Search Publications
Dust reddening and extinction curves toward gamma-ray bursts at z > 4
Greiner, J.; Schady, P.; Krühler, T. +4 more
Context. Dust is known to be produced in the envelopes of asymptotic giant branch (AGB) stars, the expanded shells of supernova (SN) remnants, and in situ grain growth within the interstellar medium (ISM), although the corresponding efficiency of each of these dust formation mechanisms at different redshifts remains a topic of debate. During the f…
Detailed chemical compositions of the wide binary HD 80606/80607: revised stellar properties and constraints on planet formation
Mustill, A. J.; Yong, D.; Asplund, M. +5 more
Differences in the elemental abundances of planet-hosting stars in binary systems can give important clues and constraints about planet formation and evolution. In this study we performed a high-precision, differential elemental abundance analysis of a wide binary system,
Chemical content of the circumstellar envelope of the oxygen-rich AGB star R Doradus. Non-LTE abundance analysis of CO, SiO, and HCN
de Koter, A.; Decin, L.; Wyrowski, F. +5 more
Context. The stellar outflows of low- to intermediate-mass stars are characterised by a rich chemistry. Condensation of molecular gas species into dust grains is a key component in a chain of physical processes that leads to the onset of a stellar wind. In order to improve our understanding of the coupling between the micro-scale chemistry and mac…
Low-frequency photospheric and wind variability in the early-B supergiant HD 2905
Grundahl, F.; Fredslund Andersen, M.; Pallé, P. L. +5 more
Context. Despite important advances in space asteroseismology during the last decade, the early phases of evolution of stars with masses above 15 M⊙ (including the O stars and their evolved descendants, the B supergiants) have been only vaguely explored up to now. This is due to the lack of adequate observations for a proper characteriz…
An X-ray survey of the central molecular zone: Variability of the Fe Kα emission line
Ponti, G.; Morris, M. R.; Terrier, R. +4 more
There is now abundant evidence that the luminosity of the Galactic super-massive black hole (SMBH) has not always been as low as it is nowadays. The observation of varying non-thermal diffuse X-ray emission in molecular complexes in the central 300 pc has been interpreted as delayed reflection of a past illumination by bright outbursts of the SMBH…
Reanalysis of nearby open clusters using Gaia DR1/TGAS and HSOY
Reffert, Sabine; Piskunov, Anatoly E.; Kharchenko, Nina V. +3 more
Context. Open clusters have long been used to gain insights into the structure, composition, and evolution of the Galaxy. With the large amount of stellar data available for many clusters in the Gaia era, new techniques must be developed for analyzing open clusters, as visual inspection of cluster color-magnitude diagrams is no longer feasible. An…
First direct detection of a polarized companion outside a resolved circumbinary disk around CS Chamaeleonis
Ménard, F.; Schmidt, T. O. B.; Ginski, C. +18 more
Aims: To understand planet formation it is necessary to study the birth environment of planetary systems. Resolved imaging of young planet forming disks allows us to study this environment in great detail and find signs of planet-disk interaction and disk evolution. In the present study we aim to investigate the circumstellar environment of t…
Gaia DR2 reveals a very massive runaway star ejected from R136
Anderson, J.; Crowther, P. A.; Lennon, D. J. +14 more
A previous spectroscopic study identified the very massive O2 III star VFTS 16 in the Tarantula Nebula as a runaway star based on its peculiar line-of-sight velocity. We use the Gaia DR2 catalog to measure the relative proper motion of VFTS 16 and nearby bright stars to test if this star might have been ejected from the central cluster, R136, via …
Distances from the tip of the red giant branch to the dwarf galaxies dw1335-29 and dw1340-30 in the Centaurus group
Müller, Oliver; Jerjen, Helmut; Rejkuba, Marina
Context. The abundance and spatial distribution of dwarf galaxies are excellent empirical benchmarks against which to test models of structure formation on small scales. The nearby Centaurus group, with its two subgroups centered on Cen A and M 83, stands out as an important alternative to the Local Group for scrutinizing cosmological model predic…
Multi-wavelength campaign on NCG 7469. IV. The broad-band X-ray spectrum
Kriss, G. A.; Arav, N.; Bianchi, S. +17 more
We conducted a multi-wavelength 6-month campaign to observe the Seyfert Galaxy NGC 7469, using the space-based observatories HST, Swift, XMM-Newton and NuSTAR. We report the results of the spectral analysis of the seven simultaneous XMM-Newton and NuSTAR observations. The source shows significant flux variability within each observation, but the a…