Related papers: On the evolutionary status of lambda Bootis stars …
Recent theoretical work has shown that the pre-main-sequence (PMS) evolution of stars is much more complex than previously envisioned. Instead of the traditional steady, one-dimensional solution, accretion may be episodic and not…
Although the means of the ages of stars in young groups determined from Li depletion often agree with mean ages determined from Hertzsprung - Russell diagram isochrones, there are often statistically significant differences in the ages of…
The early stages of the pre-Main-Sequence (PMS) evolution of young stars are characterized by a substantial interaction between the central star and the surrounding disk. Among the processes that take place, the accretion of material from…
Stellar masses are a fundamental property to understand models of pre-main sequence evolution, but their values derived from Hertzsprung-Russell (HR) diagrams are strongly model dependent. We benchmark pre-main sequence stellar evolutionary…
The problem of the determination of T Tauri stars masses and ages using their evolutionary status is discussed. We test of pre-main sequence evolutionary models of D'Antona \& Mazzitelli (1994), Dotter et al. (2008), Bressan et al. (2012)…
The evolutionary status of the chemically peculiar class of $\lambda$ Boo stars has been intensely debated. It is now agreed that the $\lambda$ Boo phenomenon affects A stars of all ages, from star formation to the terminal age main…
Lithium abundances and rotation, determined for 120 subgiant stars in Lebre et al. (1999) are analyzed. To this purpose, the evolutionary status of the sample as well as the individual masses have been determined using the HIPPARCOS…
It is still a matter of debate if the group of lambda Bootis stars is homogeneously defined. A widely discussed working hypothesis formulates that two apparent solar abundant stars of an undetected spectroscopic binary system mimic a single…
This work presents a spectroscopic study of 163 Herbig Ae/Be stars. Amongst these, we present new data for 30 objects. Stellar parameters such as temperature, reddening, mass, luminosity and age are homogeneously determined. Mass accretion…
The lambda Bootis (LB) stars are located at the upper main sequence of the H-R diagram and exhibit a peculiar abundance pattern. The light elements (C, N, O, and S) present solar abundances whereas all other elements are moderately to…
One-dimensional stellar evolution models have been successful at representing the structure and evolution of stars in diverse astrophysical contexts, but complications have been noted in the context of young, magnetically active stars, as…
Field Horizontal branch (HB) stars can be used as tracers for the study of early stages of the evolution of our galaxy. Since the age of individual HB stars is not known a priori, we have studied the kinematics of a sample of field HB stars…
The temporal decay of mass accretion in young stars is a fundamental tracer of the early evolution of circumstellar disks. Through population syntheses, we study how correlated uncertainties between the estimated parameters of young stars…
Growing evidence suggests that protoplanetary discs may be influenced by late stage infall from the interstellar medium (ISM). It remains unclear the degree to which infall shapes disc populations at ages $\gtrsim 1$~Myr. We explore…
We have analysed around 170 000 individual photometric WASP measurements of 15 well established lambda Bootis stars to search for variability. The lambda Bootis stars are a small group of late-B to early-F, Pop. I, stars that show moderate…
We discuss the impact of Population II and Globular Cluster (GCs) stars on the derivation of the age of the Universe, and on the study of the formation and early evolution of galaxies, our own in particular. The long-standing problem of the…
During this last decade our knowledge of the evolutionary properties of stars has significantly improved. This result has been achieved thanks to our improved understanding of the physical behavior of stellar matter in the thermal regimes…
In the age of high-resolution spectroscopic stellar surveys of the Milky Way, the number of stars with detailed abundances of multiple elements is rapidly increasing. These elemental abundances are directly influenced by the evolutionary…
The process that leads to the formation and early evolution of low-mass stars is in a broad sense well understood theoretically and carefully traced observationally. The largest uncertainties in this framework reside in the poorly known…
$\lambda$ Bo\"otis stars are a subset of chemically peculiar A-stars that display Solar abundances in lighter elements (C, N, O, S, etc.) but a deficiency in Iron-peak elements. This difference has been attributed to the A-stars accreting…