The solar-like CoRoT target HD 170987: spectroscopic and seismic observations

Mathur, S.; García, R. A.; Catala, C.; Bruntt, H.; Mosser, B.; Appourchaux, T.; Ballot, J.; Creevey, O.; Gaulme, P.; Hekker, S.; Huber, Daniel; Karoff, C.; Piau, L.; Régulo, C.; Roxburgh, I. W.; Salabert, D.; Verner, G. A.; Auvergne, M.; Baglin, A.; Chaplin, W. J.; Elsworth, Y.; Michel, E.; Samadi, R.; Sato, Kumiko; Stello, Dennis

doi:10.1051/0004-6361/201014103

Cited by 78 publications

(66 citation statements)

References 71 publications

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“…Spectral types for binary stars were taken from the respective catalogues. [Fe/H] and σ are mean and standard deviations of metallicity determinations contained in the PASTEL catalogue (publications from 1990 and later), except for the following stars, for which individual measurements and uncertainties were taken from the sources in parentheses: HD 6980 (Andersen et al 1988); HD 20301 (Andersen et al 1991); HD 49385 (Deheuvels et al 2010); HD 74057 (Sowell et al 2012); HD 82434 (Fuhrmann & Chini 2012); HD 146051 (Smith et al 2013); HD 170987 (Mathur et al 2010); HD 181907 (Morel et al 2014); HD 189349 (Huber et al 2012); HD 217906 (Smith & Lambert 1985); BD +44 493 (Ito et al 2009). Fuhrmann et al (2011).…”

Section: Discussionmentioning

confidence: 99%

GaiaFGK benchmark stars: Effective temperatures and surface gravities

Heiter

Jofré

Gustafsson

et al. 2015

A&A

287

414

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Context. In the era of large Galactic stellar surveys, carefully calibrating and validating the data sets has become an important and integral part of the data analysis. Moreover, new generations of stellar atmosphere models and spectral line formation computations need to be subjected to benchmark tests to assess any progress in predicting stellar properties. Aims. We focus on cool stars and aim at establishing a sample of 34 Gaia FGK benchmark stars with a range of different metallicities. The goal was to determine the effective temperature and the surface gravity independently of spectroscopy and atmospheric models as far as possible. Most of the selected stars have been subjected to frequent spectroscopic investigations in the past, and almost all of them have previously been used as reference, calibration, or test objects. Methods. Fundamental determinations of T eff and log g were obtained in a systematic way from a compilation of angular diameter measurements and bolometric fluxes and from a homogeneous mass determination based on stellar evolution models. The derived parameters were compared to recent spectroscopic and photometric determinations and to gravity estimates based on seismic data. Results. Most of the adopted diameter measurements have formal uncertainties around 1%, which translate into uncertainties in effective temperature of 0.5%. The measurements of bolometric flux seem to be accurate to 5% or better, which contributes about 1% or less to the uncertainties in effective temperature. The comparisons of parameter determinations with the literature in general show good agreements with a few exceptions, most notably for the coolest stars and for metal-poor stars. Conclusions. The sample consists of 29 FGK-type stars and 5 M giants. Among the FGK stars, 21 have reliable parameters suitable for testing, validation, or calibration purposes. For four stars, future adjustments of the fundamental T eff are required, and for five stars the log g determination needs to be improved. Future extensions of the sample of Gaia FGK benchmark stars are required to fill gaps in parameter space, and we include a list of suggested candidates.

