Photometric Monitoring of Mrk 501: A Model for Measuring the Optical Variability of BL Lacs

BL Lacertae objects\u27 (BL Lacs) relativistic jets are oriented close to our line of sight, producing a variation in flux density over time. The physical mechanisms behind these fluctuations are still poorly known. Variability surveys such as ours that combine high photometric accuracy, sufficiently long time baselines, and a high number of observation epochs hold the promise of significant progress. We present a pipeline that produces calibrated photometry from imaging data. Our first set of photometric observations are of Markarian 501 (Mrk 501), imaged in three optical (VRI) bands from 2010 to 2015 using the 0.4m telescope at the Challis Astronomical Observatory (CAO). Astrometric calibration was performed on each image using Astrometry.net. Images that were recognized and calibrated formed the data for our analysis. Artifacts were removed by resampling and co-adding images using SWarp. For each co-added image, we generated an SExtractor catalog and computed an on-sky separation by matching field stars with star catalogs. We used this solution to match Mrk 501 to reference catalogs for modeling light curves. Our first set of light curves presented here form the basis of a long-term photometric variability study of BL Lacs. Future research will produce light curve data for new sources. This data will be cross correlated with catalogs in high energies in order to better understand the source structure and physical processes of BL Lacs