Multi-epoch L-band Spectroscopy of the Be Star μ Centauri Prior to Outburst

MENNICKENT, R.; AGUAYO, G.; OTERO, S.; GRANADA, A.

ASTRONOMICAL JOURNAL

IOP PUBLISHING LTD

Lugar: Londres; Año: 2018 vol. 156

0004-6256

With the aim of contributing to the understanding of the disk formation process in Be stars, we pursued a one-year spectroscopic observing campaign of the Be star μ Centauri in the L-band, using VLT/ISAAC. Wepresent the nine near-IR spectra we obtained in an epoch of relativephotometric quiescence prior to an outburst of ΔV = 0.4 magnitude.Visual estimates during the epoch of our L-band spectroscopy are alsopresented for the first time, together with the unpublished completevisual light curve between the years 1998 and 2014. We observesignificant and monotonic changes in emission line strength ofBracket-α and Pfund-γ lines relative to Humphreys lines, andalso in the continuum slope. We interpret these observed changes interms of important changes to the column density of the line emittingregions, moving from an optically thin to an optically thick stage justprior to a major outburst. For each observing date, we provide estimatesfor the column density and relative extension of the line emittingregion. If the changes observed toward the end of our observing campaignwere related to mass-loss chan