Properties of the
 Scorpii Circumstellar Disk
from Continuum Modeling
A. C. Carciofi1,
A. S. Miroshnichenko2,3,
A. V. Kusakin4,
J. E. Bjorkman3,
K. S. Bjorkman3,
F. Marang6,
K. S. Kuratov5,
P. García-Lario7,
J. V. Perea Calderón8,
J. Fabregat9, and
A. M. Magalhães1
1
Instituto de Astronomia, Geofísica e Ciências
Atmosféricas, Universidade de São Paulo,
Rua do Matão 1226,
Cidade Universitária, São Paulo, SP, 05508-900, Brazil
2Department of Physics and Astronomy, University of
North Carolina at Greensboro, P.O. Box 26170, Greensboro, NC
27402-6170, USA
3Ritter Observatory, Department of
Physics and Astronomy, University of Toledo, Toledo, OH 43606-3390,
USA
4Sternberg Astronomical Institute,
Universitetskij pr. 13, Moscow, Russia
5Fesenkov
Astrophysical Institute, Kamenskoe plato, Almaty 480068, Kazakhstan
6South African Astronomical Observatory, PO Box 9,
Observatory 7935, South Africa
7European Space
Astronomy Centre, Research and Scientific Support Department of ESA,
Villafranca del Castillo, Apartado de Correos 50727, E-28080
Madrid, Spain
8European Space Astronomy Centre,
Villafranca del Castillo, Apartado de Correos 50727, E-28080
Madrid, Spain
9Observatorio Astronómico,
Universidad de Valencia, 46100 Burjassot, Spain
We present optical WBVR and infrared JHKL photometric
observations of the Be binary system
 Sco, obtained in
2000--2005, mid-infrared (10 and 18µm) photometry and optical
( 3200--10500Å)
spectropolarimetry obtained in
2001. Our optical photometry confirms the results of a frequent
visual monitoring being done by amateurs. The 2001 spectral energy
distribution and polarization are successfully modeled with a
three-dimensional non-LTE Monte Carlo code which calculates
self-consistently the hydrogen level populations, electron
temperature, and gas density for hot star disks. Our disk model is
hydrostatically supported in the vertical direction and radially
controlled by viscosity. Such a disk model has, essentially, only
two free parameters, viz., the equatorial mass loss rate and the
disk outer radius, if one assumes a prescription for the viscosity.
We find that the primary companion is surrounded by a small (7
R ), geometrically-thin disk,
which is highly non-isothermal
and fully ionized. Our model requires an average equatorial mass
loss rate of
1.5×10-9 M yr-1
to successfully explain the observations. In 2005, we detected a
significant simultaneous decrease in the object's optical and
near-infrared brightness which is associated with a continuous rise
in the hydrogen line equivalent widths. We discuss possible causes
for this unusual phenomenon, which is difficult to explain in view
of current models of Be star disks.
Accepted by ApJ
Preprints from
carciofi@usp.br
or on the web at
http://arxiv.org/abs/astro-ph/0603274
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