The origin of the observed diversity of planetary system architectures is one of the main topic of the exoplanetary research. The detection of a statistically significant sample of planets around ...young stars allows us to study the early stages of planet formation and evolution, but only a handful of them is known so far. In this regard, a considerable contribution is expected from the NASA TESS satellite, which is now performing a survey of \(\sim 85 \%\) of the sky to search for short-period transiting planets In its first month of operations, TESS found a planet candidate with an orbital period of 8.14 days around a member of the Tuc-Hor young association (\(\sim\) 40 Myr), the G6V main component of the binary system DS\,Tuc. If confirmed, it would be the first transiting planet around a young star suitable for radial velocity and/or atmospheric characterization. We aim to validate the planetary nature of this companion and to measure its orbital and physical parameters. We obtain accurate planet parameters by coupling an independent reprocessing of the TESS light curve with improved stellar parameters and the dilution caused by the binary companion; we analyse high precision archival radial velocities to impose an upper limit of about 0.1 M\(_{\rm Jup}\) on the planet mass; we finally rule out the presence of external companions beyond 40 au with adaptive optics images. We confirm the presence of a young, giant (\({\rm R} = 0.50\) R\(_{\rm Jup}\)) planet having a not negligible possibility to be inflated (theoretical mass \(\lesssim 20\) M\(_{\oplus}\)) around DS\,Tuc~A. We discuss the feasibility of mass determination, Rossiter-McLaughlin analysis and atmosphere characterization, allowed by the brightness of the star.
In this paper we report the discovery of TOI-220 $b$, a new sub-Neptune
detected by the Transiting Exoplanet Survey Satellite (TESS) and confirmed by
radial velocity follow-up observations with the ...HARPS spectrograph. Based on
the combined analysis of TESS transit photometry and high precision radial
velocity measurements we estimate a planetary mass of 13.8 $\pm$ 1.0
M$_{Earth}$ and radius of 3.03 $\pm$ 0.15 R$_{Earth}$, implying a bulk density
of 2.73 $\pm$ 0.47 $\textrm{g cm}^{-3}$. TOI-220 $b$ orbits a relative bright
(V=10.4) and old (10.1$\pm$1.4 Gyr) K dwarf star with a period of $\sim$10.69
d. Thus, TOI-220 $b$ is a new warm sub-Neptune with very precise mass and
radius determinations. A Bayesian analysis of the TOI-220 $b$ internal
structure indicates that due to the strong irradiation it receives, the low
density of this planet could be explained with a steam atmosphere in
radiative-convective equilibrium and a supercritical water layer on top of a
differentiated interior made of a silicate mantle and a small iron core.
We present the discovery of a unique object, a chemically peculiar Ap-type
star showing $\delta$ Scuti pulsations which is bound in an eclipsing binary
system with an orbital period shorter than 3 ...days. HD 99458 is, therefore, a
complex astrophysical laboratory opening doors for studying various, often
contradictory, physical phenomena at the same time. It is the first Ap star
ever discovered in an eclipsing binary. The orbital period of 2.722 days is the
second shortest among all known chemically peculiar (CP2) binary stars.
Pulsations of $\delta$ Scuti type are also extremely rare among CP2 stars and
no unambiguously proven candidate has been reported. HD 99458 was formerly
thought to be a star hosting an exoplanet, but we definitely reject this
hypothesis by using photometric observations from the K2 mission and new radial
velocity measurements. The companion is a low-mass red dwarf star
($M_{2}=0.45(2)$ M$_{\odot}$) on an inclined orbit ($i=73.2(6)$ degrees) that
shows only grazing eclipses. The rotation and orbital periods are synchronized,
while the rotation and orbital axes are misaligned. HD 99458 is an interesting
system deserving of more intense investigations.
The Transiting Exoplanet Survey Satellite, TESS, is currently carrying out an all-sky search for small planets transiting bright stars. In the first year of the TESS survey, steady progress was made ...in achieving the mission's primary science goal of establishing bulk densities for 50 planets smaller than Neptune. During that year, TESS's observations were focused on the southern ecliptic hemisphere, resulting in the discovery of three mini-Neptunes orbiting the star TOI-125, a V=11.0 K0 dwarf. We present intensive HARPS radial velocity observations, yielding precise mass measurements for TOI-125b, TOI-125c and TOI-125d. TOI-125b has an orbital period of 4.65 days, a radius of \(2.726 \pm 0.075 ~\mathrm{R_{\rm E}}\), a mass of \( 9.50 \pm 0.88 ~\mathrm{M_{\rm E}}\) and is near the 2:1 mean motion resonance with TOI-125c at 9.15 days. TOI-125c has a similar radius of \(2.759 \pm 0.10 ~\mathrm{R_{\rm E}}\) and a mass of \( 6.63 \pm 0.99 ~\mathrm{M_{\rm E}}\), being the puffiest of the three planets. TOI-125d, has an orbital period of 19.98 days and a radius of \(2.93 \pm 0.17~\mathrm{R_{\rm E}}\) and mass \(13.6 \pm 1.2 ~\mathrm{M_{\rm E}}\). For TOI-125b and TOI-125d we find unusual high eccentricities of \(0.19\pm 0.04\) and \(0.17^{+0.08}_{-0.06}\), respectively. Our analysis also provides upper mass limits for the two low-SNR planet candidates in the system; for TOI-125.04 (\(R_P=1.36 ~\mathrm{R_{\rm E}}\), \(P=\)0.53 days) we find a \(2\sigma\) upper mass limit of \(1.6~\mathrm{M_{\rm E}}\), whereas TOI-125.05 ( \(R_P=4.2^{+2.4}_{-1.4} ~\mathrm{R_{\rm E}}\), \(P=\) 13.28 days) is unlikely a viable planet candidate with upper mass limit \(2.7~\mathrm{M_{\rm E}}\). We discuss the internal structure of the three confirmed planets, as well as dynamical stability and system architecture for this intriguing exoplanet system.
