The Dust, Planetesimals, and Planets of HD 38529

Abstract

HD 38529 is a post-main-sequence G8 III/IV star (3.5 Gyr old) with a planetary system consisting of at least two planets having Msini of 0.8 and 12.2 MJup, semimajor axes of 0.13 and 3.74 AU, and eccentricities of 0.25 and 0.35, respectively. Spitzer observations show that HD 38529 has an excess emission above the stellar photosphere, with a signal-to-noise ratio (S/N) at 70 μm of 4.7, a small excess at 33 μm (S/N=2.6), and no excess <30 μm. We discuss the distribution of the potential dust-producing planetesimals from the study of the dynamical perturbations of the two known planets, considering in particular the effect of secular resonances. We identify three dynamically stable niches at 0.4-0.8, 20-50, and beyond 60 AU. We model the spectral energy distribution (SED) of HD 38529 to find out which of these niches show signs of harboring dust-producing planetesimals. The secular analysis, together with the SED modeling results, suggest that the planetesimals responsible for most of the dust emission are likely located within 20-50 AU, a configuration that resembles that of the Jovian planets + Kuiper Belt in our solar system. Finally, we place upper limits (8×10-6 lunar masses of 10 μm particles) to the amount of dust that could be located in the dynamically stable region that exists between the two planets (0.25-0.75 AU).