Search Publications
The Relationship between Luminosity and Broad-Line Region Size in Active Galactic Nuclei
Kaspi, Shai; Peterson, Bradley M.; Maoz, Dan +3 more
We reinvestigate the relationship between the characteristic broad-line region size (RBLR) and the Balmer emission-line, X-ray, UV, and optical continuum luminosities. Our study makes use of the best available determinations of RBLR for a large number of active galactic nuclei (AGNs) from Peterson et al. Using their determina…
Evolution of the Solar Activity over Time and Effects on Planetary Atmospheres. I. High-Energy Irradiances (1-1700 Å)
Güdel, Manuel; Guinan, Edward F.; Audard, Marc +1 more
We report on the results of the Sun in Time multiwavelength program (X-rays to UV) of solar analogs with ages covering ~0.1-7 Gyr. The chief science goals are to study the solar magnetic dynamo and to determine the radiative and magnetic properties of the Sun during its evolution across the main sequence. The present paper focuses on the latter go…
First Results from the CHARA Array. I. An Interferometric and Spectroscopic Study of the Fast Rotator α Leonis (Regulus)
Gies, D. R.; Berger, D. H.; McAlister, H. A. +13 more
We report on K-band interferometric observations of the bright, rapidly rotating star Regulus (type B7 V) made with the CHARA Array on Mount Wilson, California. Through a combination of interferometric and spectroscopic measurements, we have determined for Regulus the equatorial and polar diameters and temperatures, the rotational velocity and per…
High-Resolution Radio Observations of the Colliding-Wind Binary WR 140
Dougherty, S. M.; Claussen, M. J.; Zauderer, B. A. +2 more
Milliarcsecond resolution Very Long Baseline Array (VLBA) observations of the archetype W-R+O star colliding-wind binary (CWB) system WR 140 are presented for 23 epochs between orbital phases 0.74 and 0.97. At 8.4 GHz, the emission in the wind-collision region (WCR) is clearly resolved as a bow-shaped arc that rotates as the orbit progresses. We i…
UVBLUE: A New High-Resolution Theoretical Library of Ultraviolet Stellar Spectra
Chavez, M.; Rodríguez-Merino, L. H.; Buzzoni, A. +1 more
We present an extended ultraviolet-blue (850-4700 Å) library of theoretical stellar spectral energy distributions computed at high resolution, λ/Δλ=50,000. The UVBLUE grid, as we named the library, is based on LTE calculations carried out with ATLAS9 and SYNTHE codes developed by R. L. Kurucz and consists of nearly 1800 entries that cover a large …
The Ionized Gas and Nuclear Environment in NGC 3783. V. Variability and Modeling of the Intrinsic Ultraviolet Absorption
Kaiser, Mary Elizabeth; Brandt, W. N.; Kaspi, Shai +13 more
We present results on the location, physical conditions, and geometry of the outflow in the Seyfert 1 galaxy NGC 3783 from a study of the variable intrinsic UV absorption. Based on analysis of 18 observations with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope and six observations with the Far Ultraviolet Spectroscopi…
The Optical and Ultraviolet Spectral Energy Distributions of Short-Period Black Hole X-Ray Transients in Outburst
Hynes, R. I.
We compile optical and UV spectra of a sample of ``typical'' short-period black hole X-ray transients in outburst. We also survey determinations of interstellar extinction and distance to deredden spectra and compare absolute fluxes. Hence, we perform a comparative study of the broadband spectral energy distributions (SEDs). We find that, given su…
On the Limb Darkening, Spectral Energy Distribution, and Temperature Structure of Procyon
Ludwig, H. -G.; Kervella, P.; Aufdenberg, J. P.
We have fit synthetic visibilities from three-dimensional (CO5BOLD+PHOENIX) and one-dimensional (PHOENIX, ATLAS 12) model stellar atmospheres of Procyon (F5 IV) to high-precision interferometric data from the VLT Interferometer (K band) and from the Mark III interferometer (500 and 800 nm). These data sets provide a test of theoretical …
FUSE Measurements of Far-Ultraviolet Extinction. II. Magellanic Cloud Sight Lines
Martin, P. G.; Gordon, Karl D.; Sofia, Ulysses J. +8 more
We present an extinction analysis of nine reddened/comparison star pairs in the Large and Small Magellanic Clouds (LMC and SMC) based on Far-Ultraviolet Spectroscopic Explorer (FUSE) FUV observations. To date, just two LMC sight lines have probed dust grain composition and size distributions in the Magellanic Clouds using spectral data for wavelen…
Coronagraphic Imaging of Pre-Main-Sequence Stars with the Hubble Space Telescope Space Telescope Imaging Spectrograph. I. The Herbig Ae Stars
Roberge, A.; Gull, T. R.; Sitko, M. L. +10 more
STIS white-light coronagraphic imaging has been carried out for 14 nearby, lightly reddened Herbig Ae stars, providing data on the environments and disks associated with these stars. No disks are detected in our data when the Herbig Ae star is accompanied by a stellar companion at r<=2''. We find that the optical visibility of protop…