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  • 1
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    Gamma-ray burst color-color diagrams (1993)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: We calculate the spectral hardness ratios for several intense gamma-ray bursts (GRBs) which have sufficient statistics in four energy channels. We study the evolution of these hardness ratios during the events using color-color diagrams (CCDs) and we attempt a preliminary classification of GRBs based on their CCD evolution.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics Supplement Series (ISSN 0365-0138); 97; 1; p. 55-57.
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  • 2
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    The (C-12)O/(C-13)O ratio toward Zeta Ophiuchi (1992)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: A tentative detection of the J = 1 - 0 emission line of (C-13)O has been obtained with SEST from a 24.4 hour integration. The velocity resolution used was 0.23 km/s and the FWHP beamwidth was 45 arcsec. If the (C-13)O line data are conservatively interpreted as an upper limit, the (C-12)O/(C-13)O ratio is not less than 60. Our result supports the previous determination of a large value of the isotope ratio in this cloud, made using radio emission lines with a 1.6-arcmin beam, and extends the ratio based on emission lines to a smaller region. When interpreted as a lower limit, our data is consistent with the ratio obtained from UV absorption line data for (C-12)O and (C-13)O.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 262; 1; p. 248-250.
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  • 3
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    Searching gamma-ray bursts for gravitational lensing echoes - Implications for compact dark matter (1993)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The first available 44 gamma-ray bursts (GRBs) detected by the Burst and Transient Source Experiment on board the Compton Gamma-Ray Observatory have been inspected for echo signals following shortly after the main signal. No significant echoes have been found. Echoes would have been expected were the GRBs distant enough and the universe populated with a sufficient density of compact objects composing the dark matter. Constraints on dark matter abundance and GRB redshifts from the present data are presented and discussed. Based on these preliminary results, a universe filled to critical density of compact objects between 10 exp 6.5 and 10 exp 8.1 solar masses are now marginally excluded, or the most likely cosmological distance paradigm for GRBs is not correct. We expect future constraints to be able either to test currently popular cosmological dark matter paradigms or to indicate that GRBs do not lie at cosmological distances.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 414; 1; p. 36-40.
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  • 4
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    The consistency of standard cosmology and the BATSE number versus brightness relation (1993)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The integrated number-peak-flux relation measured by the Burst and Transient Source Experiment (BATSE) on board the Compton Gamma Ray Observatory is compared with several standard cosmological distributions for gamma-ray bursts (GRBs). Friedmann-Robertson-Walker models were used along with the assumption that the bursts are standard candles and have no number or luminosity evolution. For a given Omega spectral shape, we used a free parameter, essentially the comoving number density of bursts, to generate a best fit between the cosmology and the measured relation. Our results are shown for a subsample of the first 260 GRBs recorded by BATSE. We find acceptable fits between simple cosmological models and the brightness distribution data, as determined by the Kolmogorov-Smirnov one-distribution statistical test. One cannot distinguish a single best cosmological model from the goodness of the fits. The best fit implies that BATSE GRBs are complete out to a redshift of about unity. However, significantly higher and lower redshifts, by as much as a factor of 2, are possible for other marginally acceptable fits.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 411; 2; p. L55-L58.
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  • 5
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    A multi-transition study of carbon monoxide in the Orion A molecular cloud. II - C(O-18) (1993)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: We present an analysis of density, temperature, and excitation conditions in a one half square degree region around BN/KL in Orion A using new C(O-l8) J = 1 yields 0 and J = 2 yields 1 data. This paper extends a previous study of Orion A, based on a multitransition analysis of (C-13)O, to the optically thinner C(O-18) species that traces better the dense inner regions of giant molecular clouds. From the C(O-18) maps we identify several condensations and are able to derive their size, linewidth, average density, mass, and virial mass.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 270; 1-2; p. 468-476.
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  • 6
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    Periodically spaced fragmentation in Orion A (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Evidence is found for periodic density structure in the highly fragmented interior of the Orion A molecular cloud from analysis of a large scale map of C(O-18) J = 1 - 0 emission. The spatial wavelength is about 1 parsec, and extends at least over 2 degrees along the main filament of Orion A and is also observed in other filamentary structures in Orion. This periodicity in the clumps is a result of externally triggered and magnetically mediated cloud collapse and fragmentation.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 247; 1, Ju
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  • 7
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    The relationship between carbon monoxide abundance and visual extinction in interstellar clouds (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Carbon monoxide column densities are compared to visual extinctions toward field stars in the rho Oph and Taurus molecular cloud complexes. The relationship of C(0-18) column density to extinction is established, and new determinations for (C-13)O column densities are given for a range of visual extinctions extended to beyond 20 mag. A prescription for determining hydrogen column densities and masses of molecular clouds from observations of CO isotopes is presented and discussed critically. These measurements agree well with the predictions of gas phase chemistry models which include chemical fractionation and selective isotopic photodestruction. The functional dependence of the C(O-18) column density on extinction is characterized by two different regimes separated by a distinct transition observed to occur at 4 mag in both molecular cloud complexes, whereas the functional dependence of (C-13)O is quite different in the two regions. Some saturation is found to occur for C(O-18) emission at high visual extinction and use the rarer isotopic species C(O-17) and (C-13)(O-18) to correct for it.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 262
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  • 8
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    The observations of the X-ray source HZ Herculis/Hercules X-1 (1980)
    In:  Other Sources
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    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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  • 9
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    The BATSE experiment on the Compton Gamma Ray Observatory: Status and some early results (1992)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The Burst and Transient Source Experiment (BATSE) on the Compton Gamma Ray Observatory (GRO) is a sensitive all-sky detector system. It consists of eight uncollimated detectors at the corners of the spacecraft which have a total energy range of 15 keV to 100 MeV. The primary objective of BATSE is the detection, location, and study of gamma ray bursts and other transient sources. The instrement also has considerable capability for the study of pulsars, solar flares, and other discrete high energy sources. The experiment is now in full operation, detecting about one gamma ray burst per day. A brief description of the on-orbit performance of BATSE is presented, along with examples of early results from some of the gamma ray bursts.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center, The Compton Observatory Science Workshop; p 26-34
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  • 10
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    Preliminary calibration results for the BATSE instrument on CGRO (1992)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Preliminary results pertaining to spectral reconstruction using Burst and Transient Source (BATSE) Large Area Detector measurements of solar flares are presented. The solar flare measurements are currently being used to fine tune the calibration of our data analysis software. The current status of the stability of spectral analysis, given the systematic errors present in burst location, are given. A brief description is given of enhancements to the input data for the atmospheric scattering algorithm that will be implemented in the data analysis software.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center, The Compton Observatory Science Workshop; p 47-52
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