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  • 1
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    NGC 315 - High-velocity H I in an active elliptical galaxy (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The detection of high-velocity H I in absorption against the nuclear continuum source in the giant elliptical galaxy NGC 315 is reported. The absorption line is found to be highly blueshifted in the reference frame of the galaxy with a projected velocity toward the galaxy of 490 km/s. The absorption line is very strong (244 + or - 4 mJy), consisting of two components with very narrow velocity widths of 2.5 km/s (FWHM) each and peak optical depths of 0.9 and 0.2. The kinetic temperature must be 150 K if the line widths are due entirely to thermal broadening, while the neutral gas column densities implied are 2-5 x 10 to the 20th hydrogen atoms/sq cm. No OH in absorption was detected in these clouds to a limiting peak optical depth of 0.04, although this result is consistent with either a galactic or extragalactic origin of the clouds. It is suggested that these clouds may have condensed out of a large unobserved galactic halo of gas, or they may reside in or have been captured from the intracluster medium.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 266
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  • 2
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    A search for FeH in M and S giants (1980)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: The strongest lines of FeH in the visible spectrum fall in the domain of TiO and ZrO bands. Analysis exists for TiO, but nothing is yet available for the weak but important ZrO lines. Using plate measurements and microphotometer tracings, high dispersion spectra of the following cool stars have been searched for FeH lines: Beta Peg, Mu UMa, Alpha Her, Omicron Cet, Chi Cyg, HR 105, HR 8714, R And, R Cyg, R Cam, T Sgr, R CMi, Cy Cyg, and RU Cam. The strongest FeH lines are unimpressive in R Cyg, where the strong infrared bands of FeH have already been identified. Identification of the blue-green FeH lines in other spectra must be considered inconclusive until a rotational analysis of the FeH spectrum is available.
    Keywords: ASTROPHYSICS
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  • 3
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    The observations of the X-ray source HZ Herculis/Hercules X-1 (1980)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: 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.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 237
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  • 4
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    Theoretical mean colors for RR Lyrae variables (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A hydrodynamically pulsating 0.6 solar mass model of a typical RR Lyrae variable was studied with a radiation transport-hydrodynamic computer program to predict theoretical T sub 3 and colors at many phases and to find the proper methods for getting mean colors and the consequent mean effective temperatures. The variable Eddington radiation approximation method was used with gray and with multifrequency absorption coefficients to represent the radiation flow in the outer optically thin layers. Comparison between observed and computed B-V colors indicate that these low Z population 2 models are reasonably accurate using King 1A composition opacities. The well known Oke, Giver, and Searle relation between B-V and T sub e reproduced. Mean colors were found by four different averaging methods. The method that gives a mean color and the mean T sub e closest to the nonpulsating model was the separate intensity means of B and V.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center Current Probl. in Stellar Pulsation Instabilities; p 293-310
    Format: application/pdf
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  • 5
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    Light curves for bump Cepheids computed with a dynamically zoned pulsation code (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The dynamically zoned pulsation code developed by Castor, Davis, and Davison was used to recalculate the Goddard model and to calculate three other Cepheid models with the same period (9.8 days). This family of models shows how the bumps and other features of the light and velocity curves change as the mass is varied at constant period. The use of a code that is capable of producing reliable light curves demonstrates that the light and velocity curves for 9.8 day Cepheid models with standard homogeneous compositions do not show bumps like those that are observed unless the mass is significantly lower than the 'evolutionary mass.' The light and velocity curves for the Goddard model presented here are similar to those computed independently by Fischel, Sparks, and Karp. They should be useful as standards for future investigators.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center Current Probl. in Stellar Pulsation Instabilities; p 175-186
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  • 6
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    Constraints on the inclination and masses of the HDE 226868/Cygnus X-1 system from the observations (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Analyses of two high-dispersions IUE spectra of HDE 226868 (the optical counterpart of Cygnus X-1) are combined with studies of low-dispersion IUE spectra to provide a more accurate determination of the variation of C IV stellar wind absorption as a function of orbital phase. By incorporating these observational results into an analysis of the structure of the X-ray ionization cavity in the stellar wind, it is found that the orbital inclination must lie between 36 and 67 deg, leading to a mass for the compact object between 5.7 and 11.2 solar masses.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 270; July 15
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  • 7
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    On the mass of the Cepheid X Cygni (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Using a new non-Lagrangian hydrodynamic radiation transport code, models of the Cepheid X Cygni have been calculated and compared with new observations. Adopting an effective temperature of 5300 K, the luminosity was varied for stellar masses of 6, 8, and 9 solar masses in order to obtain a period of 16.4d. The results indicate that in order to find reasonable agreement between the light curves as calculated and observed, the mass used in the models must be nearly the evolutionary mass, not some 60% less as found in earlier work for Cepheids with periods from 7d to 10d. In addition, the new observations support the physical reality of the so-called 'artificial viscosity dip'.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 246
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  • 8
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    Simultaneous ultraviolet, optical, and X-ray observations of the X-ray source Vela X-1 /HD 77581/ (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: 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.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 238
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  • 9
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    HEAO 1 identification of the X-ray emitting poor cluster of galaxies, AWM 7 (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The X-ray source 2A 0251 + 413 is identified with the AWM 7 group of galaxies. The source is extended, with a FWHM of roughly 9 arcmin if an isothermal sphere profile is assumed. The spectrum is best fitted by thermal bremsstrahlung at 4.0 + or - 0.5 keV, with a significant Fe line emission of equivalent width 0.63 keV centered at 6.6 keV. This temperature is consistent with a measured dispersion velocity of 600 km/s of the central galaxies.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 238
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  • 10
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    Airborne observations of the Orion molecular hydrogen emission spectrum (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The Orion near-infrared H2 emission spectrum was observed from an altitude of 12.5 km in order to measure line intensities free from interference by terrestrial H2O. For the peak source, the observations indicate that the differential extinction between 4126 and 4712 per cm is 0.59 + or -0.06 mag, and the relative line intensities are consistent with those expected from a homogeneous source in approximate LTE at 1540 + or -100 K. An anomalous ortho/para H2 abundance ratio of 3.5(+ or - 0.2):1 is found, and the estimated total luminosity in vibrationally excited H2 lines is 300 + or - 100 solar luminosities. Rough molecular abundance limits, based on the missing H2 Q(6) line and the good agreement between other line intensities and the LTE model, place the H2 region no deeper within OMC-1 than the IR cluster and no shallower than 50 percent of the depth to the cluster.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 259
    Format: text
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