Search Publications
Hydrogenated Amorphous Carbon Grains in Comet Halley?
Colangeli, L.; Fonti, S.; Bussoletti, E. +3 more
Recent IR observations of Comets Halley, Wilson, and Bradfield have shown the existence of an emission feature falling at around 3.4 microns. In this paper, it is shown that a good fit of both the IR continuum and the band can be obtained by assuming a simple thermal emission model based upon the optical properties of hydrogenated amorphous carbon…
High-Velocity Interstellar Gas in the Lines of Sight to the Wolf-Rayet Stars HD 97152 and HD 96548
Nichols-Bohlin, Joy; Fesen, Robert A.
The interstellar medium was studied in the direction to the WR stars HD 96548 and HD 97152, and the results are reported. New observational data on the UV spectra of several field stars near both these WR stars are presented. The high-velocity gas seen in the spectra of these stars suggests that the detected expanding interstellar gas structure co…
CO Observations of the Cepheus Flare. II. Gamma Rays from the Interstellar Gas and a Possible New COS B Source
Grenier, I. A.; Lebrun, F.
The correlation between the distribution of the interstellar gas in the Cepheus Flare region (100^deg^ <= l <= 141^deg^, 8^deg^ <= b <= 22^deg^) and that of the diffuse gamma radiation originating in these nearby clouds has been studied in detail. A maximum-likelihood analysis has been applied to compare maps of the atomic and molecula…
EXOSAT Observations of the Blazar PKS 1510-089
Singh, K. P.; Rao, A. R.; Vahia, M. N.
A detailed study of X-ray emission from the high-polarization quasar PKS 1510-089, also known as a blazar, is presented, based on the EXOSAT observations in 1984 and 1985. The data were obtained from the EXOSAT archives. There is no evidence for any variations in the X-ray intensity on hourly time scales during either of the two observations. The …
Orbital Variability in the Wind of the Massive X-Ray Binary HD 153919/4U 1700-37
Hammerschlag-Hensberge, G.; Howarth, Ian D.; Kallman, Timothy R.
A set of forty high-dispersion IUE spectra of HD 153919, the Of-type primary in the 4U 1700-37 X-ray binary system, have been examined for evidence of orbital profile variability associated with the Hatchett-McCray effect. Although the effect is negligible in the resonance lines of C IV, Si IV, and N V, some subordinate lines show clear orbital ch…
Search for Millisecond X-Ray Pulsations from the Galactic Bulge X-Ray Source GX 9+1
Michelson, P. F.; Norris, J. P.; Wood, K. S. +2 more
The recent discoveries of millisecond radio-pulsars with small period derivatives and quasi-periodic oscillations in bright Galactic X-ray sources have given rise to theories which predict that low-mass X-ray binaries should have low-amplitude X-ray pulsations with short, possibly millisecond, periods. Most previous searches for these pulsations s…
Differential Line Development and the Complex Structure of the Broad-Line Region in Fairall 9
Zheng, Wei; O'Brien, Paul T.
We find that the profiles of the UV emission lines Lyα, C IV λ1549, and Mg II λ2798, in the Seyfert 1 galaxy Fairall 9 vary such that the lines are broader when the object is brighter. The profile changes occur mainly near the line center for Lyα and C IV and in the wings for Mg II. These results indicate that the broad-line region (BLR) has a com…
Ultraviolet Observations of the Enigmatic Bipolar Nebula M1-92
Feibelman, Walter A.; Bruhweiler, Frederick C.
IUE observations of the bipolar nebula M1-92 indicate that this object is an evolved object and possibly a preplanetary nebula. Data acquired in the SWP camera clearly show a flat UV continuum indicative of a relatively unobscured O subdwarf. Data acquired in the long wavelength region of the SWP and in the LWP camera reveal an object which mimics…
EXOSAT Observations of the Rapidly Rotating Flare Star Gliese 890
Singh, K. P.; Rao, A. R.
This paper presents the first X-ray observations of the late-type dwarf flare star Gliese 890 using the low-energy (LE) and the medium energy (ME) detectors of the Exosat Observatory. A steady X-ray emission, most probably of coronal origin, is detected. No flaring activity is observed in X-ray observations. A combined spectral fit to the LE and M…
On the Interpretation of the EXOSAT Photometry of Two Hot DA White Dwarfs
Petre, Robert; Vennes, Stephane; Shipman, Harry L.
Exosat photometric observations of the hot DA white dwarfs GD 2 and EG 70 are presented and analyzed using model atmosphere and synthetic spectrum calculations. The numerical accuracy of the calculations and their impact on the reliability of the results are addressed. The optimum atmospheric parameters that explain the complete spectral coverage …