328 citations · 3.2k across the 59 of their papers we have counts for
15 papers · 1 filter
Puzzling X-rays from the new colliding wind binary WR65
L. M. Oskinova, W. -R. Hamann
We report the discovery of variability in the X-ray emission from the Wolf-Rayet type star WR 65. Using archival Chandra data spanning over 5 yr we detect changes of the X-ray flux…
Two extremely luminous WN stars in the Galactic center with circumstellar emission from dust and gas
A. Barniske, L. M. Oskinova, W. -R. Hamann
We study relatively isolated massive WN-type stars in the Galactic center. The K-band spectra of WR102ka and WR102c are exploited to infer the stellar parameters and to compute syn…
A new outburst in LMC-N66
Miriam Pena, M. Teresa Ruiz, Patricio Rojo +2
This is the first report on the new outburst presented by the central star of the LMC-N66 nebula. This object was classified as a planetary nebula, however, its true nature is unde…
Mass loss from late-type WN stars and its Z-dependence: very massive stars approaching the Eddington limit
G. Graefener, W. -R. Hamann
The mass loss from Wolf-Rayet (WR) stars is of fundamental importance for the final fate of massive stars and their chemical yields. Its Z-dependence is discussed in relation to th…
Determining element abundances of [WC]-type Central Stars for probing stellar evolution and nucleosynthesis
H. Todt, M. Peña, W. -R. Hamann +1
[WC]-type CSPNs are hydrogen-deficient Central Stars of Planetary Nebulae showing strong stellar winds and a carbon-rich chemistry. We have analyzed new high-resolution spectra of…
Phase-dependent X-ray observations of the beta Lyrae system: No eclipse in the soft band
R. Ignace, L. M. Oskinova, W. L. Waldron +2
We report on observations of the eclipsing and interacting binary beta Lyrae from the Suzaku X-ray telescope. This system involves an early B star embedded in an optically and geom…
Neglecting the porosity of hot-star winds can lead to underestimating mass-loss rates
L. M. Oskinova, W. -R. Hamann, A. Feldmeier
Context: The mass-loss rate is a key parameter of massive stars. Adequate stellar atmosphere models are required for spectral analyses and mass-loss determinations. Present models…
The Galactic WN stars: Spectral analyses with line-blanketed model atmospheres versus stellar evolution models with and without rotation
W. -R. Hamann, G. Graefener, A. Liermann
CONTEXT: Very massive stars pass through the Wolf-Rayet (WR) stage before they finally explode. Details of their evolution have not yet been safely established, and their physics a…
Quantitative X-ray spectroscopy of massive stars
L. M. Oskinova, W. -R. Hamann, A. Feldmeier
Radiative transfer in a clumped winds is used to describe X-ray emission line profiles observed in the XMM-Newton RGS spectrum of the OI star Zeta Puppis. It is shown that this X-r…
High resolution X-ray spectroscopy of bright O type stars
L. M. Oskinova, A. Feldmeier, W. -R. Hamann
Archival X-ray spectra of the four prominent single, non-magnetic O stars Zeta Pup, Zeta Ori, Ksi Per and Zeta Oph, obtained in high resolution with Chandra HETGS/MEG have been stu…
The metallicity dependence of WR wind models
G. Gräfener, W. -R. Hamann
With the advance of stellar atmosphere modelling during the last few years, large progress in the understanding of Wolf-Rayet (WR) mass loss has been achieved. In the present paper…
O Star X-ray Line Profiles Explained by Radiation Transfer in Inhomogeneous Stellar Wind
L. M. Oskinova, A. Feldmeier, W. -R. Hamann
It is commonly adopted that X-rays from O stars are produced deep inside the stellar wind, and transported outwards through the bulk of the expanding matter which attenuates the ra…
The VLT-FLAMES Survey of Massive Stars: Observations in the Galactic Clusters NGC 3293, NGC 4755 and NGC 6611
C. J. Evans, S. J. Smartt, J. -K. Lee +23
We introduce a new survey of massive stars in the Galaxy and the Magellanic Clouds using the Fibre Large Array Multi-Element Spectrograph (FLAMES) instrument at the Very Large Tele…
Hydrodynamic model atmospheres for WR stars: Self-consistent modeling of a WC star wind
G. Gräfener, W. -R. Hamann
We present the first non-LTE atmosphere models for WR stars that incorporate a self-consistent solution of the hydrodynamic equations. The models account for iron-group line-blanke…
Runaway Acceleration of Line-Driven Winds: the Role of the Outer Boundary
Achim Feldmeier, Isaac Shlosman, Wolf-Rainer Hamann
Observations and theory suggest that line driven winds from hot stars and luminous accretion disks adopt a unique, critical solution which corresponds to maximum mass loss rate. We…