P. G. Beck

Universidad de La Laguna

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Co-Authors

R. A. García

Délégation Paris 7

S. Mathur

Instituto de Astrofísica de Canarias

Dennis Stello

UNSW Sydney

C. Aerts

KU Leuven

T. Kallinger

University of Vienna

S. Hekker

Heidelberg Institute for Theoretical Studies

B. Mosser

Sorbonne Université

Marc H. Pinsonneault

The Ohio State University

Daniel Huber

University of Hawaii System

S. Mathis

Commissariat à l'Énergie Atomique et aux Énergies Alternatives

Cooperative Institutions

Centre National de la Recherche Scientifique

415

Max Planck Society

280

Max Planck Institute for Astronomy

209

Université Paris Cité

171

National Institute for Astrophysics

165

KU Leuven

161

Institute of Astronomy

135

Sorbonne Université

125

Instituto de Astrofísica de Canarias

116

Aarhus University

116

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Papers

Citation

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Research Field

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

Astronomy and Astrophysics (2014)

P. G. Beck K. Hambleton J. Vos T. Kallinger S. Bloemen

The unparalleled photometric data obtained by NASA's Kepler space telescope led to an 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, exhibiting ellipsoidal modulations, have been detected with Kepler. We aim to study the properties of eccentric binary systems containing a red giant star and derive the parameters of the primary giant component. We apply asteroseismic techniques to determine masses and radii of the primary component of each system. For a selected target, light and radial velocity curve modelling techniques are applied to extract the parameters of the system. The effects of stellar on the binary system are studied. 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 440days. From radial velocity measurements we find eccentricities between e=0.2 to 0.76. As a case study we present a detailed analysis of KIC5006817. From seismology we constrain the rotational period of the envelope to be at least 165 d, 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 300ppm in the light curve. Through binary modelling, we determine the mass of the secondary component to be 0.29$\pm$0.03\,$M_\odot$. For KIC5006817 we exclude pseudo-synchronous rotation of the red giant with the orbit. The comparison of the results from seismology and modelling of the light curve shows a possible alignment of the rotational and orbital axis at the 2$\sigma$ level. Red giant eccentric systems could be progenitors of cataclysmic variables and hot subdwarf B stars.

Red giant

Radial velocity

Orbital period

Orbital inclination

Spitzer Space Telescope

10.1051/0004-6361/201322477

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Citations (120)

Accretion-induced flickering variability among symbiotic stars from space photometry with NASA TESS

Astronomy and Astrophysics (2024)

J. Merc P. G. Beck S. Mathur R. A. García

Context. Symbiotic binaries exhibit a wide range of photometric variability across different timescales. These changes can be attributed to factors such as orbital motion, intrinsic variability of the individual components, or interactions between the two stars. In the range from minutes to hours, a variability induced by accretion processes that is likely to originate from the accretion disks has been detected and subsequently denoted as flickering. This variability could mimic solar-like oscillations exhibited by luminous red giants. Aims. We aim to investigate whether it is possible to utilize the precise observations of the NASA TESS mission to detect flickering in symbiotic stars, despite the fact that such studies are usually performed at shorter wavelengths than those of TESS observations. Additionally, our goal is to develop a quantitative method for the detection of accretion-induced flickering that does not rely solely on a subjective assessment of the light curves. Methods. We obtained the light curves of known symbiotic stars and a comprehensive control sample of assumed single red giants from the TESS full-frame images. To ensure consistency, all the data were processed using the same methodology, which involves filtering out the background, systematic, and long-term trends. From the processed light curves and their power spectral densities, we measured the amplitudes of the variability and other relevant parameters. Results. We introduce a method that enables a differentiation between flickering sources and stars that do not exhibit this type of variability. We detected flickering-like variability in 20 symbiotic stars utilizing TESS data, of which 13 had not previously been identified as flickering sources. Moreover, the TESS observations facilitate the detection of related variations occurring over timescales of a few days, as well as changes in the flickering behavior across multiple sectors. Conclusions. The flickering is now likely to be detected in a total of 35 known symbiotic stars. While this represents only a small subset of all symbiotic binaries, when focusing solely on accreting-only symbiotic stars where the detection of flickering is presumably more straightforward, the fraction could reach as high as ∼80%. This result suggests that accretion disks may indeed be prevalent in these binaries.

