Search Publications
The Orbit of the Classical Cepheid SU Cygni
Evans, Nancy R.
New radial velocity data are presented for the classical Cepheid SU Cyg. An orbit has been derived from the new data, CORAVEL data by Imbert (1985) and data from 1906, and is presented in the paper. The pulsation radial velocity curves are compared from the plate material from David Dunlap Observatory (DDO) and several radial velocity spectrophoto…
An Exceptionally Bright, Compact Starburst Nucleus
Anderson, Scott F.; Massey, Philip; Mateo, Mario +2 more
We report observations of a remarkably bright (V ~ 13) starburst nucleus, 0833+652, which we have detected at radio, infrared, optical, ultraviolet, and X-ray wavelengths. Despite an observed flux at each of these wavelengths which is comparable to that of NGC 7714, often considered the "prototypical" example of the starburst phenomenon, 0833+652 …
Two Compact Planetary Nebulae of Moderate Excitation: NGC 6565 (3-4.5) and NGC 6644 (8-7.2)
Aller, Lawrence H.; Feibelman, Walter; Keyes, Charles D.
Data obtained with an image-tube scanner at the 3-m Shane telescope are combined with IUE data to obtain plasma diagnostics and chemical compositions for two planetary nebulae of moderately high excitation. Theoretical nebular models were calculated using stellar fluxes given by Husfeld et al. (1984) for T(asterisk) = 85,000 K, log g = 4.72, and e…
Observations of 1.4Hz quasi-periodic oscillations in CIR X-1.
Tennant, A. F.
Cir X-1 was observed to vary by a factor of about 1000 during an Exosat observation made in August 1985. The power spectrum is about 1/f from about 10 to the -5th to about 0.02 Hz. Above 0.02 Hz the power spectrum steepens. In this paper, results from the interval in which the source flux increased to the maximum are presented. During this interva…
The quasi-periodic oscillations of GX 349+2.
Stella, L.; Ponman, T. J.; Cooke, B. A.
A 50-hr EXOSAT observation of the bright galactic bulge X-ray source GX 349+2 reveals the presence of quasi-periodic oscillations (QPO) at a constant frequency of about 6 Hz. The QPO are strongest when the source is in transition between its quiescent and peak intensities. The coherency of the oscillations is unusually low, but shows no sign of de…
A correction method for the sensitivity loss of the LWR camera on board the IUE satellite.
Clavel, J.; Gilmozzi, R.; Prieto, A.
The loss of sensitivity of the IUE LWR camera (1950-3300 A) is analyzed. A total of 308 low-resolution spectra of the five UV standard stars BD + 75 325, BD + 28 4211, BD + 33 2642, HD 93521, and HD 60753, obtained from 1978 to October 1983, are compared. The loss of sensitivity is found to vary rapidly with wavelength, reaching a maximum of 3 per…
Coordinated X-ray and optical observations of the pulsating X-ray transient A 1118-61.
Motch, C.; Janot-Pacheco, E.; Pakull, M. W. +1 more
An EXOSAT observation of the field of the X-ray transient A 1118-61 reveals the presence of a weak hard X-ray source in the detectors of the medium energy experiment (ME). The detection by the Einstein IPC instrument of a similar hard X-ray source at a position consistent with that of the Be star He3-640, the proposed optical counterpart of A 1118…
The Detection of a High-Energy Break in the X-Ray Spectrum of the BL Lacertae Object PKS 0548-32
Maccagni, D.; Giommi, P.; Barr, P.
The results of a deep EXOSAT observation of the BL Lac object PKS 0548-32 performed in 1986 March are presented. The 0.05-10 keV X-ray spectrum is characterized by a relatively flat (power-law energy spectral index α ~ 0.9) continuum below 5 keV which steepens at higher energies. There is no evidence for any excess absorption intrinsic to the BL L…
An X-Ray Flare from a B9+ Post--T Tauri Star System in the Field of the Seyfert Galaxy III ZW 2
Tagliaferri, G.; Pallavicini, R.; Giommi, P. +2 more
We report the serendipitous discovery by EXOSAT of a flaring X-ray source in the field of the Seyfert type I galaxy III Zw 2. In contrast to an earlier report that attributed the variability observed by the medium energy experiment to III Zw 2, we show that the variability was entirely due to the serendipitous source. We identify this source with …
The Algol-like Binary TT Hydrae: The Stars, Circumstellar Matter, and Superionized Plasma
Plavec, Mirek J.
The characteristics of the eclipsing binary system TT Hydrae are now determined with a reliability surpassing many other Algol-like binaries. The primary component is a B9.5 V main-sequence star with a mass of 2.25 m_sun;, radius 1.9 R_sun;, effective temperature 9800K, and surface gravity log g = 4.23. The secondary star has a mass of 0.41 m_sun;…