Search Publications
The young active star SAO 51891 (V383 Lacertae)
Frasca, A.; Biazzo, K.; Covino, E. +5 more
Aims: The aim of this work is to investigate the surface inhomogeneities of a young, late-type star, SAO 51891, at different atmospheric levels, from the photosphere to the upper chromosphere, analyzing contemporaneous optical high-resolution spectra and broad-band photometry.
Methods: The full spectral range of FOCES@CAHA (R ≃ 40 000) is used…
Simulation of a flux emergence event and comparison with observations by Hinode
Solanki, S. K.; Lagg, A.; Cheung, M. C. M. +2 more
Aims: We study the observational signature of flux emergence in the photosphere using synthetic data from a 3D MHD simulation of the emergence of a twisted flux tube.
Methods: Several stages in the emergence process are considered. At every stage we compute synthetic Stokes spectra of the two iron lines Fe I 6301.5 Å and Fe I 6302.5 Å and degr…
Analysis of extremely low signal-to-noise ratio data from INTEGRAL/PICsIT
Lubiński, P.
Context: The PICsIT detector onboard the INTEGRAL satellite was designed to provide information about emission in the soft γ-ray band for many bright sources. Due to strong and variable instrumental background, only 4 objects have been detected so far using standard software.
Aims: The moderate sensitivity of PICsIT can be compensated for in t…
Discovery of a rapidly pulsating subdwarf B star candidate in ω Centauri
Bono, G.; Calamida, A.; Randall, S. K.
We report the discovery of the first variable extreme horizontal branch star in a globular cluster (ω Cen). The oscillation uncovered has a period of 114 s and an amplitude of 32 mmag. A comparison between horizontal branch models and observed optical colours indicates an effective temperature of 31 500 ± 6300 K for this star, placing it within th…
X-ray narrow line region variability as a geometry probe. The case of NGC 5548
Kaastra, J. S.; Detmers, R. G.; McHardy, I. M.
We study the long time scale variability of the gas responsible for the X-ray narrow emission lines in the Seyfert 1 galaxy NGC 5548, in order to constrain the location and geometry of the emitting gas. Using X-ray spectra taken with the Chandra-LETGS and HETGS instruments and with XMM-Newton RGS and combining them with long-term monitoring observ…
Monitoring campaign of 1RXS J171824.2-402934, the low-mass X-ray binary with the lowest mass accretion rate
in't Zand, J. J. M.; Bassa, C. G.; Jonker, P. G. +2 more
An X-ray monitoring campaign with Chandra and Swift confirms that 1RXS J171824.2-402934 is accreting at the lowest rate among the known persistently accreting low-mass X-ray binaries. A thermonuclear X-ray burst was detected with the all-sky monitor on RXTE. This is only the second such burst seen in 1RXS J171824.2-402934 in more than 20 Ms of obs…
Two types of flare-associated coronal mass ejections
Michalek, G.
Aims: Here, we study the relationship between flares and CMEs.
Methods: For this purpose a statistical analysis of 578 flare-associated CMEs is presented. We considered two types of flare-associated CMEs: CMEs that follow and precede flare onset.
Results: We shown that both samples have quite different characteristics. The first type of CM…
A wave scattering theory of solar seismic power haloes
Hanasoge, S. M.
Spatial maps of the high-pass frequency filtered time-averaged root-mean-squared (RMS) Doppler velocities tend to show substantial decrements within regions of strong field and curiously, randomly distributed patches of enhancement in the vicinity. We propose that these haloes or enhancements are a consequence of magnetic-field-induced mode mixing…
On the statistical detection of propagating waves in polar coronal holes
Doyle, J. G.; Gupta, G. R.; Banerjee, D. +2 more
Context: Waves are important to the study of dynamical processes in coronal holes and the acceleration of the fast solar wind. A spectral time series was taken with the SUMER spectrometer on-board SoHO on 20 October 1996. The observations were obtained in the N iv 765 Å transition region line and the Ne viii 770 Å line of the low corona.
Aims:…
The Cartwheel galaxy with XMM-Newton
Wolter, A.; Trinchieri, G.; Crivellari, E.
Aims: The extreme environment provided by the Cartwheel ring is analyzed to study its X-ray and optical-UV properties. We compare the Cartwheel with the other members of its group and study the system as a whole in the X-ray band.
Methods: We analyze the data of the Cartwheel galaxy obtained with XMM-Newton in two different periods (December 2…