Search Publications
Estimating Black Hole Masses in Active Galactic Nuclei Using the Mg II λ2800 Emission Line
Ho, Luis C.; Yuan, Weimin; Zhou, Hongyan +6 more
We investigate the relationship between the linewidths of broad Mg II λ2800 and Hβ in active galactic nuclei (AGNs) to refine them as tools to estimate black hole (BH) masses. We perform a detailed spectral analysis of a large sample of AGNs at intermediate redshifts selected from the Sloan Digital Sky Survey, along with a smaller sample of archiv…
A New Dynamical Model for the Black Hole Binary LMC X-1
Remillard, Ronald A.; McClintock, Jeffrey E.; Gou, Lijun +10 more
We present a dynamical model of the high mass X-ray binary LMC X-1 based on high-resolution optical spectroscopy and extensive optical and near-infrared photometry. From our new optical data we find an orbital period of P = 3.90917 ± 0.00005 days. We present a refined analysis of the All Sky Monitor data from RXTE and find an X-ray period of P = 3…
On the Nature of the Prototype Luminous Blue Variable Ag Carinae. I. Fundamental Parameters During Visual Minimum Phases and Changes in the Bolometric Luminosity During the S-Dor Cycle
Hillier, D. J.; Rossi, C.; Whitelock, P. A. +3 more
We present a detailed spectroscopic analysis of the luminous blue variable (LBV) AG Carinae (AG Car) during the last two visual minimum phases of its S-Dor cycle (1985-1990 and 2000-2003). The analysis reveals an overabundance of He, N, and Na, and a depletion of H, C, and O, on the surface of the AG Car, indicating the presence of a CNO-processed…
Analysis of Galactic late-type O dwarfs: more constraints on the weak wind problem
Bouret, J. -C.; Martins, F.; Hillier, D. J. +3 more
Aims: We investigate the stellar and wind properties of a sample of late-type O dwarfs. Previous analyses of such stars have found very low mass-loss rates; rates much lower than predicted by theory (the weak wind problem).
Methods: Far-UV to optical spectra of five Galactic O stars were analyzed: HD 216898 (O9IV/O8.5V), HD 326329 (O9V), HD 66…
An Analysis of the Shapes of Interstellar Extinction Curves. VI. The Near-IR Extinction Law
Fitzpatrick, E. L.; Massa, D.
We combine new observations from the Hubble Space Telescope's Advanced Camera of Survey with existing data to investigate the wavelength dependence of near-IR (NIR) extinction. Previous studies suggest a power law form for NIR extinction, with a "universal" value of the exponent, although some recent observations indicate that significant sight li…
Parameters of Herbig Ae/Be and Vega-type stars
Eiroa, C.; Montesinos, B.; Mora, A. +1 more
Context: This work presents the characterization of 27 young early-type stars, most of them in the age range 1-10 Myr, and three suspected hot companions of post-T Tauri stars belonging to the Lindroos binary sample. Most of these objects show IR excesses in their spectral energy distributions, which are indicative of the presence of disks. The wo…
Searching for a link between the magnetic nature and other observed properties of Herbig Ae/Be stars and stars with debris disks
Hamaguchi, K.; Hubrig, S.; Stelzer, B. +6 more
Context: Recently, evidence for the presence of weak magnetic fields in Herbig Ae/Be stars has been found in several studies.
Aims: We seek to expand the sample of intermediate-mass pre-main sequence stars with circular polarization data to measure their magnetic fields, and to determine whether magnetic field properties in these stars are cor…
FUSE Measurements of Far-Ultraviolet Extinction. III. The Dependence on R(V) and Discrete Feature Limits from 75 Galactic Sightlines
Gordon, Karl D.; Clayton, Geoffrey C.; Cartledge, Stefan
We present a sample of 75 extinction curves derived from Far Ultraviolet Spectroscopic Explorer (FUSE) far-ultraviolet spectra supplemented by existing International Ultraviolet Explorer (IUE) spectra. The extinction curves were created using the standard pair method based on a new set of dereddened FUSE+IUE comparison stars. Molecular hydrogen ab…
The Solar Neighborhood. XXI. Parallax Results from the CTIOPI 0.9 m Program: 20 New Members of the 25 Parsec White Dwarf Sample
Henry, Todd J.; Bergeron, P.; Dufour, P. +5 more
We present accurate trigonometric parallaxes for 20 new members of the 25 pc white dwarf (WD) sample as part of the Discovery and Evalution of Nearby Stellar Embers (DENSE) project.7 http://www.DenseProject.com Previously, there were a total of 112 WD systems with trigonometric parallaxes placin…
The Extension of the Transition Temperature Plasma into the Lower Galactic Halo
Savage, Blair D.; Wakker, Bart P.
Column densities for H I, Al III, Si IV, C IV, and O VI toward 109 stars and 30 extragalactic objects have been assembled to study the extensions of these species away from the Galactic plane into the Galactic halo. H I and Al III mostly trace the warm neutral and warm ionized medium, respectively, while Si IV, C IV, and O VI trace a combination o…