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Section: Discussionmentioning

confidence: 99%

GaiaFGK benchmark stars: Effective temperatures and surface gravities

Heiter

Jofré

Gustafsson

et al. 2015

A&A

287

414

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“…On the one hand, we perform a time-frequency analysis of the light curves using a Morlet transform and we project the result on the frequency domain (e.g. Mathur et al 2010aMathur et al ,b, 2013. In most of the cases, the rotation period would be the highest peak in this periodogram.…”

Section: Observations and Data Analysismentioning

confidence: 99%

Magnetic activity of F stars observed byKepler

Mathur

García

Ballot

et al. 2014

A&A

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Context. The study of stellar activity is important because it can provide new constraints for dynamo models when combined with surface rotation rates and the depth of the convection zone. We know that the dynamo mechanism, which is believed to be the main process that rules the magnetic cycle of solar-like stars, results from the interaction between (differential) rotation, convection, and magnetic field. The Kepler mission has already been collecting data for a large number of stars during four years allowing us to investigate magnetic stellar cycles. Aims. We investigated the Kepler light curves to look for magnetic activity or even hints of magnetic activity cycles. Based on the photometric data we also looked for new magnetic indexes to characterise the magnetic activity of the stars. Methods. We selected a sample of 22 solar-like F stars that have a rotation period shorter than 12 days. We performed a timefrequency analysis using the Morlet wavelet yielding a magnetic proxy for our sample of stars. We computed the magnetic index S ph as the standard deviation of the whole time series and the index S ph , which is the mean of standard deviations measured in subseries of length five times the rotation period of the star. We defined new indicators, such as the contrast between high and low activity, to take into account the fact that complete magnetic cycles are not observed for all the stars. We also inferred the Rossby number of the stars and studied their stellar background. Results. This analysis shows different types of behaviour in the 22 F stars. Two stars show behaviour very similar to magnetic activity cycles. Five stars show long-lived spots or active regions suggesting the existence of active longitudes. Two stars in our sample seem to have a decreasing or increasing trend in the temporal variation of the magnetic proxies. Finally, the last group of stars shows magnetic activity (with the presence of spots) but no sign of cycle.

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“…García et al 2009;Ballot et al 2011;McQuillan et al 2013a;Nielsen et al 2013), which can also lead to a determination of the surface differential rotation (e.g. Barban et al 2009;Mosser et al 2009b;Mathur et al 2010a;Fröhlich et al 2012;Lanza et al 2014).…”

Section: Introductionmentioning

confidence: 99%

Rotation and magnetism ofKeplerpulsating solar-like stars

García

Ceillier

Salabert

et al. 2014

A&A

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275

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Kepler ultra-high precision photometry of long and continuous observations provides a unique dataset in which surface rotation and variability can be studied for thousands of stars. Because many of these old field stars also have independently measured asteroseismic ages, measurements of rotation and activity are particularly interesting in the context of age-rotation-activity relations. In particular, age-rotation relations generally lack good calibrators at old ages, a problem that this Kepler sample of old-field stars is uniquely suited to address. We study the surface rotation and photometric magnetic activity of a subset of 540 solar-like stars on the mainsequence and the subgiant branch for which stellar pulsations have been measured. The rotation period was determined by comparing the results from two different analysis methods: i) the projection onto the frequency domain of the time-period analysis, and ii) the autocorrelation function of the light curves. Reliable surface rotation rates were then extracted by comparing the results from two different sets of calibrated data and from the two complementary analyses. General photometric levels of magnetic activity in this sample of stars were also extracted by using a photometric activity index, which takes into account the rotation period of the stars. We report rotation periods for 310 out of 540 targets (excluding known binaries and candidate planet-host stars); our measurements span a range of 1 to 100 days. The photometric magnetic activity levels of these stars were computed, and for 61.5% of the dwarfs, this level is similar to the range, from minimum to maximum, of the solar magnetic activity. We demonstrate that hot dwarfs, cool dwarfs, and subgiants have very different rotation-age relationships, highlighting the importance of separating out distinct populations when interpreting stellar rotation periods. Our sample of cool dwarf stars with age and metallicity data of the highest quality is consistent with gyrochronology relations reported in the literature.

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The solar-like CoRoT target HD 170987: spectroscopic and seismic observations

Cited by 78 publications

References 71 publications

GaiaFGK benchmark stars: Effective temperatures and surface gravities

GaiaFGK benchmark stars: Effective temperatures and surface gravities

Magnetic activity of F stars observed byKepler

Rotation and magnetism ofKeplerpulsating solar-like stars

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