F. Carrier

KU Leuven | ku leuven · Department of Physics and Astronomy

Asteroseismology offers the possibility of probing stellar interiors and testing evolutionary and seismic models. Precise photometry and spectroscopy obtained during multi-site campaigns on young open clusters allows discovering rich samples of pulsating stars and using them in a simultaneous seismic modelling called ensemble asteroseismology. The...

NGC 6910 is the northern hemisphere open cluster known to be rich in $\beta$ Cephei-type stars. Using four-season photometry obtained in Bia\l k\'ow (Poland) and Xinglong (China) observatories, we performed variability survey of NGC 6910. As the result, we found over 100 variable stars in the field of the cluster, including many stars showing varia...

Context. The availability of asteroseismic constraints for a large sample of red giant stars from the CoRoT and Kepler missions paves the way for various statistical studies of the seismic properties of stellar populations. Aims. We use the first detailed spectroscopic study of 19 CoRoT red-giant stars (Morel et al 2014) to compare theoretical stel...

Red giants are evolved stars which exhibit solar-like oscillations. Although a multitude of stars have been observed with space telescopes, only a handful of red-giant stars were targets of spectroscopic asteroseismic observing projects. We search for solar-like oscillations in the two bright red-giant stars $\gamma$ Psc and $\theta^1$ Tau from tim...

A precise characterisation of the red giants in the seismology fields of the CoRoT satellite is a prerequisite for further in-depth seismic modelling. High-resolution FEROS and HARPS spectra were obtained as part of the ground-based follow-up campaigns for 19 targets holding great asteroseismic potential. These data are used to accurately estimate...

Recent progress in the seismic interpretation of field {\beta} Cep stars has resulted in improvements of the physical description in the stellar structure and evolution model computations of massive stars. Further asteroseismic constraints can be obtained from studying ensembles of stars in a young open cluster, which all have similar age, distance...

Despite the shallow convective envelopes of δ Scuti pulsators, solar-like oscillations are theoretically predicted to be excited in those stars as well. To search for such stochastic oscillations, we organized a spectroscopic multisite campaign for the bright, metal-rich δ Sct star ρ Puppis. We obtained a total of 2763 high-resolution spectra using...

Recent progress in the seismic interpretation of field beta Cep stars has resulted in improvements of the physics in the stellar structure and evolution models of massive stars. Further asteroseismic constraints can be obtained from studying ensembles of stars in a young open cluster, which all have similar age, distance and chemical composition. W...

A precise characterisation of the red giants in the seismology fields of the CoRoT satellite is a prerequisite for further in-depth seismic modelling. The optical spectra obtained for 19 targets have been used to accurately estimate their fundamental parameters and chemical composition. The extent of internal mixing is also investigated through the...

When the core hydrogen is exhausted during stellar evolution, the central region of a star contracts and the outer envelope expands and cools, giving rise to a red giant. Convection takes place over much of the star's radius. Conservation of angular momentum requires that the cores of these stars rotate faster than their envelopes; indirect evidenc...

The G6 giant HR\,2582 (HD\,50890) was observed by CoRoT for approximately 55 days. Mode frequencies are extracted from the observed Fourier spectrum of the light curve. Numerical stellar models are then computed to determine the characteristics of the star (mass, age, etc...) from the comparison with observational constraints. We provide evidence f...

Asteroseismology Delivers Using asteroseismology—the study of stellar oscillations, it is possible to probe the interior of stars and to derive stellar parameters, such as mass and radius (see the Perspective by Montgomery ). Based on asteroseismic data from the NASA Kepler mission, Chaplin et al. (p. 213 ) detected solarlike oscillations in 500 so...

Red giants are evolved stars that have exhausted the supply of hydrogen in their cores and instead burn hydrogen in a surrounding shell. Once a red giant is sufficiently evolved, the helium in the core also undergoes fusion. Outstanding issues in our understanding of red giants include uncertainties in the amount of mass lost at the surface before...

Context. The advent of space-borne missions such as CoRoT or Kepler providing photometric data has brought new possibilities for asteroseismology across the H-R diagram. Solar-like oscillations are now observed in many stars, including red giants and main- sequence stars. Aims. Based on several hundred identified pulsating red giants, we aim to cha...

As a result of the variability survey in χ Persei and NGC 6910, the number of β Cep stars that are members of these two open clusters is increased to twenty stars, nine in NGC 6910 and eleven in χ Persei. We compare pulsational properties, in particular the frequency spectra, of β Cep stars in both clusters and explain the differences in terms of t...

