Abstract
Nearby active stars with relatively rapid rotation and large starspot structures offer the opportunity to compare interferometric, spectroscopic, and photometric imaging techniques. In this ...paper, we image a spotted star with three different methods for the first time. The giant primary star of the RS Canum Venaticorum binary
σ
Geminorum (
σ
Gem) was imaged for two epochs of interferometric, high-resolution spectroscopic, and photometric observations. The light curves from the reconstructions show good agreement with the observed light curves, supported by the longitudinally consistent spot features on the different maps. However, there is strong disagreement in the spot latitudes across the methods.
We present an analysis of approx5 years of Lick Observatory radial velocity measurements targeting a uniform sample of 31 intermediate-mass (IM) subgiants (1.5 approx< M{sub *}/M{sub sun}approx< 2.0) ...with the goal of measuring the occurrence rate of Jovian planets around (evolved) A-type stars and comparing the distributions of their orbital and physical characteristics to those of planets around Sun-like stars. We provide updated orbital solutions incorporating new radial velocity measurements for five known planet-hosting stars in our sample; uncertainties in the fitted parameters are assessed using a Markov-Chain Monte Carlo method. The frequency of Jovian planets interior to 3 AU is 26{sup +9}{sub -8}%, which is significantly higher than the 5%-10% frequency observed around solar-mass stars. The median detection threshold for our sample includes minimum masses down to left brace0.2, 0.3, 0.5, 0.6, 1.3right brace M{sub Jup} within left brace0.1, 0.3, 0.6, 1.0, 3.0right brace AU. To compare the properties of planets around IM stars to those around solar-mass stars we synthesize a population of planets based on the parametric relationship dN propor to M {sup a}lpha P {sup b}eta dlnMdlnP, the observed planet frequency, and the detection limits we derived. We find that the values of alpha and beta for planets around solar-type stars from Cumming et al. fail to reproduce the observed properties of planets in our sample at the 4sigma level, even when accounting for the different planet occurrence rates. Thus, the properties of planets around A stars are markedly different than those around Sun-like stars, suggesting that only a small (approx50%) increase in stellar mass has a large influence on the formation and orbital evolution of planets.
Abstract
We have obtained high-dispersion spectroscopy and
BV
photometry of two F-type eclipsing binaries, HD 71636 and V1022 Cas, plus the A-type system OT And. Transiting Exoplanet Survey Satellite ...measurements for each system have also been incorporated. The photometry of HD 71636 enables a more consistent picture of this 5.01331 days, circular-orbit system to emerge. The F2 V primary has a mass of 1.506 ± 0.002
M
☉
and a radius of 1.583 ± 0.024
R
☉
. The mass of the F5 V secondary is 1.282 ± 0.002
M
☉
, and its radius is 1.314 ± 0.030
R
☉
. Comparison with evolutionary models of the Modules for Experiments in Stellar Astrophysics (MESA) series results in a good fit for a composition of Fe/H = 0.12 and an age of 0.9 Gyr. For the F6 V stars of V1022 Cas, our analysis produces a period of 12.15616 days and an eccentricity of 0.312. The two components have nearly equal masses of 1.626 ± 0.001
M
☉
and 1.607 ± 0.001
M
☉
. The radii of the primary and secondary are 2.570 ± 0.021
R
☉
and 2.445 ± 0.022
R
☉
, respectively. Comparison with the MESA evolutionary models results in Fe/H = 0.08 and an age of 1.87 Gyr. OT And consists of a pair of similar mid-A stars that have an orbital period of 20.85292 days and an eccentricity of 0.215. The primary has a mass of 2.253 ± 0.014
M
☉
and a radius of 3.167 ± 0.013
R
☉
. The corresponding parameters for the secondary are 2.147 ± 0.011
M
☉
and 2.649 ± 0.015
R
☉
, respectively. The MESA series models produce a best fit for this system with Fe/H = 0.10 and an age of 0.675 Gyr. The total apsidal motion in both eccentric systems is less than 1.°5 century
−1
.