Accretion disc

10.1051/0004-6361/202348116

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Citations (8)

Rotation and magnetism of Kepler pulsating solar-like stars : Towards asteroseismically calibrated age-rotation relations

Astronomy and Astrophysics (2014)

R. A. García T. Ceillier D. Salabert S. Mathur Jennifer L. van Saders

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 main-sequence 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.

Rotation period

Starspot

Stellar rotation

Subgiant

Asteroseismology

Source

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Citations (177)

Photospheric and chromospheric magnetic activity of seismic solar analogs Observational inputs on the solar/stellar connection from Kepler and Hermes

arXiv (Cornell University) (2016)

D. Salabert R. A. García P. G. Beck Ricky Egeland P. L. Pallé

We identify a set of 18 solar analogs among the seismic sample of solar-like stars observed by the Kepler satellite rotating between 10 and 40 days. This set is constructed using the asteroseismic stellar properties derived using either the global oscillation properties or the individual acoustic frequencies. We measure the magnetic activity properties of these stars using observations collected by the photometric Kepler satellite and by the ground-based, high-resolution Hermes spectrograph mounted on the Mercator telescope. The photospheric (Sph) and chromospheric (S index) magnetic activity levels of these seismic solar analogs are estimated and compared in relation to the solar activity. We show that the activity of the Sun is comparable to the activity of the seismic solar analogs, within the maximum-to-minimum temporal variations of the 11-year solar activity cycle 23. In agreement with previous studies, the youngest stars and fastest rotators in our sample are actually the most active. The activity of stars older than the Sun seems to not evolve much with age. Furthermore, the comparison of the photospheric, Sph, with the well-established chromospheric, S index, indicates that the Sph index can be used to provide a suitable magnetic activity proxy which can be easily estimated for a large number of stars from space photometric observations.

Helioseismology

Asteroseismology

Source

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Citations (4)

Towards probing the internal angular momentum distribution in red giants from solar-like oscillations

Astronomische Nachrichten (2010)

P. G. Beck F. Carrier C. Aerts

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 different depth. The information of rotational splitting with respect to the radial order could lead to an estimate of the magnitude of differential rotation inside their convective layers. This is a first attempt to measure the magnitude of the differential rotation in these evolved stars. An extensive spectroscopic multi-site campaign to study solar-like oscillations in two promising targets, γ Psc and θ 1 Tau is being set up for the second half of 2010. The observational result will be confronted with state-of-the-art models. Independent from the outcome on differential rotation, strong constraints on the models of red giants will be set. γ Psc and θ 1 Tau will provide an optimal case to test the underlying physics.

Solar rotation

Mode (computer interface)

Source

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Citations (1)

The ESA Passive Reflectometry and Dosimetry (Pretty) Mission

IGARSS 2022 - 2022 IEEE International Geoscience and Remote Sensing Symposium (2019)

