Showing papers by "John H. Black published in 1980"
TL;DR: In this article, the P Cygni profiles of strong resonance lines show substantial variations with orbital phase, attributed to the changing ionization state in the stellar wind caused by the X-ray emitting companion.
Abstract: UV spectra (obtained by the IUE) of HD 77581, associated with the binary X-ray source Vela X-1, show a spectrum typical of an early B-type supergiant. However, the P Cygni profiles of strong resonance lines show substantial variations with orbital phase. These variations can be ascribed to the changing ionization state in the stellar wind caused by the X-ray emitting companion. X-ray and spectroscopic and photometric optical observations, simultaneous with the IUE observations, indicate behavior consistent with previous epochs.
57 citations
40 citations
TL;DR: The analysis of IUE observations of a filament on the western edge of the Cygnus Loop yields a shock velocity of about 130 km/sec, significantly higher than the velocity estimated from the optical spectrum as discussed by the authors.
Abstract: The analysis of IUE observations of a filament on the western edge of the Cygnus Loop yields a shock velocity of about 130 km/sec, significantly higher than the velocity estimated from the optical spectrum. This velocity together with the high forbidden O III/H-beta ratio reported by Miller (1974) indicates that much of the hydrogen recombination region predicted by steady flow shock models is absent. This situation may occur because this part of the supernova remnant is in the shell-formation phase that accompanies the transition from the adiabatic to the snowplow phase or because the observed filament is a recently shocked cloud.
34 citations
15 Jun 1980
TL;DR: The analysis of IUE observations of a filament on the western edge of the Cygnus Loop yields a shock velocity of about 130 km/sec, significantly higher than the velocity estimated from the optical spectrum.
Abstract: The analysis of IUE observations of a filament on the western edge of the Cygnus Loop yields a shock velocity of about 130 km/sec, significantly higher than the velocity estimated from the optical spectrum. This velocity together with the high forbidden O III/H-beta ratio reported by Miller (1974) indicates that much of the hydrogen recombination region predicted by steady flow shock models is absent. This situation may occur because this part of the supernova remnant is in the shell-formation phase that accompanies the transition from the adiabatic to the snowplow phase or because the observed filament is a recently shocked cloud.
31 citations
TL;DR: In this paper, the ionization contours calculated by Hatchett and McCray, for a binary X-ray source in the stellar wind of the companion were discussed in terms of the ionisation contours.
Abstract: During April, May, and July of 1978, HDE 226868, the optical counterpart of Cygnus X-1, was repeatedly observed in the ultraviolet with the IUE satellite. Some X-ray and infrared observations have been made during the same period. The general shape of the spectrum is that expected from a late O supergiant. Strong absorption features are apparent in the ultraviolet, some of which have been identified. The equivalent widths of the most prominent lines appear to be modulated with the orbital phase. This modulation is discussed in terms of the ionization contours calculated by Hatchett and McCray, for a binary X-ray source in the stellar wind of the companion.
24 citations
TL;DR: Oscillator strengths (f-values) for twenty lines of the (0, 0) band and one line of the C /sup 1/Pi--X/sup 1 /..sigma../sup +/ system of HCl have been measured using quantitative photographic techniques.
Abstract: Oscillator strengths (f-values) for twenty lines of the (0, 0) band and one line of the (1, 0) band of the C /sup 1/Pi--X /sup 1/..sigma../sup +/ system of HCl have been measured using quantitative photographic techniques. The f-value for the R(0) line of the (0, 0) band at 129.0257 nm, which is the stronger of the two lines that have been searched for but not detected in diffuse interstellar clouds, is 0.185 +- 0.037. This value and the observations of absorption by chlorine species in the zeta Oph cloud have been used to reassess aspects of the chemical models of diffuse clouds.
23 citations
22 citations
TL;DR: In this article, the International Ultraviolet Explorer (IUEV) was used for observations of the absorption lines of C III, C IV, N V, Si III, and Si IV.
Abstract: Interstellar absorption lines have been observed toward 25 stars with the International Ultraviolet Explorer satellite. Results are presented for observations of interstellar lines of C III, C IV, N V, Si III, and Si IV. Strong lines of Si IV or C IV are seen toward 11 stars. The strengths of these lines are inconsistent with their formation in the same hot gas responsible for the interstellar O IV lines observed with the Copernicus ultraviolet spectrometer. Comparison with simple models of the ionization structures of H II regions around hot stars suggests that the observed column densities of Si III, Si IV, and C IV are in harmony with those expected in normal photoionized nebulae. The line of sight to HD 93250, and O3 V star near Eta Carinae, passes through highly ionized gas that shows features spanning 250 km/s in radial velocity. Stellar wind velocities are presented for 21 of the stars observed in this survey of interstellar absorption lines.
