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  • 11
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    Spectral images of HD 199178 (1988)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: High-resolution IUE spectra of the Mg II k line of HD 199178 were analyzed, applying spectral imaging techniques to derive an image of the chromospheric structure and to study the transient behavior of the chromosphere. All spectra in the IUE archives were uniformly reduced and analyzed. Results are compared with ground-based observations of the photosphere. Four ultraviolet flares on HD 199178 are observed; 3 of these occurred at roughly the same rotational phase. There is no clear phase-dependence of the SWP line fluxes, but there is for the Mg II k flux. The emission centroid of the Mg II k line varies in a quasi-sinusoidal fashion, presumably due to the rotation of a nonuniform chromosphere.
    Keywords: ASTRONOMY
    Type: ESA, A Decade of UV Astronomy with the IUE Satellite, Volume 1; p 291-293
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  • 12
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    The intrinsic H I Lyman-alpha line profiles of late-type stars (1990)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The Lyman-alpha line of neutral hydrogen is probably the most important cooling channel for chromospheric plasma in late-type stars, yet it is also the least studied major line in the far ultraviolet. The scattering of much of the stellar Lyman-alpha flux by interstellar hydrogen, coupled with the geocoronal emission foreground, seriously complicates the analysis of the Lyman-alpha spectra. The influence of the local interstellar medium on the observed profiles was circumvented by observing stars with radial velocities sufficiently high to Doppler shift the center of the stellar emission line out of the interstellar absorption core. There are several stars that have high radial velocities by virtue of their presence in close binary systems. High resolution IUE (International Ultraviolet Explorer) spectra of Ly alpha line of two such eclipsing binary stars, AR Lac and TY Pyx, are obtained, at each orbital quadrature phase, when the projected orbital velocity is a maximum. By combining the spectra from opposite quadratures it is possible to piece together the entire stellar emission profiles. The third star in this study, delta Lep, is a single star with a high space velocity.
    Keywords: ASTROPHYSICS
    Type: ESA, Evolution in Astrophysics: IUE Astronomy in the Era of New Space Missions; p 341-344
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  • 13
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    Correcting observed stellar Lyman alpha profiles for the effects of interstellar absorption and geocoronal emission (1986)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Techniques to compensate for interstellar absorption and geocoronal emission in IUE studies of late stars atmospheres were developed. Thus it is possible to determine the Lyman alpha flux from nearby cool stars using the low-resolution spectra in the IUE archives. The accuracy of such a procedure depends fundamentally upon the assumptions regarding the shape of the intrinsic profile and the density and velocity structure of the local interstellar medium, not upon measurement uncertainties of the low-resolution spectra. Geocoronal emission and saturated spectra are fatal only to a one-dimensional spectral analysis. When both the spatial and the spectral dimensions are considered, the observed Lyman alpha flux can be recovered.
    Keywords: ASTRONOMY
    Type: ESA Proceedings of an International Symposium on New Insights in Astrophysics. Eight Years of UV Astronomy with IUE; p 669-672
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  • 14
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    Where do flares occur in RS CVn systems? Analysis of the October 3, 1981 flare on V711 Tau = HR 1099 observed by IUE (1986)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A set of IUE observations of V711 Tau = HR 1099 (K1 IV and G2 V) in which high-resolution spectra with the SWP and LWR cameras were obtained during the luminous flare of October 3, 1981 is discussed. Multigaussian fits to the Mg II k and C IV 1548 A lines are consistent with the flare radial velocity being identical to that of the K star. Thus, the flare probably occurred on the K star. There is no evidence for flows as seen during a flare on UX Ari. The strongest emitters of UV radiation during the flare were the L alpha and Mg II lines, which emitted seven times as much energy as all the transition region lines combined. The peak luminosity of the flare in the UV emission lines is 1.5 times 10 to the 31st power ergs/sec, and the total emission in these lines during the flare was about 4 times 10 to the 35th power ergs.
