A5032349813- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Astro and Planetary Science
- Astronomical Observations and Instrumentation
- Gamma-ray bursts and supernovae
- Geophysics and Gravity Measurements
- Solar and Space Plasma Dynamics
- Adaptive optics and wavefront sensing
- History and Developments in Astronomy
- Scientific Research and Discoveries
- Space Exploration and Technology
- Statistical and numerical algorithms
- Galaxies: Formation, Evolution, Phenomena
- Calibration and Measurement Techniques
- Statistical Mechanics and Entropy
- Astrophysical Phenomena and Observations
- CCD and CMOS Imaging Sensors
- Pulsars and Gravitational Waves Research
- Spectroscopy and Chemometric Analyses
- Inertial Sensor and Navigation
- Reservoir Engineering and Simulation Methods
- Magnetic confinement fusion research
- Circadian rhythm and melatonin
- Chaos control and synchronization
University of Vienna
2014-2024
Laboratoire d’études spatiales et d’instrumentation en astrophysique
2009-2018
Janssen (France)
2018
KU Leuven
2009-2014
University of British Columbia
2009-2013
Institut d'Astrophysique Spatiale
2009
Université Paris-Saclay
2009
University of Birmingham
2009
Thüringer Landessternwarte Tautenburg
2009
Université Paris Cité
2009
The space mission Kepler provides us with long and uninterrupted photometric time series of red giants. We are now able to probe the rotational behaviour in their deep interiors using observations mixed modes. aim measure splittings giants derive scaling relations for rotation related seismic fundamental stellar parameters. have developed a dedicated method automated measurements large number Ensemble asteroseismology, namely examination at different stages evolution, allows global...
We have analyzed solar-like oscillations in ~1700 stars observed by the Kepler Mission, spanning from main-sequence to red clump. Using evolutionary models, we test asteroseismic scaling relations for frequency of maximum power (nu_max), large separation (Delta_nu) and oscillation amplitudes. show that difference Delta_nu-nu_max relation unevolved evolved can be explained different distributions effective temperature stellar mass, agreement with what is expected relations. For amplitudes,...
Mass-loss of red giant branch (RGB) stars is still poorly determined, despite its crucial role in the chemical enrichment galaxies. Thanks to recent detection solar-like oscillations G–K giants open clusters with Kepler, we can now directly determine stellar masses for a statistically significant sample old NGC 6791 and 6819. The aim this work constrain integrated RGB mass-loss by comparing average mass clump (RC) that low-luminosity portion [i.e. L≲L(RC)]. Stellar were determined combining...
The long and almost continuous observations by Kepler show clear evidence of a granulation background signal in large sample stars, which is interpreted as the surface manifestation convection. It has been shown that its characteristic timescale rms intensity fluctuation scale with peak frequency (\nu_{max}) solar-like oscillations. Various attempts have made to quantify observed signal, determine scaling relations, compare them theoretical predictions. We use probabilistic method different...
We present the first APOKASC catalog of spectroscopic and asteroseismic properties 1916 red giants observed in Kepler fields. The parameters provided from Apache Point Observatory Galactic Evolution Experiment project are complemented with surface gravities, masses, radii, mean densities determined by members Asteroseismology Science Consortium. assess both random systematic sources error include a discussion sample selection for Total uncertainties main order 80 K Teff , 0.06 dex [M/H],...
Context. Clear power excess in a frequency range typical for solar-type oscillations red giants has been detected more than 1000 stars, which have observed during the first 138 days of science operation NASA Kepler satellite. This sample includes stars wide mass and radius with spectral types G K, extending luminosity from bottom giant branch up to high-luminous giants, including bump clump. The high-precision asteroseismic observations provide perfect source testing stellar structure...
Asteroseismology Delivers Using asteroseismology—the study of stellar oscillations, it is possible to probe the interior stars and derive parameters, such as mass radius (see Perspective by Montgomery ). Based on asteroseismic data from NASA Kepler mission, Chaplin et al. (p. 213 ) detected solarlike oscillations in 500 solartype our Galaxy. The distribution radii these matches that expected evolution theory, but does not, which challenges knowledge star formation rates, forming stars,...
We aim to describe the oscillation power excess observed in Kepler red giants, and investigate empirical scaling relations governing these parameters. From scalings relations, we derive new physical properties of giant oscillations. Various different methods were compared order validate processes reliable output values. For consistency, a single method was then used determine for relevant global asteroseismic parameters: mean mode height, height background signal superimposed on excess,...
We have detected transits of the innermost planet "e" orbiting 55 Cnc (V=6.0), based on two weeks nearly continuous photometric monitoring with MOST space telescope. The occur period (0.74 d) and phase that had been predicted by Dawson & Fabrycky, expected duration depth for crossing a Sun-like star hot super-Earth. Assuming star's mass radius to be 0.963_{-0.029}^{+0.051} M_sun 0.943 +/- 0.010 R_sun, planet's mass, radius, mean density are 8.63 0.35 Mearth, 2.00 0.14 Rearth,...