Andreas Dielacher Heinrich Fragner Otto Koudelka P. G. Beck Jens Wickert

Passive remote sensing from space with signals of opportunity has been studied for a long time beginning in the early 90s [1]. The technique uses already existing signals, transmitted from satellites, which are reflected from ground in order to determine properties of earth surface. GNSS signals are the main interest here, due to their well-known signal properties. The Passive reflectometer acts as a bistatic radar, hence no expensive and power-consuming radar transmitter are needed. The received signal is correlated with a local code replica, where the resulting waveform shows properties of the reflected surface area. Instead of using a local code replica, the PRETTY mission will correlate the received reflected signal with the received direct signal. This technique is known as the interferometric approach. The main advantage for the interferometric approach is, that one is not bound to use known signals but can also exploit signals with unknown data modulation, opening up the possibility to use more generic signals for earth observation.The PRETTY satellite architecture will be based on the OPS-SAT architecture with modifications to accommodate the two payloads. RUAG Space GmbH as prime contractor will design the passive reflectometer payload, and Seibersdorf Laboratories is responsible for a novel dosimeter payload for measuring the space radiation environment during the PRETTY space mission. The dosimeter system will assess Total Ionizing Dose (TID) by the use of radiation integrating sensors, as well as LET spectral information, which is related to Single-Event Effects (SEE) in electronic components. Technical University Graz contributes the satellite platform based on the OPS-SAT architecture [2]. Furthermore TU Graz conducts the Manufacturing, Assembly, Integration and Test (MAIT) activities and will be in charge for the operation of the satellite. The scientific advisory group to be established will support the design of the payload and the evaluation of the raw data from the operation of the satellite. Within the present paper we will describe the architecture of the passive reflectometer payload within this 3U CubeSat mission and discuss operational routines and constraints.

Payload (computing)

SIGNAL (programming language)

Reflectometry

Passive Radar

10.1109/igarss.2019.8898720

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Citations (7)

TOI-1408: Discovery and Photodynamical Modeling of a Small Inner Companion to a Hot Jupiter Revealed by Transit Timing Variations

The Astrophysical Journal Letters (2024)

J. Korth P. Chaturvedi H. Parviainen I. Carleo Michael Endl

We report the discovery and characterization of a small planet, TOI-1408 c, on a 2.2-day orbit located interior to a previously known hot Jupiter, TOI-1408 b ($P=4.42$ d, $M=1.86\pm0.02\,M_\mathrm{Jup}$, $R=2.4\pm0.5\,R_\mathrm{Jup}$) that exhibits grazing transits. The two planets are near 2:1 period commensurability, resulting in significant transit timing variations (TTVs) for both planets and transit duration variations (TDVs) for the inner planet. The TTV amplitude for TOI-1408 c is 15% of the planet's orbital period, marking the largest TTV amplitude relative to the orbital period measured to date. Photodynamical modeling of ground-based radial velocity (RV) observations and transit light curves obtained with the Transiting Exoplanet Survey Satellite (TESS) and ground-based facilities leads to an inner planet radius of $2.22\pm0.06\,R_\oplus$ and mass of $7.6\pm0.2\,M_\oplus$ that locates the planet into the Sub-Neptune regime. The proximity to the 2:1 period commensurability leads to the libration of the resonant argument of the inner planet. The RV measurements support the existence of a third body with an orbital period of several thousand days. This discovery places the system among the rare systems featuring a hot Jupiter accompanied by an inner low-mass planet.

Commensurability (mathematics)

Orbital period

Jupiter (rocket family)

Hot Jupiter

Radial velocity

Photoevaporation

10.3847/2041-8213/ad65fd

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Citations (5)

Discovery of binarity, spectroscopic frequency analysis, and mode identification of theδ Scuti star 4 CVn

Astronomy and Astrophysics (2014)

V. S. Schmid N. Themeßl M. Breger P. Degroote C. Aerts

More than 40 years of ground-based photometric observations of the delta Sct star 4CVn revealed 18 independent oscillation frequencies, including radial as well as non-radial p-modes of low spherical degree l<=2. From 2008 to 2011, more than 2000 spectra were obtained at the 2.1-m Otto-Struve telescope at the McDonald Observatory. We present the analysis of the line-profile variations, based on the Fourier-parameter fit method, detected in the absorption lines of 4CVn, which carry clear signatures of the pulsations. From a non-sinusoidal, periodic variation of the radial velocities, we discovered that 4CVn is an eccentric binary system, with an orbital period Porb = 124.44 +/- 0.03 d and an eccentricity e = 0.311 +/- 0.003. We firmly detect 20 oscillation frequencies, 9 of which are previously unseen in photometric data, and attempt mode identification for the two dominant modes, f1 = 7.3764 c/d and f2 = 5.8496 c/d, and determine the prograde or retrograde nature of 7 of the modes. The projected rotational velocity of the star, vsini ~ 106.7 km/s, translates to a rotation rate of veq/vcrit >= 33%. This relatively high rotation rate hampers unique mode identification, since higher-order effects of rotation are not included in the current methodology. We conclude that, in order to achieve unambiguous mode identification for 4CVn, a complete description of rotation and the use of blended lines have to be included in mode-identification techniques.