Planets in the mass range from 2 to 15 MEarth are very diverse. Some of them have low densities, while others are very dense. By measuring the masses and radii, the mean densities, structure, and ...composition of the planets are constrained. These parameters also give us important information about their formation and evolution, and about possible processes for atmospheric loss.We determined the masses, radii, and mean densities for the two transiting planets orbiting K2-106. The inner planet has an ultra-short period of 0.57 days. The period of the outer planet is 13.3 days.Although the two planets have similar masses, their densities are very different. For K2-106b we derive Mb=8.36-0.94+0.96 MEarh, Rb=1.52+/-0.16 REarth, and a high density of 13.1-3.6+5.4 gcm-3. For K2-106c, we find Mc=5.8-3.0+3.3 MEarth, Rc=2.50-0.26+0.27 REarth and a relatively low density of 2.0-1.1+1.6 gcm-3.Since the system contains two planets of almost the same mass, but different distances from the host star, it is an excellent laboratory to study atmospheric escape. In agreement with the theory of atmospheric-loss processes, it is likely that the outer planet has a hydrogen-dominated atmosphere. The mass and radius of the inner planet is in agreement with theoretical models predicting an iron core containing 80+20-30% of its mass. Such a high metal content is surprising, particularly given that the star has an ordinary (solar) metal abundance. We discuss various possible formation scenarios for this unusual planet.
We present the discovery of a unique object, a chemically peculiar Ap-type star showing \(\delta\) Scuti pulsations which is bound in an eclipsing binary system with an orbital period shorter than 3 ...days. HD 99458 is, therefore, a complex astrophysical laboratory opening doors for studying various, often contradictory, physical phenomena at the same time. It is the first Ap star ever discovered in an eclipsing binary. The orbital period of 2.722 days is the second shortest among all known chemically peculiar (CP2) binary stars. Pulsations of \(\delta\) Scuti type are also extremely rare among CP2 stars and no unambiguously proven candidate has been reported. HD 99458 was formerly thought to be a star hosting an exoplanet, but we definitely reject this hypothesis by using photometric observations from the K2 mission and new radial velocity measurements. The companion is a low-mass red dwarf star (\(M_{2}=0.45(2)\) M\(_{\odot}\)) on an inclined orbit (\(i=73.2(6)\) degrees) that shows only grazing eclipses. The rotation and orbital periods are synchronized, while the rotation and orbital axes are misaligned. HD 99458 is an interesting system deserving of more intense investigations.
In this paper we report the discovery of TOI-220 \(b\), a new sub-Neptune detected by the Transiting Exoplanet Survey Satellite (TESS) and confirmed by radial velocity follow-up observations with the ...HARPS spectrograph. Based on the combined analysis of TESS transit photometry and high precision radial velocity measurements we estimate a planetary mass of 13.8 \(\pm\) 1.0 M\(_{Earth}\) and radius of 3.03 \(\pm\) 0.15 R\(_{Earth}\), implying a bulk density of 2.73 \(\pm\) 0.47 \(\textrm{g cm}^{-3}\). TOI-220 \(b\) orbits a relative bright (V=10.4) and old (10.1\(\pm\)1.4 Gyr) K dwarf star with a period of \(\sim\)10.69 d. Thus, TOI-220 \(b\) is a new warm sub-Neptune with very precise mass and radius determinations. A Bayesian analysis of the TOI-220 \(b\) internal structure indicates that due to the strong irradiation it receives, the low density of this planet could be explained with a steam atmosphere in radiative-convective equilibrium and a supercritical water layer on top of a differentiated interior made of a silicate mantle and a small iron core.
Mexican Americans are disproportionally affected by non-alcoholic fatty liver disease (NAFLD), liver fibrosis and hepatocellular carcinoma. Noninvasive means to identify those in this population at ...high risk for these diseases are urgently needed.
