Institute of Astronomy

Mapping the Transient Sky with Gaia

SpeakerTalk DateTalk Series
Simon Hodgkin21 November 2018Institute of Astronomy Seminars

Abstract

Gaia is an ESA cornerstone mission, delivering precision photometry, astrometry, spectrophotometry, and spectroscopy, all based on regular image-scanning the sky through two telescopes and the largest focal-plane array (1Gpixel) yet launched. This, by design, makes the time-domain the heart of Gaia’s scientific requirements and capabilities. Gaia is monitoring the sky with cadences of seconds (between CCDs), hours (between fields-of-view) and weeks (between visits), with real-time source detection implemented by a fixed, available, and well understood on-board algorithm. Every Gaia source obtains near-simultaneous spectrophotometry.

The GaiaAlerts system has been running routinely and reliably since January 2016, publishing 6 transients per day (see http://gsaweb.ast.cam.ac.uk/alerts/home), using well-defined selection criteria. We scan the whole sky exploring into the Galactic plane and crowded regions which are typically hard to do from the ground. I will describe the challenges we face in searching through half a billion CCD measurements every day to identify and publish Gaia's transient events. I will discuss the properties of the alerts published to date and highlight some of our most interesting discoveries. I will examine the completeness and biases in our selection criteria, and look ahead to ongoing updates to the system, including making the most of Gaia's spectrophotometry and astrometry.

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