Shining Through the Fog:
Jennifer
L. Hoffman |
| KH 15D is an unusual variable star in the
young
cluster NGC 2264. Its light curve shows a 48-day period and features
stellar
eclipses that have varied in depth and shape over the past century.
Recent
studies suggest that the object is a pre–main sequence binary system
surrounded
by a precessing circumbinary disk inclined to our line of sight. The peculiar eclipse behavior results from
occultation of varying portions of the stellar orbits by the opaque
edge of the
disk. At the current mid-eclipse phase, when both stars are occulted in
this
model, KH 15D still emits a small amount of flux, ~5% of its maximum
light.
The fact that this light is ~2% polarized suggests that it arises
from
scattering of incident starlight either from the circumbinary disk or
from nebular
or coronal regions surrounding one or both of the stars. These
scenarios should produce distinct polarimetric signatures. I have used
a multiple-scattering
radiative transfer code to calculate the flux and polarization
contributions of
these scenarios and to investigate the effects of each on the
mid-eclipse
brightness and polarization of the system. In this poster, I will
present the
results of this project, assess the likely relative contributions of
disk-like
and nebular/coronal scattering regions to the mid-eclipse light of KH
15D, and
predict the polarimetric signatures that should be observed at other
phases in
each case. Because the polarization variations of a binary-disk system
can
strongly constrain the characteristics of its scattering regions,
further
polarimetric observations of KH 15D will provide an invaluable source
of
information about the circumstellar environment of this important young
binary. J.L. Hoffman is supported by an NSF Astronomy & Astrophysics Postdoctoral Fellowship under award AST-0302123. For references and a more detailed background, see the conference abstract for this poster (PDF, 84 K). |
|
For more information, please send email to Jennifer. December 1, 2005 |