Low-Mass Stars. II. The Core Mass--Luminosity Relations for Low-Mass Stars

1988 ◽  
Vol 328 ◽  
pp. 641 ◽  
Author(s):  
Arnold I. Boothroyd ◽  
I.-Juliana Sackmann
Keyword(s):  
Low Mass Stars ◽  
Core Mass ◽  
The Core ◽  
Low Mass

scholarly journals Core-hydrogen-burning RSGs in the early globular clusters

2015 ◽  
Vol 11 (A29B) ◽  
pp. 473-473
Author(s):  
Dorottya Szécsi ◽  
Jonathan Mackey ◽  
Norbert Langer
Keyword(s):  
Globular Clusters ◽  
Stellar Population ◽  
Massive Stars ◽  
Shell Formation ◽  
Low Mass Stars ◽  
Hydrogen Burning ◽  
The Core ◽  
Anomalous Surface ◽  
Low Metallicity ◽  
Low Mass

AbstractThe first stellar generation in galactic globular clusters contained massive low-metallicity stars (Charbonnel et al. 2014). We modelled the evolution of this massive stellar population and found that such stars with masses 100-600 M⊙ evolve into cool RSGs (Szécsi et al. 2015). These RSGs spend not only the core-He-burning phase but even the last few 105 years of the core-H-burning phase on the SG branch. Due to the presence of hot massive stars in the cluster at the same time, we show that the RSG wind is trapped into photoionization confined shells (Mackey et al. 2014). We simulated the shell formation around such RSGs and find them to become gravitationally unstable (Szécsi et al. 2016). We propose a scenario in which these shells are responsible for the formation of the second generation low-mass stars in globular clusters with anomalous surface abundances.

scholarly journals A SCUBA survey of Orion – the low-mass end of the core mass function

2007 ◽  
Vol 374 (4) ◽  
pp. 1413-1420 ◽  
Author(s):  
D. Nutter ◽  
D. Ward-Thompson
Keyword(s):  
Mass Function ◽  
Core Mass ◽  
The Core ◽  
Low Mass

scholarly journals Can plume-induced internal gravity waves regulate the core rotation of subgiant stars?

2017 ◽  
Vol 605 ◽  
pp. A31 ◽  
Author(s):  
C. Pinçon ◽  
K. Belkacem ◽  
M. J. Goupil ◽  
J. P. Marques
Keyword(s):  
Angular Momentum ◽  
Differential Rotation ◽  
Internal Gravity Waves ◽  
Low Mass Stars ◽  
Rotation Rates ◽  
The Core ◽  
Low Mass ◽  
Red Giant ◽  
Core Rotation ◽  
Subgiant Stars

Context. The seismic data provided by the space-borne missions CoRoT and Kepler enabled us to probe the internal rotation of thousands of evolved low-mass stars. Subsequently, several studies showed that current stellar evolution codes are unable to reproduce the low core rotation rates observed in these stars. These results indicate that an additional angular momentum transport process is necessary to counteract the spin up due to the core contraction during the post-main sequence evolution. For several candidates, the transport induced by internal gravity waves (IGW) could play a non-negligible role. Aims. We aim to investigate the effect of IGW generated by penetrative convection on the internal rotation of low-mass stars from the subgiant branch to the beginning of the red giant branch. Methods. A semi-analytical excitation model was used to estimate the angular momentum wave flux. The characteristic timescale associated with the angular momentum transport by IGW was computed and compared to the contraction timescale throughout the radiative region of stellar models at different evolutionary stages. Results. We show that IGW can efficiently counteract the contraction-driven spin up of the core of subgiant stars if the amplitude of the radial-differential rotation (between the center of the star and the top of the radiative zone) is higher than a threshold value. This threshold depends on the evolutionary stage and is comparable to the differential rotation rates inferred for a sample of subgiant stars observed by the satellite Kepler. Such an agreement can therefore be interpreted as the consequence of a regulation mechanism driven by IGW. This result is obtained under the assumption of a smooth rotation profile in the radiative region and holds true even if a wide range of values is considered for the parameters of the generation model. In contrast, on the red giant branch, we find that IGW remain insufficient, on their own, to explain the observations because of an excessive radiative damping. Conclusions. IGW generated by penetrative convection are able to efficiently extract angular momentum from the core of stars on the subgiant branch and accordingly have to be taken into account. Moreover, agreements with the observations reinforce the idea that their effect is essential to regulate the amplitude of the radial-differential rotation in subgiant stars. On the red giant branch, another transport mechanism must likely be invoked.

The First Proto-Brown Dwarf Binary Candidate Identified through Dynamics of Jets

2015 ◽  
Vol 11 (S315) ◽  
Author(s):  
Tien-Hao Hsieh ◽  
Shih-Ping Lai ◽  
Arnaud Belloche ◽  
Friedrich Wyrowski
Keyword(s):  
Binary System ◽  
Orbital Motion ◽  
Brown Dwarf ◽  
Low Mass Stars ◽  
Core Mass ◽  
Substellar Objects ◽  
Current Mass ◽  
Low Mass ◽  
Dynamical Features ◽  
First Time

