Exoplanet detections have revolutionized astronomy, offering new insights into solar system architecture and planet demographics. While nearly 1,900 exoplanets have now been discovered and confirmed, ...none are still in the process of formation. Transition disks, protoplanetary disks with inner clearings best explained by the influence of accreting planets, are natural laboratories for the study of planet formation. Some transition disks show evidence for the presence of young planets in the form of disk asymmetries or infrared sources detected within their clearings, as in the case of LkCa 15 (refs 8, 9). Attempts to observe directly signatures of accretion onto protoplanets have hitherto proven unsuccessful. Here we report adaptive optics observations of LkCa 15 that probe within the disk clearing. With accurate source positions over multiple epochs spanning 2009-2015, we infer the presence of multiple companions on Keplerian orbits. We directly detect Hα emission from the innermost companion, LkCa 15 b, evincing hot (about 10,000 kelvin) gas falling deep into the potential well of an accreting protoplanet.
ABSTRACT We present new astrometric measurements from our ongoing monitoring campaign of the HR 8799 directly imaged planetary system. These new data points were obtained with NIRC2 on the W.M. Keck ...II 10 m telescope between 2009 and 2014. In addition, we present updated astrometry from previously published observations in 2007 and 2008. All data were reduced using the SOSIE algorithm, which accounts for systematic biases present in previously published observations. This allows us to construct a self-consistent data set derived entirely from NIRC2 data alone. From this data set, we detect acceleration for two of the planets (HR 8799b and e) at >3 . We also assess possible orbital parameters for each of the four planets independently. We find no statistically significant difference in the allowed inclinations of the planets. Fitting the astrometry while forcing coplanarity also returns χ2 consistent to within 1 of the best fit values, suggesting that if inclination offsets of 20° are present, they are not detectable with current data. Our orbital fits also favor low eccentricities, consistent with predictions from dynamical modeling. We also find period distributions consistent to within 1 with a 1:2:4:8 resonance between all planets. This analysis demonstrates the importance of minimizing astrometric systematics when fitting for solutions to highly undersampled orbits.
Directly detecting thermal emission from young extrasolar planets allows measurement of their atmospheric compositions and luminosities, which are influenced by their formation mechanisms. Using the ...Gemini Planet Imager, we discovered a planet orbiting the ∼20-million-year-old star 51 Eridani at a projected separation of 13 astronomical units. Near-infrared observations show a spectrum with strong methane and water-vapor absorption. Modeling of the spectra and photometry yields a luminosity (normalized by the luminosity of the Sun) of 1.6 to 4.0 × 10–6 and an effective temperature of 600 to 750 kelvin. For this age and luminosity, "hot-start" formation models indicate a mass twice that of Jupiter. This planet also has a sufficiently low luminosity to be consistent with the "cold-start" core-accretion process that may have formed Jupiter.
Using the integral field spectrograph OSIRIS, on the Keck II telescope, broad near-infrared H- and K-band spectra of the young exoplanet HR8799b have been obtained. In addition, six new narrowband ...photometric measurements have been taken across the H and K bands. These data are combined with previously published photometry for an analysis of the planet's atmospheric properties. Thick photospheric dust cloud opacity is invoked to explain the planet's red near-IR colors and relatively smooth near-IR spectrum. Strong water absorption is detected, indicating a hydrogen-rich atmosphere. Only weak CH4 absorption is detected at K band, indicating efficient vertical mixing and a disequilibrium CO/CH4 ratio at photospheric depths. The H-band spectrum has a distinct triangular shape consistent with low surface gravity. New giant planet atmosphere models are compared to these data with best-fitting bulk parameters, T eff = 1100 K ?100 and log (g) = 3.5 ? 0.5 (for solar composition). Given the observed luminosity (log L obs/L ~ -- 5.1), these values correspond to a radius of 0.75 R Jup +0.17 -- 0.12 and a mass of ~0.72 M Jup +2.6 -- 0.6--strikingly inconsistent with interior/evolution models. Enhanced metallicity (up to ~10X that of the Sun) along with thick clouds and non-equilibrium chemistry are likely required to reproduce the complete ensemble of spectroscopic and photometric data and the low effective temperatures (<1000 K) required by the evolution models.
The International Deep Planet Survey Galicher, R; Marois, C; Macintosh, B ...
Astronomy and astrophysics (Berlin),
10/2016, Volume:
594
Journal Article
Peer reviewed
Context. Radial velocity and transit methods are effective for the study of short orbital period exoplanets but they hardly probe objects at large separations for which direct imaging can be used. ...Aims. We carried out the international deep planet survey of 292 young nearby stars to search for giant exoplanets and determine their frequency. Methods. We developed a pipeline for a uniform processing of all the data that we have recorded with NIRC2/Keck II, NIRI/Gemini North, NICI/Gemini South, and NACO/VLT for 14 yr. The pipeline first applies cosmetic corrections and then reduces the speckle intensity to enhance the contrast in the images. Results. The main result of the international deep planet survey is the discovery of the HR8799 exoplanets. We also detected 59 visual multiple systems including 16 new binary stars and 2 new triple stellar systems, as well as 2279 point-like sources. We used Monte Carlo simulations and the Bayesian theorem to determine that (ProQuest: Formulae and/or non-USASCII text omitted) of stars harbor at least one giant planet between 0.5 and 14M sub(J) and between 20 and 300AU. This result is obtained assuming uniform distributions of planet masses and semi-major axes. If we consider power law distributions as measured for close-in planets instead, the derived frequency is (ProQuest: Formulae and/or non-USASCII text omitted), recalling the strong impact of assumptions on Monte Carlo output distributions. We also find no evidence that the derived frequency depends on the mass of the hosting star, whereas it does for close-in planets. Conclusions. The international deep planet survey provides a database of confirmed background sources that may be useful for other exoplanet direct imaging surveys. It also puts new constraints on the number of stars with at least one giant planet reducing by a factor of two the frequencies derived by almost all previous works.
