Dust Distribution in the Β Pictoris Circumstellar Disks

The Astrophysical Journal, 2013

Recently, a new planet candidate was discovered on direct images around the young (10-17 Myr) Atype star HD95086. The strong infrared excess of the system indicates that, similarly to HR8799, β Pic, and Fomalhaut, the star harbors a circumstellar disk. Aiming to study the structure and gas content of the HD95086 disk, and to investigate its possible interaction with the newly discovered planet, here we present new optical, infrared and millimeter observations. We detected no CO emission, excluding the possibility of an evolved gaseous primordial disk. Simple blackbody modeling of the spectral energy distribution suggests the presence of two spatially separate dust belts at radial distances of 6 and 64 AU. Our resolved images obtained with the Herschel Space Observatory reveal a characteristic disk size of ∼ 6. ′′ 0 × 5. ′′ 4 (540×490 AU) and disk inclination of ∼25 • . Assuming the same inclination for the planet candidate's orbit, its re-projected radial distance from the star is 62 AU, very close to the blackbody radius of the outer cold dust ring. The structure of the planetary system at HD95086 resembles the one around HR8799. Both systems harbor a warm inner dust belt and a broad colder outer disk and giant planet(s) between the two dusty regions. Modelling implies that the candidate planet can dynamically excite the motion of planetesimals even out to 270 AU via their secular perturbation if its orbital eccentricity is larger than about 0.4. Our analysis adds a new example to the three known systems where directly imaged planet(s) and debris disks co-exist.

Arxiv preprint astro-ph/ …, 2006

Over the past 10 years abundant evidence has emerged that many (if not all) stars are born with circumstellar disks. Understanding the evolution of post-accretion disks can provide strong constraints on theories of planet formation and evolution. In this review, we focus on developments in understanding: a) the evolution of the gas and dust content of circumstellar disks based on observational surveys, highlighting new results from the Spitzer Space Telescope; b) the physical properties of specific systems as a means to interpret the survey results; c) theoretical models used to explain the observations; d) an evolutionary model of our own solar system for comparison to the observations of debris disks around other stars; and e) how these new results impact our assessment of whether systems like our own are common or rare compared to the ensemble of normal stars in the disk of the Milky Way.

Nature, 2013

show a variety of non-trivial structures attributed to planetary perturbations and used to constrain the properties of the planets 1-3 . However, these analyses have largely ignored the fact that some debris disks are found to contain small quantities of gas 4-9 , a component that all such disks should contain at some level 10, 11 . Several debris disks have been measured with a dust-to-gas ratio around unity 4-9 at which the effect of hydrodynamics on the structure of the disk cannot be ignored 12, 13 . Here we report linear and nonlinear modelling that shows that dust-gas interactions can produce some of 1 arXiv:1307.5916v2 [astro-ph.EP] 2 Aug 2013 the key patterns attributed to planets. We find a robust clumping instability that organizes the dust into narrow, eccentric rings, similar to the Fomalhaut debris disk 14 . The conclusion that such disks might contain planets is not necessarily required to explain these systems.

2001

The imaging of disks around young stars presents extreme challenges in high dynamic range, angular resolution, and sensitivity. Recent instrumental advances have met these challenges admirably, leading to a marked increase in imaging discoveries. These have opened up a new era in studies of the origin of planetary systems. Questions about our own solar system's formation, and of the prevalence of extra-solar planets, are now addressed with complementary techniques at different wavelengths. Optical and near-infrared images detail scattered light from disks at the highest possible resolution. Mid-infrared, sub-millimeter, and millimeter-wave techniques probe thermal dust continuum radiation. Millimeter-wave interferometry details the small-scale structure of the molecular gas. Kinematic imaging studies affirm the disk interpretation of mm-wave continuum surveys, and the high incidence rate for solar nebula analogs. Inner holes, azimuthal asymmetries, and gaps suggest the presence of underlying planetary bodies. The combined techniques provide a multi-dimensional picture of disks in time and have strengthened our understanding of the connection between disks and planets. Future progress is assured by the presence of much-improved imaging capability looming on the horizon.

The Astrophysical Journal, 2007

We observed 69 A3-F8 main sequence binary star systems using the Multiband Imaging Photometer for Spitzer onboard the Spitzer Space Telescope. We find emission significantly in excess of predicted photospheric flux levels for 9 +4 −3 % and 40 +7 −6 % of these systems at 24 and 70 µm, respectively. Twenty two systems total have excess emission, including four systems that show excess emission at both wavelengths. A very large fraction (nearly 60%) of observed binary systems with small (<3 AU) separations have excess thermal emission. We interpret the observed infrared excesses as thermal emission from dust produced by collisions in planetesimal belts. The incidence of debris disks around main sequence A3-F8 binaries is marginally higher than that for single old AFGK stars. Whatever combination of nature (birth conditions of binary systems) and nurture (interactions between the two stars) drives the evolution of debris disks in binary systems, it is clear that planetesimal formation is not inhibited to any great degree. We model these dust disks through fitting the spectral energy distributions and derive typical dust temperatures in the range 100-200 K and typical fractional luminosities around 10 −5 , with both parameters similar to other Spitzerdiscovered debris disks. Our calculated dust temperatures suggest that about half the excesses we observe are derived from circumbinary planetesimal belts

