References of "Kallinger, T"
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See detailExtensive study of HD 25558, a long-period double-lined binary with two SPB components
Sódor, Á.; De Cat, P.; Wright, D. J. et al

in Monthly Notices of the Royal Astronomical Society (2014), 438(4), 3535-3556

We carried out an extensive observational study of the Slowly Pulsating B (SPB) star, HD 25558. The ~2000 spectra obtained at different observatories, the ground-based and MOST satellite light curves ... [more ▼]

We carried out an extensive observational study of the Slowly Pulsating B (SPB) star, HD 25558. The ~2000 spectra obtained at different observatories, the ground-based and MOST satellite light curves revealed that this object is a double-lined spectroscopic binary with an orbital period of about 9 years. The observations do not allow the inference of an orbital solution. We determined the physical parameters of the components, and found that both lie within the SPB instability strip. Accordingly, both show line-profile variations due to stellar pulsations. Eleven independent frequencies were identified in the data. All the frequencies were attributed to one of the two components based on Pixel-by-pixel variability analysis of the line profiles. Spectroscopic and photometric mode identification was also performed for the frequencies of both stars. These results suggest that the inclination and rotation of the two components are rather different. The primary is a slow rotator with ~6 d period, seen at ~60 deg inclination, while the secondary rotates fast with ~1.2 d period, and is seen at ~20 inclination. Spectropolarimetric measurements revealed that the secondary component has a magnetic field with at least a few hundred Gauss strength, while no magnetic field can be detected in the primary. [less ▲]

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See detailObservations of Red Giants in the Cluster NGC 6633 by the CoRoT Space Mission and the HARPS and SOPHIE Spectrometers
Barban, C.; Baudin, F.; Poretti, E. et al

in Astronomical Society of the Pacific Conference Series (2013, December 01)

The CoRoT space mission and the HARPS and SOPHIE ground-based spectrometers have observed red giants belonging to the open cluster NGC 6633. Solar-like oscillations are detected in the CoRoT data obtained ... [more ▼]

The CoRoT space mission and the HARPS and SOPHIE ground-based spectrometers have observed red giants belonging to the open cluster NGC 6633. Solar-like oscillations are detected in the CoRoT data obtained for four red giants. Spectroscopic data questions the cluster membership of one of these stars. The combination of these photometric and spectroscopic data will be a unique opportunity to estimate their global parameters as well as to probe their internal structure. [less ▲]

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See detailAn abundance study of the red giants in the seismology fields of the CoRoT satellite
Morel, Thierry ULg; Miglio, A.; Lagarde, N. et al

in European Physical Journal Web of Conferences (2013, March 01)

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 ... [more ▼]

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 abundances of Li, CNO and Na (as well as [SUP]12[/SUP]C/[SUP]13[/SUP]C in a few cases). [less ▲]

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See detailModelling a high-mass red giant observed by CoRoT
Baudin, F.; Barban, C.; Goupil, M. J. et al

in Astronomy and Astrophysics (2012), 538

Context. The advent of space-borne photometers such as CoRoT and Kepler has opened up new fields in asteroseismology. This is especially true for red giants as only a few of these stars were known to ... [more ▼]

Context. The advent of space-borne photometers such as CoRoT and Kepler has opened up new fields in asteroseismology. This is especially true for red giants as only a few of these stars were known to oscillate with small amplitude, solar-like oscillations before the launch of CoRoT. <BR /> Aims: The G6 giant HR 2582 (HD 50890) was observed by CoRoT for approximately 55 days. We present here the analysis of its light curve and the characterisation of the star using different observables, such as its location in the Hertzsprung-Russell diagram and seismic observables. <BR /> Methods: 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. <BR /> Results: We provide evidence for the presence of solar-like oscillations at low frequency, between 10 and 20 μHz, with a regular spacing of (1.7 ± 0.1) μHz between consecutive radial orders. Only radial modes are clearly visible. From the models compatible with the observational constraints used here, We find that HR 2582 (HD 50890) is a massive star with a mass in the range (3-5 M[SUB]&sun;[/SUB]), clearly above the red clump. It oscillates with rather low radial order (n = 5-12) modes. Its evolutionary stage cannot be determined with precision: the star could be on the ascending red giant branch (hydrogen shell burning) with an age of approximately 155 Myr or in a later phase (helium burning). In order to obtain a reasonable helium amount, the metallicity of the star must be quite subsolar. Our best models are obtained with a mixing length significantly smaller than that obtained for the Sun with the same physical description (except overshoot). The amount of core overshoot during the main-sequence phase is found to be mild, of the order of 0.1 H[SUB]p[/SUB]. <BR /> Conclusions: HR 2582 (HD 50890) is an interesting case as only a few massive stars can be observed due to their rapid evolution compared to less massive red giants. HR 2582 (HD 50890) is also one of the few cases that can be used to validate the scaling relations for massive red giants stars and its sensitivity to the physics of the star. The CoRoT space mission, launched on 2006 December 27, was developed and is operated by the CNES with participation of the Science Programs of ESA; ESA's RSSD, Austria, Belgium, Brazil, Germany and Spain. [less ▲]

