Periodic stellar variability from almost a million NGTS light curves. Issue 1 (5th April 2022)

• Record Type: Journal Article
• Authors: Briegal, Joshua T; Gillen, Edward; Queloz, Didier; Hodgkin, Simon; Acton, Jack S; Anderson, David R; Armstrong, David J; Battley, Matthew P; Bayliss, Daniel; Burleigh, Matthew R; Bryant, Edward M; Casewell, Sarah L; Costes, Jean C; Eigmüller, Philipp; Gill, Samuel; Goad, Michael R; Günther, Maximilian N; Henderson, Beth A; Jackman, James A G; Jenkins, James S; Kreutzer, Lars T; Moyano, Maximiliano; Lendl, Monika; Smith, Gareth D; Tilbrook, Rosanna H; Watson, Christopher A; West, Richard G; Wheatley, Peter J
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 513:Issue 1(2022)
• Page Start: 420
• Page End: 438
• Publication Date: 2022-04-05
• Subjects: methods: data-analysis -- techniques: photometric -- stars: activity -- Hertzprung–Russell and colour–magnitude diagrams -- stars: rotation -- stars: variables: general; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stac898
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: We analyse 829 481 stars from the Next Generation Transit Survey (NGTS) to extract variability periods. We utilize a generalization of the autocorrelation function (the G-ACF), which applies to irregularly sampled time series data. We extract variability periods for 16 880 stars from late-A through to mid-M spectral types and periods between ∼0.1 and 130 d with no assumed variability model. We find variable signals associated with a number of astrophysical phenomena, including stellar rotation, pulsations, and multiple-star systems. The extracted variability periods are compared with stellar parameters taken from Gaia DR2, which allows us to identify distinct regions of variability in the Hertzsprung–Russell Diagram. We explore a sample of rotational main-sequence objects in period-colour space, in which we observe a dearth of rotation periods between 15 and 25 d. This 'bi-modality' was previously only seen in space-based data. We demonstrate that stars in sub-samples above and below the period gap appear to arise from a stellar population not significantly contaminated by excess multiple systems. We also observe a small population of long-period variable M-dwarfs, which highlight a departure from the predictions made by rotational evolution models fitted to solar-type main-sequence objects. The NGTS data spans a period and spectral type range that links previous rotation studies such as those using data from Kepler, K2, and MEarth.