Author(s): , ,
Institution(s): 1. IAG - Universidade de Sao Paulo, 2. Universidade Estadual de Ponta Grossa
Classical Be stars are rapid rotators of spectral type B and luminosity class V-III which have an equatorially concentrated circumstellar disk. The disk often exhibits Balmer emission lines and an infrared excess fed by discrete mass loss events called outbursts. Hot Be stars display nonradial pressure pulsation modes, whereas cooler ones display gravity modes.
The Be Star HD 171219 was observed with the CoRoT satellite in order to investigate its nonradial pulsations with unprecedented details. We benefited from the high temporal resolution obtained with the satellite during a 77.56 day run. High-resolution ground-based spectroscopic observations with HARPS and SOPHIE were also obtained during the month preceeding the CoRoT observations. Low-resolution spectra from the BeSS database were used as additional information.
CoRoT, HARPS and SOPHIE data were analyzed with the CLEANEST algorithm. Spectral data were too sparse to allow a good frequency resolution but results of the two data sets agreed. Circumstellar activity was analyzed through the variation of the violet over red emission ratio of the Hα line.
We detected dozens of frequencies in HD 171219 due to nonradial p-modes. A multiplet could be identified corresponding to a pulsation degree l∼3. The star underwent at least 6 small outbursts during the CoRoT observations. The relative intensity of the main frequencies varied after each outburst suggesting that the stability of the star and the feeding of the envelope are linked to the pulsation regime.
The pulsation and other physical characteristics of the star have been determined.