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See detailAsteroseismology of old open clusters with Kepler: direct estimate of the integrated red giant branch mass-loss in NGC 6791 and 6819
Miglio, A.; Brogaard, K.; Stello, D. et al

in Monthly Notices of the Royal Astronomical Society (2012), 419

Mass-loss of red giant branch (RGB) stars is still poorly determined, despite its crucial role in the chemical enrichment of galaxies. Thanks to the recent detection of solar-like oscillations in G-K ... [more ▼]

Mass-loss of red giant branch (RGB) stars is still poorly determined, despite its crucial role in the chemical enrichment of galaxies. Thanks to the recent detection of solar-like oscillations in G-K giants in open clusters with Kepler, we can now directly determine stellar masses for a statistically significant sample of stars in the old open clusters NGC 6791 and 6819. The aim of this work is to constrain the integrated RGB mass-loss by comparing the average mass of stars in the red clump (RC) with that of stars in the low-luminosity portion of the RGB [i.e. stars with L≲L(RC)]. Stellar masses were determined by combining the available seismic parameters ν[SUB]max[/SUB] and Δν with additional photometric constraints and with independent distance estimates. We measured the masses of 40 stars on the RGB and 19 in the RC of the old metal-rich cluster NGC 6791. We find that the difference between the average mass of RGB and RC stars is small, but significant [? (random) ±0.04 (systematic) M[SUB]&sun;[/SUB]]. Interestingly, such a small ? does not support scenarios of an extreme mass-loss for this metal-rich cluster. If we describe the mass-loss rate with Reimers prescription, a first comparison with isochrones suggests that the observed ? is compatible with a mass-loss efficiency parameter in the range 0.1 ≲η≲ 0.3. Less stringent constraints on the RGB mass-loss rate are set by the analysis of the ˜2 Gyr old NGC 6819, largely due to the lower mass-loss expected for this cluster, and to the lack of an independent and accurate distance determination. In the near future, additional constraints from frequencies of individual pulsation modes and spectroscopic effective temperatures will allow further stringent tests of the Δν and ν[SUB]max[/SUB] scaling relations, which provide a novel, and potentially very accurate, means of determining stellar radii and masses. [less ▲]

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See detailSolar-like oscillations from the depths of the red-giant star KIC 4351319 observed with Kepler
di Mauro, M. P.; Cardini, D.; Catanzaro, G. et al

in Monthly Notices of the Royal Astronomical Society (2011), 415

We present the results of the asteroseismic analysis of the red-giant star KIC 4351319 (TYC 3124-914-1), observed for 30 d in short-cadence mode with the Kepler satellite. The analysis has allowed us to ... [more ▼]

We present the results of the asteroseismic analysis of the red-giant star KIC 4351319 (TYC 3124-914-1), observed for 30 d in short-cadence mode with the Kepler satellite. The analysis has allowed us to determine the large and small frequency separations, ?Hz and ?Hz, respectively, and the frequency of maximum oscillation power, ?Hz. The high signal-to-noise ratio of the observations allowed us to identify 25 independent pulsation modes whose frequencies range approximately from 300 to ?Hz. The observed oscillation frequencies together with the accurate determination of the atmospheric parameters (effective temperature, gravity and metallicity), provided by additional ground-based spectroscopic observations, enabled us to theoretically interpret the observed oscillation spectrum. KIC 4351319 appears to oscillate with a well-defined solar-type p-mode pattern due to radial acoustic modes and non-radial nearly pure p modes. In addition, several non-radial mixed modes have been identified. Theoretical models well reproduce the observed oscillation frequencies and indicate that this star, located at the base of the ascending red-giant branch, is in the hydrogen-shell-burning phase, with a mass of ˜1.3 M[SUB]&sun;[/SUB], a radius of ? and an age of ˜5.6 Gyr. The main parameters of this star have been determined with an unprecedented level of precision for a red-giant star, with uncertainties of 2 per cent for mass, 7 per cent for age, 1 per cent for radius and 4 per cent for luminosity. [less ▲]

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See detailKepler Detected Gravity-Mode Period Spacings in a Red Giant Star
Beck, P. G.; Bedding, T. R.; Mosser, B. et al

in Science (2011), 332

Stellar interiors are inaccessible through direct observations. For this reason, helioseismologists made use of the Sun’s acoustic oscillation modes to tune models of its structure. The quest to detect ... [more ▼]

