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X-Ray Spectrum of the TYCHO SNR Observed with EXOSAT
Robba, N. R.; Taylor, B. G.; Morini, M. +2 more
The Gas Scintillation and Medium Energy instruments onboard EXOSAT measured the continuum and line emission spectrum in the Tycho supernova remnant. For the first time the iron line at 6.53 keV is clearly resolved from the continuum, in addition to the lines from S, Ar and Ca. The comparison with a non-equilibrium ionisation model (Hamilton et al …
A search for X-ray emitting coronal structures in algol
Parmar, A. N.; White, N. E.; Culhane, J. L. +3 more
Algol was observed with the low energy imaging X-ray telescope and the medium energy detectors on the ESA EKOSAT spacecraft during the time of secondary optical eclipse when the B star passes in front of its K type companion. An examination of the X-ray light curves allows us to set preliminary lower limits to the size of an X-ray emitting corona …
Space Telescope observations of aurorae on the giant planets
Caldwell, J.; Wagener, R.
For the distant giant planets, Uranus and Neptune, the observation of aurorae may be the best astronomical technique for the detection of planetary magnetic fields, with implications for the structure and composition of their interiors. Aurorae may be detected by emssion of H I Ly α (1216 Å) and by H2 bands near 1600 Å. The latter are i…
Constraints on the Galactic Distribution of Cosmic Rays from the Cos-B Gamma-Ray Data
Strong, A. W.; Hermsen, W.; Lebrun, F. +7 more
The diffuse component of the galactic high energy gamma rays results mainly from the interaction of CR nuclei and electrons with the nuclei of the interstellar gas. An additional contribution is obtained from the interaction of CR electrons with the interstellar photons through the inverse-Compton (IC) process. Gamma ray astronomy therefore offers…
EXOSAT results on the X-ray burster 2S 1254-690.
Parmar, A. N.; Courvoisier, T. J. -L.; Peacock, T.
Exosat observations of 2S1254-690 in August 1984 have confirmed the presence of periodic dips in the X-ray intensity. These dips occurred with a period of 3.9 hours and lasted for about 50 minutes. During individual dips, the observed X-ray flux oscillated several times between the quiescent level and an undetectable level on time scales varying f…
The typical interstellar extinction in the Small Magellanic Cloud.
Lequeux, J.; Prevot, L.; Rocca-Volmerange, B. +2 more
The authors give a mean UV extinction curve for the Small Magellanic Cloud which corresponds to the most common case and consequently to the most probable typical extinction law. The curve is almost linear in λ-1 without any evidence of the 2200 Å galactic feature. This is consistent with almost pure silicate interstellar grains and lit…
Comet Bowell 1980b
Feldman, P. D.; A'Hearn, M. F.; Schleicher, D. G. +2 more
The authors have carried out optical filter photometry and optical and ultraviolet spectrophotometry of Comet Bowell over the period November 1980 - June 1982. They have observed emission by OH at heliocentric distances to nearly 5 AU preperihelion with the OH emission implying a production rate which decreased, but with outbursts, as the comet ap…
The nature of symbiotic stars.
Kenyon, S. J.; Webbink, R. F.
Synthetic spectra from 0.1 to 3.5 µm are computed for various binary models of symbiotic stars. These models consist of three components: (1) a late-type giant or bright giant, (2) a hot companion, and (3) a surrounding nebula which is photoionized by the hot component. Hot stellar sources, disk accretion onto white dwarf stars, and disk acc…
The nature of magnetic activity in lower main sequence stars.
Vilhu, O.
The chromospheric-coronal emission of lower main sequence single and binary stars is correlated with an activity parameter of the form R = g(B-V)P-1, where P is the rotation period and g(B-V) is a function of the colour resembling the convective turnover time. A more general form of R, including also gravity, is suggested. The functiona…
The atmosphere of sublumious B stars.
Heber, U.; Kudritzki, R. P.; Hunger, K. +1 more
The spectra of eight high galactic latitude B stars, suspected to be subluminous, are analyzed for effective temperature, gravity, and helium to hydrogen ratio. Model atmospheres include (LTE) UV line blanketing (for T/eff/ less than or equal to 30,000 K) and NLTE effects (for T/eff/ greater than 30,000 K). Among the eight confirmed subdwarfs, six…