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Title: Centroid vetting of transiting planet candidates from the Next Generation Transit Survey
Authors: Günther, Maximilian N.
Queloz, Didier
Gillen, Edward
McCormac, James
Bayliss, Daniel
Bouchy, Francois
Walker, Simon R.
West, Richard G.
Eigmüller, Philipp
Smith, Alexis M. S.
Armstrong, David J.
Burleigh, Matthew
Casewell, Sarah L.
Chaushev, Alexander P.
Goad, Michael R.
Grange, Andrew
Jackman, James
Jenkins, James S.
Louden, Tom
Moyano, Maximiliano
Pollacco, Don
Poppenhaeger, Katja
Rauer, Heike
Raynard, Liam
Thompson, Andrew P. G.
Udry, Stéphane
Watson, Christopher A.
Wheatley, Peter J.
First Published: 27-Jul-2017
Publisher: Oxford University Press (OUP), Royal Astronomical Society
Citation: Monthly Notices of the Royal Astronomical Society, 2017, 472 (1), pp. 295–307
Abstract: The Next Generation Transit Survey (NGTS), operating in Paranal since 2016, is a wide-field survey to detect Neptunes and super-Earths transiting bright stars, which are suitable for precise radial velocity follow-up and characterisation. Thereby, its sub-mmag photometric precision and ability to identify false positives are crucial. Particularly, variable background objects blended in the photometric aperture frequently mimic Neptune-sized transits and are costly in follow-up time. These objects can best be identified with the centroiding technique: if the photometric flux is lost off-centre during an eclipse, the flux centroid shifts towards the centre of the target star. Although this method has successfully been employed by the Kepler mission, it has previously not been implemented from the ground. We present a fully-automated centroid vetting algorithm developed for NGTS, enabled by our high-precision auto-guiding. Our method allows detecting centroid shifts with an average precision of 0.75 milli-pixel, and down to 0.25 milli-pixel for specific targets, for a pixel size of 4.97 arcsec. The algorithm is now part of the NGTS candidate vetting pipeline and automatically employed for all detected signals. Further, we develop a joint Bayesian fitting model for all photometric and centroid data, allowing to disentangle which object (target or background) is causing the signal, and what its astrophysical parameters are. We demonstrate our method on two NGTS objects of interest. These achievements make NGTS the first ground-based wide-field transit survey ever to successfully apply the centroiding technique for automated candidate vetting, enabling the production of a robust candidate list before follow-up.
DOI Link: 10.1093/mnras/stx1920
ISSN: 0035-8711
eISSN: 1365-2966
Version: Post-print
Status: Peer-reviewed
Type: Journal Article
Rights: Copyright ©2017, Oxford University Press (OUP), Royal Astronomical Society. Deposited with reference to the publisher’s open access archiving policy.
Appears in Collections:Published Articles, Dept. of Physics and Astronomy

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