We have measured solar-like oscillations in red giants using time-series photometry from the first 34 days of science operations Kepler Mission. The light curves, obtained with 30 minute sampling, reveal clear a large sample G and K giants, extending luminosity clump down to bottom giant branch. confirm strong correlation between separation (Δν) frequency maximum power (νmax). focus on 50 low-luminosity stars (νmax > 100 μHz, L ≲ L☉) having high signal-to-noise ratios showing unambiguous...
We report for the first time a parametric fit to pattern of \ell = 1 mixed modes in red giants, which is powerful tool identify gravity-dominated modes. With these modes, share characteristics pressure and gravity we are able probe directly helium core surrounding shell where hydrogen burning. propose two ways describing so-called mode bumping that affects frequencies Firstly, phenomenological approach used describe main features bumping. Alternatively, quasi-asymptotic mixed-mode relation...
The granulation pattern that we observe on the surface of Sun is due to hot plasma from interior rising photosphere where it cools down, and descends back into at edges granules. This visible manifestation convection taking place in outer part solar zone. Because red giants have deeper zones more extended atmospheres than Sun, cannot a priori assume scaled version granulation. Until now, neither observations nor 1D analytical models could put constraints giants. However, thanks...
<i>Context. <i/>Observations and analysis of solar-type oscillations in red-giant stars is an emerging aspect asteroseismic with a number open questions yet to be explored. Although stochastic have previously been detected red giants from both radial velocity photometric measurements, those data were either too short or had sampling that was not complete enough perform detailed the variability. The quality quantity as provided by CoRoT satellite necessary provide breakthrough observing...
We report the discovery of a group apparently young CoRoT red-giant stars exhibiting enhanced [alpha/Fe] abundance ratios (as determined from APOGEE spectra) with respect to Solar values. Their existence is not explained by standard chemical evolution models Milky Way, and shows that chemical-enrichment history Galactic disc more complex. find similar in previously published samples for which isochrone-ages could be robustly obtained, although smaller relative numbers, explain why these have...
The CoRoT and Kepler satellites have provided thousands of red-giant oscillation spectra. analysis these spectra requires efficient methods for identifying all eigenmode parameters. assumption new scaling laws allows us to construct a theoretical pattern. We then obtain highly precise determination the large separation by correlating observed patterns with this reference. demonstrate that pattern is universal are able unambiguously assign radial orders angular degrees. This solves one...
The Sloan Digital Sky Survey III's Apache Point Observatory Galactic Evolution Experiment (APOGEE) is a high-resolution near-infrared spectroscopic survey covering all of the major components Galaxy, including dust-obscured regions inner Milky Way disk and bulge. Here we present sample 10,341 likely red-clump stars (RC) from first two years APOGEE operations, selected based on their position in color–metallicity–surface-gravity–effective-temperature space using new method calibrated stellar...
Asteroseismology allows us to probe stellar interiors. Mixed modes can be used the physical conditions in red giant cores. However, we still need identify mechanisms that transport angular momentum inside giants, leading slow-down observed for core rotation. Thus large-scale measurements of rotation are prime importance obtain tighter constraints on efficiency internal transport, and study how this changes with parameters. This work aims at identifying components rotational multiplets dipole...
We have studied solar-like oscillations in ~800 red-giant stars using Kepler long-cadence photometry. The sample includes ranging evolution from the lower part of branch to Helium main sequence. investigate relation between large frequency separation (Delta nu) and maximum power (nu_max) show that it is different for red giants than main-sequence stars, which consistent with evolutionary models scaling relations. distributions nu_max Delta nu are qualitative agreement a simple stellar...
We studied solar-like oscillations in 115 red giants the three open clusters NGC 6791, 6811, and 6819, based on photometric data covering more than 19 months with NASA's Kepler space telescope. present asteroseismic diagrams of asymptotic parameters \delta\nu_02, \delta\nu_01 \epsilon, which show clear correlation fundamental stellar such as mass radius. When populations from are compared, we see evidence for a difference giant branch stars, possibly structure clump our measurements small...
(Abridged) We present the first APOKASC catalog of spectroscopic and asteroseismic data for 415 dwarfs subgiants. Asteroseismic have been obtained by Kepler in short cadence. The parameters are based on spectra taken as part APOGEE correspond to DR13 SDSS. analyze our using two Teff scales, values from those derived SDSS griz photometry. use differences results arising these choices a test systematic Teff, find that they can lead significant stellar properties. Determinations surface gravity...
We present initial results on some of the properties open clusters NGC 6791 and 6819 derived from asteroseismic data obtained by NASA's Kepler mission. In addition to estimating mass, radius log g stars red-giant branch these clusters, we estimate distance their ages. Our model-independent modulus is (m-M)_0= 13.11\pm 0.06. find 11.85\pm 0.05 for 6819. The average mass 1.20 \pm 0.01 M_sun, while that 1.68\pm 0.03M_sun. It should be noted do not have cover entire actual will somewhat lower....
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 constrain the properties giants. In addition eclipsing binaries, eccentric non-eclipsing exhibiting ellipsoidal modulations, have been detected with Kepler. We aim study systems containing a star derive parameters primary component. apply asteroseismic techniques determine masses radii component each system. For selected...