Related papers: Monitoring of FR Cnc Flaring Activity
Intense outbursts in blazars are among the most extreme phenomena seen in extragalactic objects. Studying these events can offer important information about the energetic physical processes taking place within the innermost regions of…
By studying the variability of blazars across the electromagnetic spectrum, it is possible to resolve the underlying processes responsible for rapid flux increases, so-called flares. We report on an extremely bright X-ray flare in the…
We present the first images of a coordinated campaign to follow active region NOAA 12709 on 2018 May 13 as part of a joint effort between three observatories (China-Europe). The active region was close to disk center and enclosed a small…
Cherenkov telescopes are also sensitive to the atmospheric fluorescence produced by the extensive air showers. However this contribution is neglected by the reconstruction algorithms of imaging air Cherenkov telescopes IACTs and wide-angle…
Optical, near-infrared, and radio observations of the BL Lac object PKS2155-304 were obtained simultaneously with a continuous UV/EUV/X-ray monitoring campaign in 1994 May. Further optical observations were gathered throughout most of 1994.…
For several decades we have been performing photometric monitoring of some of the star formation regions. Significant place in our program take observations of objects of the type FU Orionis, EX Lupi, UX Orionis and other similar but…
We report on optical-near-infrared photopolarimetric observations of a blazar 3C 454.3 over 200 d. The object experienced an optical outburst in July 2007. This outburst was followed by a short state fainter than $V=15.2$ mag lasting $\sim…
Context. Blazars are the most numerous class of High Energy (HE; E about 50 MeV - few 100 GeV) and Very High Energy (VHE; E about 100 GeV - 10 TeV) gamma-ray emitters. As of today, a measured spectroscopic redshift is available for only…
A small-scale flare SOL2012-09-21T02:19 (B2) occurred in a spotless active region that we observed at a ground-based telescope equipped with a spectrograph. During the flare, we registered an increase in absorption in the He I 10830 \AA\…
For studying variable sources like blazars, it is crucial to achieve unbiased monitoring, either with dedicated telescopes in pointing mode or survey instruments. At TeV energies, the High Altitude Water Cherenkov (HAWC) observatory…
Subsequent to announcements by the AGILE and by the Fermi-LAT teams of the discovery of gamma-ray flares from the Crab Nebula in the fall of 2010, an international collaboration has been monitoring X-Ray emission from the Crab on a regular…
The young active flare star AU~Mic is the planet host star with the highest flare rate from TESS data. Therefore, it represents an ideal target for dedicated ground-based monitoring campaigns with the aim to characterize its numerous flares…
We present an analysis of the cross-correlation between optical brightness and polarization degree in different types of blazars. The aim is to identify objects with simultaneous and consistent changes in characteristics and to determine if…
The CELESTE atmospheric Cherenkov detector ran until June 2004. It has detected several gamma-ray flares of Mrk 421 since 1999. The new data analysis provides better background rejection. We compare our light curves with X-ray data. We…
We compile the catalog of Hvar Observatory solar observations in the time period corresponding to regular digitally stored chromospheric and photospheric observations 2010-2019. We make basic characterisation of observed phenomena and…
The High Altitude Water Cherenkov Observatory (HAWC) has a wide field-of-view (FOV, $\sim$2sr) and a high duty cycle ($\sim$95\%), which make it a powerful survey and monitoring experiment for sources of TeV gamma rays. We present a…
Observations of a large solar flare of December 13, 2006, using Solar Optical Telescope (SOT) on Hinode spacecraft revealed high-frequency oscillations excited by the flare in the sunspot chromosphere. These oscillations are observed in the…
We report results of an observing campaign to study the dwarf M flare star EV Lacertae. Between October 2021 and January 2022 we obtained concurrent B band photometry and low resolution spectroscopy of EV Lac on 39 occasions during 10 of…
We report the serendipitous discovery of a flare star observed with the ROSAT X-ray observatory. From optical spectra, which show strong and variable emission lines of the hydrogen Balmer series and neutral helium, we classify this object…
Proxima b is a terrestrial-mass planet in the habitable-zone of Proxima Centauri. Proxima Centauri's high stellar activity however casts doubt on the habitability of Proxima b: sufficiently bright and frequent flares and any associated…