The Variable Sky of Deep Synoptic Surveys

Abstract

The discovery of variable and transient sources is an essential product of synoptic surveys. The alert stream will require filtering for personalized criteria -- a process managed by a functionality commonly described as a Broker. In order to understand quantitatively the magnitude of the alert generation and Broker tasks, we have undertaken an analysis of the most numerous types of variable targets in the sky -- Galactic stars, QSOs, AGNs and asteroids. It is found that LSST will be capable of discovering ~10^5 high latitude |b| > 20 deg) variable stars per night at the beginning of the survey. (The corresponding number for |b| < 20 deg is orders of magnitude larger, but subject to caveats concerning extinction and crowding.) However, the number of new discoveries may well drop below 100/night within 2 years. The same analysis applied to GAIA clarifies the complementarity of the GAIA and LSST surveys. Discovery of variable galactic nuclei (AGNs) and Quasi Stellar Objects (QSOs) are each predicted to begin at ~3000 per night, and decrease by 50X over 4 years. SNe are expected at ~1100/night, and after several survey years will dominate the new variable discovery rate. LSST asteroid discoveries will start at > 10^5 per night, and if orbital determination has a 50% success rate per epoch, will drop below 1000/night within 2 years.

Published in ApJ, 22 pages, 26 figures, 3 tables; subsequent correction of an important error in interpretation of the Besancon models reduces stellar variable numbers significantly, as seen in figures 6-13

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• Serendipitous Discoveries of Kilonovae in the LSST Main Survey: Maximising Detections of Sub-Threshold Gravitational Wave Events
• SNIa-Cosmology Analysis Results from Simulated LSST Images: from Difference Imaging to Constraints on Dark Energy
• First Data Release of the All-sky NOAO Source Catalog
• ANTARES: Progress towards building a `Broker' of time-domain alerts
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• Paving the way to simultaneous multi-wavelength astronomy
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• RoboTAP - target priorities for robotic microlensing observations
• Synergies of THESEUS with the large facilities of the 2030s and guest observer opportunities
• Multiplexing lobster-eye optics: a concept for wide-field X-ray monitoring
• Detecting long-period variability in SDSS Stripe 82 standards catalog
• Multi-scale stamps for real-time classification of alert streams