Search Publications
Imaging the circumstellar envelopes of AGB stars
Mauron, N.; Huggins, P. J.
Aims.We report the results of an exploratory program to image the extended circumstellar envelopes of asymptotic giant branch (AGB) stars in dust-scattered galactic light. The goal is to characterize the morphology of the envelopes as a probe of the mass-loss process.
Methods: .The observations consist of short exposures with the VLT and longe…
Spectral changes during dipping in low-mass X-ray binaries due to highly-ionized absorbers
Kaastra, J. S.; Díaz Trigo, M.; Parmar, A. N. +2 more
X-ray observations have revealed that many microquasars and low-mass X-ray binaries (LMXBs) exhibit narrow absorption features identified with resonant absorption from Fe XXV and Fe XXVI and other abundant ions. In many well studied systems there is evidence for blue-shifts, indicating outflowing plasmas. We succesfully model the changes in both t…
The multi-phase gaseous halos of star forming late-type galaxies. I. XMM-Newton observations of the hot ionized medium
Pietsch, W.; Dettmar, R. -J.; Rossa, J. +2 more
This study presents first results from an X-ray mini-survey carried out with XMM-Newton to investigate the diffuse Hot Ionized Medium in the halos of nine nearby star-forming edge-on spiral galaxies. Diffuse gaseous X-ray halos are detected in eight of our targets, covering a wide range of star formation rates from quiescent to starburst cases. Fo…
The luminosity function of young star clusters: implications for the maximum mass and luminosity of clusters
Bastian, N.; Larsen, S. S.; Gieles, M. +1 more
We introduce a method to relate a possible truncation of the star cluster mass function at the high mass end to the shape of the cluster luminosity function (LF). We compare the observed LFs of five galaxies containing young star clusters with synthetic cluster population models with varying initial conditions. The LF of the SMC, the LMC and NGC 5…
X-ray sources and magnetic reconnection in the X3.9 flare of 2003 November 3
Magdalenić, J.; Temmer, M.; Veronig, A. M. +5 more
Context: .Recent RHESSI observations indicate an apparent altitude decrease of flare X-ray loop-top (LT) sources before changing to the commonly observed upward growth of the flare loop system.
Aims: .We performed a detailed study of the LT altitude decrease for one well observed flare in order to find further hints on the physics of this phen…
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…