New observations and asteroseismic analysis of the subdwarf B pulsator PG 1219+534

Abstract

We present a new asteroseismic modeling of the hot B subdwarf (sdB) pulsator PG 1219+534, based on a 3-month campaign with the Mont4K/Kuiper combination at Mt Bigelow (Arizona) and on updated atmospheric parameters from high S/N low and medium resolution spectroscopy. On the basis of the nine independent pulsation periods extracted from the photometric light curve, we carried out an astroseismic analysis by applying the forward modeling approach using our latest (third and fourth generation) sdB models. Atmospheric parameters (T-eff = 34 258 +/- 170 K, log g = 5.838 +/- 0.030) were used as independent constraints, as well as partial mode identification based on observed multiplet structures we ascribed to stellar rotation. The optimal model found is remarkably consistent between various analyses with third and fourth generation of sdB models, and also with previously published analysis with second generation sdB models. It corresponds to a sdB with a canonical mass (0.46 +/- 0.02 M-circle dot), rather thin H-He envelope (log q(envl) = -3.75 +/- 0.12), and close to He-burning exhaustion (X-core(C + O) = 0.86 +/- 0.05). We also investigate the internal rotation of the star. We find that PG 1219+534 rotates very slowly (P-rot = 34.91 +/- 0.84 days) and that solid-body rotation is reached at least down to similar to 60% of the radius.