Preparation of <i>Kepler</i> light curves for asteroseismic analyses

García, Rafael A.; Hekker, S.; Stello, Dennis; Gutiérrez‐Soto, J.; Handberg, R.; Huber, Daniel; Karoff, C.; Uytterhoeven, K.; Appourchaux, T.; Chaplin, W. J.; Elsworth, Y.; Mathur, S.; Ballot, J.; Christensen‐Dalsgaard, J.; Gilliland, Ronald L.; Houdek, G.; Jenkins, Jon M.; Kjeldsen, H.; McCauliff, Sean; Metcalfe, T. S.; Middour, C. K.; Molenda‐Żakowicz, J.; Monteiro, M. J. P. F. G.; Smith, Jeffrey C.; Thompson, M. J.

doi:10.1111/j.1745-3933.2011.01042.x

Cited by 280 publications

(270 citation statements)

References 36 publications

(49 reference statements)

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“…Exploiting rotational splitting of mixed modes in a large sample of red giants in various evolutionary stages will provide an excellent tool to inspect how the internal angular-momentum distribution evolves with time towards the end of the life of the star. We present three cases of firm detections of rotational splitting in red giants from around 500 day-long time series of photometric data obtained with the Kepler satellite in long-cadence mode (about 30-min time sampling) 23 . KIC, stars' identifiers in the Kepler Input Catalog.…”

Section: Research Lettermentioning

confidence: 99%

Fast core rotation in red-giant stars as revealed by gravity-dominated mixed modes

Beck

Montalbán

Kallinger

et al. 2011

Nature

486

544

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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 evidence supports this 1,2 . Information about the angular-momentum distribution is inaccessible to direct observations, but it can be extracted from the effect of rotation on oscillation modes that probe the stellar interior. Here we report an increasing rotation rate from the surface of the star to the stellar core in the interiors of red giants, obtained using the rotational frequency splitting of recently detected 'mixed modes' 3,4 . By comparison with theoretical stellar models, we conclude that the core must rotate at least ten times faster than the surface. This observational result confirms the theoretical prediction of a steep gradient in the rotation profile towards the deep stellar interior 1,5,6 .The asteroseismic approach to studying stellar interiors exploits information from oscillation modes of different radial order n and angular degree l, which propagate in cavities extending at different depths 7 . Stellar rotation lifts the degeneracy of non-radial modes, producing a multiplet of (2l 1 1) frequency peaks in the power spectrum for each mode. The frequency separation between two mode components of a multiplet is related to the angular velocity and to the properties of the mode in its propagation region. More information on the exploitation of rotational splitting of modes may be found in the Supplementary Information. An important new tool comes from mixed modes that were recently identified in red giants 3,4 . Stochastically excited solar-like oscillations in evolved G and K giant stars 8 have been well studied in terms of theory [9][10][11][12] , and the main results are consistent with recent observations from space-based photometry 13,14 . Whereas pressure modes are completely trapped in the outer acoustic cavity, mixed modes also probe the central regions and carry additional information from the core region, which is probed by gravity modes. Mixed dipole modes (l 5 1) appear in the Fourier power spectrum as dense clusters of modes around those that are best trapped in the acoustic cavity. These clusters, the components of which contain varying amounts of influence from pressure and gravity modes, are referred to as 'dipole forests'.We present the Fourier spectra of the brightness variations of stars KIC 8366239 (Fig. 1a), KIC 5356201 ( Supplementary Fig. 3a) and KIC 12008916 ( Supplementary Fig. 5a), derived from observations with the Kepler spacecraft. The three spectra show split modes, the spherical degree of which we identify as l 5 1. These detected multiplets cannot have been caused by finite mode lifetime effects from mode damping, because that would not lead to a consistent multiplet appearance over several orders such as that shown in Fig. 1. ...

