Radiation pressure cross-sections of fluffy interstellar grains

Saija, Rosalba; Iatí, Maria Antonia; Giusto, Arianna; Borghese, Ferdinando; Denti, P.; Aiello, S.; Cecchi‐Pestellini, C.

doi:10.1046/j.1365-8711.2003.06490.x

Cited by 28 publications

(28 citation statements)

References 30 publications

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“…Mukai et al (1992) showed that the ratio β of the forces of radiation and gravity on a grain decreases with increasing porosity for a 1 μm, regardless of grain composition. Saija et al (2003) confirmed this result and emphasized that the decreasing β was limited to ultraviolet and visible wavelengths. Mukai et al (1992) also showed that β increases with porosity for absorptive grains (e.g., magnetite and graphite) with a 1 μm, and it becomes nearly independent of grain size at the highest porosities.…”

Section: Composition and Porositysupporting

confidence: 64%

HUBBLEANDSPITZER SPACE TELESCOPEOBSERVATIONS OF THE DEBRIS DISK AROUND THE NEARBY K DWARF HD 92945

Golimowski

Krist

Stapelfeldt

et al. 2011

The Astronomical Journal

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We present the first resolved images of the debris disk around the nearby K dwarf HD 92945, obtained with the Hubble Space Telescope's (HST 's) Advanced Camera for Surveys. Our F606W (Broad V) and F814W (Broad I) coronagraphic images reveal an inclined, axisymmetric disk consisting of an inner ring about 2. 0-3. 0 (43-65 AU) from the star and an extended outer disk whose surface brightness declines slowly with increasing radius approximately 3. 0-5. 1 (65-110 AU) from the star. A precipitous drop in the surface brightness beyond 110 AU suggests that the outer disk is truncated at that distance. The radial surface-density profile is peaked at both the inner ring and the outer edge of the disk. The dust in the outer disk scatters neutrally but isotropically, and it has a low V-band albedo of 0.1. This combination of axisymmetry, ringed and extended morphology, and isotropic neutral scattering is unique among the 16 debris disks currently resolved in scattered light. We also present new infrared photometry and spectra of HD 92945 obtained with the Spitzer Space Telescope's Multiband Imaging Photometer and InfraRed Spectrograph. These data reveal no infrared excess from the disk shortward of 30 μm and constrain the width of the 70 μm source to 180 AU. Assuming that the dust comprises compact grains of astronomical silicate with a surface-density profile described by our scattered-light model of the disk, we successfully model the 24-350 μm emission with a minimum grain size of a min = 4.5 μm and a size distribution proportional to a −3.7 throughout the disk, but with maximum grain sizes of 900 μm in the inner ring and 50 μm in the outer disk. Together, our HST and Spitzer observations indicate a total dust mass of ∼0.001M ⊕ . However, our observations provide contradictory evidence of the dust's physical characteristics: its neutral V-I color and lack of 24 μm emission imply grains larger than a few microns, but its isotropic scattering and low albedo suggest a large population of submicron-sized grains. If grains smaller than a few microns are absent, then stellar radiation pressure may be the cause only if the dust is composed of highly absorptive materials like graphite. The dynamical causes of the sharply edged inner ring and outer disk are unclear, but recent models of dust creation and transport in the presence of migrating planets support the notion that the disk indicates an advanced state of planet formation around HD 92945.

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Section: Composition and Porositysupporting

confidence: 64%

HUBBLEANDSPITZER SPACE TELESCOPEOBSERVATIONS OF THE DEBRIS DISK AROUND THE NEARBY K DWARF HD 92945

Golimowski

Krist

Stapelfeldt

et al. 2011

The Astronomical Journal

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“…Saija et al (2003) for instance show that the A17, page 12 of 16 fluffiness of the grains tends to decrease their radiation pressure cross-section, as if aggregates behaved like their elemental constituents. This would make grains below the theoretical blowout size less sensitive to radiation pressure, and allow them to remain bound to the star.…”

Section: Blowout Sizementioning

confidence: 99%

An icy Kuiper belt around the young solar-type star HD 181327

Lebreton

Augereau

Thi

et al. 2012

A&A

105

161

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Context. HD 181327 is a young main sequence F5/F6 V star belonging to the β Pictoris moving group (age ∼ 12 Myr). It harbors an optically thin belt of circumstellar material at radius ∼90 AU, presumed to result from collisions in a population of unseen planetesimals. Aims. We aim to study the dust properties in the belt in details, and to constrain the gas-to-dust ratio. Methods. We obtained far-infrared photometric observations of HD 181327 with the PACS instrument onboard the Herschel Space Observatory , complemented by new 3.2 mm observations carried with the ATCA array. The geometry of the belt is constrained with newly reduced HST/NICMOS scattered light images that allow the degeneracy between the disk geometry and the dust properties to be broken. We then use the radiative transfer code GRaTeR to compute a large grid of models, and we identify the grain models that best reproduce the spectral energy distribution (SED) through a Bayesian analysis. We attempt to detect the oxygen and ionized carbon fine-structure lines with Herschel/PACS spectroscopy, providing observables to our photochemical code ProDiMo. Results. The HST observations confirm that the dust is confined in a narrow belt. The continuum is detected with Herschel/PACS completing nicely the SED in the far-infrared. The disk is marginally resolved with both PACS and ATCA. A medium integration of the gas spectral lines only provides upper limits on the [OI] and [CII] line fluxes. We show that the HD 181327 dust disk consists of micron-sized grains of porous amorphous silicates and carbonaceous material surrounded by an important layer of ice, for a total dust mass of ∼0.05 M ⊕ (in grains up to 1 mm). We discuss evidences that the grains consists of fluffy aggregates. The upper limits on the gas atomic lines do not provide unambiguous constraints: only if the PAH abundance is high, the gas mass must be lower than ∼17 M ⊕ . Conclusions. Despite the weak constraints on the gas disk, the age of HD 181327 and the properties of the dust disk suggest that it has passed the stage of gaseous planets formation. The dust reveals a population of icy planetesimals, similar to the primitive Edgeworth-Kuiper belt, that may be a source for the future delivery of water and volatiles onto forming terrestrial planets.

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“…For particles much smaller than 100 µm radiation pressure gets important (Saija et al 2003;Krauss and Wurm 2004). This is added to the photophoretic force.…”

Section: Fu-orionis Disks and Caismentioning

confidence: 99%

Outward transport of CAIs during FU‐Orionis events

Wurm¹,

Haack

2009

Meteorit & Planetary Scien

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available online at http://meteoritics.org Abstract-Evidence from meteorites shows that the first solids to form in the solar system, calciumaluminum-rich inclusions (CAIs), were transported outward from the Sun by several AU in the early solar system. We introduce a new concept of levitation and outward transport of CAIs at the surface of protoplanetary disks. Thermal radiation from the disk and the Sun can cause particles to levitate above the disk and drift outward through a process known as photophoresis. During normal conditions this process only works for dust-sized particles but during high luminosity events like FU-Orionis Outward transport of CAIs during FU-Orionis events

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Radiation pressure cross-sections of fluffy interstellar grains

Cited by 28 publications

References 30 publications

HUBBLEANDSPITZER SPACE TELESCOPEOBSERVATIONS OF THE DEBRIS DISK AROUND THE NEARBY K DWARF HD 92945

HUBBLEANDSPITZER SPACE TELESCOPEOBSERVATIONS OF THE DEBRIS DISK AROUND THE NEARBY K DWARF HD 92945

An icy Kuiper belt around the young solar-type star HD 181327

Outward transport of CAIs during FU‐Orionis events

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