Astronomy and Astrophysics, 2009

Context. Previous observations with the Infrared Astronomical Satellite and the Infrared Space Observatory, and ongoing observations with Spitzer and AKARI have led to the discovery of over 200 debris disks, based on detected mid-and far infrared excess emission, indicating warm circumstellar dust. In order to constrain the properties of these systems, e.g., to more accurately determine the dust mass, temperature and radial extent, follow-up observations in the submillimetre wavelength region are needed. Aims. The β Pictoris Moving Group is a nearby stellar association of young (∼12 Myr) co-moving stars including the classical debris disk star β Pictoris. Due to their proximity and youth they are excellent targets when searching for submillimetre emission from cold, extended, dust components produced by collisions in Kuiper-Belt-like disks. They also allow an age independent study of debris disk properties as a function of other stellar parameters. Methods. We observed 7 infrared-excess stars in the β Pictoris Moving Group with the LABOCA bolometer array, operating at a central wavelength of 870 µm at the 12-m submillimetre telescope APEX. The main emission at these wavelengths comes from large, cold dust grains, which constitute the main part of the total dust mass, and hence, for an optically thin case, make better estimates on the total dust mass than earlier infrared observations. Fitting the spectral energy distribution with combined optical and infrared photometry gives information on the temperature and radial extent of the disk.

Astronomy & Astrophysics, 2011

Context. Studying the physical conditions in circumstellar disks is a crucial step toward understanding planet formation and disk evolution. Of particular interest is the case of HD 100546, a Herbig Be star that presents a gap within the first 13 AU of its protoplanetary disk, a gap that may originate in the dynamical interactions of a forming planet with its hosting disk. Aims. We seek a more detailed understanding of the structure of the circumstellar environment of HD 100546 and refine our previous disk model that is composed of a tenuous inner disk, a gap and a massive outer disk (see Benisty et al. 2010b). We also investigate whether planetary formation processes can explain the complex density structure observed in the disk. Methods. We gathered a large amount of new interferometric data using the AMBER / VLTI instrument in the H-and K-bands to spatially resolve the warm inner disk and constrain its structure. Then, combining these measurements with photometric observations, we analyze the circumstellar environment of HD 100546 in the light of a passive disk model based on 3D Monte-Carlo radiative transfer. Finally, we use hydrodynamical simulations of gap formation by planets to predict the radial surface density profile of the disk and test the hypothesis of ongoing planet formation. Results. The SED (spectral energy distribution) from the UV to the millimeter range, and the NIR (near-infrared) interferometric data are adequately reproduced by our model. We show that the H-and K-band emissions are coming mostly from the inner edge of the internal dust disk, located near 0.24 AU from the star, i.e., at the dust sublimation radius in our model. At such a short distance, the survival of hot (silicate) dust requires the presence of micron-sized grains, heated at ∼ 1750K. We directly measure an inclination of 33 • ± 11 • and a position angle of 140 • ± 16 • for the inner disk. This is similar to the values found for the outer disk (i 42 • , PA 145 • ), suggesting that both disks may be coplanar. We finally show that 1 to 8 Jupiter mass planets located at ∼ 8 AU from the star would have enough time to create the gap and the required surface density jump of three orders of magnitude between the inner and outer disk. However, no information on the amount of matter left in the gap is available, which precludes us from setting precise limits on the planet mass, for now.

Astronomy and Astrophysics, 2009

Context. Since the discovery of its dusty disk in 1984, β Pictoris has become the prototype of young early-type planetary systems, and there are now various indications that a massive Jovian planet is orbiting the star at ∼ 10 au. However, no planets have been detected around this star so far. Aims. Our goal was to investigate the close environement of β Pic, searching for planetary companion(s). Methods. Deep adaptive-optics L ′ -band images of β Pic were recorded using the NaCo instrument at the Very Large Telescope. Results. A faint point-like signal is detected at a projected distance of ≃ 8 au from the star, within the North-East side of the dust disk. Various tests were made to rule out with a good confidence level possible instrumental or atmospheric artefacts. The probability of a foreground or background contaminant is extremely low, based in addition on the analysis of previous deep HST images. Its L ′ = 11.2 apparent magnitude would indicate a typical temperature of ∼ 1500 K and a mass of ∼ 8 M Jup . If confirmed, it could explain the main morphological and dynamical peculiarities of the β Pic system. The present detection is unique among A-stars by the proximity of the resolved planet to its parent star. Its closeness and location inside the β Pic disk suggest a formation process by core accretion or disk instabilities rather than binary like formation processes.

Nature, 2004

Eprint Arxiv Astro Ph 9912392, 1999

A clear understanding of the chemical processing of matter, as it is transferred from a molecular cloud to a planetary system, depends heavily on knowledge of the physical conditions endured by gas and dust as these accrete onto a disk and are incorporated into planetary bodies. Reviewed here are astrophysical observations of circumstellar disks which trace their evolving properties. Accretion disks that are massive enough to produce a solar system like our own are typically larger than 100 AU. This suggests that the chemistry of a large fraction of the infalling material is not radically altered upon contact with a vigorous accretion shock. The mechanisms of accretion onto the star and eventual dispersal are not yet well understood, but timescales for the removal of gas and optically thick dust appear to be a few times 10$^6$ yrs. At later times, tenuous ``debris disks'' of dust remain around stars as old as a few times 10$^8$ yrs. Features in the morphology of the latter, such as inner holes, warps, and azimuthal asymmetries, are likely to be the result of the dynamical influence of large planetary bodies. Future observations will enlighten our understanding of chemical evolution and will focus on the search for disks in transition from a viscous accretion stage to one represented by a gas-free assemblage of colliding planetesimals. In the near future, comparative analysis of circumstellar dust and gas properties within a statistically significant sample of young stars at various ages will be possible with instrumentation such as SIRTF and SOFIA. Well-designed surveys will help place solar system analogs in a general context of a diversity of possible pathways for circumstellar evolution, one which encompasses the formation of stellar and brown-dwarf companions as well as planetary systems.