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This paper reports the ULTRACAM discovery of dipolar surface spots in two cool magnetic white dwarfs with Balmer emission lines, while a third system exhibits a single spot, similar to the prototype GD 356. The light curves are modeled with…

Solar and Stellar Astrophysics · Physics 2023-07-26 J. Farihi , J. J. Hermes , S. P. Littlefair , I. D. Howarth , N. Walters , S. G. Parsons

We report the discovery of an X-ray/UV stellar flare from the source LMC 335, captured by XMM-Newton in the field of the Large Magellanic Cloud. The flare event was recorded continuously in X-ray for its first 10 hours from the precursor to…

Solar and Stellar Astrophysics · Physics 2015-06-05 B. T. H. Tsang , C. S. J. Pun , R. Di Stefano , K. L. Li , A. K. H. Kong

Emission spectroscopy is an invaluable tool for probing the atmospheres of brown dwarfs and exoplanets, but interpretations based on flux spectra alone often suffer from degeneracies among temperature structure, chemical composition, and…

Earth and Planetary Astrophysics · Physics 2025-12-16 Fei Wang , Yuka Fujii , Ben Burningham , Jinping He

Searches for optical transients are usually performed with a cadence of days to weeks, optimised for supernova discovery. The optical fast transient sky is still largely unexplored, with only a few surveys to date having placed meaningful…

In this paper we present the differential emission measures (DEMs) of two sub-A class microflares observed in hard X-rays (HXRs) by the FOXSI-2 sounding rocket experiment, on 2014 December 11. The second FOXSI (Focusing Optics X-ray Solar…

We explore methods for the identification of stellar flare events in irregularly sampled data of ground-based time domain surveys. In particular, we describe a new technique for identifying flaring stars, which we have implemented in a…

Solar and Stellar Astrophysics · Physics 2019-09-04 Kellen D. Lawson , John P. Wisniewski , Eric C. Bellm , Adam F. Kowalski , David L. Shupe

Over the past years, thousands of stellar flares have been detected by harvesting data from large photometric surveys. These detections, however, do not account for potential sources of contamination such as background stars appearing in…

In this paper, we study stellar light curves from the TESS satellite (Transiting Exoplanet Survey Satellite) for the presence of stellar flares. The main aim is to detect stellar flares using two-minutes cadence data and to perform…

Solar and Stellar Astrophysics · Physics 2022-08-31 Małgorzata Pietras , Robert Falewicz , Marek Siarkowski , Kamil Bicz , Paweł Preś

We present the results of constraining the angular diameter distance to blazar TXS 0506+056. We used data obtained with the 15 GHz VLBA in MJD 54838-60262 and data from the 15 GHz OVRO 40 m single dish telescope in MJD 54474-59023. We used…

Astrophysics of Galaxies · Physics 2025-12-05 Chanwoo Song , Sang-Sung Lee , Sincheol Kang , Whee Yeon Cheong

During solar flares, spectral lines formed in the photosphere have been shown to exhibit changes to their profiles despite the challenges of energy transfer to these depths. Recent work has shown that deep-forming spectral lines are subject…

Solar and Stellar Astrophysics · Physics 2024-01-05 Aaron J. Monson , Mihalis Mathioudakis , Adam F. Kowalski

We present a study of photometric flares on 154 low-mass ($\leq 0.2 \textrm{M}_{\odot}$) objects observed by the SPECULOOS-South Observatory from 1st June 2018 to 23rd March 2020. In this sample we identify 85 flaring objects, ranging in…

In the study of stellar flares, traditional method of calculating total energy emitted in the continuum assumes the emission originating from a narrow chromospheric condensation region with a constant temperature of 10000 K and variable…

Solar and Stellar Astrophysics · Physics 2025-05-15 K. Bicz , R. Falewicz , P. Heinzel , P. Preś , D. Moździerski , A. Pigulski , D. Marchev , K. Kotysz , T. Atanasova , G. Yordanova , A. Georgiev

The near-ultraviolet and optical (white-light) continuum radiation in M dwarf flares exhibits a range of observed characteristics, suggesting that the amount of heating at large optical depth varies among impulsive-type and gradual-type…

Solar and Stellar Astrophysics · Physics 2019-03-06 Adam F. Kowalski , Mihalis Mathioudakis , Suzanne L. Hawley

Cool stars are known to produce flares probably as a result of magnetic reconnection in their outer atmospheres. We present simultaneous XMM-Newton optical V band and X-ray observations of the M8 dwarf LP412-31. During the observation a…

Astrophysics · Physics 2009-11-11 B. Stelzer , J. H. M. M. Schmitt , G. Micela , C. Liefke

Increase in the Balmer continuum radiation during solar flares was predicted by various authors but never firmly confirmed observationally using ground-based slit spectrographs. Here we describe a new post-focal instrument - Image Selector…

Solar and Stellar Astrophysics · Physics 2016-02-02 P. Kotrč , O. Procházka , P. Heinzel

The statistical characteristic of stellar flares at optical bands has received an extensive study, but it remains to be studied at soft X-ray bands, in particular for solar-type stars. Here, we present a statistical study of soft X-ray…

Solar and Stellar Astrophysics · Physics 2024-01-19 Zhanhao Zhao , Ziqian Hua , Xin Cheng , Zhiyuan Li , Mingde Ding

In previous works we have developed a method to convert solar X-ray data, collected with the Yohkoh/SXT, into templates of stellar coronal observations. Here we apply the method to several solar flares, for comparison with stellar X-ray…

Astrophysics · Physics 2009-11-06 F. Reale , G. Peres , S. Orlando

We developed a reliable probabilistic solar flare forecasting model using a deep neural network, named Deep Flare Net-Reliable (DeFN-R). The model can predict the maximum classes of flares that occur in the following 24 h after observing…

Solar and Stellar Astrophysics · Physics 2020-09-02 Naoto Nishizuka , Yûki Kubo , Komei Sugiura , Mitsue Den , Mamoru Ishii

Stellar flares have been extensively studied in soft X-rays (SXR) by basically every X-ray mission. Hard X-ray (HXR) emission from stellar superflares, however, have only been detected from a handful of objects over the past years. One very…

High Energy Astrophysical Phenomena · Physics 2017-12-20 Stefan Ohm , Clemens Hoischen

The Folded-port InfraRed Echellette (FIRE) has recently been commissioned on the Magellan 6.5m Baade Telescope. This single object, near-infrared spectrometer simultaneously covers the 0.85-2.45 micron window in both cross-dispersed (R ~…