Professor of Astronomy,
Director of Tuorla Observatory
my web site.
After 12 years in Oulu close to the polar circle and the Santa Claus village,
I have moved to
Tuorla Observatory, University of Turku.
This is almost in the tropics, since it lies at
60.4 degrees North only.
studies accretion-powered high energy sources
such as neutron stars and black holes.
Our strength is the
combination of observational and theoretical
research. We are actively involved in the
analysis of the data on blazars, black holes X-ray binaries, X-ray pulsars and X-ray bursters,
as well as ultraluminous X-ray sources
obtained with the X-ray
and gamma-ray observatories such as RXTE,
XMM-Newton, INTEGRAL, Fermii and Nustar. We also
develop theoretical models for accretion discs
around neutron stars and black holes, particularly super-Eddington
accretion discs around black holes and X-ray pulsars. We have
pioneered theoretical modelling of the light
curves from rapidly rotating neutron stars and
have developed state-of-the-art computer code
for modelling the radiative processes in
We have developed the most accurate atmosphere models for hot neutron stars with the aim
to understand the emission properties during X-ray bursts and to obtain useful constraints on the
neutron star masses and radii and therefore on the equation of state of cold dense matter.
Furthermore, we work on physical models for the correlated optical/X-ray variability of accreting black holes,
in particular, we developed models for quasi-period oscillations.
We also make polarimetric observations in the optical of accreting black holes with the state-of-the-art
We work on the analysis of the Fermi/LAT
data from blazars, which are supermassive
blackholes with relativistic jets pointing
towards us and emitting most of the energy in
the GeV range. We have found that their
spectra have significant breaks in the GeV
range that are well described by the
absorption of the gamma-rays due to the
photon-photon pair production on He II Lyman
recombination continuum and lines. This has
resolved a long-standing question of gamma-ray
production and proved that gamma-rays are
produced within the broad-band line region. We
have also proposed a novel particle
acceleration mechanism--"photon breeding"--
that operates in relativistic jets emanating
from active galactic nuclei.
Faculty of Science and Engineering
] > [Dept. of
Physics and Astronomy ] > [Tuorla Observatory]