Abstract
HD 166620 was recently identified as a Maunder minimum candidate based on nearly 50 years of Ca
ii
H and K activity data from Mount Wilson and Keck HIRES. These data showed clear cyclic ...behavior on a 17 yr timescale during the Mount Wilson survey that became flat when picked up later with Keck HIRES planet-search observations. Unfortunately, the transition between these two data sets—and therefore the transition into the candidate Maunder minimum phase—contained little to no data. Here, we present additional Mount Wilson data not present in Baum et al., along with photometry over a nearly 30 yr baseline that definitively traces the transition from cyclic activity to a prolonged phase of flat activity. We present this as conclusive evidence of the star entering a grand magnetic minimum and therefore the first true Maunder minimum analog. We further show that neither the overall brightness nor the chromospheric activity level (as measured by
S
HK
) is significantly lower during the grand magnetic minimum than its activity cycle minimum, implying that an anomalously low mean or instantaneous activity levels are not a good diagnostic or criterion for identifying additional Maunder minimum candidates. Intraseasonal variability in
S
HK
, however,
is
lower in the star’s grand minimum; this may prove a useful symptom of the phenomenon.
We present an in-depth analysis of stellar activity and its effects on radial velocity (RV) for the M2 dwarf GJ 176 based on spectra taken over 10 yr from the High Resolution Spectrograph on the ...Hobby-Eberly Telescope. These data are supplemented with spectra from previous observations with the HIRES and HARPS spectrographs, and V- and R-band photometry taken over six years at the Dyer and Fairborn observatories. Previous studies of GJ 176 revealed a super-Earth exoplanet in an 8.8-day orbit. However, the velocities of this star are also known to be contaminated by activity, particularly at the 39-day stellar rotation period. We have examined the magnetic activity of GJ 176 using the sodium I D lines, which have been shown to be a sensitive activity tracer in cool stars. In addition to rotational modulation, we see evidence of a long-term trend in our Na I D index, which may be part of a long-period activity cycle. The sodium index is well correlated with our RVs, and we show that this activity trend drives a corresponding slope in RV. Interestingly, the rotation signal remains in phase in photometry, but not in the spectral activity indicators. We interpret this phenomenon as the result of one or more large spot complexes or active regions which dominate the photometric variability, while the spectral indices are driven by the overall magnetic activity across the stellar surface. In light of these results, we discuss the potential for correcting activity signals in the RVs of M dwarfs.
We present a new optical (400-950 nm) transmission spectrum of the hot Jupiter WASP-31b (M = 0.48 MJ; R = 1.54 RJ; P = 3.41 days), obtained by combining four transit observations. These transits were ...observed with IMACS on the Magellan Baade Telescope at Las Campanas Observatory as part of the ACCESS project. We investigate the presence of clouds/hazes in the upper atmosphere of this planet, as well as the contribution of stellar activity on the observed features. In addition, we search for absorption features of the alkali elements Na i and K i, with particular focus on K i, for which there have been two previously published disagreeing results. Observations with Hubble Space Telescope (HST)/STIS detected K i, whereas ground-based low- and high-resolution observations did not. We use equilibrium and nonequilibrium chemistry retrievals to explore the planetary and stellar parameter space of the system with our optical data combined with existing near-IR observations. Our best-fit model is that with a scattering slope consistent with a Rayleigh slope ( ), high-altitude clouds at a log cloud top pressure of −3.6 bars, and possible muted H2O features. We find that our observations support other ground-based claims of no K i. Clouds are likely why signals like H2O are extremely muted and Na or K cannot be detected. We then juxtapose our Magellan/IMACS transmission spectrum with existing VLT/FORS2, HST/WFC3, HST/STIS, and Spitzer observations to further constrain the optical-to-infrared atmospheric features of the planet. We find that a steeper scattering slope ( = 8.3 1.5) is anchored by STIS wavelengths blueward of 400 nm and only the original STIS observations show significant potassium signal.
Abstract
We present a comprehensive analysis of the 0.3–5
μ
m transit spectrum for the inflated hot Jupiter HAT-P-41b. The planet was observed in transit with Hubble STIS and WFC3 as part of the ...Hubble Panchromatic Comparative Exoplanet Treasury (PanCET) program, and we combine those data with warm Spitzer transit observations. We extract transit depths from each of the data sets, presenting the STIS transit spectrum (0.29–0.93
μ
m) for the first time. We retrieve the transit spectrum both with a free-chemistry retrieval suite (AURA) and a complementary chemical equilibrium retrieval suite (PLATON) to constrain the atmospheric properties at the day–night terminator. Both methods provide an excellent fit to the observed spectrum. Both AURA and PLATON retrieve a metal-rich atmosphere for almost all model assumptions (most likely O/H ratio of
and
, respectively); this is driven by a 4.9
σ
detection of H
2
O as well as evidence of gas absorption in the optical (>2.7
σ
detection) due to Na, AlO, and/or VO/TiO, though no individual species is strongly detected. Both retrievals determine the transit spectrum to be consistent with a clear atmosphere, with no evidence of haze or high-altitude clouds. Interior modeling constraints on the maximum atmospheric metallicity (
) favor the AURA results. The inferred elemental oxygen abundance suggests that HAT-P-41b has one of the most metal-rich atmospheres of any hot Jupiters known to date. Overall, the inferred high metallicity and high inflation make HAT-P-41b an interesting test case for planet formation theories.
