![astrometry local astrometry local](http://www.pogona.it/files/astrometry/astrometry.jpg)
Such a slowly rotating disk oscillation has been used to explain the well-known periodic V/R spectral profile variability in these stars, as well as the observed V/R cycle phase shifts between different disk emission lines. The gravitational potential of a rotationally flattened Be star is expected to induce a one-armed density perturbation in the circumstellar disk. Thus, spectro-interferometric astrometry opens the opportunity to directly connect the different observed line profiles of Br γ and Pfund in the total and correlated flux to different disk radii. The data suggest that the continuum and Pf -emission originates in significantly more compact regions, inside the Br γ -emission zone. For the first time, we resolve several Pfund emission lines, in addition to Br γ, in a single interferometric spectrum, with adequate spatial and spectral resolution and precision to analyze the radial disk structure in 48 Lib. In addition to indirect methods such as multi-wavelength spectroscopy and polarimetry, the spectro-interferometric astrometry described here provides a new tool to directly constrain the radial density structure in the disk. The scientific potential of this mode is demonstrated by the presented observations of the circumstellar disk of the evolved Be-star 48 Lib.
#Astrometry local verification#
We report on the successful science verification phase of a new observing mode at the Keck Interferometer, which provides a line-spread function width and sampling of 150 km s -1 at the K-band, at a current limiting magnitude of K- ∼ 7 mag with a spatial resolution of λ/2B ≈ 2.7mas and a measured differential phase stability of unprecedented precision (3 mrad at K = 5mag, which represents 3μ as on the sky or a centroiding precision of 10 -3).