Search Publications
Reduced Wolf-Rayet line luminosities at low metallicity
Crowther, P. A.; Hadfield, L. J.
New NTT/EMMI spectrophotometry of single WN2-5 stars in the Small and Large Magellanic Clouds are presented, from which He ii λ4686 line luminosities have been derived, and compared with observations of other Magellanic Cloud Wolf-Rayet stars. SMC WN3-4 stars possess line luminosities which are a factor of 4 times lower than LMC counterparts, inco…
A Lyman-α blob in the GOODS South field: evidence for cold accretion onto a dark matter halo
Fynbo, J. P. U.; Nilsson, K. K.; Møller, P. +2 more
We report on the discovery of a z = 3.16 Lyman-α emitting blob in the Great Observatories Origins Deep Survey (GOODS) South field. The discovery was made with the VLT, through narrow-band imaging. The blob has a total Lyα luminosity of ∼1043 erg s-1 and a diameter larger than 60 kpc. The available multi-wavelength data in the…
Size and properties of the narrow-line region in Seyfert-2 galaxies from spatially-resolved optical spectroscopy
Komossa, S.; Haas, M.; Chini, R. +2 more
Context: .While [O III] narrow-band imaging is commonly used to measure the size of the narrow-line regions (NLRs) in active galactic nuclei (AGNs), it can be contaminated by emission from surrounding starbursts. Recently, we have shown that long-slit spectroscopy provides a valuable alternative approach to probe the size in terms of AGN photoioni…
Quantitative spectroscopy of BA-type supergiants
Butler, K.; Kudritzki, R. P.; Przybilla, N. +1 more
Luminous BA-type supergiants have enormous potential for modern astrophysics. They allow topics ranging from non-LTE physics and the evolution of massive stars to the chemical evolution of galaxies and cosmology to be addressed. A hybrid non-LTE technique for the quantitative spectroscopy of these stars is discussed. Thorough tests and first appli…
A VLT/NACO survey for triple and quadruple systems among visual pre-main sequence binaries
Correia, S.; Zinnecker, H.; Ratzka, Th. +1 more
Aims.This paper describes a systematic search for high-order multiplicity among wide visual Pre-Main Sequence (PMS) binaries.
Methods: .We conducted an Adaptive Optics survey of a sample of 58 PMS wide binaries from various star-forming regions, which include 52 T Tauri systems with mostly K- and M-type primaries, with the NIR instrument NACO…
Magnetars as persistent hard X-ray sources: INTEGRAL discovery of a hard tail in SGR 1900+14
Tiengo, A.; Götz, D.; Mereghetti, S. +1 more
Using 2.5 Ms of data obtained by the INTEGRAL satellite in 2003-2004, we discovered persistent hard X-ray emission from the soft gamma-ray repeater SGR 1900+14. Its 20-100 keV spectrum is well described by a steep power law with photon index Γ=3.1±0.5 and flux 1.5×10-11 erg cm-2 s-1. Contrary to SGR 1806-20, the on…
Elemental abundances in the atmosphere of clump giants
Soubiran, C.; Korotin, S. A.; Bienaymé, O. +4 more
Aims.The aim of this paper is to provide the fundamental parameters and abundances for a large sample of local clump giants with a high accuracy. This study is a part of a big project, in which the vertical distribution of the stars in the Galactic disc and the chemical and dynamical evolution of the Galaxy are being investigated.
Methods: .Th…
The XMM-Newton/Chandra monitoring campaign of the Galactic center region. Description of the program and preliminary results
Wijnands, R.; Homan, J.; van der Klis, M. +10 more
We present the first results of our X-ray monitoring campaign on a 1.7 square degree region centered on Sgr A* using the satellites XMM-Newton and Chandra. The purpose of this campaign is to monitor the behavior (below 10 keV) of X-ray sources (both persistent and transient) which are too faint to be detected by monitoring instruments aboard other…
The Chandra view of the 3C/FR I sample of low luminosity radio-galaxies
Capetti, A.; Grandi, P.; Balmaverde, B.
We present results from Chandra observations of the 3C/FR I sample of low luminosity radio-galaxies. We detected a power-law nuclear component in 12 objects out of the 18 with available data. In 4 galaxies we detected nuclear X-ray absorption at a level of NH ∼ (0.2{-}6) × 1022 cm-2. X-ray absorbed sources are asso…
The sky distribution of positronium annihilation continuum emission measured with SPI/INTEGRAL
Knödlseder, J.; Shrader, C. R.; Schanne, S. +15 more
We present a measurement of the sky distribution of positronium (Ps) annihilation continuum emission obtained with the SPI spectrometer on board ESA's INTEGRAL observatory. The only sky region from which significant Ps continuum emission is detected is the Galactic bulge. The Ps continuum emission is circularly symmetric about the Galactic centre,…