A5076968660- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Astronomical Observations and Instrumentation
- Astro and Planetary Science
- Gamma-ray bursts and supernovae
- Adaptive optics and wavefront sensing
- Calibration and Measurement Techniques
- Space Exploration and Technology
- Astronomical and nuclear sciences
- Solar and Space Plasma Dynamics
- Geological and Geophysical Studies
- Geophysics and Gravity Measurements
- Galaxies: Formation, Evolution, Phenomena
- History and Developments in Astronomy
- Spectroscopy and Laser Applications
Aarhus University
2015-2024
University of Bologna
2023-2024
Netherlands Institute for Radio Astronomy
2023-2024
Vilnius University
2020-2022
University of Birmingham
2017-2018
University of Victoria
2011-2016
Ages have been derived for 55 globular clusters (GCs) which Hubble Space Telescope Advanced Camera Surveys photometry is publicly available. For most of them, the assumed distances are based on fits theoretical zero-age horizontal-branch (ZAHB) loci to lower bound observed distributions HB stars, assuming reddenings from empirical dust maps and metallicities latest spectroscopic analyses. The age isochrone that provides best fit stars in vicinity turnoff (TO) taken be estimate cluster age....
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...
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...
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....
Models of stellar structure and evolution can be constrained by measuring accurate parameters detached eclipsing binaries in open clusters. Multiple binary stars provide the means to determine helium abundances these old systems, turn, improve estimates their age. In first paper this series, we demonstrated how measurements multiple cluster NGC6791 sets tighter constraints on properties models than has previously been possible, thereby potentially improving both accuracy precision Here add...
Deciphering the assembly history of Milky Way is a formidable task, which becomes possible only if one can produce high-resolution chrono-chemo-kinematical maps Galaxy. Data from large-scale astrometric and spectroscopic surveys will soon provide us with well-defined view current chemo-kinematical structure Way, but enable blurred on temporal sequence that led to present-day As demonstrated by (ongoing) exploitation data pioneering photometric missions CoRoT, Kepler, K2, asteroseismology...
We aim to establish and improve the accuracy level of asteroseismic estimates mass, radius, age giant stars. This can be achieved by measuring independent, accurate, precise masses, radii, effective temperatures metallicities long period eclipsing binary stars with a red component that displays solar-like oscillations. measured properties three systems KIC 7037405, 9540226, 9970396 estimated their ages $5.3\pm0.5$, $3.1\pm0.6$, $4.8\pm0.5$ Gyr. The measurements were compared corresponding...
établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics privés.
Studying star clusters offers significant advances in stellar astrophysics due to the combined power of having many stars with essentially same distance, age, and initial composition. This makes excellent test benches for verification evolution theory. To fully exploit this potential, it is vital that sample uncontaminated by are not members cluster. Techniques determining cluster membership therefore play a key role investigation clusters. We present results on three Kepler field view based...
Detached eclipsing binaries (dEBs) are ideal targets for accurate measurement of masses and radii ther component stars. If at least one the stars has evolved off main sequence (MS), give a strict constraint on age Several dEBs containing bright K giant fainter MS star have been discovered by Kepler satellite. The mass radius red (RG) can also be derived from its asteroseismic signal. parameters determined in this way depend stellar models may contain systematic errors. It is important to...
We present an extensive peakbagging effort on Kepler data of $\sim$50 red giant stars in the open star cluster NGC 6819. By employing sophisticated pre-processing time series and Markov Chain Monte Carlo techniques we extracted individual frequencies, heights linewidths for hundreds oscillation modes. show that "average" asteroseismic parameter $\delta\nu_{02}$, derived from these, can be used to distinguish stellar evolutionary state between branch (RGB) clump (RC) stars. Masses radii are...
We report the first asteroseismic results obtained with Hertzsprung SONG Telescope from an extensive high-precision radial-velocity observing campaign of subgiant muHerculis. The data set was collected during 215 nights in 2014 and 2015. detected a total 49 oscillation modes l values 0 to 3, including some = 1 mixed modes. Based on rotational splitting observed modes, we determine period 52 days stellar inclination angle 63 degrees. parameters through modeling frequencies agree very well...
Asteroseismic constraints on K giants make it possible to infer radii, masses and ages of tens thousands field stars. Tests against independent estimates these properties are however scarce, especially in the metal-poor regime. Here, we report detection solar-like oscillations eight stars belonging red-giant branch (RGB) red-horizontal (RHB) globular cluster M4. The detections were made photometric observations from K2 Mission during its Campaign 2. Making use distance, estimate by utilizing...
