Search Publications
On the precision of X-ray source parameters estimated from ROSAT data
Boese, F. G.
The precision of the point source parameters, i.e. those for source position, source counts and source extension obtained via Maximum Likelihood Estimation from ROSAT data, is investigated. The various categories of error in X-ray observatories are identified. An analytic perturbation analysis is set forth. This means in the ROSAT case a perturbat…
Light Elements for V353 Hydrae, a Hipparcos Eclipsing Binary
Stephan, C.; Otero, S. A.
The Hipparcos eclipsing binary V353 Hydrae has been observed visually in order to determine its period. Results of this campaign are presented. The system is an eclipsing binary in a circular orbit. The combination of visual, Hipparcos, and ASAS-3 data finally revealed that the period is 7.56 days.
The optical to X-ray spectrum of the broad-line ultrasoft AGN RE J2248-511
Mason, K. O.; Starling, R. L. C.; Romero-Colmenero, E. +1 more
We present a series of monitoring observations of the ultrasoft broad-line Seyfert galaxy RE J2248-511 with XMM-Newton. Previous X-ray observations showed a transition from a very soft state to a harder state five years later. We find that the ultrasoft X-ray excess has re-emerged, yet there is no change in the hard power-law. Reflection models wi…
Disentangling X-ray Reprocessing Sites in EXO 0748-676
Charles, P. A.; Horne, K.; O'Brien, K. +5 more
We present first results from a coordinated multiwavelength study of the neutron star low-mass X-ray binary EXO 0748-676. Fast UV, X-ray, and optical data were obtained including both spectral and timing information. We discuss how this study allows us to probe the temperature distribution within the binary and hence the geometry and efficiency of…
The entropy in groups a clue to galaxy formation
Mushotzky, Richard
The entropy in the hot X-ray gas in groups of galaxies is a fossil of the process of galaxy formation The amount of entropy in these low mass systems considerably exceeds that predicted from structure formation models. To explain these results requires "extra" energy which is a relic of the process of star formation and active galaxy heating. We p…
Solar wind velocity at solar maximum: A search for latitudinal effects
Bavassano, B.; Bruno, R.; D'Amicis, R.
Observations by Ulysses during its second out-of-ecliptic orbit have shown that near the solar activity maximum the solar wind appears as a highly variable flow at all heliolatitudes. In the present study Ulysses data from polar latitudes are compared to contemporary ACE data in the ecliptic plane to search for the presence of latitudinal effects …
The XMM-Newton/2dF survey - V. The radio properties of the X-ray population
Georgakakis, A.; Georgantopoulos, I.; Akylas, A. +3 more
In this paper, we cross-correlate the FIRST (Faint Images of the Radio Sky at Twenty centimeters) 1.4-GHz radio survey with a wide-field (1.6 deg2) shallow [fX(0.5 - 8keV) ~ 10-14erg s-1]XMM-Newton survey. We find 12 X-ray/radio matches representing 4 per cent of the X-ray-selected sample. Most of them a…
VISPO project: visible image-spectrometer for planetary observations
Piccioni, G.; Capaccioni, F.; De Petris, M. +3 more
Satellite instrumentations designed for planetary studies are often open to other interesting applications from ground: not only one can efficiently carry out detailed calibrations before space data become available, but also the prototypes of the satellite instruments can be successfully employed in different fields ranging from astrophysics to c…
Simulation studies of high-latitude magnetospheric boundary dynamics
Zhang, H.; Liu, Z. X.; Shi, Q. Q. +4 more
X-ray Archaeology of Galaxy Groups
Ponman, T. J.; Osmond, J. P. F.
We have assembled a sample of 60 galaxy groups in order to study the hot intragroup medium and better understand the processes by which it formed. We have analysed ROSAT data for all 60 groups and have obtained XMM data for a small subset. Here we present an initial analysis of the XMM data for NGC 5171, and a comparison with the ROSAT data. This …