Masao Takata

Asteroseismic measurement of surface-to-core rotation in a main-sequence A star, KIC 11145123

We have discovered rotationally split core g-mode triplets and surface p-mode triplets and quintuplets in a terminal age main-sequence A star, KIC 11145123, that shows both δ Sct pmode pulsations and γ Dor g-mode pulsations. This gives the first robust determination of the rotation of the deep core and surface of a main-sequence star, essentially model independently. We find its rotation to be nearly uniform with a period near 100 d, but we show with high confidence that the surface rotates slightly faster than the core. A strong angular momentum transfer mechanism must be operating to produce the nearly rigid rotation, and a mechanism other than viscosity must be operating to produce a more rapidly rotating surface than core. Our asteroseismic result, along with previous asteroseismic constraints on internal rotation in some B stars, and measurements of internal rotation in some subgiant, giant and white dwarf stars, has made angular momentum transport in stars throughout their lifetimes an observational science.

Asteroseismic measurement of slow, nearly-uniform surface-to-core rotation in the main sequence F star KIC 9244992

We have found a rotationally split series of core g-mode triplets and surface p-mode multiplets in a main sequence F star, KIC 9244992. Comparison with models shows that the star has a mass of about 1.45 M⊙, and is at an advanced stage of main sequence evolution in which the central hydrogen abundance mass fraction is reduced to about 0.1. This is the second case, following KIC 11145123, of an asteroseismic determination of the rotation of the deep core and surface of an A-F main-sequence star. We have found, essentially model-independently, that the rotation near the surface, obtained from p-mode splittings, is 66 d, slightly slower than the rotation of 64 d in the core, measured by g-mode splittings. KIC 9244992 is similar to KIC 11145123 in that both are near the end of main-sequence stage with very slow and nearly uniform rotation. This indicates the angular momentum transport in the interior of an A-F star during the main sequence stage is much stronger than that expected from standard theoretical formulations.

Nearly uniform internal rotation of solar-like main-sequence stars revealed by space-based asteroseismology and spectroscopic measurements

The rotation rates in the deep interior and at the surface of 22 main-sequence stars with masses between

Solar Models Based on Helioseismology and the Solar Neutrino Problem

1.0

Flow velocity profile of the pulmonary artery measured by the continuous cardiac output monitoring catheter

and

Period spacings in red giants - III. Coupling factors of mixed modes

1.6\,{\rm M}_{\odot}

Dipole modes with depressed amplitudes in red giants are mixed modes

are constrained by combining asteroseismological analysis with spectroscopic measurements. The asteroseismic data of each star are taken by the {\it Kepler} or CoRoT space mission. It is found that the difference between the surface rotation rate and the average rotation rate (excluding the convective core) of most of stars is small enough to suggest that an efficient process of angular momentum transport operates during and/or before the main-sequence stage of stars. If each of the surface convective zone and the underlying radiative zone, for individual stars, is assumed to rotate uniformly, the difference in the rotation rate between the two zones turns out to be no more than a factor of two in most of the stars independently of their ages.

Evaluation of an extracorporeal membrane oxygenation system using a nonporous membrane oxygenator and a new method for heparin coating

We have determined the sound-speed profile in the Sun by carrying out an asymptotic inversion of the helioseismic data from the Low-Degree (l) Oscillation Experiment (LOWL), the Global Oscillation Network Group (GONG), VIRGO on SOHO, the High-l Helioseismometer (HLH), and observations made at the South Pole. We then deduce the density, pressure, temperature, and elemental composition profiles in the solar radiative interior by solving the basic equations governing the stellar structure, with the imposition of the determined sound-speed profile and with a constraint on the depth of the convection zone obtained from helioseismic analysis and the ratio of the metal abundance to the hydrogen abundance at the photosphere. With the exception of the treatment of elements relevant to nuclear reactions, we assume that Z is homogeneous. The chemical composition profiles of hydrogen and helium are then obtained as a part of the solutions. Using the resulting seismic model, we estimate the neutrino fluxes and the neutrino capture rates for the chlorine, gallium, and water Cerenkov experiments. Even if we take into account uncertainties in various input physics, the estimated capture rates are still significantly larger than the observation.

