Sublimation temperature of circumstellar dust particles and its importance for dust ring formation

Interstellar dust particles, which are supposedly aggregates, penetrate dust disks around stars because of the star's motion relative to the surrounding interstellar medium (ISM). We discuss the interrelation of the physical properties of local interstellar dust, the relative motion of the star and the surrounding ISM, and the evolution of the circumstellar disk.

Download Full-text

Efficient dust ring formation in misaligned circumbinary discs

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz3633 ◽

2020 ◽

Vol 492 (3) ◽

pp. 3306-3315 ◽

Cited By ~ 1

Author(s):

Hossam Aly ◽

Giuseppe Lodato

Keyword(s):

Binary Systems ◽

Stokes Number ◽

Dust Particles ◽

Strongly Coupled ◽

Dust Trap ◽

Aspect Ratios ◽

Pile Up ◽

New Phenomena ◽

Gas Component ◽

Dust Ring

ABSTRACT Binary systems exert a gravitational torque on misaligned discs orbiting them, causing differential precession which may produce disc warping and tearing. While this is well understood for gas-only discs, misaligned cirumbinary discs of gas and dust have not been thoroughly investigated. We perform SPH simulations of misaligned gas and dust discs around binaries to investigate the different evolution of these two components. We choose two different disc aspect ratios: A thin case for which the gas disc always breaks, and a thick one where a smooth warp develops throughout the disc. For each case, we run simulations of five different dust species with different degrees of coupling with the gas component, varying in Stokes number from 0.002 (strongly coupled dust) to 1000 (effectively decoupled dust). We report two new phenomena: First, large dust grains in thick discs pile up at the warp location, forming narrow dust rings, due to a difference in precession between the gas and dust components. These pile ups do not form at gas pressure maxima, and hence are different from conventional dust traps. This effect is most evident for St ∼ 10–100. Secondly, thin discs tear and break only in the gas, while dust particles with St ≥ 10 form a dense dust trap due to the steep pressure gradient caused by the break in the gas. We find that dust with St ≤ 0.02 closely follow the gas particles, for both thin and thick discs, with radial drift becoming noticeable only for the largest grains in this range.

Download Full-text

SIRTF: A Unique Opportunity for Probing the Zodiacal Cloud

International Astronomical Union Colloquium ◽

10.1017/s0252921100501468 ◽

1996 ◽

Vol 150 ◽

pp. 159-162

Author(s):

Sumita Jayaraman ◽

Stanley F. Dermott ◽

Michael Werner

Keyword(s):

Thermal Emission ◽

Dust Cloud ◽

Thermal Characteristics ◽

Dust Particles ◽

Infrared Telescope ◽

The Earth ◽

Telescope Facility ◽

Asteroidal Dust ◽

Infrared Telescope Facility ◽

Dust Ring

AbstractThe Space Infrared Telescope Facility (SIRTF) is planned for launch by NASA in 2001 in a heliocentric orbit at 1.01 AU The spacecraft will drift away from the Earth slowly, reaching a distance of 0.3 AU behind the Earth at the end of its 2.5 year mission. This implies that SIRTF will spiral through the Earth's resonant dust ring (Wright et al., 1995) and, in particular, that it will traverse the dust cloud in the ring that trails the Earth in its orbit. We have used a dynamical model of the ring (Dermott et al., 1994) followed by simulation of the SIRTF orbit to predict the variations in the zodiacal thermal emission due to the trailing dust cloud as seen by SIRTF. Because the dust ring is inclined to the ecliptic, the latitude of peak flux of the trailing cloud will have yearly oscillations about the ecliptic. The amplitude of the oscillations will increase as SIRTF approaches the cloud, reaching a maximum of 20 during the mission. The magnitude of the flux variations can be as high as 4 – 5% or 2–3 MJy/Sr, SIRTF's measurements of these effects will allow us to model the number density and thermal characteristics of asteroidal dust particles near the Earth.

