New Quasars Detected via Variability in the QUEST1 Survey

• Published in: The Astrophysical journal 2004-05, Vol.606 (2), p.741-748
• Main Authors: Rengstorf, A. W, Mufson, S. L, Abad, C, Adams, B, Andrews, P, Bailyn, C, Baltay, C, Bongiovanni, A, Briceño, C, Bruzual, G, Coppi, P, Della Prugna, F, Emmet, W, Ferrín, I, Fuenmayor, F, Gebhard, M, Hernández, J, Honeycutt, R. K, Magris, G, Musser, J, Naranjo, O, Oemler, A, Rosenzweig, P, Sabbey, C. N, Sánchez, Ge, Sánchez, Gu, Schaefer, B, Schenner, H, Sinnott, J, Snyder, J. A, Sofia, S, Stock, J, van Altena, W, Vivas, A. K
• Format: Article
• Language: English
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1086/383183

By observing the high Galactic latitude equatorial sky in drift-scan mode with the QUEST (Quasar Equatorial Survey Team) Phase 1 camera, we have collected multibandpass photometry on a large strip of sky, resolved over a large range of timescales (from hourly to biennially). A robust method of ensemble photometry reveals those objects within the scan region that fluctuate in brightness at a statistically significant level. Subsequent spectroscopic observations of a subset of those varying objects easily discriminated the quasars from stars. For a 13 month time span, 38% of the previously known quasars within the scan region were seen to vary in brightness, and subsequent spectroscopic observation revealed that similar to 7% of all variable objects in the scan region are quasars. Increasing the time baseline to 26 months increased the percentage of previously known quasars that vary to 61% and confirms via spectroscopy that 7% of the variable objects in the region are quasars. This reinforces previously published trends and encourages additional and ongoing synoptic searches for new quasars and their subsequent analysis. During two spectroscopic observing campaigns, a total of 30 quasars were confirmed, 11 of which are new discoveries and 19 of which were determined to be previously known. Using the previously cataloged quasars as a benchmark, we find we can better optimize future variability surveys. This paper reports on the subset of variable objects that are spectroscopically confirmed as quasars.