The Transiting Exoplanet Survey Satellite (TESS) is performing a near all-sky survey for planets that transit bright stars. In addition, its excellent photometric precision enables asteroseismology ...of solar-type and red-giant stars, which exhibit convection-driven, solar-like oscillations. Simulations predict that TESS will detect solar-like oscillations in nearly 100 stars already known to host planets. In this paper, we present an asteroseismic analysis of the known red-giant host stars HD 212771 and HD 203949, both systems having a long-period planet detected through radial velocities. These are the first detections of oscillations in previously known exoplanet-host stars by TESS, further showcasing the mission's potential to conduct asteroseismology of red-giant stars. We estimate the fundamental properties of both stars through a grid-based modeling approach that uses global asteroseismic parameters as input. We discuss the evolutionary state of HD 203949 in depth and note the large discrepancy between its asteroseismic mass (\(M_\ast = 1.23 \pm 0.15\,{\rm M}_\odot\) if on the red-giant branch or \(M_\ast = 1.00 \pm 0.16\,{\rm M}_\odot\) if in the clump) and the mass quoted in the discovery paper (\(M_\ast = 2.1 \pm 0.1\,{\rm M}_\odot\)), implying a change \(>30\,\%\) in the planet's mass. Assuming HD 203949 to be in the clump, we investigate the planet's past orbital evolution and discuss how it could have avoided engulfment at the tip of the red-giant branch. Finally, HD 212771 was observed by K2 during its Campaign 3, thus allowing for a preliminary comparison of the asteroseismic performances of TESS and K2. We estimate the ratio of the observed oscillation amplitudes for this star to be \(A_{\rm max}^{\rm TESS}/A_{\rm max}^{\rm K2} = 0.75 \pm 0.14\), consistent with the expected ratio of \(\sim0.85\) due to the redder bandpass of TESS.
Stellar rotation is a key in our understanding of both mass-loss and evolution of intermediate and massive stars. It can lead to anisotropic mass-loss in the form of radiative wind or an excretion ...disk. We wished to spatially resolve the photosphere and gaseous environment of 51 Oph, a peculiar star with a very high vsin(i) of 267km s\(^{-1}\) and an evolutionary status that remains unsettled. It has been classified by different authors as a Herbig, a \(\beta\) Pic, or a classical Be star. We used the VEGA visible beam combiner installed on the CHARA array that reaches a submilliarcsecond resolution. Observation were centered on the H\(\alpha\) emission line. We derived, for the first time, the extension and flattening of 51 Oph photosphere. We found a major axis of \(\theta_{{\mathrm{eq}}}\)=8.08\(\pm\)0.70\(R_\odot\) and a minor axis of \(\theta_{{\mathrm{pol}}}\)=5.66\(\pm\)0.23\(R_\odot\) . This high photosphere distortion shows that the star is rotating close to its critical velocity. Finally, using spectro-interferometric measurements in the H\( \alpha\) line, we constrained the circumstellar environment geometry and kinematics and showed that the emission is produced in a 5.2\(\pm\)2R\(_{*}\) disk in Keplerian rotation. From the visible point of view, 51 Oph presents all the features of a classical Be star: near critical-rotation and double-peaked H\(\alpha \) line in emission produced in a gaseous disk in Keplerian rotation. However, this does not explain the presence of dust as seen in the mid-infrared and millimeter spectra, and the evolutionary status of 51 Oph remains unsettled.
Dans son sens originaire, le principe compétence-compétence permet au tribunal arbitral, comme à tout juge, de statuer sur sa compétence. En droit français, il s'est transformé en règle de conflit ...entre justice publique et justice privée doublement originale : d'une part, il repose sur l'exercice coordonné du pouvoir de juger de la compétence ; d'autre part, il est pluraliste. Enclenché par l'apparence vraisemblable d'une convention d'arbitrage, le principe compétence-compétence consiste en un mécanisme composite se déployant dans le temps du procès arbitral et dans l'espace des deux ordres juridiques considérés. Ainsi, trois règles distinctes permettent à chacune des justices - justice française et justice arbitrale - de connaître de sa propre compétence de manière coordonnée. Tout d'abord, en amont et en parallèle de l'instance arbitrale, l'effet négatif de la compétence-compétence paralyse le pouvoir des juridictions étatiques de statuer sur leur compétence. Ensuite, le temps du procès arbitral, l'effet positif de la compétence-compétence des tribunaux arbitraux reconnaît à ces derniers le pouvoir de juger de leur compétence. Enfin, au stade post-arbitral, l'effet positif de la compétence-compétence des juridictions publiques permet à ces dernières de retrouver le pouvoir de statuer sur leur compétence lors des recours ouverts contre la sentence. Chacune des règles examinées connait limites ou écueils. Parfois, l'équilibre est rompu soit au profit des juridictions d'Etat, soit au profit des juridictions arbitrales. Force est de constater que le caractère pluraliste du principe compétence-compétence est tantôt réalité, tantôt mirage.
Classical Be stars are hot non-supergiant stars surrounded by a gaseous circumstellar disk that is responsible for the observed IR-excess and emission lines. The influence of binarity on these ...phenomena remains controversial. delta Sco is a binary system whose primary suddently began to exhibit the Be phenomenon at the last periastron in 2000. We want to constrain the geometry and kinematics of its circumstellar environment. We observed the star between 2007 and 2010 using spectrally-resolved interferometry with the VLTI/AMBER and CHARA/VEGA instruments. We found orbital elements that are compatible with previous estimates. The next periastron should take place around July 5, 2011 (+- 4,days). We resolved the circumstellar disk in the HAlpha (FWHM = 4.8+-1.5mas), BrGamma (FWHM = 2.9 0.,mas), and the 2.06\( \mu\)m HeI (FWHM = 2.4+-0.3mas) lines as well as in the K band continuum (FWHM ~2.4mas). The disk kinematics are dominated by the rotation, with a disk expansion velocity on the order of 0.2km/s. The rotation law within the disk is compatible with Keplerian rotation. As the star probably rotates at about 70% of its critical velocity the ejection of matter doesn't seems to be dominated by rotation. However, the disk geometry and kinematics are similar to that of the previously studied quasi-critically rotating Be stars, namely Alpha Ara, Psi Per and 48 Per.
