scholarly journals The rotational evolution of young low mass stars

2007 ◽  
Vol 3 (S243) ◽  
pp. 231-240 ◽  
Author(s):  
Jérôme Bouvier
Keyword(s):  
Angular Momentum ◽  
Accretion Disk ◽  
Main Sequence ◽  
Young Stars ◽  
Sequence Evolution ◽  
Main Sequence Stars ◽  
Low Mass Stars ◽  
Rotational Evolution ◽  
Low Mass

AbstractStar-disk interaction is thought to drive the angular momentum evolution of young stars. In this review, I present the latest results obtained on the rotational properties of low mass and very low mass pre-main sequence stars. I discuss the evidence for extremely efficient angular momentum removal over the first few Myr of pre-main sequence evolution and describe recent results that support an accretion-driven braking mechanism. Angular momentum evolution models are presented and their implication for accretion disk lifetimes discussed.

scholarly journals Effect of mass gain on stellar evolution

1981 ◽  
Vol 59 ◽  
pp. 361-371
Author(s):  
R. Ebert ◽  
H. Zinnecker
Keyword(s):  
Stellar Evolution ◽  
Main Sequence ◽  
Accretion Rate ◽  
Mass Gain ◽  
Point Mass ◽  
Sequence Evolution ◽  
Main Sequence Stars ◽  
Low Mass Stars ◽  
Low Mass ◽  
Cloud Material

AbstractIn this paper we present a fully hydrodynamical treatment of the stationary isothermal accretion problem onto a moving gravitating point mass. The derivation is purely analytical. We find that the accretion rate is more than a factor of 50 higher than the accretion rate derived from the partially non-hydrodynamical treatment by Hoyle and Lyttleton (1939) or Bondi and Hoyle (1944). This result may have some bearing on the evolutionary tracks of young pre-Main Sequence stars still embedded in their parent protocluster cloud. We discuss the work by Federova (1979) who investigated the pre-Main Sequence evolution of degenerate low mass ‘stars’ with strong accretion of protocluster cloud material. We suggest that the stars which lie below the Main Sequence in young clusters could strongly accrete matter at the pre-Main Sequence stage.

scholarly journals Planetary tidal interactions and the rotational evolution of low-mass stars

2018 ◽  
Vol 619 ◽  
pp. A80 ◽  
Author(s):  
F. Gallet ◽  
E. Bolmont ◽  
J. Bouvier ◽  
S. Mathis ◽  
C. Charbonnel
Keyword(s):  
Angular Momentum ◽  
Main Sequence ◽  
Open Cluster ◽  
Rotation Period ◽  
Rotational Period ◽  
Low Mass Stars ◽  
General Behaviour ◽  
Period Distribution ◽  
Rotational Evolution ◽  
Low Mass

Context. The surface angular velocity evolution of low-mass stars is now globally understood and the main physical mechanisms involved in it are observationally quite constrained. However, while the general behaviour of these mechanisms is grasped, their theoretical description is still under ongoing work. This is the case, for instance, about the description of the physical process that extracts angular momentum from the radiative core, which could be described by several theoretical candidates. Additionally, recent observations showed anomalies in the rotation period distribution of open cluster, main sequence, early K-type stars that cannot be reproduced by current angular momentum evolution models. Aims. In this work, we study the parameter space of star-planet system’s configurations to investigate if including the tidal star-planet interaction in angular momentum evolution models could reproduce the anomalies of this rotation period distribution. Methods. To study this effect, we use a parametric angular momentum evolution model that allows for core-envelope decoupling and angular momentum extraction by magnetized stellar wind that we coupled to an orbital evolution code where we take into account the torque due to the tides raised on the star by the planet. We explore different stellar and planetary configurations (stellar mass from 0.5 to 1.0 M⊙ and planetary mass from 10 M⊕ to 13 Mjup) to study their effect on the planetary orbital and stellar rotational evolution. Results. The stellar angular momentum is the most impacted by the star-planet interaction when the planet is engulfed during the early main sequence phase. Thus, if a close-in Jupiter-mass planet is initially located at around 50% of the stellar corotation radius, a kink in the rotational period distribution opens around late and early K-type stars during the early main sequence phase. Conclusions. Tidal star-planet interactions can create a kink in the rotation period distribution of low-mass stars, which could possibly account for unexpected scatter seen in the rotational period distribution of young stellar clusters.

