Search Publications
XMM-Newton observations of the Seyfert 1 galaxy ESO 141-G55
Gondoin, P.; Orr, A.; Lumb, D.
We report on an observation of the Seyfert 1 galaxy ESO 141-G55 performed in October 2001 with the EPIC MOS cameras and Reflection Grating Spectrometers (RGS) on board the XMM-Newton observatory. We find the hard (3-10 keV) continuum slope, including reflection, to be somewhat flatter (Gamma = 1.72 +/- 0.06) than that of a typical broad-line Seyfe…
Fragmentation of Globules in H II Regions: Hubble Space Telescope Images of Thackeray's Globules
Reipurth, Bo; Heathcote, Steve; Raga, Alex
We present Hubble Space Telescope WFPC2 images through an Hα filter of Thackeray's globules in the southern H II region IC 2944. The images document the state of the globule complex during its current highly dynamical phase of breakup. A population of very small and short-lived splinters suggests that continuous fragmentation must play an importan…
Stellar collisions in galactic centres: black hole growth and colour gradients
Yu, Qingjuan
We study the effects of stellar collisions, particularly on feeding massive black holes (BHs) and colour gradients, in realistic galactic centres. We find that the mass released by stellar collisions is not sufficient to account for the present BH mass in galactic centres, especially in bright galaxies. This study, together with the study by Magor…
Structural analysis of periodic surface waves on the magnetospheric boundary
Roth, M.; De Keyser, J.
In situ observations of the flanks of the magnetospheric boundary (magnetopause and boundary layer) sometimes show periodic surface waves to be present. We propose a straightforward but powerful technique for analyzing such periodic boundary waves. The result of this analysis is a two-dimensional picture of the structure of the wave in a reference…
The global heliospheric magnetic field polarity distribution as seen at Ulysses
Balogh, A.; Jones, G. H.
The Ulysses spacecraft is in a near-polar solar orbit with a period of 6.2 years. The heliospheric magnetic field polarity detected by Ulysses from its 1992 Jupiter encounter to the current time is presented, following ballistic mapping of the polarity information to the solar wind source surface, at approximately 2.5 solar radii. The spacecraft's…
Consequences of the Solar System passage through dense interstellar clouds
Fahr, H. J.; Yeghikyan, A. G.
Several consequences of the passage of the solar system through dense interstellar molecular clouds are discussed. These clouds, dense (more than 100 cm-3), cold (10-50 K) and extended (larger than 1 pc), are characterized by a gas-to-dust mass ratio of about 100, by a specific power grain size spectrum (grain radii usually cover the range 0.001-3…
Grey extinction in the solar neighbourhood?
Galazutdinov, G. A.; Strobel, A.; Skórzyński, W.
Some of the close O and B dwarfs appear to be fainter than indicated by their Hipparcos distances, intrinsic absolute magnitudes attributed to their spectral types, and estimated selective interstellar extinction. This discrepancy is explained in the paper by the grey (neutral) interstellar extinction in the visual range of spectrum. The measure o…
A study of the causal relationship between the emergence of a twisted magnetic flux rope and a small Hα two-ribbon flare
Brooks, D. H.; Kurokawa, H.; Berger, T. E. +2 more
We present results from an analysis of a small two-ribbon flare which occurred above emerging flux in solar active region NOAA 8218 on 1998, May 13th and which was observed by the Swedish Vacuum Solar Telescope (SVST) on the island of La Palma, Spain. The relatively simple magnetic morphology and small size of the flare together with the high qual…
The HST survey of the B2 sample of radio galaxies: Detection of two optical jets
Bondi, M.; Capetti, A.; Morganti, R. +5 more
We present HST observations of previously undetected optical jets in the low-luminosity radio galaxies B2 0755+37 and B2 1553+24. We show that there is accurate spatial coincidence between optical and radio emission, implying that the former is likely to be synchrotron radiation. The physical properties of the jets are similar to those known previ…
Evolution of the galactic cosmic ray electron to proton ratio: Ulysses COSPIN/KET observations
Kunow, H.; Ferreira, S. E. S.; Potgieter, M. S. +3 more
The Ulysses orbit provides a unique opportunity to study the propagation of cosmic rays in a wide range of heliographic latitudes and during different solar activity and polarity in the inner heliosphere. Around July 2000 the solar magnetic field reversed its global polarity. In late 2000, the electron to proton ratio at the rigidities of 1.2 GV a…