Tile or stare? Cadence and sky-monitoring observing strategies that maximize the number of discovered transients

Document Type

Article

Publication Date

5-1-2003

Abstract

To maximize the number of transients discovered on the sky, should sky-monitoring projects stare at one location or continually jump from location to location, tiling the sky? If tiling is preferred, what cadence maximizes the discovery rate? As sky monitoring is a growing part of astronomical observing, utilized to find such phenomena as supernovae, microlensing, and planet transits, well-thought-out answers to these questions are increasingly important. Answers are sky-, source-, and telescope-dependent and should include information about the source luminosity distribution near the observation limit, the duration of variability, the nature of the dominant noise, and the magnitude of down and slew times. Usually, a critical slope of the effective cumulative transient apparent luminosity distribution (log N-log S) at the limiting magnitude will define when "tile" or "stare" is superior. For shallower slopes, when "tile" is superior, we discuss optimal cadences and pointing algorithms. For transients discovered on a single exposure or time-contiguous series of exposures, when down and slew times are small and the character of the noise is unchanged, the most productive cadence for Isotropic power-law luminosity distributions is the duration of the transient-faster cadences waste time rediscovering known transients, while slower cadences neglect transients occurring in other fields. A "cadence creep" strategy might find an optimal discovery cadence experimentally when one is not uniquely predetermined theoretically. Guest investigator programs might diversify previously dedicated sky-monitoring telescopes by implementing bandpasses and cadences chosen to optimize the discovery of different types of transients. Example analyses are given for SuperMACHO, LSST, and GLAST.

Publication Title

Astronomical Journal

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