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Ultraviolet flare emission can drive photochemistry in exoplanet atmospheres and even serve as the primary source of uncertainty in atmospheric retrievals. Additionally, flare energy budgets are not well-understood due to a paucity of…

We present near ultraviolet (NUV:1750 - 2800\AA) and far ultraviolet (FUV: 1350 - 1750\AA) light-curves for flares on 4 nearby dMe-type stars (GJ 3685A, CR Dra, AF Psc and SDSS J084425.9+513830.5) observed with the GALEX satellite. Taking…

In this study, a new method is presented to classify flares derived from the photoelectric photometry of UV Ceti type stars. This method is based on statistical analyses using an independent samples t-test. The data used in analyses were…

Solar and Stellar Astrophysics · Physics 2012-06-27 H. A. Dal , S. Evren

Stellar flares are sudden brightenings caused by magnetic reconnection and are frequently observed on late-type stars. High-cadence photometry of flares provides valuable insights into the mechanisms of these events, yet such observations…

Solar and Stellar Astrophysics · Physics 2026-02-26 B. Schmercz , B. Seli , K. Vida , L. Kriskovics , A. Görgei , K. Oláh , Zs. Regály

The hydrogen Paschen lines are known activity indicators, but studies of them in M~dwarfs during quiescence are as rare as their reports in flare studies. This situation is mostly caused by a lack of observations, owing to their location in…

I present a systematic study of gamma-ray flares in blazars. For this purpose, I propose a very simple and practical definition of a flare as a period of time, associated with a given flux peak, during which the flux is above half of the…

High Energy Astrophysical Phenomena · Physics 2015-06-12 Krzysztof Nalewajko

The CLASH X-ray selected sample of 20 galaxy clusters contains ten brightest cluster galaxies (BCGs) that exhibit significant ($>$5 $\sigma$) extinction-corrected star formation rates (SFRs). Star formation activity is inferred from…

Astrophysics of Galaxies · Physics 2015-11-11 Kevin Fogarty , Marc Postman , Thomas Connor , Megan Donahue , John Moustakas

We investigate the old star clusters in the sample of cluster candidates from Froebrich, Scholz & Raftery 2007 -- the FSR list. Based on photometry from the 2-Micron All Sky Survey we generated decontaminated colour-magnitude and…

Astrophysics of Galaxies · Physics 2015-05-19 D. Froebrich , S. Schmeja , D. Samuel , P. W. Lucas

Using the Kepler K2 data, we studied the flare-activity of young K-and M-stars in the Upper Sco region and found that they have 10000 to 80000 times as many super-flares with E> 5E34 erg than solar like stars. The power-law index for flares…

Earth and Planetary Astrophysics · Physics 2019-11-25 E. W. Guenther , D. Woeckel , P. Muheki

Aims. With the aim to reveal the effects of the magnetic field to the multi-band activity of dwarf stars, we search for associated radio emission for an extensive list of 14 915 brown dwarfs and 15 124 flaring stars. Methods. We utilised…

Solar and Stellar Astrophysics · Physics 2025-06-30 K. Perger , B. Seli , K. Vida

Although late-type dwarfs and giant stars are substantially different, their flares are thought to originate in similar physical processes and differ only by a scale factor in the energy levels. We study the validity of this approach. We…

Solar and Stellar Astrophysics · Physics 2022-12-14 Katalin Oláh , Bálint Seli , Zsolt Kővári , Levente Kriskovics , Krisztián Vida

We present continuous, high-precision photometric monitoring data with 1 minute cadence of the dM3e flare star AD Leo with the {\it MOST} satellite. We observed 19 flares in 5.8 days, and find a flare frequency distribution that is similar…

Solar and Stellar Astrophysics · Physics 2015-06-05 Nicholas M. Hunt-Walker , Eric J Hilton , Adam F. Kowalski , Suzanne L. Hawley , Jayme M. Matthews

Flares and CMEs can have deleterious effects on their surroundings: they can erode atmospheres of orbiting planets over time and also have high importance in stellar evolution. Most of the CME detections in the literature are single events…

We present the results of fast spectrophotometry of flares on the RS CVn-type star AR Lac with a time resolution of 34 s and a spectroscopic resolution R $\sim $ 1300. The observations were performed on July 21-22, 2021 with the 2.0 m Karl…

Solar and Stellar Astrophysics · Physics 2022-04-26 Ya. S. Markus , B. E. Zhilyaev

We present results of our 5-years-long program of ground-based spectroscopic and photometric observations of individual Kepler asteroseismic targets and the open clusters NGC6866 and NGC6811 from the Kepler field of view.We determined the…

Flares from the Sun and other stars are most prominently observed in the soft X-ray band. Most of the radiated energy, however, is released at optical/UV wavelengths. In spite of decades of investigation, the physics of flares is not fully…

Solar and Stellar Astrophysics · Physics 2018-12-05 E. Flaccomio , G. Micela , S. Sciortino , A. M. Cody , M. G. Guarcello , M. Morales-Calderòn , L. Rebull , J. R. Stauffer

Short duration flares are well known to occur on cool main-sequence stars as well as on many types of `exotic' stars. Ordinary main-sequence stars are usually pictured as being static on time scales of millions or billions of years. Our sun…

Astrophysics · Physics 2009-10-31 Bradley E. Schaefer , Jeremy R. King , Constantine P. Deliyannis

Variations in stellar flux can potentially overwhelm the photometric signal of a transiting planet. Such variability has not previously been well-characterized in the ultraviolet lines used to probe the inflated atmospheres surrounding hot…

Solar and Stellar Astrophysics · Physics 2014-02-26 R. O. Parke Loyd , Kevin France

Solar radio emission at low frequencies (<1 GHz) can provide valuable information on processes driving flares and coronal mass ejections (CMEs). Radio emission has been detected from active M dwarf stars, suggestive of much higher levels of…

The ultraviolet (UV) emission of stellar flares may have a pivotal role in the habitability of rocky exoplanets around low-mass stars. Previous studies have used white-light observations to calibrate empirical models which describe the…

Solar and Stellar Astrophysics · Physics 2022-11-09 James A. G. Jackman , Evgenya Shkolnik , Chase Million , Scott Fleming , Tyler Richey-Yowell , Parke Loyd