Eclipsing binaries (EBs) are unique targets for measuring accurate stellar properties and constraining stellar evolution models. In particular, it is possible to measure masses and radii at the few ...percent level for both components of a double-lined spectroscopic EB (SB2-EB). On the one hand, detached EBs hosting at least one star with detectable solar-like oscillations constitute ideal test objects to verify the ability of ensemble asteroseismology to derive stellar properties. On the other hand, the oscillations and surface activity of stars that belong to EBs offer unique information about the evolution of binary systems. This paper builds upon previous works dedicated to red giant stars (RG) in EBs; so far 20 known systems have been discovered by the NASA
Kepler
mission. We report the discovery of 16 RGs in EBs, which are also from the
Kepler
data, leading to a total of 36 confirmed RG stars in EBs from the original
Kepler
mission. This new sample includes three SB2-EBs with oscillations, resulting in a total of 14 known SB2-EBs with an oscillating RG component. This sample also includes six close systems in which the RG display a clear surface activity and complete oscillation suppression. Based on dedicated high-resolution spectroscopic observations (Apache Point Observatory, Observatoire de Haute Provence), we focus on three main aspects. Firstly, from the extended sample of 14 SB2-EBs, we confirm that the simple application of the asteroseismic scaling relations to RGs overestimates masses and radii of RGs by about 15% and 5%. This bias can be reduced by employing either new asteroseismic reference values for RGs or model-based corrections of the asteroseismic parameters. Secondly, we confirm that close binarity leads to a high level of photometric modulation (up to 10%) and a suppression of solar-like oscillations. In particular, we show that it reduces the lifetime of radial modes by a factor of up to 10. Thirdly, we use our 16 new systems to complement previous observational studies that aimed to constrain tidal dissipation in interacting binaries. We confirm the important role of the equilibrium tide in binary evolution, but we also identify systems with circular orbits despite relatively young ages, which suggests the need to explore complementary tidal dissipation mechanisms in the future. Finally, as a by-product, we report the measurements of mass, radius, and age of three M-dwarf companion stars.
Context. The present work deals with the detection of phase changes in an exoplanetary system. HD 46375 is a solar analog known to host a non-transiting Saturn-mass exoplanet with a 3.0236 day ...period. It was observed by the CoRoT satellite for 34 days during the fall of 2008. Aims. We attempt to identify at optical wavelengths, the changing phases of the planet as it orbits its star. We then try to improve the star model by means of a seismic analysis of the same light curve and the use of ground-based spectropolarimetric observations. Methods. The data analysis relies on the Fourier spectrum and the folding of the time series. Results. We find evidence of a sinusoidal signal compatible in terms of both amplitude and phase with light reflected by the planet. Its relative amplitude is Δ Fp/$F_{\star}$ = 13.0, 26.8 ppm, implying an albedo A = 0.16, 0.33 or a dayside visible brightness temperature Tb $\simeq$ 1880, 2030 K by assuming a radius R = 1.1 RJup and an inclination i = 45°. Its orbital phase differs from that of the radial-velocity signal by at most 2 $\sigma_{\rm RV}$. However, the tiny planetary signal is strongly blended by another signal, which we attribute to a telluric signal with a 1 day period. We show that this signal is suppressed, but not eliminated, when using the time series for HD 46179 from the same CoRoT run as a reference. Conclusions. This detection of reflected light from a non-transiting planet should be confirmable with a longer CoRoT observation of the same field. In any case, it demonstrates that non-transiting planets can be characterized using ultra-precise photometric lightcurves with present-day observations by CoRoT and Kepler. The combined detection of solar-type oscillations on the same targets (Gaulme et al. 2010a) highlights the overlap between exoplanetary science and asteroseismology and shows the high potential of a mission such as Plato.
