scholarly journals Dust Evolution in Protoplanetary Disks

1996 ◽  
Vol 150 ◽  
pp. 513-516
Author(s):  
Thomas Henning ◽  
Wolfgang Schmitt ◽  
Hubert Klahr ◽  
Rastislav Mucha
Keyword(s):  
Numerical Study ◽  
Dynamical Evolution ◽  
Dynamical Behaviour ◽  
Young Stellar Objects ◽  
Dust Particles ◽  
Circumstellar Disk ◽  
Stellar Objects ◽  
One Dimensional ◽  
First Results ◽  
Dust Evolution

AbstractThe evolution of dust particles in circumstellar disk-like structures around protostars and young stellar objects is discussed. We especially consider the coagulation of grains due to collisional aggregation and the influence of this process on the optical properties of the particles. These dust opacities are important for both the derivation of the circumstellar dust mass from submillimetre continuum observations and the dynamical behaviour of the disks.We present first results of a numerical study of the coagulation of dust grains in a turbulent protoplanetary accretion disk described by a time-dependent one-dimensional (radial) “alpha” model. The influence of grain opacity changes due to dust coagulation on the dynamical evolution of a protostellar disk is investigated. In addition, we consider the grain motion in two-dimensional disks.

scholarly journals Episodic accretion in focus: revealing the environment of FU Orionis-type stars

2018 ◽  
Vol 14 (S345) ◽  
pp. 87-90
Author(s):  
O. Fehér ◽  
Á. Kóspál ◽  
P. Ábrahám ◽  
M. R. Hogerheijde ◽  
Ch. Brinch ◽  
...  
Keyword(s):  
Accretion Disks ◽  
Accretion Rate ◽  
Central Star ◽  
Systematic Investigation ◽  
Young Stars ◽  
Young Stellar Objects ◽  
Circumstellar Disk ◽  
Stellar Objects ◽  
Evolutionary Phase ◽  
Intense Mass

AbstractThe earliest phases of star formation are characterised by intense mass accretion from the circumstellar disk to the central star. One group of young stellar objects, the FU Orionis-type stars exhibit accretion rate peaks accompanied by bright eruptions. The occurance of these outbursts might solve the luminosity problem of protostars, play a key role in accumulating the final star mass, and have a significant effect on the parameters of the envelope and the disk. In the framework of the Structured Accretion Disks ERC project, we are conducting a systematic investigation of these sources with millimeter interferometry to examine whether they represent normal young stars in exceptional times or they are unusual objects. Our results show that FU Orionis-type stars can be similar to both Class I and Class II systems and may be in a special evolutionary phase between the two classes with their infall-driven episodic eruptions being the main driving force of the transition.

scholarly journals A Search for Disks around Massive Young Stellar Objects

2004 ◽  
Vol 221 ◽  
pp. 425-430 ◽  
Author(s):  
A. G. Gibb ◽  
M. G. Hoare ◽  
L. G. Mundy ◽  
F. Wyrowski
Keyword(s):  
Near Infrared ◽  
Young Stellar Objects ◽  
Continuum Emission ◽  
Circumstellar Disk ◽  
Mass Yield ◽  
Stellar Objects ◽  
Strong Emission ◽  
Yield Values ◽  
Infrared Data ◽  
The Continuum

We present subarcsecond observations at 2.7 and 1.4 mm of a sample of massive young stellar objects made with the BIMA millimetre array. For most sources the continuum emission on the smallest scales at 2.7 mm is dominated by free-free emission from the stellar wind or jet. Strong emission at 1.4 mm shows the presence of significant dust associated with Cep A and GL 490 but our resolution is not sufficient to resolve any structure. The 2.7-mm emission from GL 490 is resolved but it is not clear whether we are seeing a single circumstellar disk or a secondary companion, although near-infrared data support the disk hypothesis. Estimates of the dust mass yield values of ∼1–4 M⊙ within radii of 150 to 1000 AU.

scholarly journals Modeling of Circumstellar Dust by the DUSTY Code

2011 ◽  
Vol 7 (S282) ◽  
pp. 247-250
Author(s):  
Tomislav Jurkić ◽  
Dubravka Kotnik-Karuza
Keyword(s):  
Near Infrared ◽  
Dynamical Behaviour ◽  
Light Curves ◽  
Young Stellar Objects ◽  
Numerical Code ◽  
Circumstellar Dust ◽  
Be Stars ◽  
Stellar Objects ◽  
Near Ir ◽  
Dust Temperature

AbstractWe present a circumstellar dust model around the symbiotic Mira RR Tel obtained by modeling the near-infrared JHKL magnitudes and ISO spectra. In order to follow the evolution of infrared colours in time, the published JHKL magnitudes were corrected by removing the Mira pulsations. The RR Tel light curves show three obscuration events in the near-IR. Using the simultaneously available JHKL magnitudes and ISO spectra in three different epochs, we obtained SEDs in the near- and mid-IR spectral region (1-20 μm) in epochs with and without obscuration.The DUSTY numerical code was used to solve the radiative transfer and to determine the circumstellar dust properties of the inner dust regions around the Mira, assuming a spherical dust temperature distribution in its close neighbourhood. The physical properties of the dust, mass loss and optical depth during intervals with and without obscuration have been obtained. Both JHKL and ISO observations during the obscuration period can be reproduced with a spherical dust envelope, while ISO spectra outside obscuration show a different behaviour. The dynamical behaviour of the circumstellar dust was obtained by modeling the JHKL magnitudes observed during the span of more than 30 years.The DUSTY code was also successfully applied in the modeling of circumstellar dust envelopes of young stellar objects, such as Herbig Ae/Be stars.

scholarly journals Studies of the Perseus Region.I.

