Theoretical investigation on the mass loss impact on asteroseismic grid-based estimates of mass, radius, and age for RGB stars

¹ INAF–Osservatorio Astronomico di Collurania, via Maggini, 64100 Teramo, Italy
e-mail: valle@df.unipi.it
² INFN, Sezione di Pisa, Largo Pontecorvo 3, 56127 Pisa, Italy
³ Dipartimento di Fisica “Enrico Fermi”, Università di Pisa, Largo Pontecorvo 3, 56127 Pisa, Italy

Received: 28 March 2017
Accepted: 27 October 2017

Abstract

Aims. We aim to perform a theoretical evaluation of the impact of the mass loss indetermination on asteroseismic grid based estimates of masses, radii, and ages of stars in the red giant branch (RGB) phase.

Methods. We adopted the SCEPtER pipeline on a grid spanning the mass range [0.8; 1.8] M_⊙. As observational constraints, we adopted the star effective temperatures, the metallicity [Fe/H], the average large frequency spacing Δν, and the frequency of maximum oscillation power ν_max. The mass loss was modelled following a Reimers parametrization with the two different efficiencies η = 0.4 and η = 0.8.

Results. In the RGB phase, the average random relative error (owing only to observational uncertainty) on mass and age estimates is about 8% and 30% respectively. The bias in mass and age estimates caused by the adoption of a wrong mass loss parameter in the recovery is minor for the vast majority of the RGB evolution. The biases get larger only after the RGB bump. In the last 2.5% of the RGB lifetime the error on the mass determination reaches 6.5% becoming larger than the random error component in this evolutionary phase. The error on the age estimate amounts to 9%, that is, equal to the random error uncertainty. These results are independent of the stellar metallicity [Fe/H] in the explored range.

Conclusions. Asteroseismic-based estimates of stellar mass, radius, and age in the RGB phase can be considered mass loss independent within the range (η ∈ [0.0,0.8]) as long as the target is in an evolutionary phase preceding the RGB bump.