Search Publications
The Ultraviolet Spectroscopic Properties of Local Starbursts: Implications at High Redshift
Robert, Carmelle; Heckman, Timothy M.; Leitherer, Claus +2 more
We report the results of a systematic study of the vacuum ultraviolet (λ ~= 1150-2000 Å) spectra of a sample of 45 starburst and related galaxies observed with the IUE satellite. These span broad ranges in metallicity (from 0.02 to 3 times solar), bolometric luminosity (~107-4 × 1011 L⊙), and galaxy properties (e.g…
Multiwavelength Observations of a Dramatic High-Energy Flare in the Blazar 3C 279
Maraschi, L.; Ghisellini, G.; Pian, E. +69 more
The blazar 3C 279, one of the brightest identified extragalactic objects in the γ-ray sky, underwent a large (factor of ~10 in amplitude) flare in γ-rays toward the end of a 3 week pointing by Compton Gamma Ray Observatory (CGRO), in 1996 January-February. The flare peak represents the highest γ-ray intensity ever recorded for this object. During …
Starburst-like Dust Extinction in the Small Magellanic Cloud
Gordon, Karl D.; Clayton, Geoffrey C.
The recent discovery that the ultraviolet (UV) dust extinction in starburst galaxies is similar to that found in the Small Magellanic Cloud (SMC) motivated us to reinvestigate the UV extinction found in the SMC. We have been able to improve significantly on previous studies by carefully choosing pairs of well-matched reddened and unreddened stars.…
New Constraints on the Continuum Emission Mechanism of Active Galactic Nuclei: Intensive Monitoring of NGC 7469 in the X-Ray and Ultraviolet
Malkan, M. A.; Nandra, K.; Clavel, J. +5 more
We have undertaken near-continuous monitoring of the Seyfert 1 galaxy NGC 7469 in the X-ray with RXTE over a ~30 day baseline. The source shows strong variability with a root mean square (rms) amplitude of ~16% and peak-to-peak variations of a factor of order 2. Simultaneous data over this period were obtained in the ultraviolet (UV) using IUE, ma…
Hubble Space Telescope Goddard High Resolution Spectrograph Observations of the Be + sdO Binary φ Persei
Gies, Douglas R.; Peters, Geraldine J.; Ferrara, Elizabeth C. +4 more
Mass transfer during the evolution of intermediate-mass stars in a close binary system can result in a rejuvenated and spun-up secondary star (which may appear as a rapidly rotating Be star) orbiting an unseen, stripped-down, remnant companion. One of the best candidates for such a system is the long-period (127 days) binary φ Per. Here we present…
Steps toward Determination of the Size and Structure of the Broad-Line Region in Active Galactic Nuclei. XIII. Ultraviolet Observations of the Broad-Line Radio Galaxy 3C 390.3
Shull, J. M.; Malkan, M. A.; Martin, P. G. +44 more
As part of an extensive multiwavelength monitoring campaign, the International Ultraviolet Explorer satellite was used to observe the broad-line radio galaxy 3C 390.3 during the period 1994 December 31-1996 March 5. Spectra were obtained every 6-10 days. The UV continuum varied by a factor of 7 through the campaign, while the broad emission lines …
Sirius B: A New, More Accurate View
Barstow, M. A.; Bruhweiler, F. C.; Holberg, J. B. +2 more
Long-standing questions regarding the temperature, gravity, mass, and radius of the well-known white dwarf Sirius B are considered in light of new data. Recently obtained Extreme Ultraviolet Explorer (EUVE) observations and reprocessed IUE NEWSIPS data have produced a new, well-defined effective temperature of 24,790 +/- 100 K and a surface gravit…
Coronal and Transition Region Structure in the RS Canum Venaticorum Binaries V711 Tauri, AR Lacertae, and II Pegasi. I. Data Analysis and Emission Measure Distributions
Jordan, C.; Griffiths, N. W.
We present a study of the transition regions and coronae of the RS CVn binaries V711 Tau, AR Lac, and II Peg. Archival data from the Extreme Ultraviolet Explorer (EUVE), International Ultraviolet Explorer (IUE), Goddard High-Resolution Spectrograph (GHRS), and a variety of X-ray telescopes have been analyzed and modeled. Emission measure distribut…
Color-Luminosity Relations for the Resolved Hot Stellar Populations in the Centers of M31 and M32
Ferguson, Henry C.; Brown, Thomas M.; Stanford, S. A. +1 more
We present Faint Object Camera (FOC) ultraviolet images of the central 14" × 14" of Messier 31 and Messier 32. The hot stellar populations detected in the composite UV spectra of these nearby galaxies are partially resolved into individual stars, and their individual colors and apparent magnitudes are measured. We detect 433 stars in M31 and 138 s…
Hyperfine Induced Transitions as Diagnostics of Isotopic Composition and Densities of Low-Density Plasmas
Judge, Philip G.; Jönsson, Per; Brage, Tomas +5 more
The J = 0 --> J' = 0 radiative transitions, usually viewed as allowed through two-photon decay, may also be induced by the hyperfine (HPF) interaction in atoms or ions having a nonzero nuclear spin. We compute new and review existing decay rates for the nsnp 3PoJ --> ns2 1SJ'=0