The Gaia-ESO survey: Mixing processes in low-mass stars traced by lithium abundance in cluster and field stars

Recently, an analysis of Gaia Data Release 2 revealed a gap in the mid-M dwarf main sequence. The authors suggested the feature is linked to the onset of full convection in M dwarfs. Following the announcement of this discovery, an explanation has been proposed based on standard stellar evolution models. In this paper we re-examine this explanation. We confirm that nuclear burning and mixing processes of 3He provide the best explanation for the observed feature. We also find that a change in the energy transport from convection to radiation does not induce structural changes that could be visible. Regarding the very details of the process, however, we disagree with the details of the published explanation and propose an alternative.

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The Shape of the Red Giant Branch Bump as a Diagnostic of Partial Mixing Processes in Low‐Mass Stars

The Astrophysical Journal ◽

10.1086/324695 ◽

2002 ◽

Vol 565 (2) ◽

pp. 1231-1238 ◽

Cited By ~ 38

Author(s):

Santi Cassisi ◽

Maurizio Salaris ◽

Giuseppe Bono

Keyword(s):

Low Mass Stars ◽

Mixing Processes ◽

Low Mass ◽

Red Giant

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Lithium-rotation connection in the newly discovered young stellar stream Psc–Eri (Meingast 1)

Astronomy and Astrophysics ◽

10.1051/0004-6361/201937137 ◽

2020 ◽

Vol 635 ◽

pp. L13 ◽

Cited By ~ 3

Author(s):

J. Arancibia-Silva ◽

J. Bouvier ◽

A. Bayo ◽

P. A. B. Galli ◽

W. Brandner ◽

...

Keyword(s):

Rotation Rate ◽

Main Sequence ◽

Lithium Content ◽

Physical Processes ◽

Low Mass Stars ◽

Lithium Abundance ◽

Low Mass ◽

Stellar Interiors ◽

Tight Correlation ◽

The Relationship

Context. As a fragile element, lithium is a sensitive probe of physical processes occurring in stellar interiors. Aims. We aim to investigate the relationship between lithium abundance and rotation rate in low-mass members of the newly discovered 125 Myr-old Psc–Eri stellar stream. Methods. We obtained high-resolution optical spectra and measured the equivalent width of the 607.8 nm LiI line for 40 members of the Psc–Eri stream, whose rotational periods have been previously derived. Results. We show that a tight correlation exists between the lithium content and rotation rate among the late-G to early-K-type stars of the Psc–Eri stream. Fast rotators are systematically Li rich, while slow rotators are Li depleted. This trend mimics that previously reported for the similar age Pleiades cluster. Conclusions. The lithium-rotation connection thus seems to be universal over a restricted effective temperature range for low-mass stars at or close to the zero-age main sequence, and does not depend on environmental conditions.

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Thermohaline mixing in low-mass giants

Proceedings of the International Astronomical Union ◽

10.1017/s1743921308022540 ◽

2008 ◽

Vol 4 (S252) ◽

pp. 103-109 ◽

Cited By ~ 6

Author(s):

M. Cantiello ◽

N. Langer

Keyword(s):

Differential Rotation ◽

Main Sequence ◽

Red Giants ◽

Helium Burning ◽

Low Mass Stars ◽

Mixing Processes ◽

Low Mass ◽

Magnetic Mixing ◽

Red Giant

AbstractThermohaline mixing has recently been proposed to occur in low mass red giants, with large consequences for the chemical yields of low mass stars. We investigate the role of thermohaline mixing during the evolution of stars between 1 M⊙ and 3 M⊙, in comparison to other mixing processes acting in these stars. We confirm that thermohaline mixing has the potential to destroy most of the 3He which is produced earlier on the main sequence during the red giant stage. In our models we find that this process is working only in stars with initial mass M ≲ 1.5 M⊙. Moreover, we report that thermohaline mixing can be present during core helium burning and beyond in stars which still have a 3He reservoir. While rotational and magnetic mixing is negligible compared to the thermohaline mixing in the relevant layers, the interaction of thermohaline motions with differential rotation and magnetic fields may be essential to establish the time scale of thermohaline mixing in red giants.

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CNO abundance pattern in the red clump stars of the Milky Way

Proceedings of the International Astronomical Union ◽

10.1017/s1743921310003583 ◽

2009 ◽

Vol 5 (S262) ◽

pp. 434-435

Author(s):

G. Tautvaišienė ◽

E. Puzeras ◽

Y. Chorniy ◽

G. Barisevičius ◽

I. Ilyin

Keyword(s):

High Resolution ◽

Stellar Evolution ◽

Milky Way ◽

Low Mass Stars ◽

Mixing Processes ◽

Abundance Pattern ◽

Galactic Field ◽

Low Mass ◽

Red Clump

AbstractHipparcos orbiting observatory has revealed a large number of helium-core- burning “clump” stars of the Galactic field. These low-mass stars exhibit signatures of extra-mixing processes that require modeling beyond the standard stellar theory. In this contribution we overview available results of 12C, 13C, N and O abundances obtained by high-resolution spectra for clump stars and discuss them in the light of current predictions of stellar evolution models.

