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The ultraviolet spectra of the O and B stars in the young galactic cluster NGC 6530.
Boehm-Vitense, E.; Hodge, P.; Boggs, D.
The UV spectra between 1200 and 3000 A of stars in the young galactic cluster NGC 6530 and the surrounding association are studied. From the UBV colors and empirical as well as theoretical calibrations, the T(eff) and L for those stars which follow a sequence in the H-R diagram corresponding to the main sequence are determined. From a comparison w…
Observations of narrow absorption components in the ultraviolet spectrum of zeta Ophiuchi.
Howarth, I. D.; Willis, A. J.; Prinja, R. K.
Narrow absorption components due to the resonance transitions of C IV and N V are noted to be present in all 33 high resolution IUE spectra of Zeta Ophiuchi obtained between 1978 and 1981, though Doppler shifted by -1385 km/sec. An examination of previous observations shows these features to have been present for at least 12 years, and it is deter…
The depletion of pre-interstellar matter and an examination of NI II oscillator strengths.
Cardelli, J. A.
IUE observations of the B2.5 V star α Sco B have been used to analyze the absorption lines that arise in the circumstellar shell around the M1.5 Iab star α Sco A. In addition to resonant lines of Fe II, Si II, Mg II, Mn II, and S II, most of the resonant lines of Ni II are also present at strengths above 40 mÅ. A fit of these Ni II lines to a curv…
The chromospheres of classical cepheids. III. A search for transition region emission lines.
Parsons, S. B.; Schmidt, E. G.
In previous studies of Cepheid chromospheres with the IUE, we found that the chromospheric emission is strongly dependent on the period of the star and varies substantially through the cycle. For the shortest period star in our sample, δ Cep, we were able to detect little significant chromospheric emission in the short wavelength region, and we we…
Ultraviolet high-resolution spectroscopy of the X-ray binary SK 160/SMC X-1.
Howarth, I. D.; Hammerschlag-Hensberge, G.; Kallman, T. R.
High-resolution IUE spectra of Sk 160, the optical counterpart of the X-ray source SMC X-1, show substantial variations with orbital phase of the resonance P Cygni profiles. These variations are ascribed to the changing ionization state in the stellar wind caused by the X-rays emitted by the companion, as suggested by Hatchett and McCray and first…
The eclipse of epsilon Aurigae in the ultraviolet.
Ferluga, S.; Hack, M.; Boehm, C.
Ultraviolet low-resolution spectra of Epsilon Aurigae (F0Ia +) have been taken with IUE during the partial and total phase of the present eclipse; they are compared with a set of corresponding pre-eclipse spectra. The following conclusions are derived. A hot component, dominant in far UV, is associated with the extended body that eclipses the prim…
Spectroscopic analysis of the suspected AM star 15 Vulpeculae.
Takeda, Y. -I.
The suspected Am star 15 Vul is characterized using the ATLAS-6 model-atmosphere program of Kurucz (1979) and spectrograms (resolution 10 and 4 A/mm) obtained with the coudespectrograph of the 1.88-m reflector at Okayama Astrophysical Observatory during September and October 1981; comparison stars are 28 And and 9 Aur. The data and calculated abun…
Ultraviolet and visible flare observations of EQ Pegasi B.
Raymond, J. C.; Baliunas, S. L.
EQ Peg AB (dM43+dM5.5e) was monitored in the visible at the Whipple Observatory and ultraviolet with IUE on September 2, 1981. In the visible spectrophotometry of EQ Peg B the H-beta emission strengthened by a factor of 2 relative to the nearby stellar continuum within a few minutes and decayed over an hour. This flare in EQ Peg B was coincident w…
IUE observations of the X-ray binary A0538-66 : spectroscopic study of a strange stellar system.
Howarth, I. D.; Willis, A. J.; Prinja, R. K. +1 more
The results of extensive IUE monitoring of the optical counterpart of the recurrent periodic LMC X-ray transient A0538-66 are presented. Even when the system is not in outburst dramatic spectral variations occur, accompanied by changes in the temperature and surface area of the continuum emitting region. It is shown that, in spite of these variati…
The UV spectrum of the Seyfert 1 galaxy NGC 7469.
Westin, B. A. M.
Results from an investigation of thirty-two IUE spectra of the Seyfert 1 galaxy NGC 7469 are presented. During the observation period, from June 1978 to December 1982, the continuum at 1500 Å (observed wavelength) has been found to vary by a factor of about two. The strong emission lines are broad (FWZI 10,000 - 25,000 km s-1) and asymm…