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An X-ray flaring source was found near the galaxy NGC 4697. Two flares were seen, separated by four years. The flux increased by a factor of 90 on a timescale of about one minute. Both flares were very brief. There is no optical counterpart…

We study the chromosphere and corona of the ultra-fast rotator AB Dor A at high temporal and spectral resolution using simultaneous observations with XMM-Newton in the X-rays, VLT/UVES in the optical, and the ATCA in the radio. Our optical…

Solar and Stellar Astrophysics · Physics 2015-06-17 S. Lalitha , B. Fuhrmeister , U. Wolter , J. H. M. M. Schmitt , D. Engels , M. H. Wieringa

Fast radio bursts (FRBs) are bright, millisecond-duration radio pulses whose origins are unknown. To date, only one (FRB 121102) out of several dozen has been seen to repeat, though the extent to which it is exceptional remains unclear. We…

High Energy Astrophysical Phenomena · Physics 2018-07-11 Liam Connor , Emily Petroff

We report a NuSTAR observation of a solar microflare, SOL2015-09-01T04. Although it was too faint to be observed by the GOES X-ray Sensor, we estimate the event to be an A0.1 class flare in brightness. This microflare, with only 5 counts…

Since the end of the eighties, in response to a reported increase of the total neutrino flux in the Homestake experiment in coincidence with solar flares, neutrino detectors have searched for signals of neutrinos associated with solar flare…

High Energy Astrophysical Phenomena · Physics 2016-06-03 G. de Wasseige

The rapid variability observed in very-high-energy (VHE) sources-such as pulsars, gamma-ray bursts (GRBs), and flares from active galactic nuclei (AGN)-can be used to detect or constrain a potential violation of Lorentz invariance (LIV).…

High Energy Astrophysical Phenomena · Physics 2026-04-14 Cyann Plard , Sami Caroff , the CTAO-LST project

A M-class behind-the-limb solar flare on 1 May 2013 (SOL2013-05-01T02:32), accompanied by a ($\sim$ 400 km/s) CME was observed by several space-based observatories with different viewing angles. We investigated the RHESSI-observed occulted…

This short paper reviews several recent key observations of the processes occurring in the lower atmosphere (chromosphere and photosphere) during flares. These are: evidence for compact and fragmentary structure in the flare chromosphere,…

Solar and Stellar Astrophysics · Physics 2013-12-02 Lyndsay Fletcher , Paulo J. A. Simoes

Future experiments based on the observation of Earth's atmosphere from sub-orbital and orbital altitudes plan to include optical Cherenkov cameras to observe extensive air showers produced by high-energy cosmic radiation via its interaction…

Instrumentation and Methods for Astrophysics · Physics 2021-09-22 Austin Cummings , Roberto Aloisio , Johannes Eser , John Krizmanic

Flares and CMEs are very powerful events in which energetic radiation and particles are ejected within a short time. These events thus can strongly affect planets that orbit these stars. This is particularly relevant for planets of M-stars,…

Solar and Stellar Astrophysics · Physics 2020-10-21 Priscilla Muheki , Eike W Guenther , Tom Mutabazi , Edward Jurua

Flares and CMEs are known to be the dominating high-energy phenomena on cool stars. Superflares were thoroughly investigated using broadband photometry predominantly from Kepler, K2, and TESS. Here we present a spectroscopic investigation…

We report the detection of high polarization in the first detailed optical linear polarization measurements on the BL Lac object CGRaBS J0211+1051, which flared in $\gamma$-rays on 2011 January 23 as reported by Fermi. The observations were…

High Energy Astrophysical Phenomena · Physics 2015-05-27 Sunil Chandra , Kiran S Baliyan , Shashikiran Ganesh , Umesh Joshi

We present a new automated algorithm to identify, track, and characterize small-scale brightening associated with solar eruptive phenomena observed in H{\alpha}. The temporal spatially-localized changes in chromospheric intensities can be…

Solar and Stellar Astrophysics · Physics 2015-05-30 M. S. Kirk , K. S. Balasubramaniam , J. Jackiewicz , B. J. McNamara , R. T. J. McAteer

We present here an overview of the status of the Chandra X-ray Observatory which has now been operating for five years. The Observatory is running smoothly, and the scientific return continues to be outstanding. We provide some details on…

Astrophysics · Physics 2007-05-23 Martin C. Weisskopf

Improved statistics and mass-composition-sensitive observation are required to clarify the origin of ultra-high energy cosmic rays (UHECRs). Inevitably in the future, the UHECR observatories will have to be expanded due to the small flux;…

Instrumentation and Methods for Astrophysics · Physics 2019-03-06 Yuichiro Tameda , Takayuki Tomida , Mashu Yamamoto , Hirokazu Iwakura , Daisuke Ikeda , Katsuya Yamazaki

In 2010, the Fermi Gamma-ray Space Telescope observed two gamma-ray emitting structures, the Fermi Bubbles (FBs), that extend up to 55{\deg} above and below the Galactic plane and that seem to emanate from the Galactic center region.…

High Energy Astrophysical Phenomena · Physics 2025-12-18 Francesco Xotta , Nina Bavdaž , Christopher Eckner , Dmitry Malyshev , Judit Pérez-Romero , Gabrijela Zaharijas

We analyze high cadence high resolution observations of a C3.2 flare obtained by AIA/SDO on August 1, 2010. The flare is a long duration event with soft X-ray and EUV radiation lasting for over four hours. Analysis suggests that magnetic…

Solar and Stellar Astrophysics · Physics 2015-06-03 Jiong Qiu , Wen-Juan Liu , Dana W. Longcope

Highly luminous rapid flares are characteristic of processes around compact objects like white dwarfs, neutron stars or black holes. In the high energy regime of X- and gamma-rays, outbursts with variability time-scales of seconds and…

Astrophysics · Physics 2009-07-09 A. Stefanescu , G. Kanbach , A. Słowikowska , J. Greiner , S. McBreen , G. Sala

The Cherenkov Telescope Array is a next generation ground-based gamma-ray observatory de- signed to detect photons in the 20 GeV to 300 TeV energy range. With a sensitivity improvement of up to one order of magnitude on the entire energy…

High Energy Astrophysical Phenomena · Physics 2019-08-14 Roberta Zanin , Jamie Holder