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.
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).
CitationMonthly 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
VersionVoR (Version of Record)
Published inMonthly Notices of the Royal Astronomical Society
PublisherOxford University Press (OUP), Royal Astronomical Society