Differential interferometric phases at high spectral resolution as a sensitive physical diagnostic of circumstellar disks
Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de
São Paulo, Rua do Matão 1226, Cidade Universitária,
e-mail: email@example.com; firstname.lastname@example.org
2 European Organisation for Astronomical Research in the Southern Hemisphere, Casilla 19001, Santiago 19, Chile
3 European Organisation for Astronomical Research in the Southern Hemisphere/ALMA, Alonso de Córdova 3107, Santiago, Chile
4 European Organisation for Astronomical Research in the Southern Hemisphere, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany
5 Lab. J.-L. Lagrange, UMR 7293 – Observatoire de la Côte d’Azur (OCA), Univ. de Nice-Sophia Antipolis (UNS), CNRS, Valrose, 06108 Nice, France
Received: 18 February 2013
Accepted: 30 May 2013
Context. The circumstellar disks ejected by many rapidly rotating B stars (so-called Be stars) offer the rare opportunity of studying the structure and dynamics of gaseous disks at high spectral as well as angular resolution.
Aims. This paper explores a newly identified effect in spectro-interferometric phase that can be used for probing the inner regions of gaseous edge-on disks on a scale of a few stellar radii.
Methods. The origin of this effect (dubbed central quasi-emission phase signature, CQE-PS) lies in the velocity-dependent line absorption of photospheric radiation by the circumstellar disk. At high spectral and marginal interferometric resolution, photocenter displacements between star and isovelocity regions in the Keplerian disk reveal themselves through small interferometric phase shifts. To investigate the diagnostic potential of this effect, a series of models are presented, based on detailed radiative transfer calculations in a viscous decretion disk.
Results. Amplitude and detailed shape of the CQE-PS depend sensitively on disk density and size and on the radial distribution of the material with characteristic shapes in differential phase diagrams. In addition, useful lower limits to the angular size of the central stars can be derived even when the system is almost unresolved.
Conclusions. The full power of this diagnostic tool can be expected if it can be applied to observations over a full life-cycle of a disk from first ejection through final dispersal, over a full cycle of disk oscillations, or over a full orbital period in a binary system.
Key words: techniques: interferometric / circumstellar matter / stars: emission-line, Be
© ESO, 2013