The physico-chemical history of Falling Evaporating Bodies around β Pictoris: The sublimation of refractory material

Abstract

Abstract. Transient spectral redshifted absorption events in the spectrum of β Pictoris (β Pic) have been attributed to cometlike bodies falling toward the star (Falling Evaporating Bodies, or FEB) and evaporating in its immediate vicinity. Dynamical models shows that these bodies originate from circular orbits at > ∼ 4 AU. After an eccentricity increase due to planetary perturbations, they end up as star-grazers. The physics of the cloud generated by the body's sublimation is highly influenced by the physico-chemical conditions inside the body. Thus it is necessary to investigate the composition and the behavior of the materials within the body in order to explain the observed features. The physico-chemical evolution of the bodies has been simulated during all the phases before and during their FEB state. First the fluctuations in the gas production rates of volatile solids in the first phase when the refractory materials have not yet evaporated has been studied. Later on, the refractory crust of the object evaporates even if the core still contains volatile solids. The simulation then shows a phase lag between the production rate of volatiles and of refractory materials during the periastron passage. The influence of dynamical and physical parameters on the FEB phenomenon are also investigated. We find that only a heterogenous population of bodies can produce all the absorption features that have been observed so far. These results are important for the understanding of the FEB phenomenon and can lead to a revision of the FEB sublimation model.

Young Stars Near the Sun

“…Turning to β Pic's extensive surrounding disk, recent papers have focused on one of three areas: (a) the FEB model, (b) the structure of the dusty disk, and (c) the gaseous content of the disk. Karmann et al (2001), Thebault & Beust (2001), and Karmann et al (2003) have considered the flux of FEBs onto β Pic, the need to invoke the gravitational influence of a massive planet, and the physics and chemistry of the sublimation of the volatile and refractory components of the FEBs. Thebault et al (2003) investigated connections between the FEB phenomenon and the production and size distribution of dust particles in the disk within ∼10 AU of β Pic.…”

Survival of icy grains in debris discs

“…We take this system as our reference case, since it is still by far the most extensively studied and best known debris disc system. Countless observational and theoretical studies have been dedicated to this system (e.g., the most recent ones: Chen et al 2007;Golimowski et al 2006;Tamura et al 2006;Galland et al 2006;Roberge et al 2006;Fernández et al 2006;Telesco et al 2005;Thébault & Augereau 2005;Brandeker et al 2004;Karmann et al 2003;Augereau et al 2001). The disc has a wide radial extension (up to 1000 AU), but most of the detected dust is thought to reside in a relatively narrow region between 80 and 120 AU (see for example the fit of the scattered and thermal light profiles derived by Augereau et al 2001).…”

High latitude gas in theβPictoris system

“…They enter the FEB regime when their periastron reaches a threshold value (∼0.4 AU) that allows the refractory material to evaporate. The details of the evaporation process of the bodies as their periastron decreases down to a few stellar radii are described in Karmann et al (2003). The bodies start to evaporate at each periastron passage, and their evaporation rate increases as the periastron distance gets smaller.…”