Formation history of open clusters constrained by detailed asteroseismology of red giant stars observed byKepler

2018 ◽

Vol 14 (A30) ◽

pp. 257-257

Author(s):

Friedrich Anders ◽

Ivan Minchev ◽

Cristina Chiappini

Keyword(s):

Milky Way ◽

Past History ◽

Open Clusters ◽

Dynamical Models ◽

Giant Stars ◽

The Past ◽

The Status ◽

History Of ◽

Abundance Profile ◽

Red Giant

AbstractThe time evolution of the radial metallicity gradient is one of the most important constraints for Milky Way chemical and chemo-dynamical models. In this talk we reviewed the status of the observational debate and presented a new measurement of the age dependence of the radial abundance gradients, using combined asteroseismic and spectroscopic observations of red giant stars. We compared our results to state-of-the-art chemo-dynamical Milky Way models and recent literature results obtained with open clusters and planetary nebulae, and propose a new method to infer the past history of the Galactic radial abundance profile.

Download Full-text

A seismic scaling relation for stellar age II: the red giant branch

Monthly Notices of the Royal Astronomical Society Letters ◽

10.1093/mnrasl/slz178 ◽

2019 ◽

Vol 492 (1) ◽

pp. L50-L55 ◽

Cited By ~ 3

Author(s):

Earl Patrick Bellinger

Keyword(s):

Scaling Relations ◽

Red Giants ◽

Giant Stars ◽

Stellar Ages ◽

History Of ◽

Red Giant Stars ◽

Red Giant ◽

Computationally Intensive ◽

Age Relations ◽

Grid Based

ABSTRACT Owing to their simplicity and ease of application, seismic scaling relations are widely used to determine the properties of stars exhibiting solar-like oscillations, such as solar twins and red giants. So far, no seismic scaling relations for determining the ages of red giant stars have been developed. Such relations would be desirable for Galactic Archaeology, which uses stellar ages to map the history of the Milky Way. The ages of red giants must instead be estimated with reference to grids of theoretical stellar models, which can be computationally intensive. Here, I present an exhaustive search for scaling age relations involving different combinations of observable quantities. The candidate scaling relations are calibrated and tested using more than 1000 red giant stars whose ages were obtained via grid-based modelling. I report multiple high-quality scaling relations for red giant branch stars, the best of which are shown to be approximately as accurate as grid-based modelling with typical uncertainties of 15 per cent. Additionally, I present new scaling mass and radius relations for red giants as well.

Download Full-text

Stellar loci IV. red giant stars

Research in Astronomy and Astrophysics ◽

10.1088/1674-4527/21/12/319 ◽

2022 ◽

Vol 21 (12) ◽

pp. 319

Author(s):

Ruo-Yi Zhang ◽

Hai-Bo Yuan ◽

Xiao-Wei Liu ◽

Mao-Sheng Xiang ◽

Yang Huang ◽

...

Keyword(s):

Galactic Halo ◽

Signal To Noise Ratio ◽

Sloan Digital Sky Survey ◽

Red Giants ◽

Giant Stars ◽

Sky Survey ◽

History Of ◽

Red Giant Stars ◽

Red Giant ◽

A New Technique

Abstract In the fourth paper of this series, we present the metallicity-dependent Sloan Digital Sky Survey (SDSS) stellar color loci of red giant stars, using a spectroscopic sample of red giants in the SDSS Stripe 82 region. The stars span a range of 0.55 – 1.2 mag in color g – i, –0.3 – –2.5 in metallicity [Fe/H], and have values of surface gravity log g smaller than 3.5 dex. As in the case of main-sequence (MS) stars, the intrinsic widths of loci of red giants are also found to be quite narrow, a few mmag at maximum. There are however systematic differences between the metallicity-dependent stellar loci of red giants and MS stars. The colors of red giants are less sensitive to metallicity than those of MS stars. With good photometry, photometric metallicities of red giants can be reliably determined by fitting the u – g, g – r, r – i, and i – z colors simultaneously to an accuracy of 0.2 – 0.25 dex, comparable to the precision achievable with low-resolution spectroscopy for a signal-to-noise ratio of 10. By comparing fitting results to the stellar loci of red giants and MS stars, we propose a new technique to discriminate between red giants and MS stars based on the SDSS photometry. The technique achieves completeness of ∼70 per cent and efficiency of ∼80 per cent in selecting metal-poor red giant stars of [Fe/H] ≤ –1.2. It thus provides an important tool to probe the structure and assemblage history of the Galactic halo using red giant stars.

