A ΔR ∼ 9.5 mag Superflare of an Ultracool Star Detected by the SVOM/GWAC System

Xin, L. P.; Li, H. L.; Wang, J.; Han, X. H.; Xu, Yang; Meng, Xia; Cai, Hongbo; Huang, Liang; Lū, Xiaomeng; Qiu, Y. L.; Wang, X. G.; Liang, En-Si; Dai, Z. G.; Wang, X. Y.; Wu, Chenjie; Zhang, J. B.; Li, G. W.; Turpin, D.; Feng, Q. C.; Deng, J. S.; Sun, S.; Zheng, Tian-Ci; Yang, Yuangen; Wei, J. Y.

doi:10.3847/1538-4357/abdd1b

Cited by 14 publications

(19 citation statements)

References 49 publications

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“…In Fig. B1, we illustrate a scenario that represents the flare with the largest flaring region in our sample (first flare on TIC 237), which is comparable to some of the largest region sizes derived for flares on fully convective dwarfs in the literature (Schmidt et al 2014b;Xin et al 2021). The effect is negligible compared to the noise in the light curves in our sample.…”

Section: Appendix A: Alternative and Disfavoured Fits To The Light Cu...supporting

confidence: 63%

Giant white-light flares on fully convective stars occur at high latitudes

Ilin,

Poppenhaeger,

Schmidt

et al. 2021

Preprint

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White-light flares are magnetically driven localized brightenings on the surfaces of stars. Their temporal, spectral, and statistical properties present a treasury of physical information about stellar magnetic fields. The spatial distributions of magnetic spots and associated flaring regions help constrain dynamo theories. Moreover, flares are thought to crucially affect the habitability of exoplanets that orbit these stars. Measuring the location of flares on stars other than the Sun is challenging due to the lack of spatial resolution. Here we present four fully convective stars observed with the Transiting Exoplanet Survey Satellite (TESS) that displayed large, long-duration flares in white-light which were modulated in brightness by the stars' fast rotation. This allowed us to determine the loci of these flares directly from the light curves. All four flares occurred at latitudes between 55 • and 81 • , far higher than typical solar flare latitudes. Our findings are evidence that strong magnetic fields tend to emerge close to the stellar rotational poles for fully convective stars, and suggest that the impact of flares on the habitability of exoplanets around small stars could be weaker than previously thought.

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Section: Appendix A: Alternative and Disfavoured Fits To The Light Cu...supporting

confidence: 63%

Giant white-light flares on fully convective stars occur at high latitudes

Ilin,

Poppenhaeger,

Schmidt

et al. 2021

Preprint

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show abstract

“…This approach enables time-resolved detections of fast optical transients, and poses unique challenges and opportunities for real-time data reduction. Rapid localizations of transients across wide fields of view have recently been used to make spectroscopic observations of flares using the Ground-based Wide-Angle Camera system, with latencies as low as 20 minutes (Wang et al 2021;Xin et al 2021).…”

Section: Introductionmentioning

confidence: 99%

The Evryscope Fast Transient Engine: Real-time Detection for Rapidly Evolving Transients

Corbett

Carney

Gonzalez

et al. 2023

ApJS

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Astrophysical transients with rapid developments on subhour timescales are intrinsically rare. Due to their short durations, events like stellar superflares, optical flashes from gamma-ray bursts, and shock breakouts from young supernovae are difficult to identify on timescales that enable spectroscopic follow-up. This paper presents the Evryscope Fast Transient Engine (EFTE), a new data reduction pipeline that is designed to provide low-latency transient alerts from the Evryscopes—a north–south pair of ultra-wide-field telescopes with an instantaneous footprint covering 38% of the entire sky—and tools for building long-term light curves from Evryscope data. EFTE leverages the optical stability of the Evryscopes by using a simple direct image subtraction routine that is suited to continuously monitoring the transient sky at a cadence of a minute. Candidates are produced within the base Evryscope 2 minute cadence for 98.5% of images, and internally filtered using vetnet, a convolutional neural network real–bogus classifier. EFTE provides an extensible and robust architecture for transient surveys probing similar timescales, and serves as the software test bed for the real-time analysis pipelines and public data distribution systems for the Argus Array, a next-generation all-sky observatory with a data rate 62 times higher than that of Evryscope.

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“…It has been known for a long time that solar-like and latetype main-sequence stars show highly energetic flares. The flares with total energies of 10 33−39 erg can be detected at multiple wavelengths from radio to X-ray (e.g., Pettersen 1989;Schmitt 1994;Osten et al 2004Osten et al , 2005Huenemoerder et al 2010;Maehara et al 2012;Kowalski et al 2013;Balona 2015;Davenport et al 2016;Notsu et al 2016;Van Doorsselaere et al 2017;Chang et al 2018;Paudel et al 2018;Schmidt et al 2019;Xin et al 2021). Given the comprehensive studies on the Sun, an analogy with solar flares leads to a common knowledge that these stellar flares can be ascribed to stellar magnetic activity, such as magnetic reconnection (e.g., Noyes et al 1984;Wright et al 2011;Shulyak et al 2017).…”

Section: Introductionmentioning

confidence: 99%

Flaring-associated Complex Dynamics in Two M Dwarfs Revealed by Fast, Time-resolved Spectroscopy

Wang

Xin

et al. 2022

ApJ

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Habitability of an exoplanet is believed to be profoundly affected by activities of the host stars, although the related coronal mass ejections (CMEs) are still rarely detected in solar-like and late-type stars. We here report an observational study on the flares of two M dwarfs triggered by the high-cadence survey performed by the Ground-based Wide Angle Camera system. In both events, the fast, time-resolved spectroscopy enables us to identify symmetric broad Hα emission with not only a nearly zero bulk velocity, but also a large projected maximum velocity as high as ∼700–800 km s−1. This broadening could be resulted from either the Stark (pressure) effect or a flaring-associated CME at the stellar limb. In the context of the CME scenario, the CME mass is estimated to be ∼4 × 1018 and 2 × 1019 g. In addition, our spectral analysis reveals a temporal variation of the line center of the narrow Hα emission in both events. The variation amplitudes are at tens of kilometers per second, which could be ascribed to the chromospheric evaporation in one event, and to a binary scenario in the other one. With the total flaring energy determined from our photometric monitor, we show a reinforced trend in which the larger the flaring energy, the higher the CME mass is.

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A ΔR ∼ 9.5 mag Superflare of an Ultracool Star Detected by the SVOM/GWAC System

Cited by 14 publications

References 49 publications

Giant white-light flares on fully convective stars occur at high latitudes

Giant white-light flares on fully convective stars occur at high latitudes

The Evryscope Fast Transient Engine: Real-time Detection for Rapidly Evolving Transients

Flaring-associated Complex Dynamics in Two M Dwarfs Revealed by Fast, Time-resolved Spectroscopy

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