Aims. We aim to give a reliable estimate of the number of flaring giant stars in the Kepler field. By analyzing the flaring activity of these stars, we explored their flare statistics and the ...released flare energies. The role of oscillation in suppressing magnetic activity was also investigated. We searched for flaring specialities that may be associated with the giant nature across a sample of flaring giant stars. Methods. We searched for flares using the ≈4 yr long Kepler data on a sample of 706 stars compiled from two lists of flaring giants (log g ≤ 3.5) found in the literature. To lessen the probability of false positives two different pipelines are used independently for flare detection. Tests are carried out to correct the detection bias at low flare energies for a subsample of 19 further studied, frequently flaring stars. For these 19 stars flare energy distributions and flare frequency diagrams (FFDs) are constructed. For comparison purposes KIC 2852961 is re-analyzed with our present approach. Results. From the 706 Kepler flaring giant candidates, we ruled out those where oscillations or pulsations were misclassified and those that turned out to be dwarf stars. Finally, we confirm only 61 stars as flaring giants. Among these 61 flaring giants, we found only six that also show oscillations; we suggest that a large fraction of the 61 flaring giants are members of spectroscopic binaries, which has already been proven for 11 of them. The number of detected flares on giant stars correlate only weakly with the rotational periods. The FFDs for the 19 most flaring stars were fit by power-law functions. Regarding log–log representation, the slopes of the individual fits lead to an average α = 2.01 ± 0.16 power-law index, but the ranges of flare energies scatter within almost two orders, showing the inherent heterogeneity of the sample of flaring giants. Broken power-law fits are applied for two giant stars that have similar flare energy ranges; however, the energy at the breakpoints of the power laws are different, unveiling possible differences in the magnetic field strengths and atmospheric structures of these stars. The average power-law index of α ≈ 2 is the same for the flaring giants, the (super)flaring G-dwarfs, and dwarf stars between spectral types M6 and L0. Conclusions. The 61 confirmed flaring giant stars make up only ≈0.3% of the entire giant star population in the Kepler database, which is in contrast with previous estimates of about an order higher percentage. We found that most of the false positives are in fact oscillating red giants. No strong correlation was found between the stellar properties and the flaring characteristics. The majority of the flaring specialities are hardly related to the giant nature, if at all. This, together with the finding that the observed flare durations correlate with flare energies, regardless of the flare energy level and stellar luminosity class, suggests common background physics in flaring stars, or in other words, a general scaling effect behind the flares on different stars.
We use asteroseismic data obtained by the NASA Kepler mission to estimate the fundamental properties of more than 500 main-sequence and sub-giant stars. Data obtained during the first 10 months of ...Kepler science operations were used for this work, when these solar-type targets were observed for one month each in survey mode. Stellar properties have been estimated using two global asteroseismic parameters and complementary photometric and spectroscopic data. Homogeneous sets of effective temperatures, Tsubeff , were available for the entire ensemble from complementary photometry; spectroscopic estimates of Tsubeff and Fe/H were available from a homogeneous analysis of ground-based data on a subset of 87 stars. We adopt a grid-based analysis, coupling six pipeline codes to 11 stellar evolutionary grids. Future analyses using individual oscillation frequencies will offer significant improvements on up to 150 stars, in particular for estimates of the ages, where having the individual frequency data is most important.
Solar-like oscillations have been observed by Kepler and CoRoT in many solar-type stars, thereby providing a way to probe stars using asteroseismology. The derivation of stellar parameters has ...usually been done with single stars. The aim of the paper is to derive the stellar parameters of a double-star system (HIP 93511), for which an interferometric orbit has been observed along with asteroseismic measurements. We used a time series of nearly two years of data for the double star to detect the two oscillation-mode envelopes that appear in the power spectrum. Using a new scaling relation based on luminosity, we derived the radius and mass of each star. We derived the age of each star using two proxies: one based upon the large frequency separation and a new one based upon the small frequency separation. Using stellar modeling, the mode frequencies allowed us to derive the radius, the mass, and the age of each component.
