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  • Other Sources  (17)
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  • 1
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    The Mg II line profile in the Seyfert galaxy NGC 4151 - A new outflowing component (1987)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: This paper examines the Mg II 2795-2802 A doublet in the Seyfert galaxy NGC 4151 at a higher resolution than has previously been used, searching for velocity systems in absorption and emission. Evidence is presented for a new, narrow, outflowing absorption system in Mg II having a velocity of 825 km/s relative to the sun, and -165 km/s relative to the systemic velocity of NGC 4151. This feature is not present in Ly-alpha or C IV and possible explanations for this are considered. For the Mg II and C IV lines, a model decomposition of the line profile is presented.
    Keywords: ASTROPHYSICS
    Type: Royal Astronomical Society, Montly Notices (ISSN 0035-8711); 225; 837-849
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  • 2
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    The interstellar spectrum of the supernova 1980k in NGC 6946 (1982)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Bright supernovae in external galaxies offer a rare opportunity to probe the intervening interstellar media over very extended path-lengths, including the disk and halo of the Galaxy and the parent galaxy of the supernova. SN 1980k was discovered in NGC 6946 on 1980 October 29. In the first month after discovery, high resolution optical and ultraviolet observations were obtained to exploit the supernova as a probe of the intervening interstellar media. The obtained data are discussed. In the spectra, absorption lines were observed of Mg I, Mg II, Fe II, Mn II, Ca II and Na I. The absorption lines are attributed to the intervening interstellar media distributed over the very extended line of sight sampled, of order 7 Mpc. These lines are wider and stronger than any previously measured in the quiescent interstellar gas in the halo and disk of the Milky Way and of external galaxies
    Keywords: ASTRONOMY
    Type: Royal Astronomical Society; vol. 199
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  • 3
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    The Mg II line profile in the Seyfert galaxy NGC 4151: A new outflowing component (1986)
    In:  Other Sources
    Details
    Publication Date: 2013-08-29
    Description: The Mg II 2795, 2802A doublet in the Seyfert galaxy NGC 4151 was examined to search for velocity systems in absorption and emission. Evidence for a narrow, outflowing absorption system in Mg II having a velocity of +825 km/sec relative to the Sun, -165 km/sec relative to the systemic velocity of NGC 4151 is presented. This feature is not present in Ly alpha or C IV and possible explanations for this are considered. For the Mg II and C IV lines a model decomposition of the line profile is shown.
    Keywords: ASTRONOMY
    Type: ESA Proceedings of an International Symposium on New Insights in Astrophysics. Eight Years of UV Astronomy with IUE; p 633-640
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  • 4
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    The missing UV absorption lines of NGC 4151 (1990)
    In:  CASI
    Details
    Publication Date: 2013-08-29
    Description: Near simultaneous high dispersion long and short wavelength International Ultraviolet Explorer (IUE) observations of the Seyfert galaxy NGC 4151 are discussed. Previous observations revealed a narrow absorption system in Mg II not present in Ly alpha or C IV. The new observations confirm the presence of this system in Mg II and its absence in the other lines. Possible reasons for this are discussed. Future Hubble Space Telescope studies of NGC 4151 are discussed.
    Keywords: ASTROPHYSICS
    Type: ESA, Evolution in Astrophysics: IUE Astronomy in the Era of New Space Missions; p 523-525
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  • 5
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    Fast spectroscopic variations on rapidly-rotating, cool dwarfs. 3: Masses of circumstellar absorbing clouds on AB Doradus (1989)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: New time-resolved H alpha, Ca II H and K and Mg II h and k spectra of the rapidly-rotating K0 dwarf star AB Doradus (= HD 36705). The transient absorption features seen in the H alpha line are also present in the Ca II and Mg II resonance lines. New techniques are developed for measuring the average strength of the line absorption along lines of sight intersecting the cloud. These techniques also give a measure of the projected cloud area. The strength of the resonance line absorption provides useful new constraints on the column densities, projected surface areas, temperatures and internal turbulent velocity dispersions of the circumstellar clouds producing the absorption features. At any given time the star appears to be surrounded by at least 6 to 10 clouds with masses in the range 2 to 6 x 10(exp 17) g. The clouds appear to have turbulent internal velocity dispersions of order 3 to 20 km/s, comparable with the random velocities of discrete filamentary structures in solar quiescent prominences. Night-to-night changes in the amount of Ca II resonance line absorption can be explained by changes in the amplitude of turbulent motions in the clouds. The corresponding changes in the total energy of the internal motions are of order 10(exp 29) erg per cloud. Changes of this magnitude could easily be activated by the frequent energetic (approximately 10(exp 34) erg) x ray flares seen on this star.
