Analysis of long-period spectroscopic behavior of Be stars

Abstract

Be stars are early-type objects with emission lines, that display spectroscopic variability in many timescales. This variability is associated with different phenomena taking place in their extended atmospheres. Due to the complexity of these objects the physical conditions and dynamics of their circumstellar environment are still under debate. In this work, we analyze the spectroscopic variations of two Be stars, 48 Lib and 66 Oph, whose complex phenomenology has not been explained by any of the existing envelope models. With our analysis we aim to give information on the structure and evolution of their circumstellar material. We based our study on spectroscopic observations obtained at CASLEO and material gathered from the literature. We study, in particular, the behavior of the Há line, whose profile is sensitive to structural changes taking place in the envelope. We describe the cyclic long term variations of the measured values of equivalent widths, radial velocities and intensities of the red and blue emission peaks. For 48 Lib we add more data to the variability analysis already done by Áreas and Cidale in 2006. For 66 Oph we found that the intensity of the emission in the line Há weakens from 1996, indicating a possible dilution of its gaseous envelope and thus, a beginning of a normal B phase. Since it is expected that a new phase of stellar activity begins in the near future, it would be desirable to continue following this object.

Key words: Variables stars; circumsetellar envelope; emission line.

DOI: http://dx.doi.org/10.5377/rct.v0i4.529

Revista Ciencia y Tecnología, No. 4, Segunda época, Junio 2009: 90-98