Differential interferometric phases at high spectral resolution as a sensitive physical diagnostic of circumstellar disks

Abstract

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.

References in corpus (6)

• Dynamical Evolution of Viscous Disks around Be Stars. I: photometry
• Non-LTE Monte Carlo Radiative Transfer: II. Non-Isothermal Solutions for Viscous Keplerian Disks
• The first determination of the viscosity parameter in the circumstellar disk of a Be Star
• Gas Distribution, Kinematics, and Excitation Structure in the Disks around the Classical Be Stars Beta Canis Minoris and Zeta Tauri
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Cited by in corpus (4)

• Classical Be Stars: Rapidly Rotating B Stars with Viscous Keplerian Decretion Disks
• The Be Star 66 Ophiuchi: 60 Years of Disk Evolution
• A Multi-observing-technique Study of the Dynamical Evolution of the Viscous Disk around the Be Star $\omega$ CMa
• Multitechnique testing of the viscous decretion disk model I. The stable and tenuous disk of the late-type Be star $\beta$ CMi