Associations between body mass index (BMI) and psychological distress (PD) have been reported; however, few longitudinal studies have accounted for likely life-course differences in BMI and PD ...stability, consistency, and their interplay across time.
Via random intercepts cross-lagged panel models, we assessed the predictive effects (from BMI to PD or vice-versa) across the last two centuries in the Coronary Artery Risk Development in Young Adults CARDIA, beginning in 1985-6 study using the Center for Epidemiological Studies-Depression Scale CES-D, and in the National Child Development Study NCDS, beginning in 1958 and British Cohort Study BCS, beginning in 1970 using the Malaise Inventory MI), assessed at least 4 times in adult life.
In CARDIA (n = 4724), NCDS58 (n = 7149) and BCS70 (n = 5967), autoregressive effects were stronger for BMI than for PD, meaning that carry-over effects from one occasion to the next were larger for BMI than for PD. Small interindividual correlations between traits of higher BMI and higher PD were identified among females (rfemale<|0·2|) but not males (rmale<|0·03|) in CARDIA and NCDS. Cross-lagged effects were very weak or close to zero (standardized effects η<|0·1|).
In the United States, depressive symptoms and BMI were positively correlated at the trait level among females. In the United Kingdom, relationships between PD and BMI were inconsistent between generations, with effect sizes of unlikely clinical importance, indicating negligible dominance of an intraindividual effect of BMI on PD or vice versa.
•BMI and psychological symptoms were heavily dependent on enduring traits across adulthood.•The trait of BMI was weakly correlated with the trait of psychological distress among women.•Individuals who gained BMI were more likely to continue to gain BMI at later stages.•Gaining or losing BMI did not reliably predict changes in psychological symptoms, or vice versa.
The power of shortening contractions in skeletal muscle is determined by the force-velocity relationship. Fatigue has been reported to either increase or decrease the force-velocity curvature ...depending on experimental circumstances. These discrepant findings may be related to experimental differences in oxygen availability. We therefore investigated how the curvature of the force-velocity relationship in soleus and gastrocnemius rat muscles is affected during fatigue, in both an ex vivo setup without an intact blood perfusion and in an in situ setup with an intact blood perfusion. Furthermore, we investigated the effect of reduced oxygen concentrations and reduced diffusion distance on the curvature of the force-velocity relationship in ex vivo muscles, where muscle oxygen uptake relies on diffusion from the incubation medium. Muscles were electrically stimulated to perform repeated shortening contractions and force-velocity curves were determined in rested and fatigued conditions. The curvature increased during fatigue in the soleus muscles (both in situ and ex vivo), and decreased for the gastrocnemius muscles (in situ) or remained unchanged (ex vivo). Furthermore, under ex vivo conditions, neither reduced oxygen concentrations nor reduced diffusion distance conferred any substantial effect on the force-velocity curvature. In contrast, reduced oxygen availability and increased diffusion distance did increase the loss of maximal power during fatigue, mainly due to additional decreases in isometric force. We conclude that oxygen availability does not influence the fatigue-induced changes in force-velocity curvature. Rather, the observed variable fatigue profiles with regard to changes in curvature seem to be linked to the muscle fiber-type composition.
Increasing age and carrying an APOEε4 allele are well established risk factors for Alzheimer's disease (AD). The earlier age of onset of AD observed in ε4-carriers may reflect an accelerated aging ...process. We recently reported that APOE genotype modulates brain function decades before the appearance of any cognitive or clinical symptoms. Here we test the hypothesis that APOE influences brain aging by comparing healthy ε4-carriers and non-carriers, using the same imaging protocol in distinct groups of younger and older healthy volunteers.
A cross-sectional factorial design was used to examine the effects of age and APOE genotype, and their interaction, on fMRI activation during an encoding memory task. The younger (N=36; age range 20–35; 18 ε4-carriers) and older (35 middle-age/elderly; age range 50–78years; 15 ε4-carriers) healthy volunteers taking part in the study were cognitively normal. We found a significant interaction between age and ε4-status in the hippocampi, frontal pole, subcortical nuclei, middle temporal gyri and cerebellum, such that aging was associated with decreased activity in e4-carriers and increased activity in non-carriers. Reduced cerebral blood flow was found in the older ε4-carriers relative to older non-carriers despite preserved grey matter volume.
Overactivity of brain function in young ε4-carriers is disproportionately reduced with advancing age even before the onset of measurable memory impairment. The APOE genotype determines age-related changes in brain function that may reflect the increased vulnerability of ε4-carriers to late-life pathology or cognitive decline.
►APOE genotype has different consequences for brain function depending on age. ►Differential aging processes in ε4-carriers may underlie increased risk of old-age pathology. ►Functional imaging techniques are sensitive to the effects of APOE on brain physiology. ►Our results may explain inconsistencies in the literature on APOE and brain function.
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