The Dynamical Mass and Three-Dimensional Orbit of HR7672B: A Benchmark Brown Dwarf with High Eccentricity

The companion to the G0V star HR7672 directly imaged by Liu et al. (2002) has moved measurably along its orbit since the discovery epoch, making it possible to determine its dynamical properties. Originally targeted with adaptive optics because it showed a long-term radial velocity acceleration (trend), we have monitored this star with precise Doppler measurements and have now established a 24 year time baseline. The radial velocity variations show significant curvature (change in the acceleration) including an inflection point. We have also obtained a recent image of HR7672B with NIRC2 at Keck. The astrometry also shows curvature. In this paper, we use jointly-fitted Doppler and astrometric models to calculate the three-dimensional orbit and dynamical mass of the companion. The mass of the host star is determined using a direct radius measurement from CHARA interferometry in combination with high resolution spectroscopic modeling. We find that HR7672B has a highly eccentric, $e=0.50^{+0.01}_{-0.01}$, near edge-on, $i=97.3^{+0.4}_{-0.5}$ deg, orbit with semimajor axis, $a=18.3^{+0.4}_{-0.5}$ AU. The mass of the companion is $m=68.7^{+2.4}_{-3.1}M_J$ at the 68.2% confidence level. HR7672B thus resides near the substellar boundary, just below the hydrogen-fusing limit. These measurements of the companion mass are independent of its brightness and spectrum and establish HR7672B as a rare and precious "benchmark" brown dwarf with a well-determined mass, age, and metallicity essential for testing theoretical evolutionary models and synthetic spectral models. It is presently the only directly imaged L,T,Y-dwarf known to produce an RV trend around a solar-type star.Comment: accepted to Ap

Friends of Hot Jupiters II: No Correspondence Between Hot-Jupiter Spin-Orbit Misalignment and the Incidence of Directly Imaged Stellar Companions

Multi-star systems are common, yet little is known about a stellar companion's influence on the formation and evolution of planetary systems. For instance, stellar companions may have facilitated the inward migration of hot Jupiters towards to their present day positions. Many observed short period gas giant planets also have orbits that are misaligned with respect to their star's spin axis, which has also been attributed to the presence of a massive outer companion on a non-coplanar orbit. We present the results of a multi-band direct imaging survey using Keck NIRC2 to measure the fraction of short period gas giant planets found in multi-star systems. Over three years, we completed a survey of 50 targets ("Friends of Hot Jupiters") with 27 targets showing some signature of multi-body interaction (misaligned or eccentric orbits) and 23 targets in a control sample (well-aligned and circular orbits). We report the masses, projected separations, and confirmed common proper motion for the 19 stellar companions found around 17 stars. Correcting for survey incompleteness, we report companion fractions of $48\%\pm9\%$, $47\%\pm12\%$, and $51\%\pm13\%$ in our total, misaligned/eccentric, and control samples, respectively. This total stellar companion fraction is $2.8\,\sigma$ larger than the fraction of field stars with companions approximately $50-2000\,$AU. We observe no correlation between misaligned/eccentric hot Jupiter systems and the incidence of stellar companions. Combining this result with our previous radial velocity survey, we determine that $72\% \pm 16\%$ of hot Jupiters are part of multi-planet and/or multi-star systems.Comment: typos and references updated; 25 pages, 7 figures and 10 tables, accepted for publication in Ap

No difference in orbital parameters of RV-detected giant planets between 0.1 and 5 au in single vs multi-stellar systems

Our Keck/NIRC2 imaging survey searches for stellar companions around 144 systems with radial velocity (RV) detected giant planets to determine whether stellar binaries influence the planets' orbital parameters. This survey, the largest of its kind to date, finds eight confirmed binary systems and three confirmed triple systems. These include three new multi-stellar systems (HD 30856, HD 86081, and HD 207832) and three multi-stellar systems with newly confirmed common proper motion (HD 43691, HD 116029, and HD 164509). We combine these systems with seven RV planet-hosting multi-stellar systems from the literature in order to test for differences in the properties of planets with semimajor axes ranging between 0.1-5 au in single vs multi-stellar systems. We find no evidence that the presence or absence of stellar companions alters the distribution of planet properties in these systems. Although the observed stellar companions might influence the orbits of more distant planetary companions in these systems, our RV observations currently provide only weak constraints on the masses and orbital properties of planets beyond 5 au. In order to aid future efforts to characterize long period RV companions in these systems, we publish our contrast curves for all 144 targets. Using four years of astrometry for six hierarchical triple star systems hosting giant planets, we fit the orbits of the stellar companions in order to characterize the orbital architecture in these systems. We find that the orbital plane of the secondary and tertiary companions are inconsistent with an edge-on orbit in four out of six cases.Comment: 34 pages, 10 figures, 16 tables, including 4 tables in machine readable format and 7 tables with online supplemental dat