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Section: Research Lettermentioning

confidence: 99%

Fast core rotation in red-giant stars as revealed by gravity-dominated mixed modes

Beck

Montalbán

Kallinger

et al. 2011

Nature

486

544

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“…The light curve was prepared from public data available through the KASOC website. The raw light curve was detrended using a simple smoothing algorithm and then the power spectrum was computed following the procedure of García et al (2011). The mode power spectrum, and the section in frequency we fitted our detailed model to, can be found in Figs.…”

Section: The Power Spectrummentioning

confidence: 99%

Asteroseismology of red giants: From analysing light curves to estimating ages

Davies

Miglio

2016

Astron Nachr

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Asteroseismology has started to provide constraints on stellar properties that will be essential to accurately reconstruct the history of the Milky Way. Here we look at the information content in data sets representing current and future space missions (CoRoT, Kepler, K2, TESS, and PLATO) for red giant stars. We describe techniques for extracting the information in the frequency power spectrum and apply these techniques to Kepler data sets of different observing length to represent the different space missions. We demonstrate that for KIC 12008916, a low-luminosity red giant branch star, we can extract useful information from all data sets, and for all but the shortest data set we obtain good constraint on the g-mode period spacing and core rotation rates. We discuss how the high precision in these parameters will constrain the stellar properties of stellar radius, distance, mass and age. We show that high precision can be achieved in mass and hence age when values of the g-mode period spacing are available. We caution that tests to establish the accuracy of asteroseismic masses and ages are still "work in progress".

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“…To produce light curves which are robust against long period instrumental drifts, we extracted the photometric flux from the pixel data following the methods described by Bloemen (2013). The light curves were corrected following García et al (2011). The target pixel data were also used to inspect whether the light curve was contaminated by neighbouring field stars.…”

Section: Observationsmentioning

confidence: 99%

Pulsating red giant stars in eccentric binary systems discovered fromKeplerspace-based photometry

Beck

Hambleton

Vos

et al. 2014

A&A

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134

151

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Context. The unparalleled photometric data obtained by NASA's Kepler Space Telescope has led to improved understanding of red giant stars and binary stars. Seismology allows us to constrain the properties of red giants. In addition to eclipsing binaries, eccentric non-eclipsing binaries that exhibit ellipsoidal modulations have been detected with Kepler. Aims. We aim to study the properties of eccentric binary systems containing a red giant star and to derive the parameters of the primary giant component. Methods. We applied asteroseismic techniques to determine the masses and radii of the primary component of each system. For a selected target, light and radial velocity curve modelling techniques were applied to extract the parameters of the system and its primary component. Stellar evolution and its effects on the evolution of the binary system were studied from theoretical models. Results. The paper presents the asteroseismic analysis of 18 pulsating red giants in eccentric binary systems, for which masses and radii were constrained. The orbital periods of these systems range from 20 to 440 days. The results of our ongoing radial velocity monitoring programme with the Hermes spectrograph reveal an eccentricity range of e = 0.2 to 0.76. As a case study we present a detailed analysis of KIC 5006817, whose rich oscillation spectrum allows for detailed seismic analysis. From seismology we constrain the rotational period of the envelope to be at least 165 d, which is roughly twice the orbital period. The stellar core rotates 13 times faster than the surface. From the spectrum and radial velocities we expect that the Doppler beaming signal should have a maximum amplitude of 300 ppm in the light curve. Fixing the mass and radius to the asteroseismically determined values, we find from our binary modelling a value of the gravity darkening exponent that is significantly larger than expected. Through binary modelling, we determine the mass of the secondary component to be 0.29 ± 0.03 M . Conclusions. For KIC 5006817 we exclude pseudo-synchronous rotation of the red giant with the orbit. The comparison of the results from seismology and modelling of the light curve shows a possible alignment of the rotational and orbital axis at the 2σ level. Red giant eccentric systems could be progenitors of cataclysmic variables and hot subdwarf B stars.

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Preparation of Kepler light curves for asteroseismic analyses

Cited by 280 publications

References 36 publications

Fast core rotation in red-giant stars as revealed by gravity-dominated mixed modes

Fast core rotation in red-giant stars as revealed by gravity-dominated mixed modes

Asteroseismology of red giants: From analysing light curves to estimating ages

Pulsating red giant stars in eccentric binary systems discovered fromKeplerspace-based photometry

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