Search Publications
Present-day cosmic abundances. A comprehensive study of nearby early B-type stars and implications for stellar and Galactic evolution and interstellar dust models
Przybilla, N.; Nieva, M. -F.
Context. Early B-type stars are ideal indicators for present-day cosmic abundances since they preserve their pristine abundances and typically do not migrate far beyond their birth environments over their short lifetimes, in contrast to older stars like the Sun. They are also unaffected by depletion onto dust grains, unlike the cold/warm interstel…
The warm gas atmosphere of the HD 100546 disk seen by Herschel. Evidence of a gas-rich, carbon-poor atmosphere?
van Dishoeck, E. F.; Bruderer, S.; Herczeg, G. J. +1 more
Context. With the Herschel Space Observatory, lines of simple molecules (C+, O, and high-J lines of CO, Jup ≳ 14) have been observed in the atmosphere of protoplanetary disks. When combined with ground-based data on [C i], all principle forms of carbon can be studied. These data allow us to test model predictions for the main…
The Galactic WC stars. Stellar parameters from spectral analyses indicate a new evolutionary sequence
Sander, A.; Hamann, W. -R.; Todt, H.
Context. The life cycles of massive stars from the main sequence to their explosion as supernovae or gamma ray bursts are not yet fully clear, and the empirical results from spectral analyses are partly in conflict with current evolutionary models. The spectral analysis of Wolf-Rayet stars requires the detailed modeling of expanding stellar atmosp…
Properties of Galactic early-type O-supergiants. A combined FUV-UV and optical analysis
Bouret, J. -C.; Hillier, D. J.; Fullerton, A. W. +1 more
Aims: We aim to constrain the properties and evolutionary status of early and mid-spectral type supergiants (from O4 to O7.5). These posses the highest mass-loss rates among the O stars, and exhibit conspicuous wind profiles.
Methods: Using the non-LTE wind code cmfgen we simultaneously analyzed the FUV-UV and optical spectral range to d…
HST-COS Observations of AGNs. I. Ultraviolet Composite Spectra of the Ionizing Continuum and Emission Lines
Shull, J. Michael; Danforth, Charles W.; Stevans, Matthew
The ionizing fluxes from quasars and other active galactic nuclei (AGNs) are critical for interpreting the emission-line spectra of AGNs and for photoionization and heating of the intergalactic medium. Using ultraviolet spectra from the Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope (HST), we have directly measured the rest-frame …
A Far-ultraviolet Atlas of Low-resolution Hubble Space Telescope Spectra of T Tauri Stars
Herczeg, Gregory J.; Valenti, Jeff A.; Brown, Alexander +6 more
We present a far-ultraviolet (FUV) spectral atlas consisting of spectra of 91 pre-main-sequence stars. Most stars in this sample were observed with the Space Telescope Imaging Spectrograph and Advanced Camera for Surveys on the Hubble Space Telescope (HST). A few archival spectra from the International Ultraviolet Explorer and the Goddard High Res…
Reexamination of the Infrared Excess-Ultraviolet Slope Relation of Local Galaxies
Inoue, Akio K.; Murata, Katsuhiro L.; Takeuchi, Tsutomu T. +2 more
The relation between the ratio of infrared (IR) and ultraviolet (UV) flux densities (the infrared excess: IRX) and the slope of the UV spectrum (β) of galaxies plays a fundamental role in the evaluation of the dust attenuation of star-forming galaxies, especially at high redshifts. Many authors, however, have pointed out that there is a significan…
HR 5907: Discovery of the most rapidly rotating magnetic early B-type star by the MiMeS Collaboration
Rivinius, Th.; Wade, G. A.; Bohlender, D. A. +14 more
We report the discovery and analysis of a very strong magnetic field in the rapidly rotating early B-type star HR 5907, based on observations obtained as part of the Magnetism in Massive Stars (MiMeS) project. We infer a rotation period of 0.508 276+0.000 015-0.000 012 d from photometric and Hα EW measurements, making this th…
Accretion-related properties of Herbig Ae/Be stars. Comparison with T Tauris
Eiroa, C.; Montesinos, B.; Mora, A. +4 more
Context. The mass accretion rate M⊙;acc) is a key parameter that has not accurately been determined for a wide sample of Herbig Ae/Be (HAeBe) stars until recently.
Aims: We look for trends relating M⊙acc and the stellar ages (t), spectral energy distributions (SEDs), and disk masses for a sample of 38 HAeBe stars, compar…
First spectro-interferometric survey of Be stars. I. Observations and constraints on the disk geometry and kinematics
Hofmann, K. -H.; Meilland, A.; Millour, F. +5 more
Context. Classical Be stars are hot non-supergiant stars surrounded by a gaseous circumstellar disk that is responsible for the observed infrared-excess and emission lines. The phenomena involved in the disk formation still remain highly debated.
Aims: To progress in the understanding of the physical process or processes responsible for the m…