AbstractThe formation mechanism of brown dwarfs (BDs) is one of the long-standing problems in star formation because the typical Jeans mass in molecular clouds is too large to form these substellar objects. To answer this question, it is crucial to study a BD at the embedded phase (proto-brown dwarf). IRAS16253 is classified as a Very Low Luminosity Object (VeLLO, Lint < 0.1L⊙), which is considered as a proto-brown dwarf candidate. We use the IRAM 30m, APEX telescopes and the SMA to probe the molecular jet/outflow driven by IRAS 16253 in CO (2–1), (6–5), and (7–6) and study its dynamical features and physical properties. We detect a wiggling pattern in the position-velocity diagrams of the jets. Assuming that this pattern is due to the orbital motion of a binary system, we obtain the current mass of the binary is ~0.026 M⊙. Together with the low parent core mass, IRAS16253 will likely form one or two proto-BD in the future. This is the first time that the current mass of a proto-BD binary system is identified through the dynamics of the jets. Since IRAS16253 is located in an isolated environment, we suggest that BDs can form through fragmentation and collapse like low mass stars.

scholarly journals Constraints on stellar evolution from white dwarf asteroseismology

2014 ◽  
Vol 9 (S307) ◽  
pp. 211-212
Author(s):  
Agnès Bischoff-Kim
Keyword(s):  
Stellar Evolution ◽  
Reaction Rate ◽  
Time Dependent ◽  
High Mass ◽  
Low Mass Stars ◽  
Capture Reaction ◽  
The Core ◽  
Inert Core ◽  
Core Phase ◽  
Low Mass

AbstractHigh mass and low mass stars follow a similar evolution until the inert core phase that follows the end of the core helium burning stage. In particular, one common phase of stellar evolution is the alpha capture reaction that turns carbon into oxygen in the core. We can obtain constraints on this reaction rate by studying the remnants of low mass stars, as this is the ultimate reaction that occurs in their core. We also present results that allow us to test the time dependent calculations of diffusion in dense interiors.

scholarly journals Modification of the Core Overshoot Treatment

2002 ◽  
Vol 207 ◽  
pp. 736-738
Author(s):  
Jong-Hak Woo ◽  
Pierre Demaque ◽  
Sukyoung Yi
Keyword(s):  
Conventional Method ◽  
Integral Constraint ◽  
Core Radius ◽  
Low Mass Stars ◽  
The Core ◽  
Upper Limit ◽  
Low Mass

Following Roxburgh's integral constraint, we implemented an upper limit of overshoot in the conventional method of α parameterization in order to remove an overly large overshoot effect for low-mass stars. The erroneously large effect of overshoot due to the failure of α parameterization can be effectively corrected by limiting the amount of overshoot to 15 % of the core radius.

scholarly journals The Effect of Coulomb Interactions on the Helium Flash

1989 ◽  
Vol 114 ◽  
pp. 81-84
Author(s):  
A. Harpaz ◽  
A. Kovetz
Keyword(s):  
Mass Loss ◽  
Charged Particles ◽  
Red Giants ◽  
Coulomb Interactions ◽  
Core Mass ◽  
The Core ◽  
Low Mass ◽  
Red Giant ◽  
Recent Claim

AbstractDetailed evolutionary calculations show that Coulomb interactions between the charged particles of a stellar plasma reduce the core mass at which a low mass red giant undergoes the helium flash (contrary to a recent claim). This has implications for the determination of the rate of mass loss from red giants.

scholarly journals Evolutionary Properties of Intermediate-Mass Stars

2004 ◽  
Vol 193 ◽  
pp. 489-497 ◽  
Author(s):  
Santi Cassisi
Keyword(s):  
Turbulent Convection ◽  
Observational Constraints ◽  
Intermediate Mass ◽  
Low Mass Stars ◽  
The Core ◽  
Intermediate Mass Stars ◽  
Low Mass ◽  
Stellar Models

AbstractWe briefly review the main problems related to the computation of the evolution of intermediate-mass stars: the treatment of turbulent convection and the occurrence of blue loops during the core He-burning phase. It is shown that, in order to obtain more accurate and reliable stellar models for this class of stars, one has to consider all possible theoretical and observational constraints. These include observations of low-mass stars to constrain the treatment of envelope convection, and the analysis of the pulsational behaviour of Cepheid stars.

scholarly journals Discs, outflows, and feedback in collapsing magnetized cores

2010 ◽  
Vol 6 (S270) ◽  
pp. 291-295 ◽  
Author(s):  
Dennis F. Duffin ◽  
Ralph E. Pudritz
Keyword(s):  
Angular Momentum ◽  
Adaptive Mesh Refinement ◽  
Adaptive Mesh ◽  
Core Region ◽  
Low Mass Stars ◽  
Disk Formation ◽  
The Core ◽  
Low Mass ◽  
Magnetic Braking ◽  
Protostellar Discs

AbstractThe pre-stellar cores in which low mass stars form are generally well magnetized. Our simulations show that early protostellar discs are massive and experience strong magnetic torques in the form of magnetic braking and protostellar outflows. Simulations of protostellar disk formation suggest that these torques are strong enough to suppress a rotationally supported structure from forming for near critical values of mass-to-flux. We demonstrate through the use of a 3D adaptive mesh refinement code – including cooling, sink particles and magnetic fields – that one produces transient 1000 AU discs while simultaneously generating large outflows which leave the core region, carrying away mass and angular momentum. Early inflow/outflow rates suggest that only a small fraction of the mass is lost in the initial magnetic tower/jet event.

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