As red giants show very low surface velocities, rotational splitting has not been detected so far in their comb-like structure from solar-like oscillations. We propose to study the rotational splitting of l=3 modes to discriminate between the competing effects of rotational splitting and finite mode lifetime. Modes of different radial orders probe...

Context. A set of long and nearly continuous observations of alpha Centauri A should allow us to derive an accurate set of asteroseismic constraints to compare to models, and make inferences on the internal structure of our closest stellar neighbour. Aims: We intend to improve the knowledge of the interior of alpha Centauri A by determining the nat...

The influence of rotational mixing on the evolution and asteroseismic properties of solar-type stars is studied. Rotational mixing changes the global properties of a solar-type star with a significant increase of the effective temperature resulting in a shift of the evolutionary track to the blue part of the HR diagram. These differences are relate...

The availability of precisely determined frequencies of radial and non-radial oscillation modes in red giants is finally paving the way for detailed studies of the internal structure of these stars. We look for the seismic signature of regions of sharp structure variation in the internal structure of the CoRoT target HR7349. We analyse the frequenc...

HR 7349 is a bright [V=5.8] red giant observed by CoRoT in the seismofield of the first long run. The outstanding CoRoT light curve allowed the detection of several solar-like oscillation modes (both radial and non-radial). On top of these seismic constraints, our observational knowledge on HR 7349 benefits as well from a precise parallax and detai...

Context. Recent progress in the seismic interpretation of field β Cep stars has resulted in improvements of the physics in the stellar structure and evolution models of massive stars. Further asteroseismic constraints can be obtained from studying ensembles of stars in a young open cluster, which all have similar age, distance and chemical composit...

We present here the light curves in the four filters of the 184 detected variable stars in NGC 884. These variable stars are listed in tables 3 and A.1 of the paper. The CCD images were calibrated and reduced as described in sections 4 and 5 of the paper. (2 data files).

We have analyzed data from a multi-site campaign to observe oscillations in the F5 star Procyon. The data consist of high-precision velocities that we obtained over more than three weeks with eleven telescopes. A new method for adjusting the data weights allows us to suppress the sidelobes in the power spectrum. Stacking the power spectrum in a so-...

We combine results from interferometry, asteroseismology and spectroscopy to determine accurate fundamental parameters of 23 bright solar-type stars, from spectral type F5 to K2 and luminosity classes III to V. For some stars we can use direct techniques to determine the mass, radius, luminosity and effective temperature, and we compare with indire...

Observations of red ( G − K ) ‐giant stars with the CoRoT satellite provide unprecedented information on the stochastically excited oscillations in these stars. The long time series of nearly uninterrupted high‐cadence and high‐precision photometry revealed the presence of non‐radial modes with long lifetimes, which opens the possibility to perf...

Context. Convection in red giant stars excites resonant acoustic waves whose frequencies depend on the sound speed inside the star, which in turn depends on the properties of the stellar interior. Therefore, asteroseismology is the most robust available method for probing the internal structure of red giant stars. Aims: Solar-like oscillations in t...

CONTEXT: Recent progress in the seismic interpretation of field beta Cep stars has resulted in improvements of the physics in the stellar structure and evolution models of massive stars. Further asteroseismic constraints can be obtained from studying ensembles of stars in a young open cluster, which all have similar age, distance and chemical compo...

Context: Observations and analysis of solar-type oscillations in red-giant stars is an emerging aspect of asteroseismic analysis with a number of open questions yet to be explored. Although stochastic oscillations have previously been detected in red giants from both radial velocity and photometric measurements, those data were either too short or...

Frequencies (in c/d and microHz) detected in the CoRoT data of HD181231 with the TiSAFT, Clean-NG, and Pasper methods. The minimum detectable frequency is 1/T=0.0064 c/d, i.e., 0.075microHz, where T is the length of the run. The error bar of the frequencies is Delta_f=1/(4T)=0.0016 c/d, i.e., 0.019 microHz. The amplitudes and phases calculated with...

Context. We present the CoRoT light curve of the $\beta\,$Cep star HD 180642, assembled during the first long run of the space mission, as well as archival single-band photometry.Aims. Our goal is to analyse the detailed behaviour present in the light curve and interpret it in terms of excited-mode frequencies.Methods. After describing the noise pr...

The known $\beta$ Cephei star HD 180 642 was observed by the CoRoT satellite in 2007. From the very high-precision light curve, its pulsation frequency spectrum could be derived for the first time (Degroote and collaborators). In this paper, we obtain additional constraints for forthcoming asteroseismic modeling of the target. Our results are based...