Aims. SYMPA is the first instrument dedicated to the observation of free oscillations of Jupiter. Its principles and theoretical performance have been presented in Paper I. This second paper ...describes the data processing method, the real instrumental performance and presents the first results of a Jovian observation run, lead in 2005 at Teide Observatory. Methods. SYMPA is a Fourier transform spectrometer which works at a fixed optical path difference. It produces Doppler shift maps of the observed object. The velocity amplitude of Jupiter's oscillations is expected to be below 60 cm s super(-1). Results. Despite light technical defects, the instrument was demonstrated to work correctly, being limited only by photon noise. A noise level of about 12 cm s super(-1) was reached on a 10-night observation run, with 21% duty cycle, which is 5 time better than similar previous observations. However, no signal from Jupiter is clearly highlighted.
Aims.
We aim to give a reliable estimate of the number of flaring giant stars in the
Kepler
field. By analyzing the flaring activity of these stars, we explored their flare statistics and the ...released flare energies. The role of oscillation in suppressing magnetic activity was also investigated. We searched for flaring specialities that may be associated with the giant nature across a sample of flaring giant stars.
Methods.
We searched for flares using the ≈4 yr long
Kepler
data on a sample of 706 stars compiled from two lists of flaring giants (log
g
≤ 3.5) found in the literature. To lessen the probability of false positives two different pipelines are used independently for flare detection. Tests are carried out to correct the detection bias at low flare energies for a subsample of 19 further studied, frequently flaring stars. For these 19 stars flare energy distributions and flare frequency diagrams (FFDs) are constructed. For comparison purposes KIC 2852961 is re-analyzed with our present approach.
Results.
From the 706
Kepler
flaring giant candidates, we ruled out those where oscillations or pulsations were misclassified and those that turned out to be dwarf stars. Finally, we confirm only 61 stars as flaring giants. Among these 61 flaring giants, we found only six that also show oscillations; we suggest that a large fraction of the 61 flaring giants are members of spectroscopic binaries, which has already been proven for 11 of them. The number of detected flares on giant stars correlate only weakly with the rotational periods. The FFDs for the 19 most flaring stars were fit by power-law functions. Regarding log–log representation, the slopes of the individual fits lead to an average
α
= 2.01 ± 0.16 power-law index, but the ranges of flare energies scatter within almost two orders, showing the inherent heterogeneity of the sample of flaring giants. Broken power-law fits are applied for two giant stars that have similar flare energy ranges; however, the energy at the breakpoints of the power laws are different, unveiling possible differences in the magnetic field strengths and atmospheric structures of these stars. The average power-law index of
α
≈ 2 is the same for the flaring giants, the (super)flaring G-dwarfs, and dwarf stars between spectral types M6 and L0.
Conclusions.
The 61 confirmed flaring giant stars make up only ≈0.3% of the entire giant star population in the
Kepler
database, which is in contrast with previous estimates of about an order higher percentage. We found that most of the false positives are in fact oscillating red giants. No strong correlation was found between the stellar properties and the flaring characteristics. The majority of the flaring specialities are hardly related to the giant nature, if at all. This, together with the finding that the observed flare durations correlate with flare energies, regardless of the flare energy level and stellar luminosity class, suggests common background physics in flaring stars, or in other words, a general scaling effect behind the flares on different stars.
Aims. The detection and measurement of acoustic modes on the giant planets of the solar system is of great interest for the study of the internal structure and evolution of the giant planets, as well ...as the study of the solar system formation. Such observations require a dedicated instrument and observing procedure. Methods. We describe the principle and the performance of an instrument dedicated to seismology of giant planets. In this first paper, we describe the principle and the optical scheme, and derive the theoretical performances. As for the Sun, it is possible to measure modes with spatial resolution, but a larger collecting area is necessary. As for asteroseismology in general, continuity in the observation is also required. Results. From results obtained at the laboratory, we derive the actual performance of the instrument and estimate its capabilities in network observations. Conclusions. We demonstrate that the proposed instrument and strategy is adapted for the seismology of giant planets. In a second paper, we will present the first data set obtained with it, explain the data reduction procedure, and present preliminary results.
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