Kepler-411 Star Activity: Connection between Starspots and Superflares

Araújo, Alexandre; Válio, Adriana

doi:10.3847/2041-8213/ac3767

Cited by 5 publications

(1 citation statement)

References 40 publications

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“…The weaker flares, however, do show an increased occurrence close to the starspot groups. A similar result was found in the case of Kepler-411, where the timing of flares and superflares were correlated with spot locations derived from planetary transit mapping [74]. One explanation for this phenomenon could be that on stars with stronger magnetic fields, reconnections between different large active nests are more frequentunlike on our Sun, where flares are detected mainly in bipolar regions.…”

Section: Flares and Superflares Of Cool Dwarf Starssupporting

confidence: 83%

Stellar Flares, Superflares and Coronal Mass Ejections – Entering the Big Data Era

Vida,

Kővári,

Leitzinger

et al. 2024

Preprint

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Flares, sometimes accompanied by coronal mass ejections (CMEs), are the result of sudden changes in the magnetic field of stars with high energy release through magnetic reconnection, which can be observed across a wide range of the electromagnetic spectrum from radio waves to the optical range to X-rays. In our review, we attempt to collect some fundamental new results, which can largely be linked to the Big data era that has arrived due to the expansion of space photometric observations of the last two decades. We list the different types of stars showing flare activity, their observation strategies, and discuss how their main stellar properties relate to the characteristics of the flares (or even CMEs) they emit. Our goal is to focus, without claiming to be complete, on those results that may in one way or another challenge the "standard" flare model based on the solar paradigm.

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Section: Flares and Superflares Of Cool Dwarf Starssupporting

confidence: 83%

Stellar Flares, Superflares and Coronal Mass Ejections – Entering the Big Data Era

Vida,

Kővári,

Leitzinger

et al. 2024

Preprint

View full text Add to dashboard Cite

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Flaring latitudes in ensembles of low-mass stars

Ilin

Angus

Luger

et al. 2023

Monthly Notices of the Royal Astronomical Society

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The distribution of small-scale magnetic fields in stellar photospheres is an important ingredient in our understanding of the magnetism of low mass stars. Their spatial distribution connects the field generated in the stellar interior with the outer corona and the large scale field, and thereby affects the space weather of planets. Unfortunately, we lack techniques that can locate them on most low-mass stars. One strategy is to localize field concentrations using the flares that occur in their vicinity. We explore a new method that adapts the spot simulation software fleck to study the modulation of flaring times as a function of active latitude. We use empirical relations to construct flare light curves similar to those available from Kepler and the Transiting Exoplanet Survey Satellite (TESS), search them for flares, and use the waiting times between flares to determine the location of active latitudes. We find that the mean and standard deviation of the waiting time distribution provide a unique diagnostic of flaring latitudes as a function of the number of active regions. Latitudes are best recovered when stars have three or less active regions that flare repeatedly, and active latitude widths below 20 deg; when either increases, the information about the active latitude location is gradually lost. We demonstrate our technique on a sample of flaring G dwarfs observed with the Kepler satellite, and furthermore suggest that combining ensemble methods for spots and flares could overcome the limitations of each individual technique for the localization of surface magnetic fields.

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Hydrogen recombination continuum as the radiative model for stellar optical flares

Simões,

Araújo,

Válio

et al. 2024

Monthly Notices of the Royal Astronomical Society

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The study of stellar flares has increased with new observations from CoRoT, Kepler, and TESS satellites, revealing the broadband visible emission from these events. Typically, stellar flares have been modelled as 104 K blackbody plasma to obtain estimates of their total energy. In the Sun, white light flares (WLFs) are much fainter than their stellar counterparts, and normally can only be detected via spatially resolved observations. Identifying the radiation mechanism for the formation of the visible spectrum from solar and stellar flares is crucial to understand the energy transfer processes during these events, but spectral data for WLFs are relatively rare, and insufficient to remove the ambiguity of their origin: photospheric blackbody radiation and/or Paschen continuum from hydrogen recombination in the chromosphere. We employed an analytical solution for the recombination continuum of hydrogen instead of the typically assumed 104 K blackbody spectrum to study the energy of stellar flares and infer their fractional area coverage. We investigated 37 events from Kepler-411 and 5 events from Kepler-396, using both radiation mechanisms. We find that estimates for the total flare energy from the H recombination spectrum are about an order of magnitude lower than the values obtained from the blackbody radiation. Given the known energy transfer processes in flares, we argue that the former is a physically more plausible model than the latter to explain the origin of the broadband optical emission from flares.

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Kepler-411 Star Activity: Connection between Starspots and Superflares

Cited by 5 publications

References 40 publications

Stellar Flares, Superflares and Coronal Mass Ejections – Entering the Big Data Era

Stellar Flares, Superflares and Coronal Mass Ejections – Entering the Big Data Era

Flaring latitudes in ensembles of low-mass stars

Hydrogen recombination continuum as the radiative model for stellar optical flares

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