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Lack of PAH emission toward low-mass embedded young stellar objects
V. C. Geers, E. F. van Dishoeck, K. M. Pontoppidan +4
PAHs have been detected toward molecular clouds and some young stars with disks, but have not yet been associated with embedded young stars. We present a sensitive mid-IR spectrosc…
Coagulation of small grains in disks: the influence of residual infall and initial small-grain content
C. Dominik, C. P. Dullemond
Turbulent coagulation in protoplanetary disks is known to operate on timescale far shorter than the lifetime of the disk. In the absence of mechanisms that replenish the small dust…
A representative particle approach to coagulation and fragmentation of dust aggregates and fluid droplets
A. Zsom, C. P. Dullemond
Context: There is increasing need for good algorithms for modeling the aggregation and fragmentation of solid particles (dust grains, dust aggregates, boulders) in various astrophy…
Soft X-ray components in the hard state of accreting black holes
Caroline D'Angelo, Dimitrios Giannios, Cornelis Dullemond +1
Recent observations of two black hole candidates (GX 339-4 and J1753.5-0127) in the low-hard state (L_X/L_Edd ~ 0.003-0.05) suggest the presence of a cool accretion disk very close…
Planetesimal formation around the snow line in MRI-driven turbulent protoplanetary disks
F. Brauer, Th. Henning, C. P. Dullemond
The formation of planetesimals in protoplanetary disks due to collisional sticking of smaller dust aggregates has to face at least two severe obstacles, namely the rapid loss of ma…
Size-sorting dust grains in the surface layers of protoplanetary disks
C. P. Dullemond, C. Dominik
Aims: We wish to investigate what the effect of dust sedimentation is on the observed 10 mum feature of protoplanetary disks and how this may affect the interpretation of the obser…
Molecular hydrogen in the circumstellar environments of Herbig Ae/Be stars probed by FUSE
C. Martin-Zaidi, M. Deleuil, J. Le Bourlot +7
We observed molecular hydrogen around a sample of pre-main sequence stars in order to better characterize their gaseous CS environments. We analyzed the FUSE (Far Ultraviolet Spect…
LkH 330: Evidence for dust clearing through resolved submillimeter imaging
J. M Brown, G. A. Blake, C. Qi +2
Mid-infrared spectrophotometric observations have revealed a small sub-class of circumstellar disks with spectral energy distributions (SEDs) suggestive of large inner gaps with lo…
A coagulation-fragmentation model for the turbulent growth and destruction of preplanetesimals
Anders Johansen, Frithjof Brauer, Cornelis Dullemond +2
To treat the problem of growing protoplanetary disc solids across the meter barrier, we consider a very simplified two-component coagulation-fragmentation model that consists of ma…
Measuring the Fraction of Obscured Quasars by the Infrared Luminosity of Unobscured Quasars
Ezequiel Treister, Julian H. Krolik, Cornelis Dullemond
Recent work has suggested that the fraction of obscured AGN declines with increasing luminosity, but it has been difficult to quantify this trend. Here, we attempt to measure this…
Characterizing the nature of embedded young stellar objects through silicate, ice and millimeter observations
A. Crapsi, E. F. van Dishoeck, M. R. Hogerheijde +2
(Abridged) Classification schemes for YSOs are based on evaluating the degree of dissipation of the surrounding envelope, whose main effects are the extinction of the optical radia…
Coagulation, fragmentation and radial motion of solid particles in protoplanetary disks
F. Brauer, C. P. Dullemond, Th. Henning
The growth of solid particles towards meter sizes in protoplanetary disks has to circumvent at least two hurdles, namely the rapid loss of material due to radial drift and particle…
A Search for Mid-Infrared Molecular Hydrogen Emission from Protoplanetary Disks
A. Carmona, M. E van den Ancker, Th. Henning +6
We observed the Herbig Ae/Be stars UX Ori, HD 34282, HD 100453, HD 101412, HD 104237 and HD 142666, and the T Tauri star HD 319139 and searched for H2 0-0 S(2) emission at 12.278 m…
Cold Disks: Spitzer Spectroscopy of Disks around Young Stars with Large Gaps
J. M. Brown, G. A. Blake, C. P. Dullemond +10
We have identified four circumstellar disks with a deficit of dust emission from their inner 15-50 AU. All four stars have F-G spectral type, and were uncovered as part of the Spit…
High spatial resolution mid-infrared observations of the low-mass young star TW Hya
Th. Ratzka, Ch. Leinert, Th. Henning +3
We want to improve knowledge of the structure of the inner few AU of the circumstellar disk around the nearby T Tauri star TW Hya. Earlier studies have suggested the existence of a…
Dust crystallinity in protoplanetary disks: the effect of diffusion/viscosity ratio
Ya. Pavlyuchenkov, C. P. Dullemond
The process of turbulent radial mixing in protoplanetary disks has strong relevance to the analysis of the spatial distribution of crystalline dust species in disks around young st…
Spatial separation of small and large grains in the transitional disk around the young star IRS 48
V. C. Geers, K. M. Pontoppidan, E. F. van Dishoeck +5
We present spatially resolved mid-infrared images of the disk surrounding the young star IRS 48 in the Ophiuchus cloud complex. The disk exhibits a ring-like structure at 18.7 micr…
Survival of the mm-cm size grain population observed in protoplanetary disks
F. Brauer, C. P. Dullemond, A. Johansen +3
Millimeter interferometry provides evidence for the presence of mm to cm size "pebbles" in the outer parts of disks around pre-main-sequence stars. The observations suggest that la…
Deep Spitzer spectroscopy of the `Flying Saucer' edge-on disk: Large grains beyond 50 AU
Klaus M. Pontoppidan, Karl R. Stapelfeldt, Geoffrey A. Blake +2
We present deep Spitzer-IRS low-resolution (lambda/Delta lambda ~ 100) 5-35 micron spectroscopy of the edge-on disk ``the Flying Saucer'' (2MASS J16281370-2431391) in the Ophiuchus…
Abundant crystalline silicates in the disk of a very low mass star
B. Merin, J. -C. Augereau, E. F. van Dishoeck +16
We announce the discovery of SST-Lup3-1, a very low mass star close to the brown dwarf boundary in Lupus III with a circum(sub)stellar disk, discovered by the `Cores to Disks' Spit…
PAH chemistry and IR emission from circumstellar disks
R. Visser, V. C. Geers, C. P. Dullemond +3
Aims. The chemistry of, and infrared (IR) emission from, polycyclic aromatic hydrocarbons (PAHs) in disks around Herbig Ae/Be and T Tauri stars are investigated. The equilibrium di…
Probing Protoplanetary Disks with Silicate Emission: Where is the silicate emission zone?
J. E. Kessler-Silacci, C. P. Dullemond, J. -C. Augereau +6
Recent results indicate that the grain size and crystallinity inferred from observations of silicate features may be correlated with spectral type of the central star and/or disk g…
Long-term infrared variability of the UX Ori-type star SV Cep
Attila Juhasz, Timo Prusti, Peter Abraham +1
We investigate the long-term optical-infrared variability of SV Cep, and explain it in the context of an existing UX Ori (UXOR) model. A 25-month monitoring programme was completed…
Chemistry and line emission from evolving Herbig Ae disks
B. Jonkheid, C. P. Dullemond, M. R. Hogerheijde +1
Aims: To calculate chemistry and gas temperature of evolving protoplanetary disks with decreasing mass or dust settling, and to explore the sensitivity of gas-phase tracers. Method…