Fast ray-tracing algorithm for circumstellar structures (FRACS)

Abstract

Context. B[e] supergiants are luminous, massive post-main sequence stars exhibiting non-spherical winds, forbidden lines, and hot dust in a disc-like structure. The physical properties of their rich and complex circumstellar environment (CSE) are not well understood, partly because these CSE cannot be easily resolved at the large distances found for B[e] supergiants (typically > ∼ 1 kpc). Aims. From mid-IR spectro-interferometric observations obtained with VLTI/MIDI we seek to resolve and study the CSE of the Galactic B[e] supergiant CPD-57 • 2874. Methods. For a physical interpretation of the observables (visibilities and spectrum) we use our ray-tracing radiative transfer code (FRACS), which is optimised for thermal spectro-interferometric observations. Results. Thanks to the short computing time required by FRACS (<10 s per monochromatic model), best-fit parameters and uncertainties for several physical quantities of CPD-57 • 2874 were obtained, such as inner dust radius, relative flux contribution of the central source and of the dusty CSE, dust temperature profile, and disc inclination. Conclusions. The analysis of VLTI/MIDI data with FRACS allowed one of the first direct determinations of physical parameters of the dusty CSE of a B[e] supergiant based on interferometric data and using a full model-fitting approach. In a larger context, the study of B[e] supergiants is important for a deeper understanding of the complex structure and evolution of hot, massive stars.

VLTI/AMBER observations of the binary B[e] supergiant HD 327083

“…The CO bandhead emission, which has a higher line-to-continuum Notes. As discussed in Domiciano de Souza et al (2011), the uncertainties reported by the Levenberg-Marquardt algorithm should be considered lower limits to the actual uncertainty in the best fitting parameters. The sizes in AU and R were calculated assuming a distance of 1500 pc.…”

“…Domiciano de Souza et al 2011). However, it has been shown that simple models of the dust emission from equatorial disks struggle to simultaneously reproduce the spectral energy distribution of the sgB[e] star R126 in the optical/near infrared (NIR) and the mid infrared (Porter 2003).…”

3D-integrated optics component for astronomical spectro-interferometry

“…The technique of spectrally resolved optical interferometry (spectro-interferometry) is used in astronomy to deliver high-resolution images of astronomical targets and study their morphological features [1]. To this end, measurements of the visibility and phase (complex visibilities) of interference fringes obtained by combining simultaneously light collected by several distant telescopes are required.…”

“…High-resolution spectro-interferometry assisted by model imaging can deliver further insights in the dynamical structure of astrophysical objects [1,9].…”

AMBER on the VLTI: Data Processing and Calibration Issues

“…However, the huge potential of the AMBER instrument has been already proved by the numerous first articles published in a special feature of A&A Tatulli et al 2007a;Meilland et al 2007b,a;Weigelt et al 2007;Millour et al 2007;Chesneau et al 2007;Domiciano de Souza et al 2007), and many other new successful observing programs can be expected for the future, even with the infrastructure-limited performances of the instrument.…”