SIGMA observations of extragalactic sources

Details SIGMA observations of extragalactic sources SIGMA observations of extragalactic sources

Publishing date

Jan 1993

URL

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993a%26as...97...89b&link_type=abstract

Journals

Astronomy and Astrophysics Supplement Series (ISSN 0365-0138), vol. 97, no. 1, p. 89-91.

Science

Astronomy and Astrophysics

Field

Astronomy

Additional info 2

6

Additional info 3

Extragalactic Radio Sources, Gamma Ray Telescopes, Quasars, Seyfert Galaxies, Sky Surveys (Astronomy), Spaceborne Astronomy, Astronomical Spectroscopy, Emission Spectra, Light Curve, Variability, X Ray Spectroscopy

Type

Scientific paper

Abstract

The imaging telescope SIGMA on board the GRANAT satellite has devoted a large amount of time to observe the sky at high galactic latitudes since the commencement of operations in December 1989. Here we briefly summarize the most exciting results obtained during the first two years of operation. In particular, we report on observatios of the Seyfert galaxy NGC4151, the quasar 3C273 and the radio source CenA. All these objects are found to be variable in the SIGMA database on long timescale, while short term variability of the order of days was observed in CenA. The spectra of these AGNs as measured by SIGMA suggest a dispersion in spectral index from 1.5 in 3C273 to about 3 in NGC4151. We also report on follow up observations of the new source GRS1227 + 025 located 15 arcmin from 3C273 and give 2-sigma upper limits at the position of 3C279 relative to a June 1990 observation.

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