Littlefair, S.P., Burningham, B. and Helling, C. (2017) Robust detection of quasi-periodic variability: A HAWK-I mini survey of late-T dwarfs. Monthly Notices of the Royal Astronomical Society, 466 (4). pp. 4250-4258. ISSN 0035-8711
Abstract
We present HAWK-I J-band light curves of five late-type T dwarfs (T6.5-T7.5) with a typical duration of four hours, and investigate the evidence for quasi-periodic photometric variability on intra-night timescales. Our photometry reaches precisions in the range 7-20 mmag, after removing instrumental systematics that correlate with sky background, seeing and airmass. Based upon a Lomb-Scargle periodogram analysis, the latest object in the sample - ULAS J2321 (T7.5) - appears to show quasi-periodic variability with a period of 1.64 hours and an amplitude of 3 mmag. Given the low amplitude of variability and presence of systematics in our lightcurves, we discuss a Bayesian approach to robustly determine if quasi-periodic variability is present in a lightcurve affected by red noise. Using this approach, we conclude that the evidence for quasi-periodic variability in ULAS J2321 is not significant. As a result, we suggest that studies which identify quasi-periodic variables using the false alarm probability from a Lomb-Scargle periodogram are likely to over-estimate the number of variable objects, even if field stars are used to set a higher false alarm probability threshold. Instead we argue that a hybrid approach combining a false alarm probability cut, followed by Bayesian model selection, is necessary for robust identification of quasi-periodic variability in lightcurves with red noise.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2016 The Authors. This is an author produced version of a paper subsequently published in Monthly Notices of the Royal Astronomical Society. Uploaded in accordance with the publisher's self-archiving policy. |
Keywords: | astro-ph.SR; astro-ph.SR |
Dates: |
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Institution: | The University of Sheffield |
Academic Units: | The University of Sheffield > Faculty of Science (Sheffield) > Department of Physics and Astronomy (Sheffield) |
Funding Information: | Funder Grant number SCIENCE AND TECHNOLOGY FACILITIES COUNCIL ST/M001350/1 |
Depositing User: | Symplectic Sheffield |
Date Deposited: | 22 Mar 2017 12:19 |
Last Modified: | 20 Mar 2018 20:07 |
Published Version: | http://dx.doi.org/10.1093/mnras/stw3376 |
Status: | Published |
Publisher: | Oxford University Press |
Refereed: | Yes |
Identification Number: | 10.1093/mnras/stw3376 |
Related URLs: | |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:113727 |