2006 ◽  
Vol 2 (S237) ◽  
pp. 405-405
Author(s):  
Srabani Datta
Keyword(s):  
Young Stellar Objects ◽  
Stellar Objects ◽  
Star Forming ◽  
Bolometer Array ◽  
Sky Survey ◽  
Multiple Imaging ◽  
First Results ◽  
Multi Wavelength ◽  
Array Camera ◽  
Infrared Array

AbstractStudies of molecular clouds have shown that they evolve from turbulent gas and dust to form coherent, dense and connected structures. We have conducted a multi-wavelength study of one such molecular cloud, the Perseus star-forming region, which includes Barnard 1 (B1), Barnard 3(B3), Barnard 5 (B5), NGC 1333, IC 348, L1455 and L1448. The data obtained using the Infrared Array Camera (IRAC), Multiple Imaging Photometer (MIPS), the Sub-mm Common User Bolometer Array(SCUBA) and the 2 Micron All Sky Survey (2MASS)provides information about the geometric structure of the dust and gas covering large areas around young stellar objects (YSO), dust temperatures, effect of turbulence and processes of molecule formation and their relevance in the chemical and physical evolution of the cloud. This paper presents our first results.

scholarly journals Young Stellar Object Variability at IRAC Wavelengths: Clues to Star and Planet Formation

2009 ◽  
Vol 5 (H15) ◽  
pp. 734-734
Author(s):  
John R. Stauffer ◽  
Maria Morales ◽  
Luisa Rebull
Keyword(s):  
Light Curve ◽  
Density Profile ◽  
Hot Spot ◽  
Light Curves ◽  
Young Stellar Objects ◽  
Circumstellar Disk ◽  
Stellar Objects ◽  
Mid Infrared ◽  
Stellar Photosphere ◽  
Disk Plane

In Morales et al. (2009), we have recently investigated the mid-infrared (3.6 to 8.0 micron) variability of young-stellar objects (YSOs) using the IRAC camera on the Spitzer Space Telescope. Specifically, we obtained synoptic photometry of about 70 YSOs in the ~1 Myr old IC1396A globule over a 14 day period. More than half of the YSOs were detectably variable, with amplitudes up to about 0.2 magnitudes. About a third of these objects showed quasi-sinusoidal light curves with apparent periods of typically 5 to 12 days. At least two families of models can explain such light curves: (a) a Class II YSO with a photospheric hot spot which locally heats the inner circumstellar disk which is viewed from slightly above the disk plane, and (b) a YSO with a warped disk or with some other non-axisymmetric inner disk density profile, also seen with a view angle slightly above the disk plane. The two models can both yield light curve shapes and amplitudes similar to what we observe in the mid-infrared, but produce very different light curves at shorter wavelengths dominated by the stellar photosphere. Because we only had IRAC photometry for IC1396A, we were not able to discriminate between the two models for this set of data.

scholarly journals First results from VLTI near-infrared interferometry on high-mass young stellar objects

2010 ◽  
Author(s):  
Stefan Kraus ◽  
Karl-Heinz Hofmann ◽  
Karl M. Menten ◽  
Dieter Schertl ◽  
Gerd Weigelt ◽  
...  
Keyword(s):  
Near Infrared ◽  
Young Stellar Objects ◽  
High Mass ◽  
Stellar Objects ◽  
First Results ◽  
Infrared Interferometry

Understanding high-mass star formation through KaVA observations of water and methanol masers

2017 ◽  
Vol 13 (S336) ◽  
pp. 259-262
Author(s):  
Kee-Tae Kim ◽  
Tomoya Hirota ◽  
Koichiro Sugiyama ◽  
Jungha Kim ◽  
Do-Young Byun ◽  
...  
Keyword(s):  
Dynamical Evolution ◽  
Young Stellar Objects ◽  
High Mass ◽  
Mass Star ◽  
Stellar Objects ◽  
Star Forming ◽  
3 Dimensional ◽  
Star Forming Regions ◽  
Large Program ◽  
Methanol Masers