Context. HD 181231 is a B5IVe star, which has been observed with the CoRoT satellite during ~5 consecutive months and simultaneously from the ground in spectroscopy and spectropolarimetry.Aims. By analysing these data, we aim to detect and characterize as many pulsation frequencies as possible, to search for the presence of beating effects possibly...

Theoretical predictions of solar‐like oscillations in cool Delta Scuti stars motivated us to organize a spectroscopic observing campaign of the metal‐rich star Rho Puppis. High precision radial velocity measurements obtained in 2008 through an iodine cell attached to UCLES at the Anglo Australian Telescope (extracted with the code iSONG) as well a...

The β Cephei star HD 180642 was observed by the CoRoT satellite during a run of 156 days in 2007. The space white light photometry revealed the rich frequency spectrum of the star (Degroote et al. 2009). In the present study, we provide additional information on the target, based on both ground-based multi-colour photometry and high-resolution spec...

We introduce the spectroscopic multi-site campaigns that are organised for a sample of slowly pulsating B and gamma Doradus stars to make a big step forward in the asteroseismic studies of these main-sequence g-mode pulsators.

Observations during the first long run (~150 days) in the exo-planet field of CoRoT increase the number of G-K giant stars for which solar-like oscillations are observed by a factor of 100. This opens the possibility to study the characteristics of their oscillations in a statistical sense. We aim to understand the statistical distribution of the f...

We present the CoRoT light curve of the Beta Cep star HD 180642, assembled during the first long run of the space mission, as well as archival single-band photometry. Our goal is to analyse the detailed behaviour present in the light curve and interpret it in terms of excited mode frequencies. After describing the noise properties in detail, we use...

Towards the end of their lives, stars like the Sun greatly expand to become red giant stars. Such evolved stars could provide stringent tests of stellar theory, as many uncertainties of the internal stellar structure accumulate with age. Important examples are convective overshooting and rotational mixing during the central hydrogen-burning phase,...

A campaign on the open cluster NGC 5617 was organized in order to characterize the pulsations and to better understand the internal structure of its stars. The variability of the cluster members was never studied before. We present the observations taken and an up-to-date analysis of the obtained time series, especially of several SPB candidates we...

To improve our comprehension of the beta Cephei stars, we set up a photometric multi-site campaign on the open cluster NGC 884 (Chi Persei). Thirteen telescopes joined the 2005-2007 campaign which resulted in almost 78000 CCD frames. We present an up-to-date status of the analysis of these data, in which several interesting oscillating stars are po...

The tables represent the results of the frequency analysis of various models: under assumption of stable, long-lasting and independent frequencies with constant amplitudes and phases, we arrive at the list in table1.dat. When assuming dependency in the form of combination frequencies, we arrive at the list presented in table2.dat. When allowing for...

Asteroseismology is a powerful method for determining fundamental properties of stars. We report the first application to a metal-poor object, namely the subgiant star ν Ind. We measured precise velocities from two sites, allowing us to detect oscillations and infer a large frequency separation of Δν = 24.25 ± 0.25 μHz. Combining this value with th...

We have made a clear detection of excess power, providing strong evidence for solar-like oscillations in the G2 subgiant β Hyi. We observed this star over five nights with the University College London Echelle Spectrograph on the 3.9 m Anglo-Australian Telescope, using an iodine absorption cell as a velocity reference. The time series of 1196 veloc...

About one year after the end of the first observational run and six months after the first CoRoT data delivery, we comment the data exploitation progress for different types of stars. We consider first results to illustrate how these data of unprecedented quality shed a new light on the field of stellar seismology.

During the past three decades, astronomers have been gathering extensive time series of high- precision spectroscopy of pulsating stars. In contrast to one-shot spectra, which provide the fundamental parameters, time-resolved spectroscopy offers a much broader variety of input for asteroseismology. The most important applications encompass the dete...

Context. Observations and analysis of solar-type oscillations in red-giant stars is an emerging aspect of asteroseismic analysis with a number of open questions yet to be explored. Although stochastic oscillations have previously been detected in red giants from both radial velocity and photometric measurements, those data were either too short or...

The computation of models of stars for which solar-like oscillations have been observed is discussed. After a brief intoduction on the observations of solar-like oscillations, the modelling of isolated stars and of stars belonging to a binary system is presented with specific examples of recent theoretical calibrations. Finally the input physics in...

Since the success of helioseismology, numerous efforts have been made to detect solar-like oscillations on other stars. The measurement of the frequencies of p-mode oscillations provides an insight into the internal structure and is nowadays the most powerful constraint on the theory of stellar evolution. The existing asteroseismic observations wer...

