An Increased Rate of Large Flares at Intermediate Rotation Periods for Mid-to-late M Dwarfs

Mondrik, Nicholas; Newton, Elisabeth R.; Charbonneau, David; Irwin, Jonathan

doi:10.3847/1538-4357/aaee64

Cited by 31 publications

(37 citation statements)

References 46 publications

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“…Paudel et al (2019) suggest that these types of flares likely appear most often on young, fast-rotating stars due to the rotation driving a more powerful magnetic dynamo. However, these results are in tension with other studies, such as Mondrik et al (2018), who find lower flaring rates in fast rotating (period < 10d) stars than at intermediate (10 − 70d) rotation periods.…”

contrasting

confidence: 99%

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Flares Big and Small: a K2 and TESS View of ASAS-SN Superflares

Zeldes,

Hinkle,

Shappee

et al. 2021

Preprint

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We investigate the flare-frequency distributions of 5 M-dwarfs that experienced superflares with energies in excess of 10 33 erg detected by ASAS-SN. We use K2 and TESS short-cadence observations along with archival ASAS-SN data to categorise the flaring behaviour of these stars across a range of flare energies. We were able to extract a rotation period for 4 of the stars. They were all fast rotators (P rot ≤ 6d), implying relative youth. We find that the flare-frequency distributions for each of the stars are well fit by a power-law, with slopes between α = 1.22 and α = 1.82. These slopes are significantly flatter than those of fast-rotating M-dwarfs not selected for their superflaring activity, corresponding to an increased number of high energy flares. Despite our specific selection of superflaring stars with shallow flare-rate distributions and more power in higher-energy flares, we find that the implied UV flux is insufficient to deplete the ozone of earth-sized planets in the habitable zone around these stars. Furthermore, we find that the flares detected on the stars in our sample are insufficient to produce the UV flux needed to fuel abiogenetic processes. These results imply that given available models, even M-dwarfs selected for extreme flaring properties may have insufficient UV emission from flares to impact exolife on earth-sized planets in the habitable zones around M-dwarfs.

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confidence: 99%

“…Kepler, and its follow-up mission K2, (Howell et al 2014) have proved crucial tools for studying flares (e.g. Davenport et al 2014;Gizis et al 2017;Mondrik et al 2018;Davenport et al 2019). Constant monitoring of targets has enabled reliable measurements of flares across many orders of magnitude in energy.…”

mentioning

confidence: 99%

Flares Big and Small: a K2 and TESS View of ASAS-SN Superflares

Zeldes,

Hinkle,

Shappee

et al. 2021

Preprint

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“…We find an increase in flaring fraction across the M dwarfs, with it peaking in our sample at ∼14 per cent for M6. Although the overall flaring fractions are moderately lower than previous work (∼ 30 per cent lower for M5), we still observe a steep increase from M4 onward, coinciding with where it is thought M dwarfs become fully convective (Kowalski et al 2009;Yang et al 2017;Günther et al 2020;Mondrik et al 2019;Rodríguez Martínez et al 2020b).…”

Section: Spectral Typescontrasting

confidence: 63%

The Deeper, Wider, Faster programme: exploring stellar flare activity with deep, fast cadenced DECam imaging via machine learning

Webb

Flynn

Cooke

et al. 2021

Monthly Notices of the Royal Astronomical Society

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We present our 500 pc distance-limited study of stellar flares using the Dark Energy Camera as part of the Deeper, Wider, Faster Program. The data was collected via continuous 20-second cadence g band imaging and we identify 19,914 sources with precise distances from Gaia DR2 within twelve, ∼3 square-degree, fields over a range of Galactic latitudes. An average of ∼74 minutes is spent on each field per visit. All light curves were accessed through a novel unsupervised machine learning technique designed for anomaly detection. We identify 96 flare events occurring across 80 stars, the majority of which are M dwarfs. Integrated flare energies range from ∼1031 – 1037 erg, with a proportional relationship existing between increased flare energy with increased distance from the Galactic plane, representative of stellar age leading to declining yet more energetic flare events. In agreement with previous studies we observe an increase in flaring fraction from M0 – M6 spectral types. Furthermore, we find a decrease in the flaring fraction of stars as vertical distance from the galactic plane is increased, with a steep decline present around ∼100 pc. We find that $\sim 70{{\ \rm per\ cent}}$ of identified flares occur on short timescales of < 8 minutes. Finally we present our associated flare rates, finding a volumetric rate of 2.9 ± 0.3 × 10−6 flares pc−3 hr−1.

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“…Symbols are the same as in Figure 4. (Jeffries et al 2011;Wright et al 2011) and more recently the possibility of a peak in the rate of large M-dwarf flares at R o ≈ 0.1 has been suggested (Mondrik et al 2019). This is also the regime in which See et al (2017) find the maximum mass and angular momentum loss rates.…”

Section: Discussionmentioning

confidence: 83%

Measuring stellar magnetic helicity density

Lund

Jardine

Lehmann

et al. 2020

Monthly Notices of the Royal Astronomical Society

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Helicity is a fundamental property of a magnetic field but to date it has only been possible to observe its evolution in one star -the Sun. In this paper we provide a simple technique for mapping the large-scale helicity density across the surface of any star using only observable quantities: the poloidal and toroidal magnetic field components (which can be determined from Zeeman-Doppler imaging) and the stellar radius. We use a sample of 51 stars across a mass range of 0.1-1.34 M to show how the helicity density relates to stellar mass, Rossby number, magnetic energy and age. We find that the large-scale helicity density increases with decreasing Rossby number R o , peaking at R o 0.1, with a saturation or decrease below that. For both fully-and partially-convective stars we find that the mean absolute helicity density scales with the mean squared toroidal magnetic flux density according to the power law: | h | ∝ B tor 2 0.86 ± 0.04 . The scatter in this relation is consistent with the variation across a solar cycle, which we compute using simulations and observations across solar cycles 23 and 24 respectively. We find a significant decrease in helicity density with age.

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An Increased Rate of Large Flares at Intermediate Rotation Periods for Mid-to-late M Dwarfs

Cited by 31 publications

References 46 publications

Flares Big and Small: a K2 and TESS View of ASAS-SN Superflares

Flares Big and Small: a K2 and TESS View of ASAS-SN Superflares

The Deeper, Wider, Faster programme: exploring stellar flare activity with deep, fast cadenced DECam imaging via machine learning

Measuring stellar magnetic helicity density

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