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