JOINT
ASTROPHYSICS/JOINT PARTICLE SEMINAR
Date:
Tuesday, 2 March
2004
Time:
4:00 pm
Place:
1114 Nat. Sci. 1
Speaker:
Julia Lee, MIT
Title:
"Probing Black Hole Environments with High Resolution X-ray
Spectroscopy"
Abstract: Black holes and accretion onto
black holes are associated with a wide range of astrophysical
phenomena. Galactic black hole systems may be associated with
gamma-ray bursts while accretion onto supermassive black holes may be
partly responsible for reionization of the early Universe.
Additionally, spectral studies of selected QSOs allow us to probe
the hotter baryonic components of the warm hot intergalactic
medium. However, despite the major advances of the past several
decades many questions about the structure and dynamics of accretion
onto black holes remain unanswered. High resolution X-ray
spectroscopy provides a powerful new tool for probing the physics of
the black hole environment. X-ray spectral signatures reveal the
dynamics and the ionization state of plasma in and around the accretion
disk, and the properties of winds and flows. I will discuss
highlights from Chandra observations of several well known stellar and
supermassive black hole systems, GRS 1915+105, MCG-6-30-15 and IRAS
18325-5926 to illustrate their similarities. These spectra reveal
(1) narrow absorption/emission lines from photoionized plasma in a wide
range of ionization states, (2) relativistically broadened emission
from regions of the accretion disk closest to the black hole, and
(3) surprisingly large amounts of outflowing material. The
astrophysical implications of these findings and directions for the
future will be discussed. A deeper understanding of these black
hole systems will be important for helping us to assess their
contribution to the energy density of the Universe, and to understand
the role of black hole formation and growth in the evolution of cosmic
structure.
Host:
G. Chanan