Senior Scientist
M.Sc., Polytechnical Institute, Leningrad, 1967
Ph.D., Ioffe Institute of Physics and Technology, Leningrad,
1974
George Pavlov has main research interests in the physics of neutron stars and their observational manifestations in the X-ray and UV-optical spectral ranges. He has been working on both theoretical models of neutron star radiation and observations of these enigmatic objects. The study of neutron stars is necessary, in particular, to understand the still poorly known properties of superdense matter (matter with densities comparable with those of atomic nuclei). The immense gravitational and magnetic fields of neutron stars make them natural laboratories to investigate the properties of matter under extreme conditions which cannot be realized in terrestrial laboratories.
One of the significant achievements made by Pavlov and his international team was the development of the first realistic models of neutron star atmospheres. Because of the huge magnetic fields associated with neutron stars, the structure of atoms in their atmospheres is strongly distorted, and radiative transitions are quite different from those in atmospheres of ordinary stars. The pioneering investigations of atomic processes in superstrong magnetic fields undertaken by Pavlov's group, have been used in modeling of the spectra, and the angular distribution and polarization of radiation emergent from surface layers of neutron stars.
Another project that Pavlov is involved in concerns the timing of X-ray
pulsars. Timing analyses are an important tool for studying the
nature of neutron stars, since it enables one to evaluate the neutron
star spin period and its time derivatives. An important achievement of
Pavlov's group was the discovery of 424 ms pulsations of the radio-silent
central source in PKS 1209-52; in fact, it is the first pulsar discovered
with CHANDRA. Even more exciting results are expected from observations of
such objects with the now-operating CHANDRA and XMM-Newton missions.
Pavlov also has a program of imaging neutron stars at optical wavelengths
It has been long anticipated that neutron stars radiate not only in the radio
and X-ray ranges, but also in the optical. However, the optical
radiation from these extremely compact objects is so faint that, until
recently, only a few very young pulsars have been detected. Since
multiwavelength observations of various astrophysical objects has proven to
be extremely useful for elucidating their nature, Pavlov has developed an
observational program to observe nearby neutron stars of different ages with
the Hubble Space Telescope. That program has been successfully implemented,
and its first results are very encouraging. In particular, Pavlov and
his coworkers detected the middle-aged pulsars PSR 0656+14 and Geminga
in several spectral bands, from IR through UV, and have shown that the
spectra consist of two components: a thermal radiation from the neutron
star atmospheres and a nonthermal radiation from their magnetospheres.
They also detected, for the first time, optical-UV radiation from the
old pulsars PSR 1929+10 and 0950+08. Further observations of these and
other pulsars are being planned for future HST observational cycles.
Pavlov holds several NASA grants, for both theoretical and observational
investigations. These investigations are expected to result in new exciting
discoveries in the rapidly developing neutron star astrophysics.
The neutron star atmosphere models have been applied to the analysis of soft
X-ray radiation from radio pulsars and from the radio-quiet isolated neutron
stars detected with the ROSAT and ASCA, and CHANDRA X-ray missions. In
particular, Pavlov and his colleagues were able to measure effective surface
temperatures of the isolated pulsars PSR 0656+14 and Geminga, as well as of
the neutron star candidates in the supernova remnants PKS 1209-52, Puppis A,
and Cassiopeia A. These results have important implications for understanding
the equation of state of the superdense matter and the properties of nucleon
superfluidity.
