Search Publications
Coupling hydrodynamics with comoving frame radiative transfer. I. A unified approach for OB and WR stars
Hamann, W. -R.; Sander, A. A. C.; Shenar, T. +2 more
Context. For more than two decades, stellar atmosphere codes have been used to derive the stellar and wind parameters of massive stars. Although they have become a powerful tool and sufficiently reproduce the observed spectral appearance, they can hardly be used for more than measuring parameters. One major obstacle is their inconsistency between …
Effective temperatures of cataclysmic-variable white dwarfs as a probe of their evolution
Reichart, D. E.; Knigge, C.; Gänsicke, B. T. +29 more
We present HST spectroscopy for 45 cataclysmic variables (CVs), observed with HST/COS and HST/STIS. For 36 CVs, the white dwarf is recognisable through its broad Ly α absorption profile and we measure the white dwarf effective temperatures (Teff) by fitting the HST data assuming log g = 8.35, which corresponds to the average mass for CV…
Beyond the Kepler/K2 bright limit: variability in the seven brightest members of the Pleiades
Aigrain, S.; Grundahl, F.; Albrecht, S. +20 more
The most powerful tests of stellar models come from the brightest stars in the sky, for which complementary techniques, such as astrometry, asteroseismology, spectroscopy and interferometry, can be combined. The K2 mission is providing a unique opportunity to obtain high-precision photometric time series for bright stars along the ecliptic. Howeve…
Revealing the structure of the outer disks of Be stars
Carciofi, A. C.; Štefl, S.; Vieira, R. G. +9 more
Context. The structure of the inner parts of Be star disks (≲ 20 stellar radii) is well explained by the viscous decretion disk (VDD) model, which is able to reproduce the observable properties of most of the objects studied so far. The outer parts, on the other hand, are not observationally well-explored, as they are observable only at radio wave…
Detection of the Ultraviolet Spectrum of the Hot Subdwarf Companion of 60 Cygni (B1 Ve) from a Survey of IUE Spectra of Be Stars
Gies, Douglas R.; Wang, Luqian; Peters, Geraldine J.
We used archival International Ultraviolet Explorer (IUE) high-dispersion, short wavelength spectra data to search for evidence of the spectra of hot subdwarf companions of six rapidly rotating Be stars in binary systems. We searched for the signature of a hot companion through an analysis of the cross-correlation functions (CCFs) of observed and …
The Tarantula Massive Binary Monitoring. II. First SB2 orbital and spectroscopic analysis for the Wolf-Rayet binary R145
Ulaczyk, K.; Sander, A.; Crowther, P. A. +19 more
We present the first SB2 orbital solution and disentanglement of the massive Wolf-Rayet binary R145 (P = 159 d) located in the Large Magellanic Cloud. The primary was claimed to have a stellar mass greater than 300 M⊙, making it a candidate for being the most massive star known to date. While the primary is a known late-type, H-rich Wol…
Super-Eddington QSO RX J0439.6-5311 - II. Multiwavelength constraints on the global structure of the accretion flow
Done, Chris; Ward, Martin; Jin, Chichuan +1 more
We present a detailed multiwavelength study of an unobscured, highly super-Eddington Type-1 QSO RX J0439.6-5311. We combine the latest XMM-Newton observation with all archival data from infrared to hard X-rays. The optical spectrum is very similar to that of 1H 0707-495 in having extremely weak [O III] and strong Fe II emission lines, although the…
Discovery of a variable lead-rich hot subdwarf: UVO 0825+15
Reed, M. D.; Jeffery, C. S.; Woolf, V. M. +8 more
UVO 0825+15 is a hot bright helium-rich subdwarf which lies in K2 Field 5 and in a sample of intermediate helium-rich subdwarfs observed the Subaru High Dispersion Spectrograph. The K2 light curve shows low-amplitude variations, whilst the Subaru spectrum shows Pb IV absorption lines, indicative of a very high lead overabundance. UVO 0825+15 also …
The Massive CO White Dwarf in the Symbiotic Recurrent Nova RS Ophiuchi
Mikołajewska, Joanna; Shara, Michael M.
If accreting white dwarfs (WDs) in binary systems are to produce type Ia supernovae (SNe Ia), they must grow to nearly the Chandrasekhar mass and ignite carbon burning. Proving conclusively that a WD has grown substantially since its birth is a challenging task. Slow accretion of hydrogen inevitably leads to the erosion, rather than the growth of …
Extending the Calibration of C IV-based Single-epoch Black Hole Mass Estimators for Active Galactic Nuclei
Treu, Tommaso; Barth, Aaron J.; Assef, Roberto J. +5 more
We provide an updated calibration of C IV λ 1549 broad emission line-based single-epoch (SE) black hole (BH) mass estimators for active galactic nuclei (AGNs) using new data for six reverberation-mapped AGNs at redshift z=0.005{--}0.028 with BH masses (bolometric luminosities) in the range {10}6.5{--}{10}7.5 {M}⊙ …