    Keywords: ASTROPHYSICS
    Type: ESA Proceedings of an International Symposium on New Insights in Astrophysics. Eight Years of UV Astronomy with IUE; p 161-164
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  • 15
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    Doppler imaging of active regions on AR Lacertae (1986)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The eclipsing RS CVn system AR Lacertae was observed with IUE in October 1981 and October 1983. The phase coverage provided by the 1983 data is adequate to determine the location and size of two plage-like regions in the atmosphere of the K star using a Doppler imaging analysis of the Mg II k lines. A third epoch data set, consisting of many spectra spaced uniformly throughout a single orbital cycle was obtained in September 1985. Rotational modulation of the SWP line fluxes and an initial look at the Mg II lines reveals clear evidence of discrete chromospheric structures. These include a localized flare on the G star, a chromospherically inactive hemisphere on the G star, and plages on the K star.
    Keywords: ASTRONOMY
    Type: ESA Proceedings of an International Symposium on New Insights in Astrophysics. Eight Years of UV Astronomy with IUE; p 153-154
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  • 16
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    Camera shutter is actuated by electric signal (1964)
    In:  CASI
    Details
    Publication Date: 2019-05-11
    Description: Rotary solenoid energized by an electric signal opens a camera shutter, and when the solenoid is de-energized a spring closes it. By the use of a microswitch, the shutter may be opened and closed in one continuous, rapid operation when the solenoid is actuated.
    Keywords: MECHANICS
    Type: ARC-20
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  • 17
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    Self-supported aluminum thin films produced by vacuum deposition process (1966)
    In:  CASI
    Details
    Publication Date: 2019-05-29
    Description: Self-supported aluminum thin film is produced by vacuum depositing the film on a polyvinyl formal resin film and then removing the resin by radiant heating in the vacuum. The aluminum film can be used as soon as the resin is eliminated.
    Keywords: MATERIALS
    Type: ARC-58
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  • 18
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    Rotational modulation of hydrogen Lyman alpha flux from 44ii Bootis (1988)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Observations with IUE that cover the entire 6.4 hr orbital cycle of the late-type contact binary 44i Bootis are presented. Intrinsic stellar hydrogen Lyman alpha emission flux was determined from low-resolution IUE spectra, compensating for geocoronal emission and for interstellar absorption. The variation of the stellar Lyman alpha emission flux correlates well with the variation of the C II and C IV emission fluxes, and shows orbital modulation in phase with the visual light curve. The ratio of Lyman alpha to CII flux (15 to 20) is similar to that observed in solar active regions. Hydrogen Lyman alpha emission is thus one of the most important cooling channels in the outer atmosphere of 44i Boo. A high-resolution spectrum of the Lyman alpha line was obtained between orbital phases 0.0 and 0.6. The integrated flux in the observed high-resolution Lyman alpha profile is consistent with the fluxes determined using low-resolution spectra, and the composite profile indicates that both components of this binary have equally active chromospheres and transition regions. The uncertainty in the interstellar hydrogen column density cannot mimic the observed variation in the integrated Lyman alpha flux, because the stellar line is very much broader than the interstellar absorption.
    Keywords: ASTRONOMY
    Type: ESA, A Decade of UV Astronomy with the IUE Satellite, Volume 1; p 299-302
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  • 19
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    Rotational modulation of hydrogen Lyman alpha flux from 44i Bootis (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: Observations with IUE that cover the entire 6.4 hr orbital cycle of the late-type contact binary 44i Bootis are presented. Intrinsic stellar hydrogen Lyman alpha emission flux was determined from low-resolution IUE spectra, compensating for geocoronal emission and for interstellar absorption. The variation of the stellar Lyman alpha emission flux correlates well with the variation of the CII and CIV emission fluxes, and shows orbital modulation in phase with the visual light curve. The ratio of Lyman alpha to CII flux (15 to 20) is similar to that observed in solar active regions. Hydrogen Lyman alpha emission is thus one of the most important cooling channels in the outer atmosphere of 44i Boo. A high-resolution spectrum of the Lyman alpha line was obtained between orbital phases 0.0 and 0.6. The integrated flux in the observed high-resolution Lyman alpha profile is consistent with the fluxes determined using low-resolution spectra, and the composite profile indicates that both components of this binary have equally active chromospheres and transition regions. The uncertainty in the interstellar hydrogen column density cannot mimic the observed variation in the integrated Lyman alpha flux, because the stellar line is very much broader than the interstellar absorption.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 208; 1-2; 201-207
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  • 20
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    Rotational modulation and flares on RS Canum Venaticorum and BY Draconis stars. X - The 1981 October 3 flare on V711 Tauri (=HR 1099) (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 211; 1 Fe; 173-186
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