Ground-based detection of G star superflares with NGTS
Abstract
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.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- July 2018
- DOI:
- 10.1093/mnras/sty897
- arXiv:
- arXiv:1804.03377
- Bibcode:
- 2018MNRAS.477.4655J
- Keywords:
-
- stars: activity;
- stars: flare;
- stars: individual: NGTS J030834.9-211322;
- stars: rotation;
- Astrophysics - Solar and Stellar Astrophysics;
- Astrophysics - Earth and Planetary Astrophysics
- E-Print:
- 11 pages, 8 figures, Accepted for Publication in Monthly Notices of the Royal Astronomical Society