In this work we investigate p-mode power variation with solar atmosphere. To this aim, we use THÉMIS observations of the Na D1 (λ5896 Å) and K (λ7699 Å) spectral lines. While the formation heights of the K spectral line are essentially located in the photospheric layer, the formation heights of the Na D1 line span a much wider region: from

HELAS is a Coordination Action funded under the European Commission's Sixth Framework Programme (FP6) since April 1st, 2006 till March 31st, 2010. The HELAS Consortium includes 10 partner institutions that host researchers active in helio- and asteroseismology. This initiative offers a unique chance to advance the field further by coordinating the

Context: PG 1159-035, a pre-white dwarf with Teff≃ 140 000 K, is the prototype of both two classes: the PG 1159 spectroscopic class and the DOV pulsating class. Previous studies of PG 1159-035 photometric data obtained with the Whole Earth Telescope (WET) showed a rich frequency spectrum allowing the identification of 122 pulsation modes. Analyzing

We present the results of a multisite photometric campaign on the pulsating B-type hot subdwarf star Balloon090100001 (Bal09). The star is one of the two known hybrid hot subdwarfs with both long- and short-period oscillations, theoretically attributed to g and p modes. The campaign involved eight telescopes with three obtaining UBVR data, four B

Aims: We present a new method that investigates the evolutionary history of the pulsating DB white dwarf GD 358 using asteroseismology. This is done considering the internal C/O profile, which describes the relative abundances of carbon and oxygen from the core of the star to its surface. Different evolutionary channels lead to the generation of

We present a pulsational stability analysis of hot post-asymptotic giant branch (AGB) H-deficient pre-white dwarf stars with active He-burning shells. The stellar models employed are state-of-the-art equilibrium structures representative of PG1159 stars derived from the complete evolution of the progenitor stars, through the thermally pulsing AGB

Context. A search programme for pulsating subdwarf B stars was conducted with the Nordic Optical Telescope on La Palma over 59 nights between 1999 and 2009. Aims: The purpose of the programme was to significantly extend the number of rapidly pulsating sdB stars to better understand the properties of this new group of variable compact stars. Methods

Context. Results from the theory of radiatively driven winds are nowadays incorporated in stellar evolutionary and population synthesis models, and are used in our interpretation of the observations of the deep Universe. Yet, the theory has been confirmed only until Small Magellanic Cloud metallicities. Observations and analyses of O-stars at lower

Since the beginning of this century we have attended a blooming of the gravity-mode research thanks to the unprecedented quality of the data available, either from space with SoHO, or from the ground-based networks as BiSON or GONG. From the first upper limit of the gravity-mode amplitudes fixed at 10 mm/s at 200 μHz given by Appourchaux et al.

One of the main drawbacks in the analysis of the dynamics of the solar core comes from the lack of consistent data sets that cover the low and intermediate degree range (ell = 1,200). It is usually necessary to merge data obtained from different instruments and/or fitting methodologies and hence one introduces undesired systematic errors. In

We present inferences of the internal solar rotation rate and its evolution during solar cycle 23. A full solar cycle of MDI observations have been analyzed using an improved fitting methodology and using time series of various lengths, up to a single 4,608 day long epoch (64 times 72 days or 12.6 yr). We used time series of spherical harmonic

Context: The dynamics of the solar core cannot be properly constrained through the analysis of acoustic oscillation modes. Gravity modes (g modes) are necessary to understand the structure and dynamics of the deepest layers of the Sun. Through recent progress on the observation of these modes - both individually and collectively - new information

Since the detection of the asymptotic properties of the dipole gravity modes in the Sun, the quest to find individual gravity modes has continued. An extensive and deeper analysis of 14 years of continuous GOLF/SoHO observational data, unveils the presence of a pattern of peaks that could be interpreted as individual dipole gravity modes in the

The solar rotation profile is well constrained down to about 0.25 R &sun; thanks to the study of acoustic modes. Since the radius of the inner turning point of a resonant acoustic mode is inversely proportional to the ratio of its frequency to its degree, only the low-degree p modes reach the core. The higher the order of these modes, the deeper

HD 172189 is a spectroscopic eclipsing binary system with a rapidly-rotating pulsating δ Scuti component. It is also a member of the open cluster IC 4756. These combined characteristics make it an excellent laboratory for asteroseismic studies. To date, HD 172189 has been analysed in detail photometrically but not spectroscopically. For this reason

Data collected recently by the helioseismic experiments aboard the SOHO spacecraft have allowed the detection of low degree p-modes with increasingly lower order n. In particular, the GOLF experiment is currently able to unambiguously identify low degree modes with frequencies as low as 1.3 mHz. The detection of p-modes with very low frequency ({i

An analysis of the impact of seismic and volcanic activity has been carried out at selected astronomical sites, namely the observatories of El Teide (Tenerife, Canary Islands), Roque de los Muchachos (La Palma, Canary Islands), Mauna Kea (Hawaii) and Paranal (Chile), and the candidate site of Cerro Ventarrones (Chile). Hazard associated with

Accurate determination of the rotation rate in the radiative zone of the Sun from helioseismic observations requires rotational frequency splittings of exceptional quality as well as reliable inversion techniques. Here we present inferences based on mode parameters calculated from 2088 day MDI, GONG, and GOLF time series that were fitted to

We present a new inversion methodology that adapts the inversion grid in both radius and co-latitude to the data set and solves the inversion problem through an iterative procedure. This method was tested on state-of-the-art global mode frequency splittings to assess the solar interior rotation rate and its temporal variation. We also explore the

One salient result of global helioseismology is the mapping of the so-called torsional oscillations below the solar surface. These subsurface flows are inferred by inverting rotational frequency splitting sets of global modes. These flows extend down to a depth of at least 0.8 R, and are likely associated with the activity cycle of our star. To