The analysis of solar-like oscillations for stars belonging to a binary system provides an opportunity to probe the internal stellar structure and to test our knowledge of stellar physics. We present asteroseismic observations of 70 Oph A performed with the HARPS spectrograph together with a comprehensive theoretical calibration of the 70 Ophiuchi...

In 2005 a photometric observation campaign started on the open cluster $chi$ Persei, involving 13 telescopes spread over the whole northern hemisphere. After two years we gathered almost 1200 hours of data. We present here preliminary results on the variability search, especially from the 60-cm telescope in Bialków (Poland), which show seven confir...

We have carried out a multi-site campaign to measure oscillations in the F5 star Procyon A. We obtained high-precision velocity observations over more than three weeks with eleven telescopes, with almost continuous coverage for the central ten days. This represents the most extensive campaign so far organized on any solar-type oscillator. We descri...

The analysis of solar-like oscillations for stars belonging to a binary system provides a unique opportunity to probe the internal stellar structure and to test our knowledge of stellar physics. Such oscillations have been recently observed and characterized for the A component of the 70 Ophiuchi system. A model of 70 Ophiuchi AB that correctly rep...

The semi-detached eclipsing binary system V621 Cen (P=3.68d) has been analysed using the Wilson–Devinney program, on the basis of light curves obtained in the Geneva 7-colour photometric system, and radial velocity curves for both components measured with the cross-correlation technique. The physical and orbital parameters have been determined thro...

We have observed oscillations in the nearby G2 subgiant star β Hyi using high-precision velocity observations obtained over more than a week with the HARPS and UCLES spectrographs. The oscillation frequencies show a regular comb structure, as expected for solar-like oscillations, but with several l = 1 modes being strongly affected by avoided cross...

Procyon A is a bright F5IV star in a binary system. Although the distance, mass and angular diameter of this star are all known with high precision, the exact evolutionary state is still unclear. Evolutionary tracks with different ages and different mass fractions of hydrogen in the core pass, within the errors, through the observed position of Pro...

Convection in stars excites resonant acoustic waves which depend on the sound speed inside the star, which in turn depends on properties of the stellar interior. Therefore, asteroseismology is an unrivaled method to probe the internal structure of a star. We made a seismic study of the metal-poor subgiant star nu Indi with the goal of constraining...

The goal is to test the structure of hot metallic stars, and in particular the structure of a near-surface convection zone using asteroseismic measurements. Indeed, stellar models including a detailed treatement of the radiative diffusion predict the existence of a near-surface convection zone in order to correctly reproduce the anomalies in surfac...

Radial velocity time series of HD 209625, obtained with the spectrograph HARPS (ESO, La Silla). (1 data file).

We review methodologies currently available to interprete time series of high-resolution high-S/N spectroscopic data of pulsating stars in terms of the kind of (non-radial) modes that are excited. We illustrate the drastic improvement of the detection treshold of line-profile variability thanks to the advancement of the instrumentation over the pas...

Context: A new hard X-ray transient has been discovered by INTEGRAL on 2006 Sep. 17 at 1 degree from the Galactic Centre. Aims: INTEGRAL, Swift/XRT and optical photometric observations are used to characterize IGR J17497-2821 and to unveil its nature. Methods: The X-ray position has been refined to arcsec level through a study of the optical variab...

A detailed spectroscopic and photometric analysis shows for the first time that HD 61273 is a close binary system, composed of a dwarf early-type star and a K0 giant. The system underwent and perhaps still undergoes a mass transfer. The most evolved star fills its Roche lobe and transfers mass to the hotter companion which is now the most massive c...

So far, solar-like oscillations have been studied using radial velocity and/or light curve variations, which reveal frequencies of the oscillation modes. Line-profile variations, however, are also a valuable diagnostic to characterise radial and non-radial oscillations, including frequencies, amplitudes, the spherical mode wavenumbers (l,m) and the...

Contents: So far, red giant oscillations have been studied from radial velocity and/or light curve variations, which reveal frequencies of the oscillation modes. To characterise radial and non-radial oscillations, line profile variations are a valuable diagnostic. Here we present for the first time a line profile analysis of pulsating red giants, t...

We present the discovery of solar-like oscillations in time-series of the G9.5 red giant $\varepsilon$ Ophiuchi. The data were obtained with the CORALIE spectrograph at the 1.2 m Swiss telescope in La Silla and the ELODIE spectrograph at the 1.93 m telescope at the Observatoire de Haute Provence. Periodic variations can be observed in the radial ve...