Search Publications
The model constraints from the observed trends for the quasi-periodic oscillation in RE J1034+396
Dovčiak, M.; Karas, V.; Czerny, B. +3 more
We analyze the time variability of the X-ray emission of RE J1034+396 - an active galactic nucleus with the first firm detection of a quasi-periodic oscillations (QPO). Based on the results of a wavelet analysis, we find a drift in the QPO central frequency. The change in the QPO frequency correlates with the change in the X-ray flux with a short …
J004457+4123 (Sharov 21): not a remarkable nova in M 31 but a background quasar with a spectacular UV flare
Pietsch, W.; Hatzidimitriou, D.; Ertel, S. +8 more
Aims: We announce the discovery of a quasar behind the disk of M 31, which was previously classified as a remarkable nova in our neighbour galaxy. It is shown here to be a quasar with a single strong flare where the UV flux has increased by a factor of 20. The present paper is primarily aimed at the remarkable outburst of J004457+4123 (Sharov…
HR 7355 - another rapidly braking He-strong CP star?
Zejda, M.; Paunzen, E.; Henry, G. W. +3 more
Context. Strong meridional mixing induced by rapid rotation is one reason why all hot main-sequence stars are not chemically peculiar. However, the finding that the He-strong CP star HR 7355 is a rapid rotator complicates this concept.
Aims: Our goal is to explain the observed behaviour of HR 7355 based on period analysis of all available pho…
New seismic analysis of the exoplanet-host star µ Arae
Vauclair, S.; Soriano, M.
Aims: We present detailed modelling of the exoplanet-host star µ Arae, using a new method for the asteroseismic analysis, and taking into account the new value recently derived for the Hipparcos parallax. The aim is to obtain precise parameters for this star and its internal structure, including constraints on the core overshooting.
High resolution X-ray spectroscopy of SN 1987 A: monitoring with XMM-Newton
Haberl, F.; Hasinger, G.; Sturm, R. +1 more
Context. The ongoing propagation of the supernova blast wave of SN 1987 A through its inner circumstellar ring has caused a drastic increase in X-ray luminosity in the past few years, which has allowed detailed high resolution X-ray spectroscopy to be performed with the Reflection Grating Spectrometer.
Aims: We report the results of our XMM-N…
Multi-zone warm and cold clumpy absorbers in three Seyfert galaxies
Audard, M.; Ricci, C.; Courvoisier, T. J. -L. +1 more
Aims: We present the first detailed X-ray analysis of three active galactic nuclei, the Seyfert 1 galaxies UGC 3142 and ESO 140-43, and the Seyfert 2 galaxy ESO 383-18, to study the geometry and the physical characteristics of their absorbers.
Methods: High-quality XMM-Newton EPIC and RGS data were analyzed as well as Swift/XRT and BAT a…
Annihilation emission from young supernova remnants
Vink, J.; Diehl, R.; Jean, P. +2 more
Context. A promising source of the positrons that contribute through annihilation to the diffuse Galactic 511 keV emission is the β+-decay of unstable nuclei like 56Ni and 44Ti synthesised by massive stars and supernovae. Although a large fraction of these positrons annihilate in the ejecta of SNe/SNRs, no point-so…
The HARPS search for southern extra-solar planets. XX. Planets around the active star BD -08°2823
Bouchy, F.; Moutou, C.; Queloz, D. +13 more
We report the detection of a planetary system around BD -08°2823 that includes at least one Uranus-mass planet and one Saturn-mass planet. This discovery serendipitously originates from a search for planetary transits in the Hipparcos photometry database. This program preferentially selected active stars and did not allow the detection of new tran…
The warm absorber and X-ray variability of the Seyfert 1 galaxy NGC 3516 as seen by the XMM-Newton RGS
Mehdipour, M.; Page, M. J.; Branduardi-Raymont, G.
Aims: We present a new analysis of the soft and medium energy X-ray spectrum of the Seyfert 1 galaxy NGC 3516 taken with the Reflection Grating Spectrometer (RGS) and European Photon Imaging Camera (EPIC) on board the XMM-Newton observatory. We examine four observations made in October 2006. We investigate whether the observed variability is …
Ground-state ammonia and water in absorption towards Sgr B2
Falgarone, E.; Larsson, B.; Olberg, M. +8 more
Context. Observations of transitions to the ground-state of a molecule are essential to obtain a complete picture of its excitation and chemistry in the interstellar medium, especially in diffuse and/or cold environments. For the important interstellar molecules H2O and NH3, these ground-state transitions are heavily absorbed…