ABSTRACT We present simultaneous ground-based radial velocity (RV) measurements and space-based photometric measurements of the young and active K dwarf Epsilon Eridani. These measurements provide a ...data set for exploring methods of identifying and ultimately distinguishing stellar photospheric velocities from Keplerian motion. We compare three methods we have used in exploring this data set: Dalmatian, an MCMC spot modeling code that fits photometric and RV measurements simultaneously; the FF′ method, which uses photometric measurements to predict the stellar activity signal in simultaneous RV measurements; and H analysis. We show that our H measurements are strongly correlated with the Microvariability and Oscillations of STars telescope (MOST) photometry, which led to a promising new method based solely on the spectroscopic observations. This new method, which we refer to as the HH′ method, uses H measurements as input into the FF′ model. While the Dalmatian spot modeling analysis and the FF′ method with MOST space-based photometry are currently more robust, the HH′ method only makes use of one of the thousands of stellar lines in the visible spectrum. By leveraging additional spectral activity indicators, we believe the HH′ method may prove quite useful in disentangling stellar signals.
Here we present the analysis of multi-epoch secondary eclipse observations of HD 189733b and HD 209458b as a probe of temporal variability in the planetary climate using both Spitzer channels 1 and 2 ...(3.6 and 4.5 m). We expect hot-Jupiter atmospheres to be dynamic environments exhibiting time varying weather. However, it is uncertain to what extent temporal variability will be observable when considering disk integrated observations. We do not detect statistically significant variability and are able to place useful upper limits on the infrared variability amplitudes in these atmospheres. There are very few planets with multi-epoch observations at the required precision to probe variability in dayside emission. The observations considered in this study span several years, providing insight into temporal variability at multiple timescales. In the case of HD 189733b, the best-fit eclipse depths for the channel 2 observations exhibit a scatter of 102 ppm about a median depth of 1827 ppm and in channel 1 exhibit a scatter of 88 ppm about a median depth of 1481 ppm. For HD 209458b, the best-fit eclipse depths for the channel 2 observations exhibit a scatter of 22 ppm about a median depth of 1406 ppm, and in channel 1 exhibit a scatter of 131 ppm about a median depth of 1092 ppm. The precision and scatter in these observations allow us to constrain variability to less than (5.6% and 6.0%) and (12% and 1.6%) for channels (1, 2) of HD 189733b and HD 209458b, respectively.
A patient's vital signs are all inextricably interrelated, and together provide critical information regarding hemodynamic and physiological status. Yet, the precise relationship between body ...temperature (T) and heart rate (HR) in adults remains a fundamental gap in our knowledge.
We performed a retrospective secondary analysis of (1) electronic medical records from a large academic center (annual ED census of 110,000) and (2) the National Hospital Ambulatory Medical Care Survey (NHAMCS), a large CDC-sponsored weighted sample of U.S. EDs and our own large tertiary care ED, extracting demographic and clinical data including vital signs.
We included 8715 local ED visits and approximately 123.3 million estimated national adult ED visits. Mean T was 36.9 °C, and 5.2% of patients had a T over 38 °C. Mean (SD) HR was 93.3 bpm, 28% had a HR over 100 bpm. Males had significantly lower HR than females (coefficient −1.6, 95%CI −2.4 to −0.8), while age was negatively associated with HR (coefficient −0.08, 95%CI −0.10 to −0.06). For national data, an increase of 1 °C in T corresponded to an increase in HR of 7.2 bpm (95%CI 6.2 to 8.3). After adjusting for age and gender, a 1 °C increase in T corresponded to a mean (95%CI) 10.4 (9.5–11.4) and 6.9 (5.9–7.8) increase in HR locally and nationally, respectively.
Among adult ED patients nationally, for every increase in T of 1 °C, the HR increases by approximately 7 bpm.
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