Search Publications
Quantitative studies of the optical and UV spectra of Galactic early B supergiants. I. Fundamental parameters
Massa, D.; Prinja, R. K.; Searle, S. C. +1 more
Aims: We undertake an optical and ultraviolet spectroscopic analysis of a sample of 20 Galactic B0-B5 supergiants of luminosity classes Ia, Ib, Iab, and II. Fundamental stellar parameters are obtained from optical diagnostics and a critical comparison of the model predictions to observed UV spectral features is made.
Methods: Fundamental param…
Disks around CQ Tauri and MWC 758: dense PDR or gas dispersal?
Chapillon, E.; Guilloteau, S.; Dutrey, A. +1 more
Context: The overall properties of disks surrounding intermediate PMS stars (HAe) are not yet well constrained by current observations. The disk inclination, which significantly affects spectral energy distribution modeling, is often unknown.
Aims: We attempted to resolve the disks around CQ Tau and MWC 758 to provide accurate constraints on t…
The weak magnetic field of the O9.7 supergiant ζOrionisA
Bouret, J. -C.; Martins, F.; Donati, J. -F. +4 more
We report here the detection of a weak magnetic field of 50-100G on the O9.7 supergiant ζOrionisA (ζOriA), using spectropolarimetric observations obtained with NARVAL at the 2-m Télescope Bernard Lyot atop Pic du Midi (France). ζOriA is the third O star known to host a magnetic field (along with θ1OriC and HD191612), and the first detec…
Variability of Disk Emission in Pre-Main-Sequence and Related Stars. I. HD 31648 and HD 163296: Isolated Herbig Ae Stars Driving Herbig-Haro Flows
Polomski, Elisha F.; Russell, Ray W.; Sitko, Michael L. +13 more
Infrared photometry and spectroscopy covering a time span of a quarter-century are presented for HD 31648 (MWC 480) and HD 163296 (MWC 275). Both are isolated Herbig Ae stars that exhibit signs of active accretion, including driving bipolar flows with embedded Herbig-Haro (HH) objects. HD 163296 was found to be relatively quiescent photometrically…
Modeling Ultraviolet Wind Line Variability in Massive Hot Stars
Blomme, R.; Lobel, A.
We model the detailed time-evolution of discrete absorption components (DACs) observed in P Cygni profiles of the Si IV λ1400 resonance doublet lines of the fast-rotating supergiant HD 64760 (B0.5 Ib). We adopt the common assumption that the DACs are caused by corotating interaction regions (CIRs) in the stellar wind. We perform 3D radiative trans…
Detection of a Hot Subdwarf Companion to the Be Star FY Canis Majoris
Gies, Douglas R.; Peters, Geraldine J.; Grundstrom, Erika D. +1 more
The rapid rotation of Be stars may be caused in some cases by past mass and angular momentum accretion in an interacting binary in which the mass donor is currently viewed as a small, hot subdwarf stripped of its outer envelope. Here we report on the spectroscopic detection of such a subdwarf in the Be binary system FY Canis Majoris from the analy…
High-resolution optical spectroscopy of Plaskett's star
Martins, F.; Gosset, E.; Rauw, G. +3 more
Context: Plaskett's star (
Constraining Cosmic Evolution of Type Ia Supernovae
Becker, A. C.; Sollerman, J.; Spyromilio, J. +27 more
We present a large-scale effort of creating composite spectra of high-redshift SNe Ia and comparing them to low-redshift counterparts in an attempt to understand possible cosmic evolution of SNe Ia, which has major implications for studies of dark energy. Through the ESSENCE project, we have obtained 107 spectra of 88 high-redshift SNe Ia with exc…
Binarity in Cool Asymptotic Giant Branch Stars: A GALEX Search for Ultraviolet Excesses
Sahai, R.; Sánchez Contreras, C.; Gil de Paz, A. +1 more
The search for binarity in AGB stars is of critical importance for our understanding of how planetary nebulae acquire the dazzling variety of aspherical shapes which characterizes this class. However, detecting binary companions in such stars has been severely hampered due to their extreme luminosities and pulsations. We have carried out a small i…
Stellar Wind Variations during the X-Ray High and Low States of Cygnus X-1
Crenshaw, D. M.; Kaper, L.; Herrero, A. +10 more
We present results from Hubble Space Telescope ultraviolet spectroscopy of the massive X-ray and black hole binary system, HD 226868 = Cyg X-1. The spectra were obtained at both orbital conjunction phases in 2002 and 2003, when the system was in the X-ray high/soft state. The UV stellar wind lines suffer large reductions in absorption strength whe…