Hyperflares of M Dwarfs

Chang, Haiyan; Lin, Chia-Lung; Ip, W.-H.; Huang, Liang; Hou, W.-C.; Yu, Po-Chieh; Song, Yujiang; Luo, A-Li

doi:10.3847/1538-4357/aae2bc

Cited by 29 publications

(14 citation statements)

References 33 publications

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“…The TESS sample profits from the mission's observing strategy, allowing us to identify 112 flaring stars with 141 individual flares that fulfill the Chang et al (2018) criterion of at least doubling the stellar brightness. A list of these targets can be created from Table 1 by sorting by the amplitude column.…”

Section: Stars Show Flares With Flux Increases Of Multiple Magnitmentioning

confidence: 99%

“…If only the T eff is available, we esti- The flare luminosity is modeled as black body radiation with an effective temperature of 9000 K. We select (9000 ± 500) K as a conservative lower limit to remain consistent with other studies (e.g. Davenport 2016;Jackman et al 2018b,a;Howard et al 2018;Chang et al 2018).…”

Section: Measuring the Flare Energymentioning

confidence: 99%

“…mate R using the updated values from Pecaut & Mamajek (2013) 1 to then calculate L .The flare luminosity is modeled as black body radiation with an effective temperature of 9000 K. We select (9000 ± 500) K as a conservative lower limit to remain consistent with other studies (e.g Davenport 2016;. Jackman et al 2018b,a;Howard et al 2018;Chang et al 2018).As discussed byShibayama et al (2013), the luminosities of the star and the flare in the observing bandpass…”

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confidence: 98%

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Stellar Flares from the First TESS Data Release: Exploring a New Sample of M Dwarfs

Günther¹,

et al. 2020

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We perform a study of stellar flares for the 24,809 stars observed with 2 minute cadence during the first two months of the TESS mission. Flares may erode exoplanets' atmospheres and impact their habitability, but might also trigger the genesis of life around small stars. TESS provides a new sample of bright dwarf stars in our galactic neighborhood, collecting data for thousands of M-dwarfs that might host habitable exoplanets. Here, we use an automated search for flares accompanied by visual inspection. Then, our public allesfitter code robustly selects the appropriate model for potentially complex flares via Bayesian evidence. We identify 763 flaring stars, 632 of which are M-dwarfs. Among 3247 flares in total, the largest superflare increased the stellar brightness by a factor of 15.7. Bolometric flare energies range from 10 31 to 10 38.7 erg, with a median of 10 32.8 erg. Furthermore, we study the flare rate and energy as a function of stellar type and rotation period. We solidify past findings that fast rotating M-dwarfs are the most likely to flare, and that their flare amplitude is independent of the rotation period. Finally, we link our results to criteria for prebiotic chemistry, atmospheric loss through coronal mass ejections, and ozone sterilization. Four of our flaring M-dwarfs host exoplanet candidates alerted on by TESS, for which we discuss how these effects can impact life. With upcoming TESS data releases, our flare analysis can be expanded to almost all bright small stars, aiding in defining criteria for exoplanet habitability.

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Section: Stars Show Flares With Flux Increases Of Multiple Magnitmentioning

confidence: 99%

Section: Measuring the Flare Energymentioning

confidence: 99%

mentioning

confidence: 98%

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Stellar Flares from the First TESS Data Release: Exploring a New Sample of M Dwarfs

Günther¹,

et al. 2020

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“…An understanding of their variability is needed to set limits on the threshold for a signature in the signal of a true transit event. Recently Chang et al (2018) analyzed evem more extreme hyperflares in Kepler data for M dwarf stars and noted 8 of them in the K1 lightcurve database. In the course of our study of Proxima Centauri, we found one very large flare that may qualify as a super flare and certainly sets a limit on the frequency of its more extreme flares.…”

Section: Observations Of Proxima Centaurimentioning

confidence: 99%

Observation of a possible superflare on Proxima Centauri

Kielkopf

Hart

Carter

et al. 2019

Monthly Notices of the Royal Astronomical Society: Letters

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We report the observation on UT 2017.07.01 of an unusually powerful flare detected in near-infrared continuum photometry of Proxima Centauri. During a campaign monitoring the star for possible exoplanet transits, we identified an increase in Sloan i' flux leading to an observed peak at BJD 2457935.996 that was at least 10% over preflare flux in this band. It was followed by a 2-component rapid decline in the first 100 seconds that became a slower exponential decay with time constant of 1350 seconds. A smaller flare event 1300 seconds after the first added an incremental peak flux increase of 1% of pre-flare flux. Since the onset of the flare was not fully time-resolved at a cadence of 62 seconds, its actual peak value is unknown but greater than the time-average over a single exposure of 20 seconds. The i' band is representative of broad optical and near-IR continuum flux over which the integrated energy of the flare is 100 times the stellar luminosity. This meets the criteria that established the concept of superflares on similar stars. The resulting implied ultraviolet flux and space weather could have had an extreme effect on the atmospheres of planets within the star's otherwise-habitable zone.

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“…There was significant evidence for superflares and solar flares to most likely share the same origin, and robust estimates of the relationship between chromospheric activity and the occurrence of superflares were presented. On the other hand, studies of flaring M dwarfs in the Kepler field have been presented in several articles by using both satellite photometry and LAMOST data (Yang et al 2017;Chang et al 2017Chang et al , 2018Lu et al 2019). Using Kepler and LK project data, research progress was reported on the chromospheric activity of periodic variable stars (Zhang et al 2018b) and long-rotation-period main-sequence stars (Cui et al 2019).…”

Section: Stellar Magnetic Activity and Flaresmentioning

confidence: 99%

Overview of the LAMOST-$Kepler$ project

Fu,

De Cat,

Zong

et al. 2020

Preprint

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The NASA Kepler mission obtained long-term high-quality photometric observations for a large number of stars in its original field of view from 2009 to 2013. In order to provide reliable stellar parameters in a homogeneous way, the LAMOST telescope began to carry out low-resolution spectroscopic observations for as many stars as possible in the Kepler field in 2012. By September 2018, 238,386 low-resolution spectra with SNR g ≥ 6 had been collected for 155,623 stars in the Kepler field, enabling the determination of atmospheric parameters and radial velocities, as well as spectral classification of the target stars. This information has been used by astronomers to carry out research in various fields, including stellar pulsations and asteroseismology, exoplanets, stellar magnetic activity and flares, peculiar stars and the Milky Way, binary stars, etc. We summarize the research progress in these fields where the usage of data from the LAMOST-Kepler (LK) project has played a role. In addition, time-domain medium-resolution spectroscopic observations have been carried out for about 12,000 stars in four central plates of the Kepler field since 2018. The currently available results show that the LAMOST-Kepler medium resolution (LK-MRS) observations provide qualified data suitable for research in additional science projects including binaries, high-amplitude pulsating stars, etc. As LAMOST is continuing to collect both low-and medium-resolution spectra of stars in the Kepler field, we expect more data to be released continuously and new scientific results to appear based on the LK project data.

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Hyperflares of M Dwarfs

Cited by 29 publications

References 33 publications

Stellar Flares from the First TESS Data Release: Exploring a New Sample of M Dwarfs

Stellar Flares from the First TESS Data Release: Exploring a New Sample of M Dwarfs

Observation of a possible superflare on Proxima Centauri

Overview of the LAMOST-$Kepler$ project

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