Search Publications
Long period oscillations in the inter-plume regions of the Sun
Doyle, J. G.; Banerjee, D.; O'Shea, E. +1 more
We examine long spectral time series of inter-plume lanes observed on the 14th and 15th March 2000 with the Coronal Diagnostic Spectrometer (CDS) on-board SoHO. The observations were obtained in lines over a wide temperature range, from the chromosphere to the corona. The statistical significance of the oscillations was estimated by using a random…
The IMF of open star clusters with Tycho-2
Geffert, M.; Sanner, J.
We studied the fields of nine nearby open star clusters based on the Tycho-2 catalogue. We determined membership probabilities for the stars in the cluster fields from the stellar proper motions and used the Tycho-2 photometry to compute the initial mass function (IMF) of the clusters from the main sequence turn-off point down to approx. 1 M_sun. …
Solar differential rotation determined by tracing coronal bright points in SOHO-EIT images. I. Interactive and automatic methods of data reduction
Vršnak, B.; Wöhl, H.; Clette, F. +3 more
Full-disc solar images obtained with the Extreme Ultraviolet Imaging Telescope (EIT) on board the Solar and Heliospheric Observatory (SOHO) were used to analyse solar differential rotation determined by tracing coronal bright points. Two different procedures were developed and compared: an interactive and an automatic method. The interactive metho…
Detection of an X-ray periodicity in the Narrow-line Seyfert 1 Galaxy Mrk 766 with XMM-Newton
Boller, Th.; O'Brien, P. T.; Trümper, J. +3 more
We have analyzed the timing properties of the Narrow-line Seyfert 1 galaxy Mrk 766 observed with XMM-Newton during the PV phase. The source intensity changes by a factor of 1.3 over the 29 000 s observation. If the soft excess is modeled by a black body component, as indicated by the EPIC pn data, the luminosity of the black body component scales …
Research Note Hipparcos photometry: The least variable stars
Adelman, S. J.
The data known as the Hipparcos Photometry obtained with the Hipparcos satellite have been investigated to find those stars which are least variable. Such stars are excellent candidates to serve as standards for photometric systems. Their spectral types suggest in which parts of the HR diagrams stars are most constant. In some cases these values s…
Oscillations in an active region filament: Observations and comparison with MHD waves
Régnier, S.; Solomon, J.; Vial, J. C.
During the MEDOC Campaign 4, on October 1999, observations of a solar active region filament were carried out by the SUMER/SoHO spectrometer. A time sequence of this filament has been obtained with a duration of 7 h 30 min and with a temporal resolution of 30 s. The Fourier analysis of the line-of-sight Doppler velocities measured in the 584.33 Å …
Low-excitation atomic gas around evolved stars. I. ISO observations of C-rich nebulae
Bujarrabal, V.; Tielens, A. G. G. M.; Meixner, M. +5 more
We present ISO LWS and SWS spectra of far-infrared (FIR) atomic fine structure lines in 12 carbon-rich evolved stars including asymptotic giant branch (AGB) stars, proto-planetary nebulae (PPNe) and planetary nebulae (PNe). The spectra include grating and Fabry-Perot measurements of the line emission of [O I], [C Ii], [Si I], [Si Ii], [S I], [Fe I…
Modelling the spin pulse profile of the isolated neutron star RX J0720.4-3125 observed with XMM-Newton
Haberl, F.; Motch, C.; Cropper, M. +2 more
We model the spin pulse intensity and hardness ratio profiles of the isolated neutron star RX J0720.4-3125 using XMM-Newton data. The observed variation is approximately sinusoidal with a peak-to-peak amplitude of 15%, and the hardness ratio is softest slightly before flux maximum. By using polar cap models we are able to derive maximum polar cap …
UV observations of the galaxy cluster Abell 1795 with the optical monitor on XMM-Newton
Kaastra, J. S.; Fabian, A. C.; Mushotzky, R. F. +8 more
We present the results of an analysis of broad band UV observations of the central regions of Abell 1795 observed with the optical monitor on XMM-Newton. As have been found with other UV observations of the central regions of clusters of galaxies, we find evidence for star formation. However, we also find evidence for absorption in the cD galaxy o…
The LMC eclipsing binary HV 2274 revisited
Salaris, M.; Groenewegen, M. A. T.
We reanalyse the UV/optical spectrum and optical broad-band data of the eclipsing binary HV 2274 in the LMC, and derive its distance following the method given by Guinan et al. (\cite{Guinan98a},\cite{Guinan98b}) of fitting theoretical spectra to the stars' UV/optical spectrum plus optical photometry. We describe the method in detail, pointing out…