Search Publications
Modelling dications in the diurnal ionosphere of Venus
Witasse, O.; Gronoff, G.; Lilensten, J. +4 more
Context: Previous studies have shown that doubly-charged positive ions, including molecular ions, can have detectable densities in the ionospheres of Mars, Titan, and the Earth.
Aims: In the present paper, we continue our approach by modelling the Venusian ionosphere. The neutral atmosphere of Venus has a similar composition to the ones encoun…
On the co-existence of chemically peculiar Bp stars, slowly pulsating B stars and constant B stars in the same part of the HR diagram
Aerts, C.; Briquet, M.; De Cat, P. +3 more
Aims: In order to better model massive B-type stars, we need to understand the physical processes taking place in slowly pulsating B (SPB) stars, chemically peculiar Bp stars, and non-pulsating normal B stars co-existing in the same part of the H-R diagram.
Methods: We carry out a comparative study between samples of confirmed and well-studied…
Solar abundances of oxygen and neon derived from solar wind observations
Bochsler, P.
Context: Recently, a revision of the solar abundances of C, N, and O to substantially lower values has led to a controversy on solar opacities in the solar standard model and to the suggestion to revise the solar abundance of neon upward by as much as a factor of 1.6 leading to enhanced solar neon/oxygen abundance ratios by a factor of 3. Neon and…
XMM-Newton observation of the NLS1 galaxy Ark 564. I. Spectral analysis of the time-average spectrum
McHardy, I.; Papadakis, I. E.; Page, M. J. +2 more
Context: We present the results from the spectral analysis of the time-average spectrum of the Narrow Line Seyfert 1 (NLS1) galaxy Ark 564 from a ~100 ks XMM-Newton observation.
Aims: Our aim is to characterize accurately the shape of the time-average, X-ray continuum spectrum of the source and search for any emission and/or absorption feature…
Diffuse gamma-ray emission from the Galactic center - a multiple energy injection model
Cheng, K. S.; Chernyshov, D. O.; Dogiel, V. A.
We suggest that the energy source of the observed diffuse gamma-ray emission from the direction of the Galactic center is the Galactic black hole Sgr A*, which becomes active when a star is captured at a rate of ~10-5 yr-1. Subsequently the star is tidally disrupted and its matter is accreted into the black hole. During the a…
Discovery of a new M 32-like "Compact Elliptical" galaxy in the halo of the Abell 496 cD galaxy
Chilingarian, I.; Adami, C.; Chemin, L. +4 more
Aims:"Compact ellipticals" are so rare that a search for M 32 analogs is needed to ensure the very existence of this class.
Methods: We report here the discovery of A496cE, a M 32 twin in the cluster Abell 496, located in the halo of the central cD.
Results: Based on CFHT and HST imaging we show that the light profile of A496cE requires a …
Three clusters of the SMC from ACS/WFC HST archive data: NGC 265, K 29 and NGC 290 and their field population
Chiosi, E.; Vallenari, A.
Aims:We determine the age, metallicity and initial mass function of three clusters, namely
Methods: We make use of ACS/WFC HST arc…
Unveiling the broad band X-ray continuum and iron line complex in Mrk 841
Maraschi, L.; Nandra, K.; Ponti, G. +7 more
Context:
Aims:
The dwarf nova SS Cygni: what is wrong?
Schreiber, M. R.; Lasota, J. -P.
Context: Since the Fine Guiding Sensor (FGS) on the Hubble Space Telescope (HST) was used to measure the distance to SS Cyg to be 166±12 pc, it became apparent that at this distance the disc instability model fails to explain the absolute magnitude during outburst. It remained, however, an open question whether the model or the distance have to be…
Can the solar wind originate from a quiet Sun region?
Tu, C. -Y.; Marsch, E.; He, J. -S.
Context: It is well known that the fast solar wind originates from coronal holes (CHs). However, the question whether it can also originate from quiet Sun regions has not yet been answered.
Aims: To study this problem we analyze SOHO data obtained from observations made in a quiet Sun area. The data set includes far-ultraviolet data from SUMER…