Evidence for a sharp structure variation inside a red-giant star

Context. The availability of precisely determined frequencies of radial and non-radial oscillation modes in red giants is finally paving the way for detailed studies of the internal structure of these stars. Aims. We look for the seismic signature of regions of sharp structure variation in the inter...

Full description

Saved in:

Bibliographic Details
Published in:	Astronomy and astrophysics (Berlin) 2010-09, Vol.520, p.L6
Main Authors:	Miglio, A., Montalbán, J., Carrier, F., De Ridder, J., Mosser, B., Eggenberger, P., Scuflaire, R., Ventura, P., D'Antona, F., Noels, A., Baglin, A.
Format:	Article
Language:	eng
Subjects:	asteroseismology Astronomy Astrophysics Aérospatiale, astronomie & astrophysique Earth, ocean, space Exact sciences and technology Physical, chemical, mathematical & earth Sciences Physics Physique, chimie, mathématiques & sciences de la terre Space science, astronomy & astrophysics stars: fundamental parameters stars: individual: HR 7349 stars: individual: HR 7349 stars: interiors stars: oscillations
Online Access:	Get full text
Tags:	Add Tag No Tags, Be the first to tag this record!

Description
Summary:	Context. The availability of precisely determined frequencies of radial and non-radial oscillation modes in red giants is finally paving the way for detailed studies of the internal structure of these stars. Aims. We look for the seismic signature of regions of sharp structure variation in the internal structure of the CoRoT target HR 7349. Methods. We analyse the frequency dependence of the large frequency separation and second frequency differences, as well as the behaviour of the large frequency separation obtained with the envelope auto-correlation function. Results. We find evidence for a periodic component in the oscillation frequencies, i.e. the seismic signature of a sharp structure variation in HR 7349. In a comparison with stellar models we interpret this feature as caused by a local depression of the sound speed that occurs in the helium second-ionization region. Using solely seismic constraints this allows us to estimate the mass (M = 1.2-0.4+0.6 $M_\odot$) and radius (R = 12.2-1.8+2.1 $R_\odot$) of HR 7349, which agrees with the location of the star in an HR diagram.
ISSN:	0004-6361 1432-0746 1432-0746