Stellar interiors are inaccessible through direct observations. For this reason, helioseismologists made use of the Sun’s acoustic oscillation modes to tune models of its structure. The quest to detect modes that probe the solar core has been ongoing for decades. We report the detection of mixed modes penetrating all the way to the core of an evolved star from 320 days of observations with the Kepler satellite. The period spacings of these mixed modes are directly dependent on the density gradient between the core region and the convective envelope. [less ▲]

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See detailAmplitudes and lifetimes of solar-like oscillations observed by CoRoT. Red-giant versus main-sequence stars
Baudin, F.; Barban, C.; Belkacem, K. et al

in Astronomy and Astrophysics (2011), 529

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 ... [more ▼]

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 characterize their oscillation amplitudes and widths. These observables are compared with those of main-sequence stars in order to test trends and scaling laws for these parameters for main-sequence stars and red giants. Methods: An automated fitting procedure is used to analyze several hundred Fourier spectra. For each star, a modeled spectrum is fitted to the observed oscillation spectrum, and mode parameters are derived. Results: Amplitudes and widths of red-giant solar-like oscillations are estimated for several hundred modes of oscillation. Amplitudes are relatively high (several hundred ppm) and widths relatively small (very few tenths of a μHz). Conclusions: Widths measured in main-sequence stars show a different variation with the effective temperature from red giants. A single scaling law is derived for mode amplitudes of red giants and main-sequence stars versus their luminosity to mass ratio. However, our results suggest that two regimes may also be compatible with the observations. [less ▲]

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See detailSolar-like Oscillations in Low-luminosity Red Giants: First Results from Kepler
Bedding, T. R.; Huber, D.; Stello, D. et al

in Astrophysical Journal (2010), 713

We have measured solar-like oscillations in red giants using time-series photometry from the first 34 days of science operations of the Kepler Mission. The light curves, obtained with 30 minute sampling ... [more ▼]

We have measured solar-like oscillations in red giants using time-series photometry from the first 34 days of science operations of the Kepler Mission. The light curves, obtained with 30 minute sampling, reveal clear oscillations in a large sample of G and K giants, extending in luminosity from the red clump down to the bottom of the giant branch. We confirm a strong correlation between the large separation of the oscillations (Πν) and the frequency of maximum power (ν[SUB]max[/SUB]). We focus on a sample of 50 low-luminosity stars (ν[SUB]max[/SUB] > 100 μHz, L <~ 30 L [SUB]sun[/SUB]) having high signal-to-noise ratios and showing the unambiguous signature of solar-like oscillations. These are H-shell-burning stars, whose oscillations should be valuable for testing models of stellar evolution and for constraining the star formation rate in the local disk. We use a new technique to compare stars on a single échelle diagram by scaling their frequencies and find well-defined ridges corresponding to radial and non-radial oscillations, including clear evidence for modes with angular degree l = 3. Measuring the small separation between l = 0 and l = 2 allows us to plot the so-called C-D diagram of δν[SUB]02[/SUB] versus Πν. The small separation δν[SUB]01[/SUB] of l = 1 from the midpoint of adjacent l = 0 modes is negative, contrary to the Sun and solar-type stars. The ridge for l = 1 is notably broadened, which we attribute to mixed modes, confirming theoretical predictions for low-luminosity giants. Overall, the results demonstrate the tremendous potential of Kepler data for asteroseismology of red giants. [less ▲]

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See detailNon-radial oscillations in the red giant HR 7349 measured by CoRoT
Carrier, F.; De Ridder, J.; Baudin, F. et al

in Astronomy and Astrophysics (2010), 509

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 ... [more ▼]

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. <BR /> Aims: Solar-like oscillations in the red giant HR 7349 are investigated. <BR /> Methods: Our study is based on a time series of 380 760 photometric measurements spread over 5 months obtained with the CoRoT satellite. Mode parameters were estimated using maximum likelihood estimation of the power spectrum. <BR /> Results: The power spectrum of the high-precision time series clearly exhibits several identifiable peaks between 19 and 40 μHz showing regularity with a mean large and small spacing of Πν = 3.47 ± 0.12 μHz and δν[SUB]02[/SUB] = 0.65 ± 0.10 μHz. Nineteen individual modes are identified with amplitudes in the range from 35 to 115 ppm. The mode damping time is estimated to be 14.7[SUP]+4.7[/SUP][SUB]-2.9[/SUB] days. The CoRoT space mission has been developed and is operated by CNES, with the contribution of Austria, Belgium, Brazil, ESA, Germany and Spain. [less ▲]

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See detailFirst asteroseismic results from CoRoT
Michel, Eric; Baglin, A.; Weiss, W. W. et al

in Communications in Asteroseismology (2008), 156

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 ... [more ▼]

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. [less ▲]

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See detailFirst asteroseismic results from CoRoT
Michel, Eric; Baglin, Annie; Weiss, W.W. et al

in Communication in Asteroseismology (2008), 157

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 ... [more ▼]

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. [less ▲]

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