The Cameron County Hispanic Cohort (CCHC) is a population-based cohort with high rates of obesity (51%), type 2 diabetes (28%) and NAFLD (49%). In a subgroup of 564 CCHC subjects, we evaluated 339 genetic variants previously reported to be associated with liver injury markers aspartate aminotransferase (AST) and alanine aminotransferase (ALT) in United Kingdom and Japanese cohorts.
Association was confirmed for 86 variants. Among them, 27 had higher effect allele frequency in the CCHC than in the United Kingdom and Japanese cohorts, and 16 had stronger associations with AST and ALT than rs738409 (
). These included rs17710008 (
)
rs2519093 (
), rs1801690 (
), rs10409243 (
), rs1800759 (
) and rs2491441 (
)
which were also associated with steatosis and/or liver fibrosis measured by vibration-controlled transient elastography. Main contributors to advanced fibrosis risk were rs11240351 (
), rs1800759 (
)
rs738409 (
) and rs1801690 (
), with advanced fibrosis detected in 37.5% of subjects with 3 of these 4 variants AOR = 11.6 (95% CI) = 3.8-35.3. AST- and ALT-associated variants implicated distinct pathways (ethanol and galactose degradation
antigen presentation and B cell development). Finally, 8 variants, including rs62292950 (
), were associated with gut microbiome changes.
These genotype-phenotype findings may have utility in risk modeling and disease prevention in this high-risk population.
Context.
Instrumental radial velocity (RV) precision has reached a level where the detection of planetary signals is limited by the ability to understand and simultaneously model stellar ...astrophysical “noise.” A common method for mitigating the effects of stellar activity is Gaussian process (GP) regression.
Aims.
In this study we present an analysis of the performance and properties of the quasi-periodic (QP) GP kernel, which is the multiplication of the squared-exponential kernel by the exponential-sine-squared kernel, based on an extensive set of synthetic RVs, into which the signature of activity was injected.
Methods.
The stellar activity within our synthetic data sets was simulated using astrophysically motivated models with different spot distributions and spot lifetimes rotating on the surface of a modeled late-type star. We used dynamic nested sampling to fit different model sets, including QP–GPs, Keplerian models, white noise models, and combinations of these, to synthetic RV time series data that in some cases included additional injected planetary signals.
Results.
We find that while the QP–GP rotation parameter matches the simulated rotation period of the star, the length scale cannot be directly connected to the spot lifetimes on the stellar surface. Regarding the setup of the priors for the QP–GP, we find that it can be advantageous to constrain the QP–GP hyperparameters in different ways depending on the application and the goal of the analysis. We find that a constraint on the length scale of the QP–GP can lead to a significant improvement in identifying the correct rotation period of the star, while a constraint on the rotation hyperparameter tends to lead to improved planet detection efficiency and more accurately derived planet parameters. Even though for most of the simulations the Bayesian evidence performed as expected, we identified not far-fetched cases where a blind adoption of this metric would lead to wrong conclusions.
Conclusions.
We conclude that modeling stellar astrophysical noise by using a QP–GP considerably improves detection efficiencies and leads to precise planet parameters. Nevertheless, there are also cases in which the QP–GP does not perform optimally, for example RV variations dynamically evolving on short timescales or a mixture of a very stable activity component and random variations. Knowledge of these limitations is essential for drawing correct conclusions from observational data.
Hispanics in South Texas have high rates of hepatocellular carcinoma (HCC) and nonalcoholic fatty liver disease (NAFLD). Liver fibrosis severity is the strongest predictive factor of NAFLD ...progression to HCC. We examined the association between free fatty acids (FA) and advanced liver fibrosis or HCC in this population.
We quantified 45 FAs in plasma of 116 subjects of the Cameron County Hispanic Cohort, 15 Hispanics with HCC, and 56 first/second-degree relatives of Hispanics with HCC. Liver fibrosis was assessed by FibroScan.
Advanced liver fibrosis was significantly associated with low expression of very long chain (VLC) saturated FAs (SFA), odd chain SFAs, and VLC n-3 polyunsaturated FAs PUFA; AOR; 95% confidence interval (CI), 10.4 (3.7-29.6);
< 0.001; 5.7 (2.2-15.2);
< 0.001; and 3.7 (1.5-9.3);
= 0.005. VLC n3-PUFAs significantly improved the performance of the noninvasive markers for advanced fibrosis - APRI, FIB-4, and NFS. Plasma concentrations of VLC SFAs and VLC n-3 PUFAs were further reduced in patients with HCC. Low concentrations of these FAs were also observed in relatives of patients with HCC and in subjects with the
rs738409 homozygous genotype.
Low plasma concentrations of VLC n-3 PUFAs and VLC SFAs were strongly associated with advanced liver fibrosis and HCC in this population. Genetic factors were associated with low concentrations of these FAs as well.
These results have implications in identifying those at risk for liver fibrosis progression to HCC and in screening this population for advanced fibrosis. They also prompt the evaluation of VLC n-3 PUFA or VLC SFA supplementation to prevent cirrhosis and HCC.
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