We report the results of a search for long-period (100<P<600 days) periodic variability in SDSS Stripe 82 standards catalog. The SDSS coverage of Stripe 82 enables such a search because there are on average 20 observations per band in ugriz bands for about 1 million sources, collected over about 6 years, with a faint limit of r∼22 mag and precisely calibrated 1-2% photometry. We calculated the periods of candidate variable sources in this sample using the Lomb-Scargle periodogram and considered the three highest periodogram peaks in each of the gri filters as relevant. Only those sources with gri periods consistent within 0.1% were later studied. We use the Kuiper statistic to ensure uniform distribution of data points in phased light curves. We present 5 sources with the spectra consistent with quasar spectra and plausible periodic variability. This SDSS-based search bodes well for future sensitive large-area surveys, such as the Rubin Observatory Legacy Survey of Space and Time, which, due to its larger sky coverage (about a factor of 60) and improved sensitivity (∼2 mag), will be more powerful for finding such sources.
@article{arxiv.2303.04600,
title = {Detecting long-period variability in SDSS Stripe 82 standards catalog},
author = {Marta Fatović and Lovro Palaversa and Krešimir Tisanić and Karun Thanjavur and Željko Ivezić and Andjelka B. Kovačević and Dragana Ilić and Luka Č. Popović},
journal= {arXiv preprint arXiv:2303.04600},
year = {2023}
}