Radial velocity

Oscillation (cell signaling)

Stellar rotation

Eccentricity (behavior)

Rotation period

Line (geometry)

10.1051/0004-6361/201423669

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Citations (18)

2006 WHOLE EARTH TELESCOPE OBSERVATIONS OF GD358: A NEW LOOK AT THE PROTOTYPE DBV

The Astrophysical Journal (2009)

J. L. Provençal Μ. H. Montgomery A. Kanaan H. L. Shipman Daniel P. Childers

We report on the analysis of 436.1 hrs of nearly continuous high-speed photometry on the pulsating DB white dwarf GD358 acquired with the Whole Earth Telescope (WET) during the 2006 international observing run, designated XCOV25. The Fourier transform (FT) of the light curve contains power between 1000 to 4000 microHz, with the dominant peak at 1234 microHz. We find 27 independent frequencies distributed in 10 modes, as well as numerous combination frequencies. Our discussion focuses on a new asteroseismological analysis of GD358, incorporating the 2006 data set and drawing on 24 years of archival observations. Our results reveal that, while the general frequency locations of the identified modes are consistent throughout the years, the multiplet structure is complex and cannot be interpreted simply as l=1 modes in the limit of slow rotation. The high k multiplets exhibit significant variability in structure, amplitude and frequency. Any identification of the m components for the high k multiplets is highly suspect. The k=9 and 8 modes typically do show triplet structure more consistent with theoretical expectations. The frequencies and amplitudes exhibit some variability, but much less than the high k modes. Analysis of the k=9 and 8 multiplet splittings from 1990 to 2008 reveal a long-term change in multiplet splittings coinciding with the 1996 "sforzando" event, where GD358 dramatically altered its pulsation characteristics on a timescale of hours. We explore potential implications, including the possible connections between convection and/or magnetic fields and pulsations. We suggest future investigations, including theoretical investigations of the relationship between magnetic fields, pulsation, growth rates, and convection.

Multiplet

Asteroseismology

10.1088/0004-637x/693/1/564

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Citations (32)

Probing seismic solar analogues through observations with the NASA Kepler space telescope and HERMES high-resolution spectrograph

arXiv (Cornell University) (2016)

P. G. Beck D. Salabert R. A. García J. D. do Nascimento T. Duarte

Stars similar to the Sun, known as solar analogues, provide an excellent opportunity to study the preceding and following evolutionary phases of our host star. The unprecedented quality of photometric data collected by the \Kepler NASA mission allows us to characterise solar-like stars through asteroseismology and study diagnostics of stellar evolution, such as variation of magnetic activity, rotation and the surface lithium abundance. In this project, presented in a series of papers by Salabert et al. (2016a,b) and Beck et al (2016a,b), we investigate the link between stellar activity, rotation, lithium abundance and oscillations in a group of 18 solar-analogue stars through space photometry, obtained with the NASA Kepler space telescope and from currently 50+ hours of ground-based, high-resolution spectroscopy with the Hermes instrument. In these proceedings, we first discuss the selection of the stars in the sample, observations and calibrations and then summarise the main results of the project. By investigating the chromospheric and photospheric activity of the solar analogues in this sample, it was shown that for a large fraction of these stars the measured activity levels are compatible to levels of the 11-year solar activity cycle 23. A clear correlation between the lithium abundance and surface rotation was found for rotation periods shorter than the solar value. Comparing the lithium abundance measured in the solar analogues to evolutionary models with the Toulouse-Geneva Evolutionary Code (TGEC), we found that the solar models calibrated to the Sun also correctly describe the set of solar/stellar analogs showing that they share the same internal mixing physics. Finally, the star KIC 3241581 and KIC 10644353 are discussed in more detail.

Asteroseismology

Rotation period

10.48550/arxiv.1611.04329

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Citations (1)