AbstractDespite their importance in the formation and evolution of stellar clusters and galaxies, the formation of high-mass stars remains poorly understood. We recently started a systematic observational study of the 22 GHz water and 44 GHz class I methanol masers in high-mass star-forming regions as a four-year KaVA large program. Our sample consists of 87 high-mass young stellar objects (HM-YSOs) in various evolutionary phases, many of which are associated with two or more different maser species. The primary scientific goals are to measure the spatial distributions and 3-dimensional velocity fields of multiple maser species, and understand the dynamical evolution of HM-YSOs and their circumstellar structures, in conjunction with follow-up observations with JVN/EAVN (6.7 GHz class II methanol masers), VERA, and ALMA. In this paper we present details of our KaVA large program, including the first-year results and observing/data analysis plans for the second year and beyond.

scholarly journals A movie of accretion/ejection of material in a high-mass YSO in Orion BN/KL at radii comparable to the Solar System

2009 ◽  
Vol 5 (H15) ◽  
pp. 750-750 ◽  
Author(s):  
C. Goddi ◽  
L. Greenhill ◽  
E. Humphreys ◽  
L. Matthews ◽  
C. Chandler
Keyword(s):  
Accretion Disks ◽  
Gas Flow ◽  
Dynamical Evolution ◽  
Young Stellar Objects ◽  
High Mass ◽  
Mass Star ◽  
Proper Motions ◽  
Compact Disk ◽  
Stellar Objects ◽  
Circumstellar Gas

Around high-mass Young Stellar Objects (YSOs), outflows are expected to be launched and collimated by accretion disks inside radii of 100 AU. Strong observational constraints on disk-mediated accretion in this context have been scarce, largely owing to difficulties in probing the circumstellar gas at scales 10-100 AU around high-mass YSOs, which are on average distant (>1 Kpc), form in clusters, and ignite quickly whilst still enshrouded in dusty envelopes. Radio Source I in Orion BN/KL is the nearest example of a high-mass YSO, and only one of three YSOs known to power SiO masers. Using VLA and VLBA observations of different SiO maser transitions, the KaLYPSO project (http://www.cfa.harvard.edu/kalypso/) aims to overcome past observational limitations by mapping the structure, 3-D velocity field, and dynamical evolution of the circumstellar gas within 1000 AU from Source I. Based on 19 epochs of VLBA observations of v=1,2 SiO masers over ~2 years, we produced a movie of bulk gas flow tracing the compact disk and the base of the protostellar wind at radii < 100 AU from Source I. In addition, we have used the VLA to map 7mm SiO v=0 emission and track proper motions over 10 years. We identify a narrowly collimated outflow with a mean motion of 18 km/s at radii 100-1000 AU, along a NE-SW axis perpendicular to that of the disk traced by the v=1,2 masers. The VLBA and VLA data exclude alternate models that place outflow from Source I along a NW-SE axis. The analysis of the complete (VLBA and VLA) dataset provides the most detailed evidence to date that high-mass star formation occurs via disk-mediated accretion.

Dynamics of jet/outflow driven by high-mass young stellar object revealed by KaVA 22 GHz water maser observations

2017 ◽  
Vol 13 (S336) ◽  
pp. 303-304
Author(s):  
Jungha Kim ◽  
Tomoya Hirota ◽  
Kee-Tae Kim ◽  
Koichiro Sugiyama ◽  
Keyword(s):  
Dynamical Evolution ◽  
Young Stellar Objects ◽  
High Mass ◽  
First Year ◽  
Stellar Objects ◽  
Large Program ◽  
Molecular Lines ◽  
Water Masers ◽  
Initial Results ◽  
Water Maser

AbstractWe have started survey observations of the 22 GHz water maser sources associated with high-mass young stellar objects (HM-YSOs) as a part of the KaVA (KVN and VERA Array) large program (LP). The aim of our LP is to understand dynamical evolution of jets/outflows from HM-YSOs by analyzing 3D velocity structures of water maser features. In the first year (2016-2017), an imaging survey toward 25 HM-YSOs has been conducted and the 22 GHz water masers are detected toward 21 sources. Spatial distributions of maser features for individual sources are mapped. To complement physical properties in the vicinity of HM-YSOs, we have carried out ALMA cycle 3 observations of thermal molecular lines and continuum emissions toward 11 selected samples. Summary of the KaVA first year observations and the initial results from the ALMA toward one of our targets, G25.82-0.17, are reported.

scholarly journals Young Stellar Objects in the Magellanic Clouds: Herschel Spectroscopy First Results

2015 ◽  
Vol 11 (S315) ◽  
Author(s):  
Joana M. Oliveira ◽  
Jacco Th. van Loon ◽  
Marta Sewiło
Keyword(s):  
Gas Phase ◽  
Magellanic Clouds ◽  
Young Stellar Objects ◽  
Space Observatory ◽  
Herschel Space Observatory ◽  
Stellar Objects ◽  
Preliminary Results ◽  
Physical Conditions ◽  
First Results

AbstractWe present preliminary results from spectroscopy obtained with PACS and SPIRE onboard the Herschel Space Observatory of a sample of massive Young Stellar Objects in the Magellanic Clouds. We analyse key gas-phase cooling species (Oi], [Cii], H2O, CO, OH), in order to characterise the physical conditions in these metal-poor environments.

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