16 citations
TL;DR: In this article, the International Ultraviolet Explorer satellite (IUE) observations of the recent egress of the eclipsing binary VV Cep(M2Iabep + B) are presented.
Abstract: Observations with the International Ultraviolet Explorer satellite (IUE) of the recent egress of the eclipsing binary VV Cep(M2Iabep + B) are presented. Egress in the ultraviolet lagged behind the visible egress by 2 to 3 months, as a result of higher opacity of the M star atmosphere in the ultraviolet. Shortly after visible egress, the low-dispersion spectrum from 1200-1900 wavelengths was dominated by fluorescent emission lines arising in the atmosphere of the M star and excited by the ultraviolet continuum of the hot companion. High-dispersion spectra show a hot continuum blanketed by absorption lines, some of which weaken or disappear as the egress continues. A year after eclipse, the absorption spectrum is still too complex to permit determination of a spectral type for the hot companion. The Mg II h and k lines both exhibit asymmetric double-peaked emission features indicative of an expanding chromosphere in the M supergiant.
14 citations
TL;DR: The results of a campaign of monitoring HZ Her with the IUE satellite are presented in this paper, where the spectrum and light variation outside of eclipse are consistent with the Milgrom and Salpeter model for emission from the X-ray heated photosphere of the primary.
Abstract: The results of a campaign of monitoring HZ Her with the IUE satellite are presented. The spectrum and light variation outside of eclipse are consistent with the Milgrom and Salpeter model for emission from the X-ray heated photosphere of the primary. Near eclipse there is UV flux in excess of the prediction of the heated photosphere model, which shows significant 35 day variations and is consistent with an origin in a precessing disk, as described by Gerend and Boynton. The spectrum shows the strong emission lines of N V and C IV, which generally vary in the sense of the continuum. The N V/C IV ratio is greater than 2 near orbital phase 0.5 and approaches unity near eclipse. It is suggested that these emission lines are optically thick and arise from both the heated photosphere and the accretion disk.
10 citations
TL;DR: In this article, a broad absorption band near 5500 A, presumably molecular, with three possible band heads was observed on only one of two spectra taken one night apart, and two known molecules with wavelengths closest to the observed band heads are C2 and H2O(+), although there are problems with either of these as possible identifications.
Abstract: Visual spectra and photometry from 0.35 to 18 microns show that AFGL 2789 may be one of the most interesting of the infrared sources now identified with reflection nebulae. It has an Ae-type shell spectrum with strong emission lines of hydrogen, Fe II, Cr II, and Ti II, but the most remarkable feature is a broad absorption band near 5500 A, presumably molecular, with three possible band heads. This absorption band was present on only one of two spectra taken one night apart. The two known molecules with wavelengths closest to the observed band heads are C2 and H2O(+), although there are problems with either of these as possible identifications.
01 Jan 1980
01 Jan 1980
TL;DR: The results of recent observations of the column densities of chlorine species in diffuse interstellar clouds are inconsistent with the column density predicted by model calculations as discussed by the authors, and the use of new atomic and molecular data fails to decrease the discrepancy.
Abstract: The results of recent observations of the column densities of chlorine species in diffuse interstellar clouds are inconsistent with the column densities predicted by model calculations. The use of new atomic and molecular data fails to decrease the discrepancy. It is speculated that the exothermic reaction Cl(+) yields HCl(+) + H may not be rapid at the low temperatures prevailing in diffuse interstellar clouds.
01 Jan 1980
TL;DR: The ultraviolet spectra of 25 early-type stars have been obtained with the International Ultraviolet Explorer observatory as discussed by the authors, and bands of the 4th-positive system of interstellar CO are seen towards 12 of these stars.
Abstract: The ultraviolet spectra of 25 early-type stars have been obtained with the International Ultraviolet Explorer observatory. Bands of the 4th-positive system of interstellar CO are seen towards 12 of these stars. Spectra of HD46223 have been examined for interstellar lines of CH, C2, CH2, OH, HCl, and H2O.