Download Full-text

Optical polarised phase function of the HR 4796A dust ring

Astronomy and Astrophysics ◽

10.1051/0004-6361/201935363 ◽

2019 ◽

Vol 626 ◽

pp. A54 ◽

Cited By ~ 11

Author(s):

J. Milli ◽

N. Engler ◽

H. M. Schmid ◽

J. Olofsson ◽

F. Ménard ◽

...

Keyword(s):

Phase Function ◽

Scattered Light ◽

Dust Particles ◽

Cometary Dust ◽

Very Large Telescope ◽

Wide Range ◽

Alternative Scenarios ◽

First Time ◽

Dust Ring ◽

Compact Spheres

Context. The scattering properties of the dust originating from debris discs are still poorly known. The analysis of scattered light is however a powerful remote-sensing tool to understand the physical properties of dust particles orbiting other stars. Scattered light is indeed widely used to characterise the properties of cometary dust in the solar system. Aims. We aim to measure the morphology and scattering properties of the dust from the debris ring around HR 4796 A in polarised optical light. Methods. We obtained high-contrast polarimetric images of HR 4796 A in the wavelength range 600–900 nm with the SPHERE/ZIMPOL instrument on the Very Large Telescope. Results. We measured for the first time the polarised phase function of the dust in a debris system over a wide range of scattering angles in the optical. We confirm that it is incompatible with dust particles being compact spheres under the assumption of the Mie theory, and propose alternative scenarios compatible with the observations, such as particles with irregular surface roughness or aggregate particles.

Download Full-text

The Characterization of the Dust Content in the Ring Around Sz 91: Indications of Planetesimal Formation?

The Astrophysical Journal ◽

10.3847/1538-4357/ac21d0 ◽

2021 ◽

Vol 923 (1) ◽

pp. 128

Author(s):

Karina Maucó ◽

Carlos Carrasco-González ◽

Matthias R. Schreiber ◽

Anibal Sierra ◽

Johan Olofsson ◽

...

Keyword(s):

Grain Growth ◽

Protoplanetary Disks ◽

Dust Particles ◽

Disk System ◽

Streaming Instability ◽

Multi Wavelength ◽

Pressure Bump ◽

Dust Ring ◽

Strong Agreement

Abstract One of the most important questions in the field of planet formation is how millimeter- and centimeter-sized dust particles overcome radial drift and fragmentation barriers to form kilometer-sized planetesimals. ALMA observations of protoplanetary disks, in particular transition disks or disks with clear signs of substructures, can provide new constraints on theories of grain growth and planetesimal formation, and therefore represent one possibility for progress on this issue. We here present ALMA band 4 (2.1 mm) observations of the transition disk system Sz 91, and combine them with previously obtained band 6 (1.3 mm) and band 7 (0.9 mm) observations. Sz 91, with its well-defined millimeter ring, more extended gas disk, and evidence of smaller dust particles close to the star, constitutes a clear case of dust filtering and the accumulation of millimeter-sized particles in a gas pressure bump. We compute the spectral index (nearly constant at ∼3.34), optical depth (marginally optically thick), and maximum grain size (∼0.61 mm) in the dust ring from the multi-wavelength ALMA observations, and compare the results with recently published simulations of grain growth in disk substructures. Our observational results are in strong agreement with the predictions of models for grain growth in dust rings that include fragmentation and planetesimal formation through streaming instability.

Download Full-text

Non-stoichiometric amorphous magnesium-iron silicates in circumstellar dust shells

Astronomy and Astrophysics ◽

10.1051/0004-6361/202038090 ◽

2020 ◽

Vol 644 ◽

pp. A139

Author(s):

Hans-Peter Gail ◽

Akemi Tamanai ◽

Annemarie Pucci ◽

Ralf Dohmen

Keyword(s):

