Search Publications
Third spectra of rare earth elements in chemically peculiar stars : IUE spectra.
Cowley, Charles R.; Greenberg, Marcella
Third spectra of the lanthanides can be identified in IUE spectra of certain chemically peculiar (CP) A stars with the help of statistical techniques. These spectra are rather weak. The intrinsically strongest lines are probably only a few tens of mA in equivalent widths, and the detections are perhaps best described as marginal. There is no doubt…
EXOSAT Observations of the TYCHO Supernova Remnant
Robba, N. R.; Taylor, B. G.; Smith, A. +3 more
The Gas Scintillation Proportional Counter and the Medium Energy Instruments on board EXOSAT were used to measure the X-ray spectrum of the Tycho supernova remnant over the range 1.5 - 10 keV. The emission lines due to S, Ar, Ca, and Fe (≡6.48 keV) are clearly resolved from the underlying continuum which is measured to have a temperature of 6.5±0.…
High-energy gamma rays as a probe of cosmic-ray spectral differences throughout the Galaxy. II - A comparison with radio synchrotron emission
Schlickeiser, R.; Bloemen, J. B. G. M.; Reich, W. +1 more
A spectral analysis of the galactic high-energy γ-ray emission (300 MeV-6 GeV) is presented using the observations obtained with the COS-B satellite. Large-scale spectral variations are found and compared with recent results from a study of the galatic radio-continuum emission at 408 and 1420 MHz. The combination of the radio and γ-ray findings es…
Variable C : an S Doradus-type variable in M 33.
Stahl, O.; Humphreys, R. M.; Leitherer, C. +2 more
Variable C is one of the Hubble-Sandage variables in M 33. Our photometric and spectroscopic observations obtained during one of its rare maxima show that Variable C's variations are typical of luminous blue variables especially those of the S Doradus type. Its spectrum at maximum light suggests a temperature of 7500 K for its expanding optically …
AG Carinae. II. IUE observations of the ring nebula.
The, P. S.; Viotti, R.; Cassatella, A. +1 more
The authors describe the first ultraviolet observations of the ring nebula surrounding the P Cyg superluminous star AG Car. The spectrum of the nebula resembles that of the central star with strong Fe II and Mg II emission lines. The nebular/stellar continuum ratio is nearly constant from 2000 to 3200 Å. This result and the derived surface brightn…
The Companion of the White Dwarf G29-38 as a Brown Dwarf
Greenstein, Jesse L.
The strong infrared excess discovered by Zuckerman and Becklin (1987) in the white dwarf G29-38 (ZZ Psc) has been ascribed to a "brown dwarf". A variety of Palomar spectra of the white dwarf shows it to be an essentially normal DA4V, without spectral peculiarities that might have arisen from accretion or interaction with a close companion. The mul…
EXOSAT observations of M dwarf stars in the solar neighborhood.
Schmitt, J. H. M. M.; Rosso, C.
The authors present EXOSAT observations of a sample of nearby (d < 6 pc) M dwarf stars most of which have not previously been observed in X-rays. All the target stars were detected except one (Gl 754, spectral type M7). The X-ray luminosities derived are in the typical range of M dwarf X-ray luminosities derived from Einstein Observatory data, …
Indirect IUE Observations of O VI from Photoexcited Fluorescence Lines of Fe ii, Present in the Spectrum of RR Telescopii
Johansson, Sveneric
A new, highly excited level of Fe II at 13.7 eV has been established by means of six lines in the laboratory spectrum below 2000 Å. Confirming transitions appear in the infrared region. Four of the ultraviolet lines coincide with previously unidentified lines in the IUE spectrum of RR Tel reported by Penston et al. (1983). One of the remaining UV …
Ultraviolet and Optical Spectrophotometry of the Seyfert 1.8 Galaxy Markarian 609
Cohen, Ross D.; Ake, T. B.; Rudy, Richard J.
We present simultaneous ultraviolet and optical observations of the Seyfert 1.8 galaxy Markarian 609. The broad hydrogen lines are in the ratio Lyα/Hβ/Hα = 16/1.0/5.0. The Hβ(broad)/[O III] ratio has increased since the 1976 measurements of Osterbrock, and the Hα/Hβ ratio is no longer as large as when he classified Mrk 609 as a type 1.8 Seyfert ga…
Large photometric variations on II Peg in Sept/Nov 1986 : implications for the starspot hypothesis.
Doyle, J. G.; Butler, C. J.; Morrison, L. V. +1 more
Large cyclic photometric variations of ΔV= 0.5 mag are observed on II Peg in late 1986. Modelled in terms of starspots, this implies a large spot group covering at least 40% (and perhaps as much as 55%) of the projected area of one hemisphere.