Collisional modelling of the debris disc around HIP 17439

¹ Astrophysikalisches Institut und Universitätssternwarte, Friedrich-Schiller-Universität Jena, Schillergäßchen 2–3, 07745 Jena, Germany
e-mail: christian.schueppler@uni-jena.de
² European Southern Observatory, Alonso de Cordova 3107, Vitacura, Casilla 19001, Santiago, Chile
³ School of Physics, University of New South Wales, Sydney, NSW 2052, Australia
⁴ Departamento de Física Teórica, Facultad de Ciencias, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain

Received: 28 January 2014
Accepted: 21 April 2014

Abstract

We present an analysis of the debris disc around the nearby K2 V star HIP 17439. In the context of the Herschel DUNES key programme, the disc was observed and spatially resolved in the far-IR with the Herschel PACS and SPIRE instruments. In a previous study, we assumed that the size and radial distribution of the circumstellar dust are independent power laws. There, several scenarios capable of explaining the observations were suggested after exploring a very broad range of possible model parameters. In this paper, we perform a follow-up in-depth collisional modelling of these scenarios to further distinguish between them. In our models we consider collisions, direct radiation pressure, and drag forces, which are the actual physical processes operating in debris discs. We find that all scenarios discussed in the first paper are physically reasonable and can reproduce the observed spectral energy distribution along with the PACS surface brightness profiles reasonably well. In one model, the dust is produced beyond 120 au in a narrow planetesimal belt and is transported inwards by Poynting-Robertson and stellar wind drag. Good agreement with the observed radial profiles would require stellar winds by about an order of magnitude stronger than the solar value, which is not confirmed – although not ruled out – by observations. Another model consists of two spatially separated planetesimal belts, a warm inner and a cold outer one. This scenario would probably imply the presence of planets clearing the gap between the two components. Finally, we show qualitatively that the observations can be explained by assuming the dust is produced in a single, but broad planetesimal disc with a surface density of solids rising outwards, as expected for an extended disc that experiences a natural inside-out collisional depletion. Prospects of distinguishing between the competing scenarios by future observations are discussed.