HR 8799 is a nearby A-type star with a debris disk and three planetary candidates, which have been imaged directly. We undertake a coherent analysis of various observational data for all known components of the system, including the central star, imaged companions, and dust. Our goal is to elucidate the architecture and evolutionary status of the system. We try to further constrain the age and orientation of the system, the orbits and masses of the companions, and the location of dust. On the basis of the high luminosity of debris dust and dynamical constraints, we argue for a rather young system's age of < ∼ 50 Myr. The system must be seen nearly, but not exactly, pole-on. Our analysis of the stellar rotational velocity yields an inclination of 13-30• , whereas i > ∼ 20• is needed for the system to be dynamically stable, which suggests a probable inclination range of 20-30• . The spectral energy distribution, including the Spitzer/IRS spectrum in the mid-infrared as well as IRAS, ISO, JCMT, and IRAM observations, is naturally reproduced by two dust rings associated with two planetesimal belts. The inner "asteroid belt" is located at ∼10 AU inside the orbit of the innermost companion and a "Kuiper belt" at > ∼ 100 AU is just exterior to the orbit of the outermost companion. The dust masses in the inner and outer ring are estimated to be ≈1 × 10 −5 and 4 × 10 −2 Earth masses, respectively. We show that all three planetary candidates may be stable in the mass range suggested in the discovery paper by Marois et al. (2008) (between 5 and 13 Jupiter masses), but only for some of all possible orientations.• is required and the line of nodes of the system's symmetry plane on the sky must lie within between 0• an 50• from north eastward. For higher masses (M b , M c , M d ) from (7, 10, 10) to (11, 13, 13), the constraints on both angles are even more stringent. Stable orbits imply a double (4:2:1) mean-motion resonance between all three companions. We finally show that in the cases where the companions themselves are orbitally stable, the dust-producing planetesimal belts are also stable against planetary perturbations.

Context. The nearby K2 V star ε Eridani hosts one known inner planet, an outer Kuiper belt analog, and an inner disk of warm dust. Spitzer/IRS measurements indicate that the warm dust is present at distances as close as a few AU from the star. Its origin is puzzling, since an "asteroid belt" that could produce this dust would be unstable because of the known inner planet. Aims. Here we test a hypothesis that the observed warm dust is generated by collisions in the outer belt and is transported inward by Poynting-Robertson drag and strong stellar winds. Methods. We simulated a steady-state distribution of dust particles outside 10 AU with a collisional code and in the inner region (r < 10 AU) with single-particle numerical integrations. By assuming homogeneous spherical dust grains composed of ice and astrosilicate, we calculated the thermal emission of the dust and compared it with observations. We investigated two different orbital configurations for the inner planet inferred from radial velocity measurements, one with a highly eccentric orbit of e = 0.7 and another one with a moderate eccentricity of e = 0.25. We also produced a simulation without a planet. Results. Our models can reproduce the shape and magnitude of the observed spectral energy distribution from mid-infrared to submillimeter wavelengths, as well as the Spitzer/MIPS radial brightness profiles. The best-fit dust composition includes both water ice and silicates. The results are similar for the two possible planetary orbits and without a planet. Conclusions. The observed warm dust in the ε Eridani system can indeed stem from the outer "Kuiper belt" and be transported inward by Poynting-Robertson and stellar wind drag. The inner planet has little effect on the distribution of dust, so that the planetary orbit could not be constrained. Reasonable agreement between the model and observations can only be achieved by relaxing the assumption of purely silicate dust and assuming a mixture of silicate and water ice in comparable amounts.

Debris discs are known to exist around many planet-host stars, but no debris dust has been found so far in systems with transiting planets. Using publicly available catalogues, we searched for infrared excesses in such systems. In the recently published Wide-Field Infrared Survey Explorer (WISE) catalogue, we found 52 stars with transiting planets. Two systems with one transiting "hot Jupiter" each, TrES-2 and XO-5, exhibit small excesses both at 12 and 22 microns at a > 3 sigma level. Provided that one or both of these detections are real, the frequency of warm excesses in systems with transiting planets of 2-4 % is comparable to that around solar-type stars probed at similar wavelengths with Spitzer's MIPS and IRS instruments. Modelling suggests that the observed excesses would stem from dust rings with radii of several AU. The inferred amount of dust is close to the maximum expected theoretically from a collisional cascade in asteroid belt analogues. If confirmed, the presence of debris discs in systems with transiting planets may put important constraints onto formation and migration scenarios of hot Jupiters.Comment: Accepted for publication in MNRAS Letter

Abstract. ε Eridani hosts one known inner planet and an outer Kuiper belt analog. Further, Spitzer/IRS measurements indicate that warm dust is present at distances as close as a few AU from the star. Its origin is puzzling, since an "asteroid belt" that could produce this dust would be unstable because of the inner planet. We tested a hypothesis that the observed warm dust is generated by collisions in the outer belt and is transported inward by P-R drag and strong stellar winds. With numerical simulation we investigated how the dust streams from the outer ring into the inner system, and calculated the thermal emission of the dust. We show that the observed warm dust can indeed stem from the outer belt. Our models reproduce the shape and magnitude of the observed SED from mid-IR to sub-mm wavelengths, as well as the Spitzer/MIPS radial brightness profiles.