scholarly journals Radio observations of jets from massive young stars

2010 ◽  
Vol 6 (S275) ◽  
pp. 367-373 ◽  
Author(s):  
Luis F. Rodríguez
Keyword(s):  
Angular Momentum ◽  
Accretion Disk ◽  
Accretion Disks ◽  
Thermal Process ◽  
Massive Stars ◽  
Surrounding Medium ◽  
Young Stars ◽  
Low Mass Stars ◽  
Molecular Outflows ◽  
Low Mass

AbstractThe formation of low mass stars takes place with the assistance of an accretion disk that transports gas and dust from the envelope of the system to the star, and a jet that removes angular momentum and allows accretion to proceed. In the radio, these ionized jets can be studied very close to the star via the thermal (free-free) emission they produce and at larger scales by the molecular outflows that result from their interaction with the surrounding medium. Is the same disk-jet process responsible for the formation of massive stars? I will review recent evidence for the presence of collimated jets and accretion disks in association with forming massive stars. The jets in massive protostars have large velocities that could produce a synchrotron component and I discuss the evidence for the presence of this non-thermal process in the jet associated with the HH 80-81 system.

scholarly journals Measurements of the Ca ii infrared triplet emission lines of pre-main-sequence stars

2020 ◽  
Vol 72 (5) ◽  
Author(s):  
Mai Yamashita ◽  
Yoichi Itoh ◽  
Yuhei Takagi
Keyword(s):  
Main Sequence ◽  
Open Clusters ◽  
Emission Lines ◽  
Main Sequence Stars ◽  
Low Mass Stars ◽  
Chromospheric Activity ◽  
Low Mass ◽  
Pms Stars ◽  
Infrared Triplet ◽  
Narrow Emission

Abstract We investigated the chromospheric activity of 60 pre-main-sequence (PMS) stars in four molecular clouds and five moving groups. It is considered that strong chromospheric activity is driven by the dynamo processes generated by stellar rotation. In contrast, several researchers have pointed out that the chromospheres of PMS stars are activated by mass accretion from their protoplanetary disks. In this study, the Ca ii infrared triplet (IRT) emission lines were investigated utilizing medium- and high-resolution spectroscopy. The observations were conducted with Nayuta/MALLS and Subaru/HDS. Additionally, archive data obtained by Keck/HIRES, VLT/UVES, and VLT/X-Shooter were used. The small ratios of the equivalent widths indicate that Ca ii IRT emission lines arise primarily in dense chromospheric regions. Seven PMS stars show broad emission lines. Among them, four PMS stars have more than one order of magnitude brighter emission line fluxes compared to the low-mass stars in young open clusters. The four PMS stars have a high mass accretion rate, which indicates that the broad and strong emission results from a large mass accretion. However, most PMS stars exhibit narrow emission lines. No significant correlation was found between the accretion rate and flux of the emission line. The ratios of the surface flux of the Ca ii IRT lines to the stellar bolometric luminosity, $R^{\prime }_{\rm IRT}$, of the PMS stars with narrow emission lines are as large as the largest $R^{\prime }_{\rm IRT}$ of the low-mass stars in the young open clusters. This result indicates that most PMS stars, even in the classical T Tauri star stage, have chromospheric activity similar to zero-age main-sequence stars.

scholarly journals The rotation of very low-mass stars and brown dwarfs

2007 ◽  
Vol 3 (S243) ◽  
pp. 241-248
Author(s):  
Jochen Eislöffel ◽  
Alexander Scholz
Keyword(s):  
Angular Momentum ◽  
Brown Dwarfs ◽  
Magnetic Interaction ◽  
Stellar Winds ◽  
Solar Mass ◽  
Low Mass Stars ◽  
Angular Momentum Loss ◽  
Rotational Evolution ◽  
Solar Type ◽  
Low Mass

AbstractThe evolution of angular momentum is a key to our understanding of star formation and stellar evolution. The rotational evolution of solar-mass stars is mostly controlled by magnetic interaction with the circumstellar disc and angular momentum loss through stellar winds. Major differences in the internal structure of very low-mass stars and brown dwarfs – they are believed to be fully convective throughout their lives, and thus should not operate a solar-type dynamo – may lead to major differences in the rotation and activity of these objects. Here, we report on observational studies to understand the rotational evolution of the very low-mass stars and brown dwarfs.

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