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  • 1
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    The Galactic halo and local intergalactic medium toward PKS 2155-304 (1993)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Low-resolution UV observations of the bright, low-redshift BL Lac object PKS 2155-304 have been obtained by the HST's high-resolution spectrograph. Attention is here given to results on the number of intergalactic H I Ly-alpha components in the line-of-sight toward this object. The highest-redshift of the observed Ly-alpha systems furnishes a lower limit on the distance of the BL Lac object; this distance is consistent with the approximate redshift deduced from CCD imagery of the probable host galaxy for PKS 2155-304.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 409; 1; p. 199-204.
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  • 2
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    Newly identified main-sequence A stars with circumstellar dust (1992)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: The IRAS Faint Source Survey data base and the ADDSCAN/SCANPI software are used to search for systems with circumstellar dust in two samples: all of the 62 A stars in Woolley's catalog, which lie near the main sequence and are typically within 25 pc of the sun, and all A stars in the Bright Star Catalogue with mV in the range 4-5 and v sin i not less than 100 km/s. In the first sample, 11 nearby A stars having (12)-(25) and (25)-(60) colors consistent with circumstellar dust are found. The analysis of the second sample demonstrates that the use of the FSS data base increases the likelihood of identifying A stars with circumstellar dust fainter than mV = 4. Three more new dusty systems are found in this sample. Beta Pictoris (A5 IV-V) is the only star within 25 pc of the sun that displays IR colors indicative of both warm and cool dust. It is inferred from the absence of cool dust in the vast majority of the systems that the dust disks of these stars are much less extended than that seen around Beta Pictoris.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 396; 2, Se
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  • 3
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    The very high rotators in the late-B and early-A stars: Shell stars with Si IV and C IV features the case of HD 119921 (1990)
    In:  CASI
    Details
    Publication Date: 2013-08-29
    Description: Study of several stars in the late B and early A spectral types shows that very high rotators are associated with shell characteristics (sometimes not detected at all in the visible spectra) and also with C IV and some Si IV spectral absorption features which can be explained by circumstellar phenomena superimposed over stellar metallic blends. These particularities are evidenced by comparison with other spectra of low and high rotators in the same spectral range. HD 119921, a star with similar characteristics to the other ones of the sample, is given special attention. A possible scenario is suggested to explain the observed superionization features.
    Keywords: ASTROPHYSICS
    Type: ESA, Evolution in Astrophysics: IUE Astronomy in the Era of New Space Missions; p 283-286
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  • 4
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    A search for Beta Pictoris analogs (1990)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The results are presented of the survey of known shell stars detected by the Infrared Astronomy Satellite (IRAS) at sufficient bandpasses to permit evaluation of the nature of the infrared excess, and having archival International Ultraviolet Explorer (IUE) high dispersion spectra suitable for identifying stars with infalling circumstellar plasma. Detection of infall in shell stars with infrared signatures of circumstellar dust is described. One star which shows infalling plasma, but apparently no circumstellar dust is described. The implications for the understanding of Beta Pictoris and similar systems are discussed.
    Keywords: ASTROPHYSICS
    Type: ESA, Evolution in Astrophysics: IUE Astronomy in the Era of New Space Missions; p 227-230
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  • 5
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    Narrow Absorption Components in Be Star Winds (1985)
    In:  CASI
    Details
    Publication Date: 2014-09-16
    Description: The stars omega Ori (B2 IIIe), 66 Oph (B2 IVe), and 59 Cyg (B1.5 IVe) are discussed. The extent to which the narrow absorption components in these Be stars differs from narrow components in the O stars and gamma Cas is explored. Any models or mechanisms for the formation of narrow absorption features in the UV resonance lines of Be star spectra must account for the presence of multiple narrow absorption features which are variable in number, radial velocity, and strength. Models predicting a high and low density structure to the stellar wind caused by instabilities in a flow driven by radiation pressure or by variable mass loss may be more successful in describing the behavior of winds in early Be stars. These models appear to be capable of producing single absorption components in the velocity range observed for O stars and very early Be stars.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Origin of Nonradiative Heating(Momentum in Hot Stars; p 57-61
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  • 6
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    Problems and programming for analysis of IUE high resolution data for variability (1981)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Observations of variability in stellar winds provide an important probe of their dynamics. It is crucial however to know that any variability seen in a data set can be clearly attributed to the star and not to instrumental or data processing effects. In the course of analysis of IUE high resolution data of alpha Cam and other O, B and Wolf-Rayet stars several effects were found which cause spurious variability or spurious spectral features in our data. Programming was developed to partially compensate for these effects using the Interactive Data language (IDL) on the LASP PDP 11/34. Use of an interactive language such as IDL is particularly suited to analysis of variability data as it permits use of efficient programs coupled with the judgement of the scientist at each stage of processing.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Universe at Ultraviolet Wavelengths: The First Two Yrs. of Intern. Ultraviolet Explorer; p 805-810
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  • 7
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    IUE observations of variability in winds from hot stars (1981)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Observations of variability in stellar winds or envelopes provide an important probe of their dynamics. For this purpose a number of O, B, Be, and Wolf-Rayet stars were repeatedly observed with the IUE satellite in high resolution mode. In the course of analysis, instrumental and data handling effects were found to introduce spurious variability in many of the spectra. software was developed to partially compensate for these effects, but limitations remain on the type of variability that can be identified from IUE spectra. With these contraints, preliminary results of multiple observations of two OB stars, one Wolf-Rayet star, and a Be star are discussed.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Universe at Ultraviolet Wavelengths: The First Two Yrs. of Intern. Ultraviolet Explorer; p 121-125
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  • 8
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    Observations of Of-star wind variability (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Nightly variations in He II 4686 A have been observed in four Of stars, HD 152408, HD 151804, 9 Sge, and Lambda Cep. Three of the stars were not previously known to show such variations. In one case, Lambda Cep, simultaneous observations with IUE showed variations in ultraviolet (UV) resonance-line profiles during the same time period as those in He II 4686 A. This implies that the perturbations causing the He II 4686 A variability affect the entire wind acceleration zone.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 271; Aug. 15
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  • 9
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    Line profile variation in delta-Orionis A, l-Orionis A, and 15 Monocerotis (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The results of a monitoring program with IUE and Einstein are presented for three stars, delta-Ori A, l-Ori A, and 15 Mon. Line profile variability is observed in the UV profiles accessible to IUE and the relation between the variation in the different ions suggests that the ionization level is varying in the winds of these stars. This is consistent with Einstein observations of soft X-ray variability for two of the stars.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 283; 218-225
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  • 10
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    Highly ionized stellar winds in Be stars. II - Winds in B6-B9.5e stars (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: The results of a UV survey of stellar winds and circumstellar shells in 40 B6-B9.5e stars covering luminosity classes V-III are presented. A graph is presented of the region from 1520-1560 A, which includes both the Si II UV multiplet 2 transitions and the C IV resonance transition for selected Be stars in the sample. The detection of shortward-shifted discrete component absorption features in nine of the program stars suggests that the material is produced in a stellar wind, which attains velocities of at least a few hundred km/s.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 339; 403-419
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