Astronomy and Astrophysics – Astronomy
Scientific paper
May 1990
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1990aj.....99.1421b&link_type=abstract
Astronomical Journal (ISSN 0004-6256), vol. 99, May 1990, p. 1421-1434.
Astronomy and Astrophysics
Astronomy
26
Active Galactic Nuclei, Bl Lacertae Objects, Hipparcos Satellite, Quasars, Charge Coupled Devices, Hubble Space Telescope, Light Curve, Seyfert Galaxies, Tables (Data)
Scientific paper
Observations of a set of 89 extragalactic objects (EGOs) will be made with the Hubble Space Telescope Fine Guidance Sensors and Planetary Camera in order to link the HIPPARCOS Instrumental System to an extragalactic coordinate system. Most of the sources chosen for observation contain compact radio sources and stellarlike nuclei; 65 percent are optical variables beyond a 0.2 mag limit. To ensure proper exposure times, accurate mean magnitudes are necessary. In many cases, the average magnitudes listed in the literature were not adequate. The literature was searched for all relevant photometric information for the EGOs, and photometric parameters were derived, including mean magnitude, maximum range, and timescale of variability. This paper presents the results of that search and the parameters derived. The results will allow exposure times to be estimated such that an observed magnitude different from the tabular magnitude by 0.5 mag in either direction will not degrade the astrometric centering ability on a Planetary Camera CCD frame.
Argue Noel A.
Bozyan Elizabeth P.
Hemenway Paul Derek
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