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We review progress in numerical simulations of star cluster formation. These simulations involve the bottom-up assembly of clusters through hierarchical mergers, which produces a fractal stellar distribution at young (~0.5 Myr) ages. The…

Astrophysics of Galaxies · Physics 2015-05-14 Cathie Clarke

It has recently been suggested that all giant stars with mass below 2 $M_{\odot}$ suffer an episode of surface lithium enrichment between the tip of the red giant branch (RGB) and the red clump (RC). We test if the above result can be…

There is a growing evidence that several globular clusters must contain multiple stellar generations, differing in helium content. This hypothesis has helped to interpret peculiar unexplained features in their horizontal branches. In this…

Astrophysics · Physics 2010-02-18 Vittoria Caloi , Francesca D'Antona

We study stellar models for Betelgeuse using the HR diagram and surface abundances as observational constraints. Previous studies on Betelgeuse have not systematically investigated the surface abundances, but we believe they can be impacted…

Solar and Stellar Astrophysics · Physics 2022-03-14 Tianyin Luo , Hideyuki Umeda , Takashi Yoshida , Koh Takahashi

We have determined new rotation periods for 404 stars in the Orion Nebula Cluster using the Wide Field Imager attached to the MPG/ESO 2.2 m telescope on La Silla, Chile. Mass estimates are available for 335 of these and most have M < 0.3…

Astrophysics · Physics 2009-11-06 W. Herbst , C. A. L. Bailer-Jones , R. Mundt

Young massive star clusters spanning $\sim 10^4 - 10^8 M_\odot$ in mass have been observed to have similar surface brightness profiles. Recent hydrodynamical simulations of star cluster formation have also produced star clusters with this…

Collisional relaxation describes the stochastic process with which a self-gravitating system near equilibrium evolves in phase space due to the fluctuating gravitational field of the system. The characteristic timescale of this process is…

Astrophysics of Galaxies · Physics 2018-03-28 Yohai Meiron , Bence Kocsis

Main-sequence stars with convective envelopes often appear larger and cooler than predicted by standard models of stellar evolution for their measured masses. This is believed to be caused by stellar activity. In a recent study, accurate…

Solar and Stellar Astrophysics · Physics 2021-12-24 Guillermo Torres , Gregory A. Feiden , Andrew Vanderburg , Jason L. Curtis

As the closest open cluster to the Sun, the Hyades is an important benchmark for many stellar properties, but its members are also scattered widely over the sky. Previous studies of stellar rotation in the Hyades relied on targeted…

Solar and Stellar Astrophysics · Physics 2016-05-25 S. T. Douglas , M. A. Agüeros , K. R. Covey , P. A. Cargile , T. Barclay , A. Cody , S. B. Howell , T. Kopytova

(Abridged) We present theoretical models of stellar angular momentum evolution from the Orion Nebula Cluster (ONC) to the Pleiades and the Hyades. We demonstrate that observations of the Pleiades and Hyades place tight constraints on the…

Astrophysics · Physics 2009-11-06 Jeremy Tinker , Marc Pinsonneault , Donald Terndrup

Stellar rotation periods measured in open clusters have proved to be extremely useful for studying stars' angular momentum content and rotationally driven magnetic activity, which are both age- and mass-dependent processes. While period…

Solar and Stellar Astrophysics · Physics 2016-05-25 Kevin R. Covey , Marcel A. Agüeros , Nicholas M. Law , Jiyu Liu , Aida Ahmadi , Russ Laher , David Levitan , Branimir Sesar , Jason Surace

We investigate the dissolution process of young embedded star clusters with different primordial mass segregation levels using fractal distributions by means of N-body simulations. We combine several star clusters in virial and subvirial…

Astrophysics of Galaxies · Physics 2021-09-29 R. Domínguez , J. P. Farias , M. Fellhauer , Ralf S. Klessen

Almost all young stars are found in multiple systems. This suggests that protostellar cores almost always fragment into multiple objects. The observed properties of multiple systems such as their separation distribution and mass ratios…

Astrophysics · Physics 2007-05-23 S. P. Goodwin , P. Kroupa , A. Goodman , A. Burkert

We investigate the pulsation properties of stellar models representative of $\delta$ Scuti and $\gamma$ Doradus variables. We have calculated a grid of stellar models from 1.2 to 2.2 M$_{\odot}$, including the effects of both rotation and…

Solar and Stellar Astrophysics · Physics 2017-11-08 C. C. Lovekin , J. A. Guzik

Lithium is a sensitive probe to mixing processes operating in stellar interiors. For many years, a connection has been suspected to exist between lithium abundances and stellar rotation, presumably the result of rotationally-induced…

Solar and Stellar Astrophysics · Physics 2020-09-07 J. Bouvier

Globular clusters were thought to be simple stellar populations, but recent photometric and spectroscopic evidence suggests that the clusters' early formation history was more complicated. In particular, clusters show star-to-star abundance…

Solar and Stellar Astrophysics · Physics 2015-05-18 Alison Sills , Evert Glebbeek

Hydra spectra of 85 G-K dwarfs in the young cluster, M35, near the Li 6708 Angstrom line region are analyzed. From velocities and Gaia astrometry, 78 are likely single-star members which, combined with previous work, produces 108 members…

Solar and Stellar Astrophysics · Physics 2018-07-18 B. J. Anthony-Twarog , C. P. Deliyannis , D. Harmer , D. B. Lee-Brown , A. Steinhauer , Q. Sun , B. A. Twarog

We present FLAMES/GIRAFFE spectroscopy obtained at the Very Large Telescope (VLT). Using these observations we have been able for the first time to observe the Li I doublet in the Main Sequence stars of a Globular Cluster. We also observed…

Astrophysics of Galaxies · Physics 2015-05-14 J. I. González Hernández , P. Bonifacio , E. Caffau , M. Steffen , H. -G. Ludwig , N. Behara , L. Sbordone , R. Cayrel , S. Zaggia

Observed mass-to-light ratios (M/L) of metal-rich globular clusters (GCs) disagree with theoretical predictions. This discrepancy is of fundamental importance since stellar population models provide the stellar masses that underpin most of…

In this review I briefly discuss the theory of pre-main-sequence (PMS) Li depletion in low-mass (0.075<M<1.2 Msun) stars and highlight those uncertain parameters which lead to substantial differences in model predictions. I then summarise…

Astrophysics · Physics 2015-12-09 R. D. Jeffries