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Very Low-Mass Stars and Brown Dwarfs

10.1017/cbo9780511564758 ◽

2000 ◽

Cited By ~ 2

Keyword(s):

Brown Dwarfs ◽

Low Mass Stars ◽

Low Mass

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Ages of Galactic and Extragalactic Star Clusters of Various Abundances

Highlights of Astronomy ◽

10.1017/s1539299600005025 ◽

1983 ◽

Vol 6 ◽

pp. 109-117 ◽

Cited By ~ 3

Author(s):

R.D. Cannon

Keyword(s):

Star Clusters ◽

Magellanic Clouds ◽

Open Clusters ◽

Simultaneous Solution ◽

Low Mass Stars ◽

Cluster Systems ◽

Distant Cluster ◽

Low Mass

In this review I shall concentrate mainly on globular star clusters in our Galaxy since these are the objects for which most work has been done recently, both observationally and theoretically. However, I shall also discuss briefly the oldest open clusters and clusters in the Magellanic Clouds. Little can be said about more distant cluster systems, since the only observations available are of integrated colours or spectra and these seem to be rather unreliable indicators of age. It is perhaps worth pointing out that the title may be slightly misleading; the problem is not so much to determine the ages of clusters of known abundances, as to obtain the best simultaneous solution for both age and composition, since some of the most important abundances (notably helium and oxygen) are virtually unobservable in little-evolved low mass stars.

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Exploring Flaring Behaviour on Low Mass Stars, Solar-type Stars and the Sun

Proceedings of the International Astronomical Union ◽

10.1017/s1743921319009980 ◽

2019 ◽

Vol 15 (S354) ◽

pp. 384-391

Author(s):

L. Doyle ◽

G. Ramsay ◽

J. G. Doyle ◽

P. F. Wyper ◽

E. Scullion ◽

...

Keyword(s):

High Energy ◽

The Sun ◽

Low Mass Stars ◽

Highly Active ◽

Rotation Phase ◽

Solar Type ◽

Low Mass ◽

Insight Into ◽

Reconnection Model ◽

High Cadence

AbstractWe report on our project to study the activity in both the Sun and low mass stars. Utilising high cadence, Hα observations of a filament eruption made using the CRISP spectropolarimeter mounted on the Swedish Solar Telescope has allowed us to determine 3D velocity maps of the event. To gain insight into the physical mechanism which drives the event we have qualitatively compared our observation to a 3D MHD reconnection model. Solar-type and low mass stars can be highly active producing flares with energies exceeding erg. Using K2 and TESS data we find no correlation between the number of flares and the rotation phase which is surprising. Our solar flare model can be used to aid our understanding of the origin of flares in other stars. By scaling up our solar model to replicate observed stellar flare energies, we investigate the conditions needed for such high energy flares.

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The effect of photoionizing feedback on the shaping of hierarchically-forming stellar clusters

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa2921 ◽

2020 ◽

Vol 499 (1) ◽

pp. 668-680

Author(s):

Alejandro González-Samaniego ◽

Enrique Vazquez-Semadeni

Keyword(s):

Star Formation ◽

Early Stage ◽

Stellar Clusters ◽

Low Mass Stars ◽

Transfer Scheme ◽

Star Forming ◽

Secondary Star ◽

Low Mass ◽

Hydrodynamical Simulations ◽

Formation Efficiency

ABSTRACT We use two hydrodynamical simulations (with and without photoionizing feedback) of the self-consistent evolution of molecular clouds (MCs) undergoing global hierarchical collapse (GHC), to study the effect of the feedback on the structural and kinematic properties of the gas and the stellar clusters formed in the clouds. During this early stage, the evolution of the two simulations is very similar (implying that the feedback from low-mass stars does not affect the cloud-scale evolution significantly) and the star-forming region accretes faster than it can convert gas into stars, causing the instantaneous measured star formation efficiency (SFE) to remain low even in the absence of significant feedback. Afterwards, the ionizing feedback first destroys the filamentary supply to star-forming hubs and ultimately removes the gas from it, thus first reducing the star formation (SF) and finally halting it. The ionizing feedback also affects the initial kinematics and spatial distribution of the forming stars because the gas being dispersed continues to form stars, which inherit its motion. In the non-feedback simulation, the groups remain highly compact and do not mix, while in the run with feedback, the gas dispersal causes each group to expand, and the cluster expansion thus consists of the combined expansion of the groups. Most secondary star-forming sites around the main hub are also present in the non-feedback run, implying a primordial rather than triggered nature. We do find one example of a peripheral star-forming site that appears only in the feedback run, thus having a triggered origin. However, this appears to be the exception rather than the rule, although this may be an artefact of our simplified radiative transfer scheme.

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