Search Publications

Detection of Boron, Cobalt, and Other Weak Interstellar Lines toward zeta Ophiuchi

Lambert, D. L.; Federman, S. R.; Gilliland, R. L. +1 more

Numerous weak lines from interstellar atomic species toward Zeta Ophiuchi were observed with the Goddard High-Resolution Spectrograph. Of particular note are the first interstellar detection of cobalt and the detection of boron in this sight line. These measurements provide estimates for the amount of depletion for the two elements. Boron, a volat…

Spectrophotometry of Wolf-Rayet Stars. I. Continuum Energy Distributions

Massey, Philip; Vacca, William D.; Conti, Peter S. +2 more

All available low-resolution IUE spectra are assembled for Galactic, LMC, and SMC W-R stars and are merged with ground-based optical and NIR spectra in order to collate in a systematic fashion the shapes of these energy distributions over the wavelength range 0.1-1 micron. They can be consistently fitted by a power law of the form F(lambda) is app…

Ultraviolet Transitions of Low Condensation Temperature Heavy Elements and New Data for Interstellar Arsenic, Selenium, Tellurium, and Lead

Federman, S. R.; Lambert, David L.; Cardelli, Jason A. +1 more

On the Lyman-Alpha Emission of Starburst Galaxies

Valls-Gabaud, David

Nearby starburst galaxies have consistently shown anomalous Lyα/Hβ ratios. By reanalyzing the published IUE/optical observations, we show that most starbursts present a normal Lyα emission, consistent with case B recombination theory, provided extinction laws appropriate to their metallicities are used. This implies that extinction is more importa…

The EXOSAT Medium Energy (ME) Sample of Dwarf Novae

Mukai, K.; Shiokawa, K.

We present our analysis of the EXOSAT medium energy (ME) archival data on dwarf novae. Many dwarf novae were observed with EXOSAT; unfortunately, a significant fraction resulted in nondetection or marginal detection with the ME instrument. Our analysis of the brightest dwarf nova, SS Cyg, shows little correlation between the count rate and the har…

Does a Luminosity-dependent Continuum Shape Cause the Baldwin Effect?

Zheng, Wei; Malkan, Matthew A.

We combine ground- and space-based spectrophotometry to measure the luminosity dependence of the shape of the optical/UV continuum in 108 QSO and 37 Seyfert 1 nuclei. The UV continuum at 1250 Å in high-luminosity QSOs, compared with the optical continuum at 6500 Å, is over one magnitude higher than that in the less luminous Seyfert galaxies. In te…

Silicon and Carbon Abundances in the Orion Nebula

Dufour, Reginald J.; Rubin, Robert H.; Walter, Donald K.

We assess the gas-phase abundances of Si and C from our recent measurements of Si(2+), C(2+), and C(+) in the Orion Nebula by expanding on our earlier 'blister' models. The C and Si abundances are derived from new IUE high-dispersion spectra of the C(2+) 1907, 1909 A and Si(2+) 1883, 1892 A lines and archival IUE data. Gas-phase Si/C = 0.016 in th…

Discovery of an Optical Synchrotron Jet in 3C 264

Boksenberg, A.; Barbieri, C.; Weigelt, G. +17 more

Observations with the Faint Object Camera on board the Hubble Space Telescope have revealed a new optical jet in the core of the elliptical galaxy NGC 3862 (3C 264). Morphologically, this jet is similar to the synchrotron jets seen in other galaxies, as it shows knots and bifurcations. The optical spectral index [-d log I(v)/d log v = α = 1.4] is …

The Quasi-periodic Oscillations and Very Low Frequency Noise of Scorpius X-1 as Transient Chaos: A Dripping Handrail?

Scargle, Jeffrey D.; Steiman-Cameron, Thomas; Young, Karl +3 more

We present evidence that the quasi-periodic oscillations (QPO) and very low frequency noise (VLFN) characteristic of many accretion sources are different aspects of the same physical process. We analyzed a long, high time resolution EXOSAT observation of the low-mass X-ray binary (LMXB) Sco X-1. The X-ray luminosity varies stochastically on time s…

GINGA Observations of the Coma Cluster and Studies of the Spatial Distribution of Iron

Hughes, John P.; Tanaka, Yasuo; Butcher, Jackie A. +1 more

The large area counters on the Japanese satellite Ginga have been used to determine the X-ray spectrum from the central region of the Coma cluster of galaxies over the energy range from 1.5 to 20 keV. The spectrum is well represented by an isothermal model of temperature 8.21+/-0.16 keV and a heavy element (iron) abundance of 0.212+/-0.027 relativ…