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Introduction
Members
Research
Master's projects
Archive of
untriggered gamma-ray bursts
Links
Supported by
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Our research covers both theoretical and observational aspects of high energy
astrophysics. Listed below is a summary of our current main topics.
Research areas
- Gamma-ray bursts
Gamma-ray bursts (GRBs) are the largest known explosions in the Universe.
Due to their huge brightness we are able to detect them from very
large distances, thereby viewing the very early universe. The
radiation processes and progenitor objects involved are still
unclear. We aim at determining the radiation and particle
acceleration processes involved producing the GRBs. Detailed studies
of the spectral and temporal data in the X- and gamma-ray bands, as
well as in-depth theoretical considerations of the photospheric
emission and the non-thermal emission from other dissipation sites,
are being performed. In particular, the Swift satellite and the Fermi Burst Monitor combined with the LAT instruments will give us a
uniquely broad spectral range from a few keV up to 100 GeV. Simulations
of such observations show that we can expect to get a better
understanding of the radiation processes of GRBs.
A better understanding of the emission processes in GRBs will allow
us to use them to study the early universe, as well as a "laboratory"
to study plasmas under extreme conditions.
- Galactic black holes
By their very nature, black holes are regions of extreme physics.
Although no direct observations of these objects can be made, several
black hole candidates have been identified. Nearly all such sources are
detected as X-ray binaries (XRBs), systems where a compact object (such
as a black hole or neutron star) and a companion star orbit each other.
Gas from the companion is accreted
by the compact object. During the accretion process, the matter is
heated up and emits strongly in X-rays. Studies of the X-ray radiation
gives information on the geometry and physical processes in the region
closest to the compact object.
The group performs both temporal and spectral analysis of X-ray
observations. Among the objects most closely studied are Cygnus X-1
and Cygnus X-3.
- Numerical simulations of extreme plasmas
Together with collaborators at Copenhagen University, we are involved in a
project to develop a model of highly relativistic astrophysical plasmas in
cases where Compton scattering, electron-positron pair production and more
generally particle processes are important. Ultimately, the
objective is to test aspects of models concerned with the internal and
external GRB shock scenarios, to explain the mechanisms behind the rapid
variability in the prompt GRB signal and early afterglows. This is a
completely novel approach to enigmas surrounding extreme astrophysical
phenomena. This project will furthermore contribute more generally to high
energy plasma astrophysics modeling and theory.
The group also hosts Stern & Tikhomirova's Archive of Untriggered Gamma-Ray Bursts.
We are always happy to talk about our work, so don't hesitate to contact us if you want to know more!
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Space observatories
PoGOLite -- The Polarised Gamma-ray Observer
PoGOLite is a new balloon-borne instrument designed to measure the
polarization of soft gamma rays. This instrument will bring a new
dimension to studies of gamma-ray emission in pulsars, AGNs
(Active Galactic Nuclei), black hole binaries and neutron star surfaces.
The group is involved in the development of the instrument, as well
as observation planning and scientific studies.
The Swedish PoGOLite homepage
Fermi -- The Gamma-ray Space Telescope.
Fermi (formerly GLAST) is a next generation high-energy gamma-ray observatory designed
for making observations of celestial gamma-ray sources in the energy range
10 MeV - 300 GeV. Launched in June 2008, some of the scientific areas
targeted by Fermi are: particle acceleration in AGNs, pulsars and
SNRs, unidentified sources and diffuse gamma-emission, gamma-ray
bursts and transients and dark matter and the early Universe. Several group
members are part of the Fermi science groups for GRBs, AGN and pulsars.
Read more about Fermi at NASA.
INTEGRAL -- The International Gamma-Ray Astrophysics Laboratory.
INTEGRAL is ESA's second Medium Size mission. The three main
instruments provide simultaneous imaging, spectroscopy and timing
from a few keV to 10 MeV. The fourth onboard instrument makes
simultaneous optical monitoring. Our group is part of the JEM-X consortium
which provides the X-ray monitor for the INTEGRAL satellite. JEM-X
and the two gamma-ray instruments are all coded mask telescopes.
Our main contribution is the development of software which from
JEM-X shadowgram images extracts individual source spectra and
lightcurves. Among the scientific goals of INTEGRAL are studies
of gamma-ray lines from the interstellar medium, observations of
pulsars, X-ray binaries and GRBs.
INTEGRAL home page at ESA
Read more about INTEGRAL...(Swedish)
Article in Populär astronomi by
Stefan Larsson
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Reports and Ph.D. theses
X-ray variability in high-mass Galactic black hole binaries, Magnus Axelsson, October 2008.
Spectral states and accretion geometries in Galactic black hole binaries, Linnea Hjalmarsdotter, June 2008.
Microphysical Conditioning of Gamma-Ray Burst Shocks, Jacob Trier Frederiksen, April 2008
Spectral and Temporal Studies of Gamma-Ray Bursts, Luis Borgonovo, May 2007
Evaluation
of Swedish Astronomy, June 2000: High Energy Astrophysics, Juri Poutanen,
2000. [download
postscript file]
Send comments to magnusa@astro.su.se.
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