    Keywords: ASTRONOMY
    Type: NASA-CR-186563 , NAS 1.26:186563
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  • 6
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    IUE observations of Fe 2 galaxies (1981)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Repeated observations of the Seyfert 1 galaxies I Zw 1 and II Zw 136, which have very strong Fe II emission lines in the optical region, were made at low resolution with the IUE Satellite. The ultraviolet spectra are very similar: both are variable and show broad emission features of Fe II (especially the UV multiplets 1, 33, 60, 62, and 63) as well as the emission lines usually strong in Seyferts and quasars. The data strongly support the hypothesis that the optical Fe II emission lines are primarily due to collisional excitation and that resonance fluorescence makes only a minor contribution to the excitation of these lines.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Universe at Ultraviolet Wavelengths: The First Two Yrs. of Intern. Ultraviolet Explorer; p 757-766
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  • 7
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    The spectra of supernovae. (1973)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Progress report on a continuing program of investigation into the nature of the spectra of supernovae. A description of these spectra is presented that is more quantitative and covers a wider wavelength range than heretofore published descriptions. Some preliminary conclusions are suggested in the light of the new data presented.
    Keywords: SPACE SCIENCES
    Type: Astrophysical Journal; 185; Oct. 1
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  • 8
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    An infrared survey of RW Aurigae stars (1974)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: An infrared photometric survey of 89 RW Aur type variables in both hemispheres has been made. JHKL magnitudes and colors are listed. The RW Aur variables include a small number of highly reddened late-type stars. All T Tauri and hot Orion population stars show infrared excesses and the infrared properties mark certain field stars as being young. The greatest infrared excesses are found for A and F stars while young variable B stars usually show no excesses. The location of the RW Aur stars in the two-color H-K, K-L diagram favor dust re-radiation over free-free emission as the mechanism responsible for the infrared excess. A weak correlation of H-K with emission class links the occurrence of circumstellar dust and gas shells.
    Keywords: ASTRONOMY
    Type: Royal Astronomical Society; vol. 167
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  • 9
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    Further observations of the Orion Nebula cluster (1975)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: New spectral types for 16 stars, UBVRI photometry for 13 stars and UBVRIHKL photometry for 35 stars in the Orion Nebula cluster are presented. Analysis of these data together with those of Penston (1973) shows that the reddening law in the cluster is normal. Previous claims for high ratios of total to selective absorption are caused by mistaking infrared emission for a hole in the absorption at that wavelength. The distance modulus of M42 is 8.0 + or - 0.1 mag. Star formation in the cluster has been in progress over the last 10 million yr. The infrared colors of cluster stars are correlated with their range of variation in the optical region.
    Keywords: ASTROPHYSICS
    Type: Royal Astronomical Society; vol. 171
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  • 10
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    Multicolor observations of stars in the vicinity of the Orion Nebula. (1973)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Photometry in nine colors from 0.3 to 3.4 microns of all stars brighter than V = 12 mag within half a degree square centered on theta super 1 Orionis is presented. Additionally about one-half of this area is searched for stars which, although visually fainter than twelfth magnitude, have 2.2-micron magnitudes brighter than about 8 mag. Several stars with infrared excesses and a few highly reddened stars are found. These two types of stars can be separated in an infrared two-color diagram. No star earlier than B9 has a significant infrared excess at 2 microns. There is a good correlation of 2-micron excess with optical variability. For those stars with spectral types, the visual absorption can be deduced. This varies greatly from star to star and does not correlate with position or luminosity and only weakly with 2-micron excess. There is, however, a probable correlation of visual absorption with optical variability. For nearly all stars more energy is absorbed in the visual region than is reemitted in the infrared at wavelengths up to 3.4 microns.
    Keywords: SPACE SCIENCES
    Type: Astrophysical Journal; 183; July 15
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