Dr. Jorge A. CombiMs.S. 1991, UNLP
Ph. D. 1995, UNLP, "High-energy
components in the regions of Upper-Sco and Ara"
[CV] [Ph.D.] [Publication
List] [Papers in ADS] [Papers in SPIRES]
Since 1992 I have been working on topics related to the
high-energy astrophysics and radio astronomy. These subjects include:
- Unidentified gamma-ray
sources. One of the
most exciting mysteries of astronomy involves the large number of unidentified gamma-ray
(EGRET) sources whose nature is unknown. Search for radio counterparts of
these detections can give us additional information about the structure
of the ISM in the line of sight to these sources. By eliminating the
background diffuse radiation originated by the galactic disk from the
radio images, with filtering techniques, we have unveiled possible radio
counterparts of several gamma-ray objects and gathered information
on the high-energy radiation mechanisms.
- Multifrequency investigations of new Supernova Remnants
(SNRs), discovered from 408 MHz, 1.4 GHz and 2.4 GHz surveys. Several
candidates for SNRs have been detected in the southern sky at these
frequencies after removing the diffuse background radiation
permeating the Galaxy. We have used these data to examine spectral index
characteristics over faint and extended regions of SNRs.
- Studies on the origin of galactic and
extragalactic cosmic rays (CR). The origin of the highest energy cosmic rays detected in the neighborhood of Earth is still an
unsettled issue. In the last years our work have been directed to the use of
multifrequency observations in order to estimate the arrival energy of protons accelerated by strong shock fronts in
the outer parts of radio galaxies and in the terminal shock of galactic superwinds generated in starburst galaxies. In a
series of papers on possible source candidates, different energy losses have been discussed for the rays as well as the associated
changes in the arrival spectra.
- Radio and optical microvariability of Active Galactic Nuclei
(AGNs). Intraday variability of AGNs like quasars and BL Lac
objects was discovered 10 years ago during extensive monitoring campaigns of
large samples of northern objects. The origin of these variations is still unknown. Shocks propagating down the parsec-scale jet of the objects have been
suggested as a possible cause, but the most extreme cases of variability impose severe constraints on the shock thickness and
required Doppler factors. Extrinsic models invoke refractive
interstellar scintillation and gravitational microlensing. Since 1990s we have made numerous observations of rapid variability in
southern AGNs, detecting many outstanding outbursts (including the
first observation of extreme intraday events with brightness
temperatures above 1021 K).
- The radio environment of accreting
sources.
The sources in this category are neutron stars or black holes -the results of a supernova
explosion- which orbit a normal star. These sources are powered by the energy released
when matter is transferred from the normal star to the compact star. I am interested in
the study of the surrounding of LMXRBs and HMXRBs. These investigations can be made searching for the presence of SNRs, cavities, shocks, or large-scale jets
using radio continuum and HI observations.
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