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Discs around A-type and related stars. Vladimir Grinin. Pulkovo Observatory of RAS. General properties of young disks The dissipative processes The Inner regions of p-p discs Interaction of discs with the low-mass companions The transitional and debris discs. A stars, Moscow 2013. - PowerPoint PPT Presentation
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Discs around A-type and related stars
Vladimir Grinin
Pulkovo Observatory of RAS
A stars, Moscow 2013
1. General properties of young disks 2. The dissipative processes3. The Inner regions of p-p discs4. Interaction of discs with the low-mass
companions 5. The transitional and debris discs
Recent reviews: Dullemond and Monnier 2010, The Inner Regions of Protoplanetary Disks
Williams and Cieza 2011, Protoplanetary Disks and Their Evolution
Initial conditions:
Gas to dust – 100:1MRN dust
Flared discs
The density distribution for the disc calculations is based on the canonical description of the alpha-disk developed by Shakura & Sunyaev (1973)
It is assumed that gas and dust are thermally coupled
Disk outer-radius is a parameter
credit: Dullemond et al. 2006
near-infrared
star inner disk rim
gaseous inner disk
• Dust-free inner hole
• Puffed-up inner rim (Natta et al. 2001)
• Shape of the inner rim
• Shadowed region (Dullemond et al.
•2001)
shadowed region
optically thick gas
magnetospheric accretion
0.5 AU Dullemond et al. 2010
Discs in IR and mm- wavelengths
Disc reprocess the stellar radiation. The viscos heating is important only at high mass accretion rate > 10E-6
Tsub = 1600 K
M disc = 0.01- 0.1 M sun
Contribution of the inner (gaseous) disc
Muzerolle et al. 2004
SED + interferometry is the most effective way
KK Oph, Kreplin et al. 2013, VLTI
inclination = 70 deg.
AB Aur Tannirkulam et al. 2008
SED + Interferometry (Keck)
Disc winds
Safier 1993 – dusty disc wind
Königl & Salmeron 2010 (review)Blandford & Payne (1982)
Bans and Konigl 2012 – NIR excess
Tambovtseva & Grinin 2008 - extinctionGrinin & Tambovtseva 2011, disc wind in HAEs
AB Aur Tannirkulam et al. 2008
Observational manifestations of CS discsIn the visual wavelengths: 1)The scattered radiation intrinsic linear polarization of YSO (Bastien & Landstreet 1979)2) Variable CS extinction UX Ori stars (Grinin et al. 1991)
WW Vul
3. The forbidden lines[OI] 6300 A)
the polarized intensity (PI) image
AB Aur (Sp = A0), Spiral waves, Hashimoto et al. 2011
The disc images
1.3 mm image of AB Aur from Dutrey et al. (2012)
ALMA will be able to reveal the structure of the protoplanetary discs in much more details.!
LkHa 101, Tuthill et al. 2001Demidova et al. 2013
SPH model: the low-mass companion on the inclined orbit
The asymmetric discs
Disc dissipation
Grain growth has a strong radial dependence due to the decreasing density and rotational velocity with increasing radius (Blum & Wurm 2008). Growth is very fast (10000 years). Fragmentation – growth- semi-equilibrium
The disc dissipation starts from the inner region of CS disc and leads to the formation of the transitional discs.
Grain growth and dust settling
.
The disc life time ~ 10 Myr (Strom et al. 1993)
(Zuckerman et al. 1995; Haisch et al. 2001)
The central cavity may be also due to the dynamical clearing by a companion, possibly planetary (Artymowicz & Lubow 1994).
Photoevaporation by radiation from the central stars
This mechanism was elaborated by Hollenbach et al. (1994) for hot YSOs and CTTS. In the case of HAE stars it is not very actual, since these stars are weaker sources of X-ray and far ultraviolet radiation.
Garcia Lopez et al. 2006
Shakura & Sunyaev (1973) – MHD – turbulence.
Viscous transport and the gas accretion
Disc dissipation
Interaction of discs with the low-mass companions
Demidova et al. 2010
Photometric catastrophes in UXORs
CQ Tau (1895-2003); Grinin et al. (2008)
What was happened with CQ Tau?
Interaction of planet with CS disk – migration – destruction in the star vicinity?
Schneider et al. 2005
Debis discs
The well known examples of debris discs around A-stars
Debis discs
Wilner et al. 2012
AU Mic is a less massive sister star β Pic, member of the same moving group.
JHK composite image, Fitzgerald et al. 2007,Keck II
Planetesimals collisions, secondary dust, Wyatt 2008Thermal and scattered radiation
r ~ 50 AU
Thank you for your attention