EAP1 regulation of GnRH promoter activity is important for human pubertal timing

The initiation of puberty is orchestrated by an augmentation of gonadotropin-releasing hormone (GnRH) secretion from a few thousand hypothalamic neurons. Recent findings have indicated that the neuroendocrine control of puberty may be regulated by a hierarchically organized network of transcriptional factors acting upstream of GnRH. These include enhanced at puberty 1 (EAP1), which contributes to the initiation of female puberty through transactivation of the GnRH promoter. However, no EAP1 mutations have been found in humans with disorders of pubertal timing. We performed whole-exome sequencing in 67 probands and 93 relatives from a large cohort of familial self-limited delayed puberty (DP). Variants were analyzed for rare, potentially pathogenic variants enriched in case versus controls and relevant to the biological control of puberty. We identified one in-frame deletion (Ala221del) and one rare missense variant (Asn770His) in EAP1 in two unrelated families; these variants were highly conserved and potentially pathogenic. Expression studies revealed Eap1 mRNA abundance in peri-pubertal mouse hypothalamus. EAP1 binding to the GnRH1 promoter increased in monkey hypothalamus at the onset of puberty as determined by chromatin immunoprecipitation. Using a luciferase reporter assay, EAP1 mutants showed a reduced ability to trans-activate the GnRH promoter compared to wild-type EAP1, due to reduced protein levels caused by the Ala221del mutation and subcellular mislocation caused by the Asn770His mutation, as revealed by western blot and immunofluorescence, respectively. In conclusion, we have identified the first EAP1 mutations leading to reduced GnRH transcriptional activity resulting in a phenotype of self-limited DP.Peer reviewe

The impact of phonological versus semantic repetition training on generalisation in chronic stroke aphasia reflects differences in dorsal pathway connectivity

It has been suggested that neuroimaging can be used to inform therapeutic intervention. The current study aimed to determine whether an individual would benefit more from training engaging their intact or their damaged neural pathway. Two males with chronic stroke aphasia participated, with DM showing milder disruption of connectivity along the dorsal language pathway relative to JS, according to distortion corrected diffusion-weighted magnetic resonance imaging. Each patient received two blocks of six repetition training sessions over two weeks, one of which was "phonological" and the other "semantic" in nature. Both phonological and semantic training produced significant gains for both patients for trained items. For the untrained control items, significant gains were specific to training type for each patient. Only phonological training elicited significant generalisation for DM, which was greater than that seen for JS. Conversely, only semantic training elicited significant generalisation for JS, which was greater than that seen for DM. This double dissociation in generalisation effects suggests that a restitutive approach is more effective for patients with milder damage while a compensatory approach may be more effective for those with more severe damage. These results indicate the utility of neuroimaging to optimise relearning strategies and promote generalisation to untrained items

WASP-12b and HAT-P-8b are Members of Triple Star Systems

We present high spatial resolution images that demonstrate that WASP-12b and HAT-P-8b orbit the primary stars of hierarchical triple star systems. In each case, two distant companions with colors and brightnesses consistent with M dwarfs co-orbit the hot Jupiter planet host as well as one another. Our adaptive optics images spatially resolve the secondary around WASP-12, previously identified by Bergfors et al. and Crossfield et al. into two distinct sources separated by 84.3 ± 0.6 mas (21 ± 3 AU). We find that the secondary to HAT-P-8, also identified by Bergfors et al., is in fact composed of two stars separated by 65.3 ± 0.5 mas (15 ± 1 AU). Our follow-up observations demonstrate physical association through common proper motion. HAT-P-8 C has a particularly low mass, which we estimate to be 0.18 ± 0.02 M☉ using photometry. Due to their hierarchy, WASP-12 BC and HAT-P-8 BC will enable the first dynamical mass determination for hot Jupiter stellar companions. These previously well studied planet hosts now represent higher-order multi-star systems with potentially complex dynamics, underscoring the importance of diffraction-limited imaging and providing additional context for understanding the migrant population of transiting hot Jupiters