Earlier measurements of the masses and radii detached eclipsing binary V20 in open cluster NGC 6791 were accurate enough to demonstrate that there are significant differences between current stellar models. Here we improve on those results add two additional binaries, members V18 V80. The enlarged sample sets much tighter constraints properties models than has hitherto been possible, thereby improving both accuracy precision age. We employed (i) high-resolution UVES spectroscopy V18, V80...
We have analyzed data from a multi-site campaign to observe oscillations in the F5 star Procyon. The consist of high-precision velocities that we obtained over more than three weeks with eleven telescopes. A new method for adjusting weights allows us suppress sidelobes power spectrum. Stacking spectrum so-called echelle diagram reveals two clear ridges identify even and odd values angular degree (l=0 2, l=1 3, respectively). interpret strong, narrow peak at 446 muHz lies close ridge as mode...
Asteroseismology of stars in clusters has been a long-sought goal because the assumption common age, distance, and initial chemical composition allows strong tests theory stellar evolution. We report results from first 34 days science data Kepler Mission for open cluster NGC 6819—one four field view. obtain clear detections solar-like oscillations red giants are able to measure large frequency separation, Δν, maximum oscillation power, νmax. find that asteroseismic parameters allow us test...
Context: Accurate fundamental parameters of stars are essential for the asteroseismic analysis data from NASA Kepler mission. Aims: We aim at determining accurate atmospheric and abundance pattern a sample 82 red giants that targets Methods: have used high-resolution, high signal-to-noise spectra three different spectrographs. iterative spectral synthesis method VWA to derive carefully selected high-quality iron lines. After determination parameters, abundances 13 elements were measured...
The M4 Core Project with HST is designed to exploit the Hubble Space Telescope investigate central regions of M4, Globular Cluster closest Sun. In this paper we combine optical and near-infrared photometry study multiple stellar populations in M4. We detected two sequences M-dwarfs containing ~38% (MS_I) ~62% (MS_II) MS stars below main-sequence (MS) knee. compare our observations those NGC2808, which only other GCs where MSs very low-mass have been studied date. calculate synthetic spectra...
ABSTRACT We present the analysis of an eccentric, partially eclipsing long-period ( P = 19.23 days) binary system KIC 9777062 that contains main-sequence stars near turnoff intermediate-age open cluster NGC 6811. The primary is a metal-lined Am star with possible convective blueshift to its radial velocities, and one (probably secondary) likely be γ Dor pulsator. component masses are 1.603 ± 0.006(stat.) 0.016(sys.) 1.419 0.003 0.008 <?CDATA ${M}_{\odot }$?> , radii 1.744 0.004 0.002 1.544...
Previously [Y/Mg] has been proven to be an age indicator for solar twins. Here, we investigate if this relation also holds helium-core-burning stars of metallicity. High resolution and high signal-to-noise ratio (S/N) spectroscopic data in the phase have obtained with FIES spectrograph on NOT 2.56m telescope HIRES Keck I 10 m telescope. They analyzed determine chemical abundances four open clusters close metallicity; NGC 6811, 6819, M67 188. The are derived from equivalent widths spectral...
Abstract In the last decade, Kepler and CoRoT space-photometry missions have demonstrated potential of asteroseismology as a novel, versatile powerful tool to perform exquisite tests stellar physics, enable precise accurate characterisations properties, with impact on both exoplanetary Galactic astrophysics. Based our improved understanding strengths limitations such tool, we argue for new small/medium space mission dedicated gathering high-precision, high-cadence, long photometric series in...
We present a new asteroseismic analysis of the stars in Globular Cluster (GC) M4 based on data collected by K2 mission. report detection solar-like oscillation 37 stars, 32 red giant branch (RGB) and 6 horizontal (rHB) largest sample for this kind study GC up to date. Combining information from asteroseismology multi-band photometry we estimate both masses radii our targets. Our estimates are agreement with independent sources, serving as crucial verification low metallicity regime. As is an...
We present the discovery of totally eclipsing long-period (P = 771.8 d) binary system WOCS 23009 in old open cluster NGC 6819 that contains both an evolved star near central hydrogen exhaustion and a low-mass (0.45 Msun) star. This was previously known to be single-lined spectroscopic binary, but eclipse apastron using data from Kepler space telescope makes it clear has inclination is very close 90 degrees. Although secondary not been identified spectra, mass primary can constrained other...
We analyze extensive BVRcIc time-series photometry and radial-velocity measurements for WOCS 40007 (Auner 259; KIC 5113053), a double-lined detached eclipsing binary member of the open cluster NGC 6819. Utilizing photometric observations from 1 m telescope at Mount Laguna Observatory spectra WIYN 3.5 telescope, we measure precise accurate masses (∼1.6% uncertainty) radii (∼0.5%) components. In addition, discover third star orbiting with period greater than 3000 days using radial velocities...