Shock fronts in the symbiotic system BI Crucis

Abstract

We investigate the symbiotic star BI Crucis (BI Cru) through a comprehensive and self-consistent analysis of the spectra emitted in three different epochs: 1960s, 1970s and late 1980s. In particular, we would like to find out the physical conditions in the shocked nebula and in the dust shells, as well as their location within the symbiotic system, by exploiting both photometric and spectroscopic data from radio to UV. We suggest a model which, on the basis of optical imaging, emission-line ratios and spectral energy distribution profile, is able to account for collision of the winds, formation of lobes and jets by accretion onto the white dwarf (WD), as well as for the interaction of the blast wave from a past, unrecorded outburst with the interstellar medium (ISM). We have found that the spectra observed throughout the years show the marks of the different processes at work within BI Cru, perhaps signatures of a post-outburst evolution. We then call for new infrared and millimeter observations, potentially able to resolve the inner structure of the symbiotic nebula

The spectral energy distribution of D-type symbiotic stars: the role of dust shells

“…BI Cru. A careful analysis of BI Cru as a colliding‐wind SS has been recently described by Contini et al (2009b). We refer to that paper for any further details about models and results.…”

“…Dust shells with different temperatures were discovered by the detailed modelling of single D‐type SSs (e.g. Paper I; Angeloni et al 2007b; Contini et al 2009b).…”

“…They blow up during the outburst of the hot component star. The presence of a disc is revealed by the jets that were observed and modelled, for instance, in BI Cru (Contini, Angeloni & Rafanelli 2009b), He2‐104 (Contini & Formiggini 2001), R Aqr (Contini & Formiggini 2003), CH Cyg (Contini, Angeloni & Rafanelli 2009c), etc. The line ratios observed in the jet regions show lower densities (∼200 cm −3 ) and velocities (full width at half‐maximum of 150–200 km s −1 ) than those corresponding to the nebulae created by the wind collision (≥10 7 cm −3 and ≤1000 km s −1 , respectively).…”

“…The observations in the different wavelength ranges provided sufficiently reliable data. Therefore, not only the red giant star but also, sometimes, the WD could be recognized throughout the SED; however today the plural nature of the emitting nebulae and of the dust shells within the SS systems is well established (Contini 1997; Contini & Formiggini 2001, 2003; Angeloni et al 2007a, hereafter Paper I; Angeloni et al 2007b,c, and references therein; Contini, Angeloni & Rafanelli 2009a; Contini et al 2009b; Contini et al 2009c, and references therein).…”

“…reliable data. Therefore, not only the red giant star but also, sometimes, the WD could be recognized throughout the SED; however today the plural nature of the emitting nebulae and of the dust shells within the SS systems is well established (Contini 1997;Contini & Formiggini 2001, 2003Angeloni et al 2007a, hereafter Paper I;Angeloni et al 2007b,c, and references therein; Contini, Angeloni & Rafanelli 2009a;Contini et al 2009b;Contini et al 2009c, and references therein). Moreover, it is difficult to explain the observed infrared (IR) SED of dusty SSs by a single temperature, and nowadays theoretical models and observations too have been confirming that several dust temperatures should be combined in order to reproduce the near-infrared (NIR)-mid-infrared (MIR) data (Anandarao, Taylor & Pottasch 1988;Schild et al 2001;Paper I).…”