Seismic solar model: Both of the radiative core and the convective envelope

The KATS catheter (continuous arterial thermodeprivation system catheter) measures the blood flow velocity of the pulmonary artery (PA) by thermodeprivation which enables continuous determination of cardiac output. The accuracy of this system may depend on the degree of uniformity of flow velocity in the PA, because small movements of the catheter within the PA are inevitable with a beating heart. We evaluated the flow velocity profile of the PA in seven anaesthetized open-chest dogs to assess these potential errors. A custom-made stiff catheter, at the tip of which was incorporated the flow velocity sensor of the KATS catheter, was used to penetrate the main PA in the short axis direction (perpendicular to flow direction) or the long axis direction (along flow direction). The stiff catheter was moved in increments of 2.5 mm, and flow velocity was recorded. The wall-to-wall distance of the PA along each direction was divided into five sections (S1 to S5 for the short axis, and L1 to L5 for the long axis). Flow velocity data for each section were averaged and presented as relative values against the control mid-point velocity. Along the short axis, flow velocity was 0.41 ± 0.20 (SD), 1.00 ± 0.10, 1.03 ± 0.10, 1.08 ± 0.13 and 0.49 ± 0.26 from S1 to S5, i.e., lower in S1 and S5 which were close to the vascular walls (P < 0.05) but uniform in other areas. Along the long axis, flow velocity was 0.28 ± 0.28, 0.88 ± 0.09, 0.94 ± 0.08, 1.06 ± 0.25 and 1.28 ± 0.50 from L1 to L5. Thus, flow velocity was lower in L1 which was close to the bifurcation (P < 0.05), slightly higher in L5 close to the pulmonary valve, but uniform in other areas. These results suggest that the profile of blood flow velocity is relatively uniform within the main PA except in areas close to the vessel walls or valve. We conclude that movement of the catheter within the vessel would not substantially influence the accuracy of the KATS catheter system as long as the flow velocity sensor of the catheter stays within the main PA.RésuméLa sonde KATS (Continuous Arterial Thermodeprivation Systems), en calculant par déperdition thermique la vitesse de l’écoulement sanguin dans l’artère pulmonaire (AP), mesure le débitcardiaque. La précision du système peut dépendre de la Constance de la vélocité sanguine dans l’AP, les battements cardiaques rendant inévitables de petits mouvements de la sonde. Pour évaluer cette source potentielle d’erreurs, nous avons mesuré le profil de la vélocité de l’écoulement sanguin sur sept chiens anesthésiés, à thorax ouvert. Nous avons intégré le senseur de vélocité de courant d’une sonde KATS à un cathéter rigide, créé sur mesure, dans le but de pénétrer l’AP principale perpendiculairement à la direction du flux sanguin (axe court) ou parallèlement à sa direction (axe long). Le cathéter rigide a été avancé par paliers de 2,5 mm et la vélocité du flux mesurée. Nous avons établi la moyenne les données et les avons présentées comme des valeurs relatives en regard d’un point-contrôle central. Sur l’axe court, la vélocité du courant a été de 0,41 ± 0,20 (SD), de 1,00 ± 0,01, de 1,03 ±0,01, de 1,08 ± 0,13 et de 0,49 ± 0,26, des points S1 à S5 respectivement; done plus basse à S1 et S5 qui sont les points les plus rapprochés des parois vasculaires (P < 0,05) mais uniforme dans les autres zones. Parallèlement, à l’axe long, la vélocité #x2019;était de 0,28 ± 0,28, de 0,88 ± 0,09, de 0,94 ± 0,08, de 1,06 ± 0,25, et de 1,28 ± 0,50 de L1 à L5 La vélocité du courant était done moindre à L1 lequel est situé près de la bifurcation (P < 0,05), légèrement plus grande a L5 pres de la valve pulmonaire, mais uniforme dans les autres zones. Ces résultats suggèrement que le profil de la vélocité de l’écoulement sanguin est relativement uniforme dans l’AP principale à l’exception des points situés à la proximité des parois et de la valve. Nous concluons que les mouvements de sonde dans un vaisseau ne devraient pas influencer de façon appréciable la précision du système de sondes KATS aussi longtemps que le senseur de vélocité reste dans l’artère pulmonaire principale.

Shape of a slowly rotating star measured by asteroseismology

The power of asteroseismology relies on the capability of global oscillations to infer the stellar structure. For evolved stars, we benefit from unique information directly carried out by mixed modes that probe their radiative cores. This third article of the series devoted to mixed modes in red giants focuses on their coupling factors that remained largely unexploited up to now. With the measurement of the coupling factors, we intend to give physical constraints on the regions surrounding the radiative core and the hydrogen-burning shell of subgiants and red giants. A new method for measuring the coupling factor of mixed modes is set up. It is derived from the method recently implemented for measuring period spacings. It runs in an automated way so that it can be applied to a large sample of stars. Coupling factors of mixed modes were measured for thousands of red giants. They show specific variation with mass and evolutionary stage. Weak coupling is observed for the most evolved stars on the red giant branch only; large coupling factors are measured at the transition between subgiants and red giants, as well as in the red clump. The measurement of coupling factors in dipole mixed modes provides a new insight into the inner interior structure of evolved stars. While the large frequency separation and the asymptotic period spacings probe the envelope and the core, respectively, the coupling factor is directly sensitive to the intermediate region in between and helps determining its extent. Observationally, the determination of the coupling factor is a prior to precise fits of the mixed-mode pattern, and can now be used to address further properties of the mixed-mode pattern, as the signature of the buoyancy glitches and the core rotation.