Photometric and spectroscopic variability of the B5IIIe star HD 171219^⋆

¹ Universidade Estadual de Ponta Grossa, Av. Carlos Cavalcanti, 4748, 84030-900 Ponta Grossa, PR, Brazil
e-mail: laerteandrade@uepg.br
² Universidade de São Paulo/IAG-USP, rua do Matão, 1226 – Cidade Universitária, 05508-900 São Paulo, SP, Brazil
³ Institute for Astronomy, University of Hawaii, Honolulu, HI 96822, USA
⁴ Royal Observatory of Belgium, 3 avenue circulaire, B 1180 Brussels, Belgium
⁵ LESIA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, UPMC Univ. Paris 06, Univ. Paris Diderot, Sorbonne Paris Cité, 5 place Jules Janssen, 92195 Meudon, France
⁶ INAF–Osservatorio Astronomico di Brera, via E. Bianchi 46, 23807 Merate (LC), Italy
⁷ Institut de Recherche en Astrophysique et Planétologie, CNRS, 14 avenue Édouard Belin, Université de Toulouse, UPS-OMP, IRAP, 31400 Toulouse, France
⁸ Universidad de Granada, Dept. Física Teórica y del Cosmos, 18071 Granada, Spain
⁹ Instituto de Astrofísica de Andalucía (CSIC), Glorieta de la Astronomía s/n, 18008 Granada, Spain
¹⁰ Instituto de Astrofísica de Canarias, 38205 La Laguna, Tenerife, Spain
¹¹ Institut d’Astrophysique et de Géophysique, Université de Liège, Quartier Agora, Allée du 6 août 19C, 4000 Liège, Belgium
¹² Depto. Didáctica de la Matemática, Universidad de Valencia, Avda. Tarongers, 4, 46022 Valencia, Spain
¹³ Observatorio Astronómico, Universidad de Valencia, 46100 Burjassot, Spain

Received: 23 June 2016
Accepted: 24 March 2017

Abstract

We analyzed the star HD 171219, one of the relatively bright Be stars observed in the seismo field of the CoRoT satellite, in order to determine its physical and pulsation characteristics. Classical Be stars are main-sequence objects of mainly B-type, whose spectra show, or have shown at some epoch, Balmer lines in emission and an infrared excess. Both characteristics are attributed to an equatorially concentrated circumstellar disk fed by non-periodic mass-loss episodes (outbursts). Be stars often show nonradial pulsation gravity modes and, as more recently discovered, stochastically excited oscillations. Applying the CLEANEST algorithm to the high-cadence and highly photometrically precise measurements of the HD 171219 light curve led us to perform an unprecedented detailed analysis of its nonradial pulsations. Tens of frequencies have been detected in the object compatible with nonradial g-modes. Additional high-resolution ground-based spectroscopic observations were obtained at La Silla (HARPS) and Haute Provence (SOPHIE) observatories during the month preceding CoRoT observations. Additional information was obtained from low-resolution spectra from the BeSS database. From spectral line fitting we determined physical parameters of the star, which is seen equator-on (i = 90°). We also found in the ground data the same frequencies as in CoRoT data. Additionally, we analyzed the circumstellar activity through the traditional method of violet to red emission Hα line variation. A quintuplet was identified at approximately 1.113 c d^-1 (12.88 μHz) with a separation of 0.017 c d^-1 that can be attributed to a pulsation degree ℓ ~ 2. The light curve shows six small- to medium-scale outbursts during the CoRoT observations. The intensity of the main frequencies varies after each outburst, suggesting a possible correlation between the nonradial pulsations regime and the feeding of the envelope.