Search Publications
Soft X-Ray and Ultraviolet Emission Relations in Optically Selected AGN Samples
Brandt, W. N.; Schneider, Donald P.; Vignali, Cristian +2 more
Using a sample of 228 optically selected active galactic nuclei (AGNs) in the 0.01-6.3 redshift range with a high fraction of X-ray detections (81%-86%), we study the relation between rest-frame UV and soft X-ray emission and its evolution with cosmic time. The majority of the AGNs in our sample (155 objects) have been selected from the Sloan Digi…
An Analysis of the Shapes of Ultraviolet Extinction Curves. IV. Extinction without Standards
Fitzpatrick, E. L.; Massa, D.
In this paper we present a new method for deriving UV through IR extinction curves, based on the use of stellar atmosphere models to provide estimates of the intrinsic (i.e., unreddened) stellar spectral energy distributions (SEDs), rather than unreddened (or lightly reddened) standard stars. We show that this ``extinction without standards'' tech…
Determining the Physical Properties of the B Stars. II. Calibration of Synthetic Photometry
Fitzpatrick, E. L.; Massa, D.
We present a new calibration of optical (UBV, Strömgren uvbyβ, and Geneva) and near-IR (Johnson RIJHK and Two Micron All Sky Survey) photometry for B and early A stars derived from Kurucz ATLAS9 model atmospheres. Our sample of stars consists of 45 normal nearby B and early A stars that have high-quality, low-resolution IUE spectra and accurate Hi…
On the Ga II and Ga III Resonance Lines and the Implication for Chemical Stratification in HgMn Stars
Nielsen, K. E.; Leckrone, D. S.; Wahlgren, G. M. +2 more
The gallium abundance in HgMn stars has been reported to be different for analyses conducted from spectral lines in the optical versus those from the ultraviolet. We pursue this ultraviolet-optical discrepancy from a line-blending perspective by investigating the Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph (STIS) spectrum of …
Escape of Lyα Emission in the Starburst Galaxy Markarian 357: a Wind's Far Side
Keel, William C.
Hubble Space Telescope imaging and slitless spectroscopy are used to examine where the strong Lyα emission escapes from the interstellar medium in the starburst galaxy Mrk 357. An Hα image shows that the ionized gas is mostly in a global wind, rather than associated with the individual star-forming regions seen in the optical and UV continuum. The…
Spin-resolved Far-Ultraviolet Observations of the Magnetic White Dwarf in YY Draconis
Szkody, Paula; Sion, Edward M.; Hoard, D. W. +1 more
We observed the intermediate polar YY Draconis with the Far Ultraviolet Spectroscopic Explorer (FUSE), yielding an average far-UV spectrum, as well as spectra and spectrophotometric light curves resolved on the spin phase of the white dwarf in this system. We utilized the BINSYN software suite to calculate model spectra based on a simple system mo…