NASA/IPAC EXTRAGALACTIC DATABASE
Date and Time of the Query: 2019-06-20 T03:01:58 PDT
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For refcode 1990AJ.....99.1421B:
Retrieve 89 NED objects in this reference.
Please click here for ADS abstract

NED Abstract

Copyright by American Astronomical Society. Reproduced by permission
1990AJ.....99.1421B OPTICAL VARIABILITY OF EXTRAGALACTIC OBJECTS USED TO TIE THE HIPPARCOS REFERENCE FRAME TO AN EXTRAGALACTIC SYSTEM USING HUBBLE SPACE TELESCOPE OBSERVATIONS ELIZABETH P. BOZYAN AND PAUL D. HEMENWAY Astronomy Department, University of Texas at Austin; Austin; Texas 78712-1083 A. NOEL ARGUE University of Cambridge, Institute of Astronomy, The Observatories; Madingley Road, Cambridge CB3 OHA, England Received 12 January 1990; revised 2 February 1990 ABSTRACT 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% 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.
Retrieve 89 NED objects in this reference.
Please click here for ADS abstract

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