Search Publications
The Carbon Chemistry in Interstellar Clouds toward Moderately Reddened Stars
Lambert, D. L.; Federman, S. R.
New data for C2 toward X Per, HD 206267, HD 207198, and Gamma Cep, for CH and CN toward X Per, and for CO toward HD 207198 have been obtained. The column densities of CH, C2, CN, and CO toward the stars in the Cepheus OB2 association are similar to reddened directions in Perseus and in Ophiuchus, indicating a similarity in physical conditions for …
Improved Bow Shock Models for Herbig-Haro Objects: Application to HH 2A
Hartigan, Patrick; Raymond, John C.; Hartmann, Lee
An improved version of the bow shock theory previously applied to Herbig-Haro objects is presented. The modifications provide a more accurate calculation of the ionization state of material entering the bow shock. The revised preionization does not drastically affect the emission-line predictions for a 200 km/s bow shock model, though the effects …
Quasi-periodic Oscillations in the X-Ray Flux of the Rapid Burster (MXB 1730-335)
Haberl, F.; Stella, L.; Parmar, A. N. +3 more
The authors report on the results of an EXOSAT observation of the "Rapid Burster" in 1985 August during an active state. Forty 1 - 10 minute long type 2 bursts were detected together with persistent emission. Quasi-periodic oscillations (QPO) were observed in 23 bursts with frequencies between 2 and 5 Hz. The average frequency of the QPO during th…
The Discovery of the 2 Hour Modulated X-Ray Source EXO 033319-2554.2, an AM Herculis System
Tagliaferri, G.; Stella, L.; Giommi, P. +2 more
The authors report the discovery of EXO 033319-2554.2, a soft X-ray source with 100% modulation of its soft X-ray flux, found during a systematic analysis of all of the EXOSAT soft X-ray data. The soft X-ray light curve, which has an on-off behavior, shows a period of 127.7±3.0 minutes. The bright part of the cycle lasts 0.55 in phase and is cut b…
High-Velocity Ultraviolet Iron, Silicon, Oxygen, and Sulfur Absorption Features Associated with the Remnant of SN 1006
Fesen, Robert A.; Wu, Chi-Chao; Hamilton, Andrew J. S. +1 more
New low-dispersion IUE spectra of a faint sdOb star located in a direction near the center of the SN 1006 remnant are presented. The UV spectrum of the star exhibits several strong absorption features which are uncharacteristic of its optical sdOB star classification. The identification by Wu et al. (1983) of very broad absorption features at 1610…
Mass Loss in a B2 IIIe Star: omega Orionis 1978--1984
Sonneborn, George; Grady, C. A.; Guinan, E. F. +4 more
Combination of long-term optical polarimetric, photometric, spectrometric, and ultraviolet spectral data have confirmed that all observed portions of ω Ori's outer atmosphere are variable on a variety of time scales. The spectacular polarization episodes are correlated with the presence of continuum flux and color changes but are not correlated wi…
A Spectral Dissection of the Ultraviolet Emissions of Capella
Ayres, Thomas R.
Phase-resolved observations of Capella (α Aurigae A: G5 III+G0 III) were conducted with the IUE in order to separate the spectrum of the core-helium-burning (CHeB) primary (Aa) from that of the fast-rotating, chromospherically active secondary (Ab). The ultraviolet emissions of the primary were compared to those of the four K0 giants of the Hyades…
X-Ray Spectrum and Variability of the Black Hole Candidate LMC X-3
Maraschi, L.; Tanzi, E. G.; Chiappetti, L. +4 more
LMC X-3 was observed on seven occasions in 1983-1984 with the EXOSAT satellite covering various orbital phases. No phase related variability was detected, while the X-ray flux increased gradually by ~ 30% in two weeks. Analysis of the short term variability in terms of autocorrelation reveals a minimum time scale of 600 s, with an rms amplitude of…
An Exceptional Change in the X-Ray Flux and Spectrum of the Seyfert 1 Galaxy E1615+061
Piro, L.; Perola, G. C.; Molteni, D. +1 more
The Seyfert 1 galaxy E1615 + 061 was found with the HEAO 1 A-2 experiment to possess a very soft X-ray spectrum, with an energy spectral index α >~ 2, much greater than typical (α ~ 0.6) for objects of the same class. The two EXOSAT observations described in this Letter show that in 1985 July this object was fainter than the HEAO 1 measurement …
Spectrophotometry and Chemical Composition of the Oxygen-poor Bipolar Nebula NGC 6164--5
Dufour, Reginald J.; Parker, Robert A. R.; Henize, Karl G.
The paper presents new ground-based and IUE spectrophotometry of several positions in NGC 6164-5 surrounding the Population I Of star HD 148937. Electron temperatures, densities, and abundances are derived for the various positions in the nebula using spectral line information. For all of the regions observed, Ne/H is depleted by an amount compara…