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The Peculiar Planetary Nebula in M22
Cohen, J. G.; Gillett, F. C.
The source discovered by the IRAS satellite near the center of the globular cluster M22, IRAS 18333-2357, has been studied using the IUE satellite and a ground-based optical telescope. The northern component of the close pair of stars is not a member of the cluster. The southern component is a hot star with T(eff) of about 50,000 K illuminating a …
X-Ray Timing and Spectral Measurements of X Persei
Robba, N. R.; Warwick, R. S.
The results of an X-ray timing and spectral study of the Be star X-ray binary system X Per are reported, based on two series of Exosat observations. The timing measurements indicate that the neutron star in the X Per system was in a net spin-down mode during the 1984-1986 period and that this trend may have been in progress since 1978. The phase-a…
On the Nature of Newly Formed Dust around the Hydrogen-deficient Star V348 Sagittarii
Drilling, J. S.; Schoenberner, D.
IUE spectra of V348 Sgr have been used to determine the extinction law from 1250 to 3080 A for circumstellar material recently ejected from it. This law differs from the standard extinction law in showing a bump at 2500 A rather than 2200 A, and in showing much lower extinction values for lambda less than 2000 A. These differences are attributed t…
Energetic Ion Fluxes in the Inner Coma of Comet P/Halley
Balsiger, H.; Young, D. T.; Goldstein, R. +3 more
The particle phenomenon observed inside the magnetic field-free cavity near the nucleus of Comet P/Halley by the Giotto Ion Mass Spectrometer High-Energy Range Spectrometer sensor is studied. The question of access to the cavity of particles ionized farther out in the coma is addressed. A quantitative model of a mechanism for creating the observed…
Non--Equilibrium Ionization Effects in the Supernova Remnant RCW 86
Kaastra, J. S.; Smith, A.; Peacock, A. +2 more
X-ray images show that the SNR RCW 86 consists of two emission regions. The electron temperature of both two regions is 3.4 keV. The low-energy flux (0.2-2 keV) is strongly enhanced compared to a simple thermal bremsstrahlung spectrum with Te = 3.4 keV fitted to the 2-10 keV data. This enhancement is most likely caused by nonequilibrium ionization…
Small-Amplitude Coherent Signals in the X-Ray Emission of NGC 4151
Piro, L.; Perola, G. C.; Fiore, F. +1 more
We present the results of the temporal analysis performed on four EXOSAT medium-energy observations of the Seyfert galaxy NGC 4151, selected for their long duration and background stability. The light curves can be adequately described in terms of regular trends (representing variations on time scales >= 1 day) to which small-amplitude fluctuat…
X-Ray Bursts from 4U 1705-44: Another Case of Burst Properties Dependent on the Strength of the Persistent Emission
Haberl, F.; van Paradijs, J.; Lewin, W. H. G. +3 more
Three Exosat observations are reported of the low-mass X-ray binary 4U 1705-44 during which X-ray bursts are detected. Seventeen bursts are recorded in the low-intensity state and seven bursts in the medium-intensity state, of which 22 are suitable for a detailed analysis. Correlations between the burst properties and the strength of the persisten…
X-Ray, Ultraviolet, and Optical Observations of the Intermediate Polar FO Aquarii (H2215-086)
Mukai, K.; Maraschi, L.; Tanzi, E. G. +9 more
An extensive set of quasi-simultaneous, multiwavelength observations of the intermediate polar FO Aqr (H2215-086) obtained in 1983-1985 with the Exosat and IUE satellites and from La Palma Observatory are presented. The rotational 21 minute period and sideband periods due to beating with the orbital modulation are observed in the optical band and …
Ultraviolet Extinction Differences within NGC 6530
Bohm-Vitense, Erika; Boggs, Don
Ultraviolet extinction curves are presented for 14 stars in the very young cluster NGC 6530. The variation of the short-wavelength extinction is consistent with that expected based on random errors alone, although the weakest extinction is found only toward the cluster center. Variations significantly larger than the measurement uncertainty are fo…
On the Possible Detection of Organic Dust-borne C 3H + Ions in the Coma of Comet Halley
Reme, H.; Korth, A.; Lin, R. P. +4 more
The heavy ion analyzer (PICCA) on board the Giotto spacecraft was used to determine the composition of positively charged ions in the environment of Comet Halley. Here it is argued that a distinct peak at 37 amu, observed in the mass spectrum inside the ionopause, is due to C3H(+). It is further argued that the dominant source of this ion, as well…