Article (Scientific journals)
Angular momentum transport in stellar interiors constrained by rotational splittings of mixed modes in red giants
Eggenberger, P.; Montalban Iglesias, Josefa; Miglio, A.
2012In Astronomy and Astrophysics, 544, p. 4
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Keywords :
stars: rotation; stars: oscillations
Abstract :
[en] Context. Recent asteroseismic observations have led to the determination of rotational frequency splittings for ℓ = 1 mixed modes in red giants. <BR /> Aims: We investigate how these observed splittings can constrain the modelling of the physical processes transporting angular momentum in stellar interiors. <BR /> Methods: We first compare models including a comprehensive treatment of shellular rotation only, with the rotational splittings observed for the red giant <ASTROBJ>KIC 8366239</ASTROBJ>. We then study how these asteroseismic constraints can give us information about the efficiency of an additional mechanism for the internal transport of angular momentum. This is done by computing rotating models of <ASTROBJ>KIC 8366239</ASTROBJ> that include a constant viscosity corresponding to this physical process, in addition to the treatment of shellular rotation. <BR /> Results: We find that models of red giant stars including shellular rotation only predict steep rotation profiles, which are incompatible with the measurements of rotational splittings in the red giant <ASTROBJ>KIC 8366239</ASTROBJ>. Meridional circulation and shear mixing alone are found to produce an insufficient internal coupling so that an additional mechanism for the internal transport of angular momentum is needed during the post-main sequence evolution. We show that the viscosity ν[SUB]add[/SUB] corresponding to this mechanism is strongly constrained to be ν[SUB]add[/SUB] = 3 × 10[SUP]4[/SUP] cm[SUP]2[/SUP] s[SUP]-1[/SUP] thanks to the observed ratio of the splittings for modes in the wings to those at the centre of the dipole forests. Such a value of viscosity may suggest that the same unknown physical process is at work during the main sequence and the post-main sequence evolution.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Eggenberger, P.;  Observatoire de Genève, Université de Genève, 51 Ch. des Maillettes, 1290, Sauverny, Switzerland
Montalban Iglesias, Josefa ;  Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Astrophysique stellaire théorique et astérosismologie
Miglio, A.;  School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK)
Language :
English
Title :
Angular momentum transport in stellar interiors constrained by rotational splittings of mixed modes in red giants
Publication date :
01 August 2012
Journal title :
Astronomy and Astrophysics
ISSN :
0004-6361
eISSN :
1432-0746
Publisher :
EDP Sciences, Les Ulis, France
Volume :
544
Pages :
L4
Peer reviewed :
Peer Reviewed verified by ORBi
Available on ORBi :
since 12 September 2012

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