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  • ASTROPHYSICS  (7)
Collection
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  • ASTROPHYSICS  (7)
Years
  • 1
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    The C-12/C-13 isotope ratio toward Zeta Ophiuchi (1985)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Observations of interstellar CH(+) toward Zeta Oph were performed to determine the C-12/C-13 isotope ratio in this diffuse cloud. The very high signal-to-noise ratio spectra yield 6 sigma detections of the (C-13)H(+) features at 4232 A and 3957 A; a weighted mean C-12/C-13 ratio of 43 + or - 6 (1 sigma) is obtained. The uncertainty includes the contribution of continuum placement errors, statistical channel-to-channel signal fluctuations, and the error introduced in deconvolving the blended isotopic lines at 4232 A. This result indicates a decrease in the local galactic C-12/C-13 ratio by a factor of 2 during the 4.6 billion yr since the formation of the sun.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 294; L131-L13
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    NASA TECHNICAL REPORTS
  • 2
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    An optical measurement of the population inversion of the ground state Lambda doublet of interstellar CH (1985)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 294; 238-241
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  • 3
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    The microwave background temperature at 2.64 and 1.32 millimeters (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Very high signal-to-noise observations of the 3874 A band of interstellar CN toward Zeta Oph are presented. Measurements are conducted of equivalent widths for the R(0), R(1), R(2), and P(1) lines which agree with previous photoelectric, but not photographic, findings. Corrected for saturation, these strengths yield excitation temperatures of 2.73 + or - 0.04 K and 2.8 + or - 0.3 K for the J = 0 to 1 and J = 1 to 2 rotational transitions at 2.64 mm and 1.32 mm respectively. Since the cosmic microwave background radiation (CMB) is primarily responsible for populating the excited rotational levels of interstellar CN toward Zeta Oph, these values are actually upper limits on the CMB brightness temperature at 2.64 mm and 1.32 mm. The results are consistent with a 2.7 K blackbody spectrum for the CMB and do not support the spectral deviations observed near these wavelengths by Woody and Richards.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 276; L1-L3
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    NASA TECHNICAL REPORTS
  • 4
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    A precise measurement of the cosmic microwave background temperature from optical observations of interstellar CN (1985)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Very precise observations (with S/N greater than 2000) of the 3874-angstrom band of interstellar CN toward zeta Per and omicron Per are presented. In the zeta Oph, zeta Per, and omicron Per lines of sight, the saturation-corrected CN line strengths yield respective excitation temperatures of 2.72 plus or minus 0.05 K, 2.76 plus or minus 0.05 K, and 2.78 plus or minus 0.07 K for the J = 0-1 rotational transition at 2.64 mm. By confirming the blackbody character of the cosmic microwave background spectrum at wavelengths near the peak of its flux, the simplest explanation of the background as primeval fireball radiation from a hot bang is reinforced.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 297; 119-132
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  • 5
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    Observations of diffuse interstellar lines toward stars with low column densities of H2 (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The diffuse interstellar band at 5780 A has been observed in lines of sight where the column density of H2 is less than 10 to the 16th/sq cm. The strength of 5780 A toward Gamma Cas, Kappa Ori, and Rho Leo argues strongly against a molecular carrier of the 5780 A feature. The interstellar band at 5797 A also appears to be present in Kappa Ori and Rho Leo. Although the exact mechanism remains unclear, it is concluded that the diffuse features at 5780 A and 5797 A are carried by dust grains.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 266
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  • 6
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    Ultraviolet interstellar extinction toward 1367 stars observed by ANS (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Five-band UV photometry is used to investigate the character of interstellar extinction toward 1367 stars of spectral type B3 and earlier, with observations producing a galactic average of 5.11, 4.78, 6.52, 4.10 and 1.95 at 1550, 1800, 2200, 2500, and 3300 A, respectively. Differences in the strengths of the UV extinction features of these stars appear to be independent, since objects with either strong or weak 2200 A extinction can have strong, normal or weak far-UV extinction. Further investigation reveals that some of the deviant stars are embedded in localized regions whose average extinction curves diverge dramatically from the galactic mean. The anomalous extinction of these regions attests to localized inhomogeneities in the UV characteristics of interstellar dust. Because the evaluation of UV extinction toward a particular star would be more accurate if based on the average curve of the region immediately surrounding that star rather than that of the entire Galaxy, it is recommended that the galactic average presented be used with caution to correct astronomical data of individual objects.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 248
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  • 7
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    Observations of neutral atoms in the Rho Ophiuchi cloud (1986)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: New observations of lines from neutral atoms in the lines of sight to three stars in the Rho Oph cloud are combined with literature data to look for evidence of density-enhanced regions with higher elemental depletions than those characterizing the cloud as a whole. The depletions inferred from neutral species, however, are comparable to those measured directly from observations of ions, suggesting that no strong density enhancements exist in the observed lines of sight. This conclusion is supported by electron densities derived from the observed ionization fractions, which also show no evidence for a strong variation of density with depth in the cloud. It appears that the overall density (and overall level of depletion) in the cloud is higher than in typical diffuse clouds, despite the apparent lack of strong condensations with enhanced relative depletions.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 303; 433-438
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