Superflares on Solar-type Stars from the First Year Observation of TESS

Abstract

Superflares, which are strong explosions on stars, have been well studied with the progress of space time-domain astronomy. In this work, we present the study of superflares on solar-type stars using Transiting Exoplanet Survey Satellite (TESS) data. Thirteen sectors of observations during the first year of the TESS mission have covered the southern hemisphere of the sky, containing 25,734 solartype stars. We verified 1216 superflares on 400 solar-type stars through automatic search and visual inspection with 2 minute cadence data. Our result suggests a higher superflare frequency distribution than the result from Kepler. This may be because the majority of TESS solar-type stars in our dataset are rapidly rotating stars. The power-law index γ of the superflare frequency distribution (dN/dE ∝ E −γ ) is constrained to be γ = 2.16 ± 0.10, which is a little larger than that of solar flares but consistent with the results from Kepler. Because only seven superflares of Sun-like stars are detected, we cannot give a robust superflare occurrence frequency. Four stars are accompanied by unconfirmed hot planet candidates. Therefore, superflares may possibly be caused by stellar magnetic activities instead of planet-star interactions. We also find an extraordinary star, TIC43472154, which exhibits about 200 superflares per year. In addition, the correlation between the energy and duration of superflares (T duration ∝ E β ) is analyzed. We derive the power-law index to be β = 0.42 ± 0.01, which is a little larger than β = 1/3 from the prediction according to magnetic reconnection theory.

Starspot Mapping with Adaptive Parallel Tempering. I. Implementation of Computational Code

“…Then, we can investigate the connection between superflares and stellar and spot properties deduced by starspot modeling and compare the results of measuring emergence and decay rates with those by other methods (Namekata et al 2020). Bright spotted stars have been observed by TESS (Ricker et al 2014), and superflares on hundreds of spotted solar-type stars have been reported (Feinstein et al 2020;Tu et al 2020). Some TESS targets are to be simultaneously observed by the Seimei telescope at Kyoto University (Kurita et al 2020) using the high dispersion spectrograph.…”

Superflares, chromospheric activities and photometric variabilities of solar-type stars from the second-year observation of TESS and spectra of LAMOST

“…In 2018, TESS began to search for exoplanets from the whole sky with 2 yr major missions. Superflares on solar-type stars as by-products of TESS data were collected by Tu et al (2020) for the first time. Not long after that, Doyle et al (2020) collected superflares observed by TESS, and found that there is no correlation between the superflare and rotational phase.…”

“…Karoff et al (2016) used cross-matching results from Kepler and LAMOST, but they have only 11 superflare stars in their database, as Kepler only observed the fixed field of the sky for almost 4 yr. We expect more superflare stars with LAMOST observations can be found through cross-matching with TESS objects, because TESS changes its observing view every ∼ 27 days and covers almost the whole sky in 2 yr (Ricker et al 2015). As the main purpose of our previous work (Tu et al 2020) was to prove and find a usable method for TESS data, we did not include estimations of photospheric variability. Besides, we also did not include evaluation of chromospheric activity before, as we did not found any free resources of spectral survey for the southern hemisphere of the sky.…”

Investigation of the Activity the Red Dwarf Exo 040830-7134.7 According to Observations of the Tess Observatory

“…4а.Рис. 4б.Рисунок 5 отображает взаимосвязь длительности вспышки с энергией, которая была получена в работе[7] (маркеры серого цвета). Маркерами черного цвета отмечены наши данные.…”

“…Маркерами черного цвета отмечены наши данные. Расхождение в результатах объясняется тем, что исследуемый нами объект является красным карликом с T eff ≈ 3000K, а в работе[7] рассматривались звёзды солнечного типа с 5100K ≤ T eff < 6000K.…”