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Rotational modulation and flares on RS CVn and BY DRA systems. VII. simultaneous X-ray, radio and optical data for the dMe star YZ CMi on 4/5 March 1985.
Doyle, J. G.; Butler, C. J.; van den Oord, G. H. J. +1 more
Broad-band photometric observations of YZ CMi show a 1.2mag U-band flare at 19:55 UT on 4 March 1985, however, simultaneous X-ray observations from EXOSAT show no detectable increase. Two possible explanations for the lack of an X-ray flare may be i) a flare occurring low in the chromosphere, where the chromosphere may not have been coupled to the…
An accretion disc in the broad-line radio galaxy 3C 390.3 ?
Penston, M. V.; Perez, E.; Moles, M. +2 more
The permitted broad component of the Hβ emission line in the broadline radio galaxy (BLRG) 3C390.3 presents a double-peaked structure, similar to that seen in cataclysmic variables. The profile of the line is well fitted by a relativistic accretion disc with an intermediate inclination to the line-of-sight.
The Ultraviolet Calibration of the Hubble Space Telescope. II. A Correction for the Change in Sensitivity of the SWP Camera on the IUE
Grillmair, Carl J.; Bohlin, Ralph C.
The IUE data on standard stars that will be the basis of UV absolute photometric calibration for the Hubble Space Telescope must be corrected for the changes that are apparent in the low-dispersion spectra of the five standard stars. A set of 895 spectra is presently analyzed in order to determine the change in sensitivity of the SWP camera for th…
The interstellar extinction in the open clusters TR 14, TR 15, TR 16/Cr 232 and CR 228 in NGC 3372 New near-infrared photometry.
Roth, M.; Ruiz, M. T.; Tapia, M. +1 more
Near-infrared JHKL photometry of more than 200 stars, members of the open clusters Tr 14, Tr 15, Tr 16, Cr 228 and Cr 232 in the Carina Nebula are presented. From comparing these results with the available visual photometry and spectroscopy, it is found that, except in Tr 15, the intracluster reddening is characterized by a 'normal' extinction law…
A Test of Synthetic Accretion Disk Spectra Using Ultraviolet Flux Distributions of Nova-like Variables
Wade, Richard A.
Ultraviolet (UV) fluxes and other data for a sample of nine novalike cataclysmic variables are assembled from the literature. The UV fluxes and colors are compared to spectra of steady state model accretion disks, constructed using either Planck functions or model stellar atmosphere spectra as elementary radiators. Deficiencies are found with both…
A non-LTE stellar atmosphere study of nitrogen-rich early-type stars.
Butler, K.; Kudritzki, R. P.; Herrero, A. +4 more
Spectrograms of a sample of nitrogen-rich early type stars (OBN stars) are analyzed differentially to normal stars of similar spectral types by means of NLTE methods. Effective temperatures, gravities and atmospheric helium contents are derived by fitting theoretical profiles of hydrogen and helium lines to the observations. The abundance analysis…
Opacity enhancements in the stellar wind of 68 Cygni - not "shells" or "puffs".
Howarth, Ian D.; Prinja, Raman K.
Results presented from a study of variability in the stellar wind of 68 Cyg [O7.5 III((f))], based on 33 IUE high-resolution spectra taken over ≡7 days in 1986 August. Significant changes are evident in the Si IV resonance line profiles on time-scales as short as ≡1 hr; these changes are characterized by broad low-velocity (≡0.55v) absorption enha…
Colliding Stellar Winds in the Eclipsing Wolf-Rayet Binary V444 Cygni
Shore, Steven N.; Brown, Douglas N.
High resolution spectra of V444 Cygni have been obtained using the International Ultraviolet Explorer Satellite. These spectra span both eclipses and include one observation at third quadrature. Together with seven archival spectra, they provide reasonably complete phase coverage for the system. The variations in the P Cygni profiles of the He(II)…
The Abundances of Carbon and Nitrogen in I ZW 18
Garnett, Donald R.; Dufour, Reginald J.; Shields, Gregory A.
We present IUE and McDonald IDS spectrophotometry of the NW H II region in the most oxygen-poor galaxy known, I Zw 18. The C III] λ1909 and [N II] λ6583 emission lines were detected for the first time in this galaxy. Using a photoionization model for the H II region, we derive 12 + log N(X)/N(H) = 6.94 +/- 0.24 for C, 5.99 +/- 0.16 for N, and 7.24…
The 1985 May superoutburst of the dwarf nova OY Carinae - II. IUE andEXOSAT observations.
Sonneborn, G.; van Paradijs, J.; Charles, P. A. +4 more
The authors present ultraviolet (IUE) and X-ray (EXOSAT) observations of the eclipsing dwarf nova OY Carinae during the superoutburst of 1985 May. From the lack of X-ray eclipse and UV behaviour they deduce that the X-ray flux originates in an optically thin corona comparable in size to the Roche lobe, and not directly from the white dwarf or boun…