Related papers: The Coronae of AR Lac
Decaying active region 10942 is investigated from 4:00-16:00 UT on February 24, 2007 using a suite of EUV observing instruments. Results from Hinode/EIS, STEREO and TRACE show that although the active region has decayed and no sunspot is…
Solar corona, the last main layer of the atmosphere of the Sun, is detectable in the EUV and X-ray. The corona is expanding into space up to millions of kilometers and is observable during the eclipse. The temperature is increasing about…
Recent observations in extreme-ultraviolet (EUV) wavelengths reveal an EUV late phase in some solar flares, which is characterized by a second peak in the warm coronal emissions (about 3 MK) occurring several tens of minutes to a few hours…
Context. Extreme ultraviolet (EUV) late-phase (ELP) flares exhibit a second peak in warm coronal emissions minutes to hours after the main peak of the flare. This phase is all but negligible, and it is still poorly understood what role it…
Recent studies of solar-type superflare stars have suggested that even old slowly rotating stars similar to the Sun can have large starspots and superflares. We conducted high dispersion spectroscopy of 49 nearby solar-analog stars (G-type…
Some galaxies show little to no sign of active galactic nucleus (AGN) activity, yet exhibit strong coronal emission lines (CLs) relative to common narrow emission lines. Many of these CLs have ionization potentials of $\geq 100$ eV, thus…
The characterization of exoplanets, their formation, evolution, and chemical changes is tightly linked to our knowledge of their host stars. In particular, stellar X-rays and UV emission have a strong impact on the dynamical and chemical…
The eclipsing binary LL Aqr consists of two late-type stars in an eccentric orbit with a period of 20.17 d. We use an extensive light curve from the SuperWASP survey augmented by published radial velocities and UBV light curves to measure…
We report on the results of our simultaneous observations of three large stellar flares with soft X-rays (SXRs) and an H$\mathrm{\alpha}$ emission line from two binary systems of RS CVn type. The energies released in the X-ray and…
Coronal density, temperature and heat flux distributions for the equatorial and polar corona have been deduced by Lemaire [2012] from Saito's model of averaged coronal white light (WL) brightness and polarization observations. They are…
Understanding the relationship among different emission components plays an essential role in the study of particle acceleration and energy conversion in solar flares. In flares where gradual and impulsive emission components can be readily…
Context: The comparison of coronal and photospheric abundances in cool stars is an essential question to resolve. In the Sun an enhancement of the elements with low first ionization potential (FIP) is observed in the corona with respect to…
The ROSAT PSPC pulse height spectrum of the peculiar He-rich hot white dwarf KPD 0005+5106 provided a great surprise when first analysed by Fleming, Werner & Barstow (1993). It defied the best non-LTE modelling attempts in terms of…
(Abridge) The relationship between coronal line (CL) emission and nuclear activity in active galactic nuclei (AGNs) is analyzed, for the first time, based on NIR spectra. The 8 CLs studied, of Si, S, Fe, Al and Ca elements and corresponding…
EUV observations of warm coronal loops suggest that they are bundles of unresolved strands that are heated impulsively to high temperatures by nanoflares. The plasma would then have the observed properties (e.g., excess density compared to…
The abundance of chlorine is determined from X-ray spectra obtained with the RESIK instrument on {\em CORONAS-F} during solar flares between 2002 and 2003. Using weak lines of He-like Cl, \ion{Cl}{16}, between 4.44 and 4.50 \AA, and with…
Four years (2010-2014) of semiannual pointings by Hubble Space Telescope Imaging Spectrograph (STIS) on nearby Alpha Centauri have yielded a detailed time history of far-ultraviolet emissions of the solar-like primary (A: G2V) and the…
We present the search for eclipsing binaries with a pulsating component in the first catalogue of optically variable sources observed by OMC/INTEGRAL, which contains photometric data for more than 1000 eclipsing binaries. Five objects were…
We discuss ROSAT, ASCA, {\it Beppo}SAX and optical observations of the young active star Gl 355. During the ROSAT observation a strong flare was detected with a peak flux more than an order of magnitude larger than the quiescent level.…
Strong solar flares and coronal mass ejections, here defined not only as the bursts of electromagnetic radiation but as the entire process in which magnetic energy is released through magnetic reconnection and plasma instability, emanate…