Related papers: X-ray activity cycles in stellar coronae
We present a simultaneous Chandra and XMM-Newton observation of the Castor sextett, focusing on Castor A and Castor B, two spectroscopic binaries with early-type primaries. Of the present day X-ray instruments only Chandra can isolate the…
Recent improvements in the modeling of solar convection and line formation led to downward revisions of the solar photospheric abundances of the lighter elements, which in turn led to changes in the radiative opacity of the solar interior…
Stars of stellar type later than about M3.5 are believed to be fully convective and therefore unable to support magnetic dynamos like the one that produces the 11-year solar cycle. Because of their intrinsic faintness, very few late M stars…
The relation between magnetic activity and rotation in late-type stars provides fundamental information on stellar dynamos and angular momentum evolution. Rotation/activity studies found in the literature suffer from inhomogeneity in the…
The cyclicity of 33 solar-type stars that are similar to 11-year and to the quasi-biennial variations of solar radiation have studied. Our calculation were based on new simultaneous observations of the flux variations of the photospheric…
We present optical identification and high-resolution spectroscopy of ROSAT sources in the field of the old open cluster M 67. For the first time it is possible to analyze coronal and chromospheric activity of active stars in a solar-age…
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…
We present the result of a study of the X-ray emission from the Galactic Centre Molecular Clouds (MC), within 15 arcmin from Sgr A*. We use XMM-Newton data spanning about 8 years. We observe an apparent super-luminal motion of a light front…
The solar magnetic activity cycle is responsible for periodic episodes of severe space weather, which can perturb satellite orbits, interfere with communications systems, and bring down power grids. Much progress has recently been made in…
We have been conducting a comprehensive survey of stellar coronae with the XMM-Newton Reflection Grating Spectrometers during the commissioning, calibration, verification, and guaranteed time phases of the mission, accompanied by…
Chromospheres and coronae are common phenomena on solar-type stars. Understanding the energy transfer to these heated atmospheric layers requires direct access to the relevant empirical data. Study of these structures has, by and large,…
A fine analysis of spectral line widths and Doppler shifts employing Fourier transform and cross-correlation techniques has been applied to Chandra HETG spectra obtained in 1999 October of the rapidly rotating young star AB Doradus in order…
We present five decades of chromospheric activity measurements in 59 Sun-like stars as time series. These include and extend the 35 yr of stellar chromospheric activity observations by the Mount Wilson Survey (1966--2001), and continued…
We present a detailed X-ray analysis and imaging of stellar coronae of five coronally connected eclipsing binaries, namely, 44 Boo, DV Psc, ER Vul, XY UMa, and TX Cnc. Both components of these binaries are found to be active. The X-ray…
We obtain contemporaneous observations of the surface and corona of AB Dor using ground-based circularly polarised spectra from the Anglo-Australian Telescope and X-ray data from the Chandra satellite. The ground-based data are used to…
We studied new simultaneous observations of the flux variations of the photospheric and chromospheric emissions of 33 solar-type stars and Sun during the HK-project that were conducted over the past 20 years. In addition to the known cyclic…
A ROSAT survey of the Alpha Per open cluster in 1993 detected its brightest star, mid-F supergiant Alpha Persei: the X-ray luminosity and spectral hardness were similar to coronally active late-type dwarf members. Later, in 2010, a Hubble…
We present the first spatially separated X-ray observation of the active UV Ceti binary with \textit{Chandra}, providing important new information on the relative X-ray activity levels of its nearly identical dM5.5e components. The two…
Several late-type stars present activity cycles similar to that of the Sun. However, these cycles have been mostly studied in F to K stars. Due to their small intrinsic brightness, M dwarfs are not usually the targets of long-term…
First results from high-resolution coronal spectroscopy of flares with the Reflection Grating Spectrometers on board the \textit{XMM-Newton} satellite are reviewed. Rotational modulation in the X-ray light curve of HR 1099 is discussed.…