The La Silla QUEST Variability Survey

The La Silla QUEST (LSQ) supernova survey ran for 6 years on the ESO 1m Schmidt telescope at La Silla Chile, using a large CCD array to replace the photographic plate of the Schmidt. The survey imaged ~1000 degrees twice per night using a single broad V band filter, covering a total area of ~25,000 square degrees from declination ~ -50 to +20 degrees. The survey magnitude limit is V~21 in a single 60 second exposure, with an average of ~200 visits for any given patch of sky and over one thousand square degrees of sky covered by more than 1000 visits. Given the large number of visits, coadds of the visits can go significantly deeper, to V> 23-24. Systematic photometric errors from the current differential photometry pipeline are at the 5-10 mmag level for bright point sources on a good night, with further improvements expected. The QUEST V filter can be absolutely calibrated against SDSS and PanSTARRS g+r data at the percent level, enabling LSQ, for example, to extend in time the SDSS Stripe 82 variability survey. The strict survey cadence provides good logarithmic time coverage on timescales from ~30 minutes to ~years, enabling a wide range of variability science. We present highlights of LSQ science, in particular for RR Lyrae stars where LSQ can reach out to ~120 kpc in the halo and provide metallicity measurements. A first public data release, funded by NSF, should become available by ~August 2021. This dataset should prove useful as a testbed for LSST science as well as for transient counterpart searches that need to identify persistent variable sources in a given error box.