Photometric observations of selected, optically bright quasars for Space Interferometry Mission and other future celestial reference frames

Ojha, Roopesh
Zacharias, Norbert
Hennessey, Gregory S.
Gaume, Ralph A.
Johnston, Kenneth J.
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Photometric observations of 235 extragalactic objects that are potential targets for the Space Interferometry Mission (SIM) are presented. Mean B, V, R, I magnitudes at the 5% level are obtained at 1 - 4 epochs between 2005 and 2007 using the 1-m telescopes at Cerro Tololo Inter-American Observatory and Naval Observatory Flagstaff Station. Of the 134 sources which have V magnitudes in the Veron & Veron-Cetty catalog a difference of over 1.0 mag is found for the observed-catalog magnitudes for about 36% of the common sources, and 10 sources show over 3 mag difference. Our first set of observations presented here form the basis of a long-term photometric variability study of the selected reference frame sources to assist in mission target selection and to support in general QSO multi-color photometric variability studies.
Comment: 40 pages, 13 figures, 4 tables
Astrophysics - Cosmology and Nongalactic Astrophysics