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…
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…
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 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…
Ultraviolet Spectroscopy of Supernovae: The First Two Years of Swift Observations
Panagia, N.; Pian, E.; Gehrels, N. +13 more
We present the entire sample of ultraviolet (UV) spectra of supernovae (SNe) obtained with the Ultraviolet/Optical Telescope (UVOT) on board the Swift satellite during the first two years of observations (2005/2006). A total of 29 UV-grism and 22 V-grism spectra of nine SNe have been collected, of which six are thermonuclear (Type Ia) and three co…
Suzaku Observation of a Hard Excess in 1H 0419 - 577: Detection of a Compton-Thick Partial-Covering Absorber
Turner, T. J.; Kraemer, S. B.; Reeves, J. N. +2 more
We present results from a 200 ks Suzaku observation of 1H 0419 - 577 taken during 2007 July. The source shows a strong excess of counts above 10 keV compared to the extrapolation of models based on previous data in the 0.5-10 keV band. The "hard excess" in 1H 0419 - 577 can be explained by the presence of a Compton-thick partial-covering absorber …
The Ultraviolet Spectrum and Physical Properties of the Mass Donor Star in HD 226868 = Cygnus X-1
Kaper, L.; Herrero, A.; Bolton, C. T. +8 more
We present an examination of high-resolution, ultraviolet (UV) spectroscopy from Hubble Space Telescope of the photospheric spectrum of the O-supergiant in the massive X-ray binary HD 226868 = Cyg X-1. We analyzed this and ground-based optical spectra to determine the effective temperature and gravity of the O9.7 Iab supergiant. Using non-LTE, lin…
HD 100453: A Link Between Gas-Rich Protoplanetary Disks and Gas-Poor Debris Disks
Carmona, A.; Hamaguchi, K.; Henning, Th. +15 more
HD 100453 has an IR spectral energy distribution (SED) which can be fit with a power law plus a blackbody. Previous analysis of the SED suggests that the system is a young Herbig Ae star with a gas-rich, flared disk. We reexamine the evolutionary state of the HD 100453 system by refining its age (based on a candidate low-mass companion) and by exa…