Infrared Emission ◽

Dust Particles ◽

Circumstellar Dust ◽

Expansion Velocity ◽

Condensation Temperature ◽

Dust Formation ◽

Dust Grains ◽

Dust Shell ◽

Dust Shells ◽

Stellar Outflows

Aims. We study the growth of dust in oxygen-rich stellar outflows in order to find out to which extent dust growth models can quantitatively reconcile with the quantities and nature of dust as derived from observations of the infrared emission from circumstellar dust shells. Methods. We use a set of nine well-observed massive supergiants with optically thin dust shells as testbeds because of the relatively simple properties of the outflows from massive supergiants, contrary to the case of AGB stars. Models of the infrared emission from their circumstellar dust shells are compared to their observed infrared spectra to derive the essential parameters that rule dust formation in the extended envelope of these stars. The results are compared with a model for silicate dust condensation. Results. For all objects, the infrared emission in the studied wavelength range, between 6 and 25 μm, can be reproduced rather well by a mixture of non-stoichiometric iron-bearing silicates, alumina, and metallic iron dust particles. For three objects (μ Cep, RW Cyg, and RS Per), the observed spectra can be sufficiently well reproduced by a stationary and (essentially) spherically symmetric outflow in the instantaneous condensation approximation. For these objects, the temperature at the onset of massive silicate dust growth is of the order of 920 K and the corresponding outflow velocity of the order of the sound velocity. This condensation temperature is only somewhat below the vapourisation temperature of the silicate dust and suggests that the silicate dust grows on the corundum dust grains that formed well inside of the silicate dust shell at a much higher temperature. The low expansion velocity at the inner edge of the silicate dust shell further suggests that, for these supergiants, the region inside the silicate dust shell has an only subsonic average expansion velocity, though a high degree of supersonic turbulence is indicated by the widths of spectral lines. Conclusions. Our results suggest that for the two major problems of dust formation in stellar outflows, that is (i) formation of seed nuclei and (ii) their growth to macroscopic dust grains, we are gradually coming close to a quantitative understanding of the second item.

Download Full-text

Resonance trapping of circumstellar dust particles by an alleged planet

Celestial Mechanics and Dynamical Astronomy ◽

10.1007/bf00699748 ◽

1993 ◽

Vol 56 (1-2) ◽

pp. 381-393 ◽

Cited By ~ 10

Author(s):

H. Scholl ◽

F. Roques ◽

B. Sicardy

Keyword(s):

Dust Particles ◽

Circumstellar Dust ◽

Resonance Trapping

Download Full-text

Mars Dust Counter on Board ISAS PLANET-B

International Astronomical Union Colloquium ◽

10.1017/s0252921100501602 ◽

1996 ◽

Vol 150 ◽

pp. 233-236 ◽

Cited By ~ 2

Author(s):

Eduard Igenbergs ◽

Sho Sasaki ◽

Georg Färber ◽

Franz Fischer ◽

Ralf Münzenmayer ◽

...

Keyword(s):

Spatial Distribution ◽

Interstellar Dust ◽

Impact Ionization ◽

Mass Range ◽

Upper Atmosphere ◽

Dust Particles ◽

Velocity Range ◽

The Earth ◽

Elliptic Orbits ◽

Dust Ring

AbstractPLANET-B is an ISAS spacecraft which will investigate the upper atmosphere and the surroundings of Mars between 1999 and 2001 To clarify the presence and characteristics of the Martian dust ring/torus, an impact ionization dust detector will be on board PLANET-B The detector (PLANET B Mars Dust Counter), which is an improved version of the Munich Dust Counters of HITEN and BREMSAT, will weigh only 630g with an aperture area 140cm2. The detectable mass range will be between 10-16g and more than 10-6g and the velocity range will be from 1km/s to more than 70km/s. Since PLANET-B executes retrograde elliptic orbits close to the zodiacal plane, our detector can investigate the spatial distribution of prograde dust particles from Phobos and Deimos with relative encounter velocity as large as or higher than 1km/s. PLANET-B MDC shall also measure the dust environment around the Earth and interplanetary and possibly interstellar dust particles.

Download Full-text