In this paper we study the dynamics of the stellar interior of the early red-giant star KIC 4448777 by asteroseismic inversion of 14 splittings of the dipole mixed modes obtained from Kepler observations. In order to overcome the complexity of the oscillation pattern typical of red-giant stars, we present a procedure which involves a combination of different methods to extract the rotational splittings from the power spectrum.We find not only that the core rotates faster than the surface, confirming previous inversion results generated for other red giants (Deheuvels et al. 2012(Deheuvels et al. , 2014), but we also estimate the variation of the angular velocity within the helium core with a spatial resolution of ∆r = 0.001R and verify the hypothesis of a sharp discontinuity in the inner stellar rotation (Deheuvels et al. 2014). The results show that the entire core rotates rigidly with an angular velocity of about Ω c /2π = 748 ± 18 nHz and provide evidence for an angular velocity decrease through a region between the helium core and part of the hydrogen burning shell; however we do not succeed to characterize the rotational slope, due to the intrinsic limits of the applied techniques. The angular velocity, from the edge of the core and through the hydrogen burning shell, appears to decrease with increasing distance from the center, reaching an average value in the convective envelope of Ω s /2π = 68 ± 22 nHz. Hence, the core in KIC 4448777 is rotating from a minimum of 8 to a maximum of 17 times faster than the envelope.We conclude that a set of data which includes only dipolar modes is sufficient to infer quite accurately the rotation of a red giant not only in the dense core but also, with a lower level of confidence, in part of the radiative region and in the convective envelope.

Abstract. We show that the inclusion of special relativistic corrections in the revised OPAL and MHD equations of state has a significant impact on the helioseismic determination of the solar age. Models with relativistic corrections included lead to a reduction of about 0.05−0.08 Gyr with respect to those obtained with the old OPAL or MHD EOS. Our best-fit value is t seis = (4.57 ± 0.11) Gyr which is in remarkably good agreement with the meteoritic value for the solar age. We argue that the inclusion of relativistic corrections is important for probing the evolutionary state of a star by means of the small frequency separations δν ,n = ν ,n − ν +2,n−1 , for spherical harmonic degrees = 0, 1 and radial order n .

Abstract. In the near future frequencies of solar-like oscillation will be observed by the several planned space missions. In order to assess the information that will be available from such observations, we consider theoretical predictions of the frequency spectrum of oscillations of the star η Bootis, which shows solar-type pulsations. We present results obtained by comparing "classical" evolution models with models computed by taking into account overshooting from the convective core.

A clear detection of excess of power, providing a substantial evidence for solar-like oscillations in the G5 subgiant µ Her, is presented. This star was observed over seven nights with the SARG echelle spectrograph operating with the 3.6-m Italian TNG Telescope, using an iodine absorption cell as a velocity reference. A clear excess of power centered at 1.2 mHz, with peak amplitudes of about 0.9 m s −1 in the amplitude spectrum is present. Fitting the asymptotic relation to the power spectrum, a mode identification for the ℓ = 0, 1, 2, 3 modes in the frequency range 900 − 1600 µHz is derived. The most likely value for the large separation turns out to be 56.5 µHz, consistent with theoretical expectations. The mean amplitude per mode (l = 0, 1) at peak power results to be 0.63 m s −1 , almost three times larger than the solar one.

The F5 IV-V star Procyon A (α−CMi) was observed in January 2001 by means of the high-resolution spectrograph SARG operating with the TNG 3.5 m Italian telescope (Telescopio Nazionale Galileo) in the Canary Islands, exploiting the iodine cell technique. The time series of about 950 spectra carried out during 6 observation nights and a preliminary data analysis (Claudi et al. 2005) showed a significant power excess between 0.5 and 1.5 mHz, with 1 m s −1 peak amplitude. Here we present a more detailed analysis of the time series, based on both radial velocity and line equivalent width analyses. From the power spectrum we found a typical p-mode frequency comb-like structure, identified 11 frequencies with a good margin of certainty in the interval 500−1400 µHz of modes with l = 0, 1, 2 and 7 ≤ n ≤ 22, and determined large and small frequency separations, ∆ν = 55.90 ± 0.08 µHz and δν 02 = 7.1 ± 1.3 µHz, respectively. The mean amplitude per mode (l = 0, 1) at peak power is 0.45 ± 0.07 m s −1 , twice larger than the solar one, and the mode lifetime is 2 ± 0.4 d, which indicates a non-coherent, stochastic source of mode excitation. Line equivalent width measurements do not show a significant excess in power in the examined spectral region but allowed us to infer an upper limit to the granulation noise.