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Rotational velocities of later B type and A type stars as determined from ultraviolet versus visual line profiles.
Sonneborn, G.; Carpenter, K. G.; Slettebak, A.
Theoretical line profiles of the Si III 1299 and Fe II 2756 lines are computed for rotating B5-A7 model stars, and compared with observed profiles from IUE spectra to derive rotational velocities. Real differences in widths for ultraviolet as compared with visual line profiles exist in the sample of B type stars (but not for the A type rapidly rot…
Similar photospheres, different mantles : a study of four O stars.
Underhill, A. B.
The present investigation is concerned with a comparison of the spectra of four O stars (10 Lac, S Mon, HD 46223, and Zeta Pup) which have similar effective temperatures, taking into account an attempt to find the reason for differences regarding the spectral type of the stars. The photospheres of the stars are examined, taking into account the ef…
A study of the expanding envelope around the pole-on Be star HR 5223.
Dachs, J.; Hanuschik, R.
A spectroscopic/photometric survey was performed on the Be star HR 5223 to characterize physical conditions in high- and low-velocity regions and the source regions of observed stellar winds and Balmer line-emitting envelopes of Be stars. Data were gathered from 1978-82 at La Silla and with the IUE spacecraft, and comprised UBV, IR, and UV photome…
IUE observations of high velocity interstellar gas toward stars within the OB association CYG OB1.
Pettini, M.; Phillips, A. P.; Welsh, B. Y.
High-velocity interstellar gas has been detected in IUE spectra of the stars HD 192639, 193514 and 193443 which are members of the OB association Cyg OB1. In all cases where blending between different absorption components is not severe, the authors have derived ion column densities appropriate to the high-velocity gas by fitting theoretical profi…
Gas in cosmic voids.
Brosch, N.; Gondhalekar, P. M.
Absorption lines at the redshifts of cosmic voids in Perseus-Pisces and Bootes have been detected in the ultraviolet spectra of background quasars. The detection of metal lines suggests chemical enrichment of gas in the voids in support of explosion dominated model of formation of galaxies (Ostriker and Cowie, 1981).
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…