Download Full-text

Metallicity effect on stellar granulation detected from oscillating red giants in open clusters

Astronomy and Astrophysics ◽

10.1051/0004-6361/201731094 ◽

2017 ◽

Vol 605 ◽

pp. A3 ◽

Cited By ~ 23

Author(s):

E. Corsaro ◽

S. Mathur ◽

R. A. García ◽

P. Gaulme ◽

M. Pinsonneault ◽

...

Keyword(s):

Time Scales ◽

Model Comparison ◽

Open Clusters ◽

Stellar Atmospheres ◽

Surface Gravity ◽

Scaling Relations ◽

Red Giants ◽

Giant Stars ◽

Red Giant Stars ◽

Red Giant

Context. The effect of metallicity on the granulation activity in stars, and hence on the convective motions in general, is still poorly understood. Available spectroscopic parameters from the updated APOGEE-Kepler catalog, coupled with high-precision photometric observations from NASA’s Kepler mission spanning more than four years of observation, make oscillating red giant stars in open clusters crucial testbeds. Aims. We aim to determine the role of metallicity on the stellar granulation activity by discriminating its effect from that of different stellar properties such as surface gravity, mass, and temperature. We analyze 60 known red giant stars belonging to the open clusters NGC 6791, NGC 6819, and NGC 6811, spanning a metallicity range from [Fe/H] ≃ − 0.09 to 0.32. The parameters describing the granulation activity of these stars and their frequency of maximum oscillation power, νmax, are studied while taking into account different masses, metallicities, and stellar evolutionary stages. We derive new scaling relations for the granulation activity, re-calibrate existing ones, and identify the best scaling relations from the available set of observations. Methods. We adopted the Bayesian code Diamonds for the analysis of the background signal in the Fourier spectra of the stars. We performed a Bayesian parameter estimation and model comparison to test the different model hypotheses proposed in this work and in the literature. Results. Metallicity causes a statistically significant change in the amplitude of the granulation activity, with a dependency stronger than that induced by both stellar mass and surface gravity. We also find that the metallicity has a significant impact on the corresponding time scales of the phenomenon. The effect of metallicity on the time scale is stronger than that of mass. Conclusions. A higher metallicity increases the amplitude of granulation and meso-granulation signals and slows down their characteristic time scales toward longer periods. The trend in amplitude is in qualitative agreement with predictions from existing 3D hydrodynamical simulations of stellar atmospheres from main sequence to red giant stars. We confirm that the granulation activity is not sensitive to changes in the stellar core and that it only depends on the atmospheric parameters of stars.

Download Full-text

Asteroseismology of Red-Giant Stars as a Novel Approach in the Search for Gravitational Waves

Proceedings of the International Astronomical Union ◽

10.1017/s1743921316005536 ◽

2015 ◽

Vol 11 (A29B) ◽

pp. 363-364

Author(s):

Tiago L. Campante ◽

Ilídio Lopes ◽

D. Bossini ◽

A. Miglio ◽

W. J. Chaplin

Keyword(s):

Gravitational Waves ◽

Open Clusters ◽

Red Giants ◽

Natural Oscillations ◽

Giant Stars ◽

Novel Approach ◽

Oscillation Modes ◽

The Mean ◽

Red Giant Stars ◽

Red Giant

AbstractStars are massive resonators that may be used as gravitational-wave (GW) detectors with isotropic sensitivity. New insights on stellar physics are being made possible by asteroseismology, the study of stars by the observation of their natural oscillations. The continuous monitoring of oscillation modes in stars of different masses and sizes (e.g., as carried out by NASA's Kepler mission) opens the possibility of surveying the local Universe for GW radiation. Red-giant stars are of particular interest in this regard. Since the mean separation between red giants in open clusters is small (a few light years), this can in principle be used to look for the same GW imprint on the oscillation modes of different stars as a GW propagates across the cluster. Furthermore, the frequency range probed by oscillations in red giants complements the capabilities of the planned eLISA space interferometer. We propose asteroseismology of red giants as a novel approach in the search for gravitational waves.

Download Full-text