Search Publications
Quasars as standard candles. III. Validation of a new sample for cosmological studies
Marconi, A.; Vignali, C.; Gilli, R. +15 more
We present a new catalogue of ∼2400 optically selected quasars with spectroscopic redshifts and X-ray observations from either Chandra or XMM-Newton. The sample can be used to investigate the non-linear relation between the ultraviolet (UV) and X-ray luminosity of quasars as well as to build a Hubble diagram up to a redshift of z ∼ 7.5. We selecte…
A naked-eye triple system with a nonaccreting black hole in the inner binary
Rivinius, Th.; Baade, D.; Klement, R. +2 more
Several dozen optical echelle spectra demonstrate that
Is HR 6819 a triple system containing a black hole?. An alternative explanation
Shenar, T.; Sana, H.; Hawcroft, C. +10 more
Context. HR 6819 was recently proposed to be a triple system consisting of an inner B-type giant plus black hole (BH) binary with an orbital period of 40 d and an outer Be tertiary. This interpretation is mainly based on two inferences: that the emission attributed to the outer Be star is stationary and that the inner star, which is used as mass c…
The stellar and wind parameters of six prototypical HMXBs and their evolutionary status
Hamann, W. -R.; Oskinova, L. M.; Sander, A. A. C. +7 more
Context. High-mass X-ray binaries (HMXBs) are exceptional astrophysical laboratories that offer a rare glimpse into the physical processes that govern accretion on compact objects, massive-star winds, and stellar evolution. In a subset of the HMXBs, the compact objects accrete matter solely from winds of massive donor stars. These so-called wind-f…
Heavy-metal enrichment of intermediate He-sdOB stars: the pulsators Feige 46 and LS IV-14°116 revisited
Heber, U.; Latour, M.; Irrgang, A. +3 more
Hot subdwarf stars of spectral types O and B represent a poorly understood phase in the evolution of low-mass stars, in particular of close compact binaries. A variety of phenomena are observed, which make them important tools for several astronomical disciplines. For instance, the richness of oscillations of many subdwarfs are important for aster…
The various accretion modes of AM Herculis: Clues from multi-wavelength observations in high accretion states
Sablowski, D.; Schwope, A. D.; Traulsen, I. +1 more
We report on XMM-Newton and NuSTAR X-ray observations of the prototypical polar, AM Herculis, supported by ground-based photometry and spectroscopy, all obtained in high accretion states. In 2005, AM Herculis was in its regular mode of accretion, showing a self-eclipse of the main accreting pole. X-ray emission during the self-eclipse was assigned…
The nature of the companion in the Wolf-Rayet system EZ Canis Majoris
Schmutz, W.; Koenigsberger, G.
Context. EZ Canis Majoris is a classical Wolf-Rayet star whose binary nature has been debated for decades. It was recently modeled as an eccentric binary with a periodic brightening at periastron of the emission originating in a shock heated zone near the companion.
Aims: The focus of this paper is to further test the binary model and to cons…
Visible and near-infrared spectro-interferometric analysis of the edge-on Be star o Aquarii
Meilland, A.; Carciofi, A. C.; Domiciano de Souza, A. +11 more
Aims: We present a detailed visible and near-infrared spectro-interferometric analysis of the Be-shell star o Aquarii from quasi-contemporaneous CHARA/VEGA and VLTI/AMBER observations.
Methods: We analyzed spectro-interferometric data in the Hα (VEGA) and Brγ (AMBER) lines using models of increasing complexity: simple geometric models, k…
Stellar wind models of central stars of planetary nebulae
Krtička, J.; Kubát, J.; Krtičková, I.
Context. Fast line-driven stellar winds play an important role in the evolution of planetary nebulae, even though they are relatively weak.
Aims: We provide global (unified) hot star wind models of central stars of planetary nebulae. The models predict wind structure including the mass-loss rates, terminal velocities, and emergent fluxes from…
Estimating black hole masses: Accretion disk fitting versus reverberation mapping and single epoch
Celotti, Annalisa; Ghisellini, Gabriele; Sbarrato, Tullia +1 more
We selected a sample of 28 Type 1 active galactic nuclei for which a black hole mass has been inferred using the reverberation mapping technique and single epoch scaling relations. All 28 sources show clear evidence of the "Big Blue Bump" in the optical-UV band whose emission is produced by an accretion disk (AD) around a supermassive black hole. …