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Discs around A-type and related stars
Vladimir Grinin
Pulkovo Observatory of RAS
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General properties of young disks
The dissipative processes
The Inner regions of p-p discs
Interaction of discs with the low-mass
companions
5. The transitional and debris discs
A stars, Moscow 2013
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 – 100:1
MRN dust
The density distribution for the disc calculations is based on the canonical
description of the alpha-disk developed by Shakura & Sunyaev (1973)
Disk outer-radius is a parameter
Flared discs
It is assumed that gas and dust are
thermally coupled
Discs in IR and mm- wavelengths
magnetospheric
accretion
gaseous inner disk
star
optically thick gas
0.5 AU
shadowed region
inner disk rim
Dullemond et al. 2010
Tsub = 1600 K
Disc reprocess the stellar radiation.
The viscos heating is important only
at high mass accretion rate > 10E-6
• Dust-free inner hole
• Puffed-up inner rim (Natta et al. 2001)
• Shape of the inner rim
• Shadowed region (Dullemond et al.
•2001)
near-infrared
M disc = 0.01- 0.1 M sun
credit: Dullemond et al. 2006
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.
SED + Interferometry (Keck)
AB Aur
Tannirkulam et al. 2008
Disc winds
Blandford & Payne (1982)
Königl & Salmeron 2010 (review)
Safier 1993 – dusty disc wind
Bans and Konigl 2012 – NIR excess
AB Aur
Tambovtseva & Grinin 2008 - extinction
Grinin & Tambovtseva 2011, disc wind in HAEs
Tannirkulam et al. 2008
Observational manifestations of CS discs
In 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 disc images
AB Aur (Sp = A0), Spiral waves, Hashimoto et al. 2011
the polarized intensity (PI) image
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.!
The asymmetric discs
Demidova et al. 2013
LkHa 101, Tuthill et al. 2001
SPH model: the low-mass companion on the inclined orbit
Disc dissipation
The disc life time ~ 10 Myr (Strom et al. 1993)
Grain growth and dust settling
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.
(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).
Disc dissipation
Viscous transport and the gas accretion
Shakura & Sunyaev (1973) – MHD – turbulence.
Garcia Lopez et al. 2006
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.
Interaction of discs with the low-mass companions
Demidova et al. 2010
Photometric catastrophes in UXORs
What was happened with CQ Tau?
CQ Tau (1895-2003); Grinin et al. (2008)
Interaction of planet with CS disk – migration – destruction in the star vicinity?
Debis discs
Schneider et al. 2005
The well known examples of debris discs around A-stars
Debis discs
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
Wilner et al. 2012
Planetesimals collisions,
secondary dust, Wyatt 2008
Thermal and scattered radiation
r ~ 50 AU
Thank you for your attention