Statistics of Long Period Gas Giant Planets in Known Planetary Systems

We conducted a Doppler survey at Keck combined with NIRC2 K-band adaptive optics (AO) imaging to search for massive, long-period companions to 123 known exoplanet systems with one or two planets detected using the radial velocity (RV) method. Our survey is sensitive to Jupiter-mass planets out to 20 au for a majority of stars in our sample, and we report the discovery of eight new long-period planets, in addition to 20 systems with statistically significant RV trends that indicate the presence of an outer companion beyond 5 au. We combine our RV observations with AO imaging to determine the range of allowed masses and orbital separations for these companions, and account for variations in our sensitivity to companions among stars in our sample. We estimate the total occurrence rate of companions in our sample to be 52 ± 5% over the range 1–20 M_(Jup) and 5–20 au. Our data also suggest a declining frequency for gas giant planets in these systems beyond 3–10 au, in contrast to earlier studies that found a rising frequency for giant planets in the range 0.01–3 au. This suggests either that the frequency of gas giant planets peaks between 3 and 10 au, or that outer companions in these systems have a different semi-major axis distribution than the overall population of gas giant planets. Our results also suggest that hot gas giants may be more likely to have an outer companion than cold gas giants. We find that planets with an outer companion have higher average eccentricities than their single counterparts, suggesting that dynamical interactions between planets may play an important role in these systems

HS6ST1 Insufficiency Causes Self-Limited Delayed Puberty in Contrast With Other GnRH Deficiency Genes

Context: Self-limited delayed puberty (DP) segregates in an autosomal-dominant pattern, but the genetic basis is largely unknown. Although DP is sometimes seen in relatives of patients with hypogonadotropic hypogonadism (HH), mutations in genes known to cause HH that segregate with the trait of familial self-limited DP have not yet been identified. Objective: To assess the contribution of mutations in genes known to cause HH to the phenotype of self-limited DP. Design, Patients, and Setting: We performed whole-exome sequencing in 67 probands and 93 relatives from a large cohort of familial self-limited DP, validated the pathogenicity of the identified gene variant in vitro, and examined the tissue expression and functional requirement of the mouse homolog in vivo. Results: A potentially pathogenic gene variant segregating with DP was identified in 1 of 28 known HH genes examined. This pathogenic variant occurred in HS6ST1 in one pedigree and segregated with the trait in the six affected members with heterozygous transmission (P = 3.01 x 10 -5 ). Biochemical analysis showed that this mutation reduced sulfotransferase activity in vitro. Hs6st1 mRNA was expressed in peripubertal wild-type mouse hypothalamus. GnRH neuron counts were similar in Hs6st1 (+/-) and Hs6st1(+/+) mice, but vaginal opening was delayed in Hs6st1(+/-) mice despite normal postnatal growth. Conclusions: We have linked a deleterious mutation in HS6ST1 to familial self-limited DP and show that heterozygous Hs6st1 loss causes DP in mice. In this study, the observed overlap in potentially pathogenic mutations contributing to the phenotypes of self-limited DP and HH was limited to this one gene.Peer reviewe

Contributions of Function-Altering Variants in Genes Implicated in Pubertal Timing and Body Mass for Self-Limited Delayed Puberty

Context: Self-limited delayed puberty (DP) is often associated with a delay in physical maturation, but although highly heritable the causal genetic factors remain elusive. Genome-wide association studies of the timing of puberty have identified multiple loci for age at menarche in females and voice break in males, particularly in pathways controlling energy balance. Objective/Main Outcome Measures: We sought to assess the contribution of rare variants in such genes to the phenotype of familial DP. Design/Patients: We performed whole-exome sequencing in 67 pedigrees (125 individuals with DP and 35 unaffected controls) from our unique cohort of familial self-limited DP. Using a whole-exome sequencing filtering pipeline one candidate gene [fat mass and obesity-associated gene (FTO)] was identified. In silico, in vitro, and mouse model studies were performed to investigate the pathogenicity of FTO variants and timing of puberty in FTO+/- mice. Results: We identified potentially pathogenic, rare variants in genes in linkage disequilibrium with genome-wide association studies of age at menarche loci in 283 genes. Of these, five genes were implicated in the control of body mass. After filtering for segregation with trait, one candidate, FTO, was retained. Two FTO variants, found in 14 affected individuals from three families, were also associated with leanness in these patients with DP. One variant (p. Leu44Val) demonstrated altered demethylation activity of the mutant protein in vitro. Fto(+/-) mice displayed a significantly delayed timing of pubertal onset (P <0.05). Conclusions: Mutations in genes implicated in body mass and timing of puberty in the general population may contribute to the pathogenesis of self-limited DP.Peer reviewe