Found 7 talks width keyword fundamental parameters
Understanding stellar structure and evolution significantly impacts our understanding of the tight-knit evolution of galaxies and exoplanet systems. However, hidden behind the luminous layers of the stellar atmosphere, the deep interior of a star is eluding from direct measurements. The seismic study of waves propagating the deep interior provides the only way to measure the internal structure, dynamics, and mixing in any given star and compare it to theoretical models.
With the photometric data from space missions, such as the NASA Kepler telescope, a golden age has begun for seismology. In particular, the seismic studies of thousands of solar-like have led to numerous breakthroughs in our understanding of the stellar structure of red-giant stars. Complimentary information on stellar binarity, tidal forces, rotation, and lithium abundance provide additional constraints to characterize the advanced evolution of stars further and provide high-resolution insights into complex internal adjustments. Approaching a sample of ~1000 identified solar-like oscillators in binary systems, provided by the ESA Gaia and NASA TESS missions draws an exciting picture on the interaction of stellar and orbital evolution.
ID de reunión: 892 7515 0368
Código de acceso: 101169
The field of Galactic archaeology has been very active in recent years, with a major influx of data from the Gaia satellite and large spectroscopic surveys. The major science questions in the field include Galactic structure and dynamics, the accretion history of the Milky Way, chemical tagging, and age-abundance relations. I will give an overview of GALAH as a large spectroscopic survey, and describe how it is complementary to other ongoing and future survey projects. I will also discuss recent science highlights from the GALAH team and compelling questions for future work.
Fundamental properties of brown dwarfs, such as luminosity and effective temperature, evolve with age. Large samples of spectroscopically-confirmed substellar objects with well-determined ages and distances are needed to constrain those parameters. We are embarked in a spectroscopic follow-up with GTC/OSIRIS of low-mass member candidates selected in several open clusters to constrain their membership. Here I will present the first L dwarf member in Praesepe confirmed by photometry, astrometry, and spectroscopy. We derived an optical spectral type of L0.3+/-0.4 and a mass placing it at the hydrogen-burning boundary. Considering the measured equivalent width of the gravity-sensitive sodium doublet, and the derived membership probability of ~80% or higher, we conclude that this object is likely to be a true member of Praesepe, with evidence of being a binary system.
The vision for the use of the WHT in the coming decade is taking shape. A key element is the construction and deployment of WEAVE, a wide-field massive-multiplex spectrograph. With 1000 fibres and spectral resolutions of 5000 and 20000, the opportunities for discovery are tremendous. Three key fields will be: Milky-Way and Local Group archaeology linked to the Gaia mission; cosmology redshift surveys; and galaxy evolution studies linked to photometric surveys such as VISTA, UKIDSS, LOFAR, EUCLID, and others. IAC has the opportunity to get involved in this important instrument for ORM from the beginning.
The Kepler spacecraft is providing photometric time series with micromagnitude precision for thousands of variable stars. The continuous time-series of unprecedented timespan open up the opportunity to study the pulsational variability in much more detail than was previously possible from the ground. We present a first general characterization of the variability of A-F type stars as observed in the Kepler light curves of a sample of 750 candidate variable A-F type stars, and investigate the relation between gamma Doradus, delta Scuti, and hybrid stars. Our results suggest a revision of the current observational instability strips, and imply an investigation of pulsation mechanisms to drive hybrid pulsations.
Instituto de Astrofísica de Canarias, Spain
We have selected the Galactic HII region M43, a close-by apparently spherical nebula ionized by a single star (HD37061, B0.5V) to investigate several topics of recent interest in the field of HII regions and massive stars. We perform a combined, comprehensive study
of the nebula and its ionizing star by using as many observational constraints as possible. For this study we collected a set of high-quality observations, including the optical spectrum of HD3706, along with nebular optical imaging and long-slit spatially resolved spectroscopy. On the one hand, we have carried out a quantitative spectroscopic analysis of the ionizing star from which we have determined the stellar parameters of HD37061 and the total number of ionizing photons emitted by the star; on the other hand, we have done a
empirical analysis of the nebular images and spectroscopy from which we have find observational evidence of scattered light from the Huygens region (the brightest part of the Orion nebula) in the M43 region. We show the importance of an adequate correction of this scattered light in both the imagery and spectroscopic observations of M43 in accurately determining the total nebular Halpha luminosity, the nebular physical
conditions. and chemical abundances. We have computed total abundances for three of the analyzed elements (O, S, and N), directly from
observable ions (no ionization correction factors are needed). The comparison of these abundances with those derived from the spectrum of the Orion nebula indicates the importance of the atomic data and, specially in the case of M42, the considered ionization correction factors.
Based on observations with the Advanced Camera for Surveys (ACS), I will present accurate relative ages for a sample of 64 Galactic globular clusters. This Hubble Space Telescope (HST) Treasury program has been designed to provide a new large, deep and homogeneous photometric database. Relative ages have been obtained using a main sequence fitting procedure between clusters in the sample. Relative ages are determined with an accuracy from 2% to 7%. It has been proved that derived ages are independent of the assumed theoretical models. The existence of two well defined Galactic globular cluster groups is found. A group of old globular clusters with an age dispersion of 6% and showing no age-metallicity relation, and, on the other hand, a younger group showing a clear age-metallicity relation similar to that found in the globular clusters associated to the Sagittarius dwarf galaxy. Roughly 1/3 of the clusters belong to the younger group. Considering these new results, it is very tempting to suggest a Milky Way's halo formation scenario in which two differentiated phases took place. A very fast collapse, where the old and coeval globular clusters where formed, followed by accretions of Milky Way's satellite galaxies.
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- TBDThursday December 14, 2023 - 10:30 GMT (Aula)
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