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Ground-based detection of G star superflares with NGTS

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journal contribution
posted on 08.06.2018, 13:44 by James A G Jackman, Peter J Wheatley, Chloe E Pugh, Boris T Gänsicke, Edward Gillen, Anne-Marie Broomhall, David J. Armstrong, Matthew R. Burleigh, Alexander Chaushev, Philipp Eigmüller, Anders Erikson, Michael R. Goad, Andrew Grange, Maximilian N. Günther, James S. Jenkins, James McCormac, Liam Raynard, Andrew P. G. Thompson, Stéphane Udry, Simon Walker, Christopher A. Watson, Richard G. West
We present high cadence detections of two superflares from a bright G8 star (V = 11.56) with the Next Generation Transit Survey (NGTS). We improve upon previous superflare detections by resolving the flare rise and peak, allowing us to fit a solar flare inspired model without the need for arbitrary break points between rise and decay. Our data also enables us to identify substructure in the flares. From changing star-spot modulation in the NGTS data, we detect a stellar rotation period of 59 h, along with evidence for differential rotation. We combine this rotation period with the observed ROSAT X-ray flux to determine that the star’s X-ray activity is saturated. We calculate the flare bolometric energies as 5.4+0.8 −0.7 × 10^34 and 2.6+0.4 −0.3 × 10^34 erg and compare our detections with G star superflares detected in the Kepler survey. We find our main flare to be one of the largest amplitude superflares detected from a bright G star. With energies more than 100 times greater than the Carrington event, our flare detections demonstrate the role that ground-based instruments such as NGTS can have in assessing the habitability of Earth-like exoplanets, particularly in the era of PLATO.

Funding

This research is based on data collected under the NGTS project at the ESO La Silla Paranal Observatory. The NGTS facility is funded by a consortium of institutes consisting of the University of Warwick, the University of Leicester, Queen’s University Belfast, the University of Geneva, the Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR; under the ‘Großinvestition GI-NGTS’), the University of Cambridge, together with the UK Science and Technology Facilities Council (STFC; project reference ST/M001962/1). JAGJ is supported by an STFC studentship. PJW, DJA, and RGW are supported by STFC consolidated grant ST/P000495/1. AMB acknowledges the support of the Institute of Advanced Study, University of Warwick and is also supported by STFC consolidated grant ST/P000320/1. JSJ acknowledges support by Fondecyt grant 1161218 and partial support by CATA-Basal (PB06, CONICYT). MNG is supported by STFC award reference 1490409 as well as the Isaac Newton Studentship. CEP acknowledges support from the European Research Council under the SeismoSun Research Project No. 321141. The research leading to these results has received funding from the European Research Council under the European Union’s Seventh Framework Programme (FP/2007–2013)/ERC Grant Agreement no. 320964 (WDTracer).

History

Citation

Monthly Notices of the Royal Astronomical Society, 2018, 477(4), pp. 4655–4664.

Author affiliation

/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Physics and Astronomy

Version

VoR (Version of Record)

Published in

Monthly Notices of the Royal Astronomical Society

Publisher

Oxford University Press (OUP), Royal Astronomical Society

issn

0035-8711

eissn

1365-2966

Acceptance date

06/04/2018

Copyright date

2018

Available date

08/06/2018

Publisher version

https://academic.oup.com/mnras/article/477/4/4655/4967002

Language

en