and ground-based observations show decreasing transit depths toward blue wavelengths, contrary to expectations from Rayleigh scattering or hazes. We infer atmospheric and stellar properties from the full near-UV to infrared transmission spectrum of WASP-79b using three independent retrieval codes, all of which yield consistent results. Our retrievals confirm previous detections of H
2
O (at 4.0
σ
confidence) while providing moderate evidence of H
−
bound–free opacity (3.3
σ
) and strong evidence of stellar contamination from unocculted faculae (4.7
σ
). The retrieved H
2
O abundance (∼1%) suggests a superstellar atmospheric metallicity, though stellar or substellar abundances remain consistent with present observations (O/H = 0.3–34× stellar). All three retrieval codes obtain a precise H
−
abundance constraint: log(
X
H
−
) ≈ −8.0 ± 0.7. The potential presence of H
−
suggests that James Webb Space Telescope observations may be sensitive to ionic chemistry in the atmosphere of WASP-79b. The inferred faculae are ∼500 K hotter than the stellar photosphere, covering ∼15% of the stellar surface. Our analysis underscores the importance of observing UV–optical transmission spectra in order to disentangle the influence of unocculted stellar heterogeneities from planetary transmission spectra.
The five-stage Society for Cardiovascular Angiography and Intervention (SCAI) cardiogenic shock classification scheme can stratify hospital mortality risk in patients admitted to the cardiac ...intensive care unit (CICU). We sought to evaluate the SCAI shock classification for prediction of post-discharge mortality in CICU survivors.
We retrospectively analyzed hospital survivors admitted to a single CICU between 2007 and 2015. SCAI CS stages A through E were classified using CICU admission data using a previously published algorithm. All-cause post-discharge mortality was compared across SCAI stages using Kaplan-Meier analysis and Cox proportional hazards models.
Among 9096 unique hospital survivors, 43.2% had acute coronary syndrome (ACS), 44.6% had heart failure (HF), and 8.7% had cardiac arrest (CA) on admission. The proportion of patients in each SCAI shock stage was: A, 49.1%; B, 30.6%; C, 15.2; D/E 5.2%. Kaplan-Meier survival at 5 years in each SCAI shock stage was: A, 88.2%; B, 81.6%; C, 76.7%; D/E, 71.7% (P < .001 by log-rank). Each higher SCAI shock stage was associated with increased adjusted post-discharge mortality compared to SCAI shock stage A (all P < .001); results were consistent among patients with ACS or HF. Late hemodynamic deterioration after 24 hours, but not an admission diagnosis of CA, was associated with higher post-discharge mortality.
The SCAI shock classification assessed at the time of CICU admission was predictive of post-discharge mortality risk among hospital survivors, although an admission diagnosis of CA was not. The SCAI shock classification can be used for post-discharge mortality risk stratification.
From an extensive number of newly acquired radial velocities we determine the orbital elements for three late-type dwarf systems, HD 96511, HR 7578, and KZ And. The orbital periods are 18.89737 ...0.00002, 46.81610 0.00006, and 3.0329113 0.0000005 days, respectively, and all three systems are eccentric, although KZ And is just barely so. We have detected lines of the secondary of HD 96511 for the first time. The orbital dimensions (a1 sin i and a2 sin i) and minimum masses (m1 sin3 i and m2 sin3 i) of the binary components all have accuracies of 0.2% or better. Extensive photometry of the chromospherically active binary HR 7578 confirms a rather long rotation period of 16.446 0.002 days and that the K3 V components do not eclipse. We have estimated the basic properties of the stars in the three systems and compared those results with evolutionary tracks. The results for KZ And that we computed with the revised Hipparcos parallax of van Leeuwen produce inconsistencies. That parallax appears to be too large, and so, instead, we used the original Hipparcos parallax of the common proper motion primary, which improves the results, although some problems remain.
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