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The La Silla QUEST Variability Survey

Published onJun 01, 2020
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 covered ~1000 degrees twice per night using a single broad V band filter, for a total survey coverage area of ~25,000 square degrees from declination ~ -50 to +20 degrees. The survey magnitude limit was V ~ 21, with the average number of visits on any given patch of sky ~200 and over one thousand square degrees of sky covered by more than 1000 visits. 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 ~100 kpc in the halo and provide metallicity measurements. A large public data release, funded by NSF, should become available on the timescale of a year. This 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.

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