Discovery of nine quasars behind the Large Magellanic Cloud

Abstract

We present the discovery of nine quasars behind the Large Magellanic Cloud, with emission redshifts ranging from 0.07 to 2.0. Six of them were identified as part of the systematic variability-based search for QSOs in the objects from the OGLE-II database. Combination of variability-based selection of candidates with the candidates' colours appears to be a powerful technique for identifying quasars, potentially reaching ca. 50% efficiency. We report an apparent correlation between variability magnitude and variability timescale, which - if confirmed - could put even more constraints on QSO candidate selection. The remaining three quasars were identified via followup spectroscopy of optical counterparts to X-ray sources found serendipitously by the Chandra X-ray Observatory satellite. Even though the locations of the candidates were quite uniformly distributed over the LMC bar, the confirmed QSOs all appear near the bar's outskirts.

7 pages, 6 figures, submitted to Astronomy and Astrophysics

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• The Magellanic Quasars Survey. II. Confirmation of 144 New Active Galactic Nuclei Behind the Southern Edge of the Large Magellanic Cloud
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• A Refined QSO Selection Method Using Diagnostics Tests: 663 QSO Candidates in the LMC
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