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  • 1
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    Broadband X-ray Spectroscopy of the ADC Source 4U 1822-37 with Suzaku (2006)
    In:  Other Sources
    Details
    Publication Date: 2019-07-19
    Description: We will present the broadband spectra of the low mass x-ray binary 4U 1822-37, recently observed with Suzaku. 4U 1822-37 is the canonical accretion disk corona (ADC) source where the compact object is obscured by an extended corona that intercepts and scatters the central continuum emission, some of which is then reprocessed in the outer regions of the accretion disk. 4U 1822-37 therefore serves as an important link between x-ray binaries and AGN. The broadband x-ray spectra from the Suzaku XIS and HXD provide a unique opportunity to probe the physical conditions in the corona and the accretion disk for this important accretion geometry.
    Keywords: Astronomy
    Type: The Extreme Universe in the Suzaku Era; Dec 03, 2006 - Dec 10, 2006; Kyoto; Japan
    Format: text
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  • 2
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    The Constellation-X Mission: The next giant step in X-ray Astronomy (2006)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: Constellation-X is the x-ray astronomy equivalent of large ground-based optical telescopes such as the Keck and the VLT, complementing the high spatial resolution capabilities of Chandra. By increasing the telescope aperture and utilizing efficient spectrometers the mission will achieve a factor of 100 increased sensitivity. with its increased capabilities, Constellation-X will address many fundamental astrophysics questions such as observing the formation and evolution of clusters of galaxies, constraining the Baryon content of the Universe, observing the effects of strong gravity close to the event horizon of black holes in AGN and using these effects to determine the black hole rotation. The Constellation-X mission has been under study for eight years and in the Presidents FY04 budget has been given approval to proceed with a launches in 2013 and 2014. In this talk I will review the science goals of the mission, and the implementation approach.
    Keywords: Astronomy
    Type: Mullard Space Science Lab., High Resolution X-ray Spectroscopy: towards XEUS and Con-X; Mar 27, 2006 - Mar 28, 2006; Dorking; United Kingdom
    Format: text
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  • 3
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    A Smoking Gun in the Carina Nebula (2009)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: The Carina Nebula is one of thc youngest, most active sites of massive star formation in our Galaxy. In this nebula, we have discovered a bright X-ray source that has persisted for approx.30 years. The soft X-ray spectrum. consistent with kT approx.130 eV blackbody radiation with mild extinction, and no counterpart in the near- and mid-infrared wavelengths indicate that it is a, approx. 10(exp 6)-year-old neutron star housed in the Carina Nebula. Current star formation theory does not suggest that the progenitor of the neutron star and massive stars in the Carina Nebula, in particular (eta)Car, are coeval. This result demonstrates that the Carina Nebula experienced at least two major episodes of massive star formation. The neutron star would be responsible for remnants of high energy activity seen in multiple wavelengths.
    Keywords: Astronomy
    Format: application/pdf
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  • 4
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    Optimal Compression Methods for Floating-point Format Images (2009)
    In:  Other Sources
    Details
    Publication Date: 2019-07-19
    Description: We report on the results of a comparison study of different techniques for compressing FITS images that have floating-point (real*4) pixel values. Standard file compression methods like GZIP are generally ineffective in this case (with compression ratios only in the range 1.2 - 1.6), so instead we use a technique of converting the floating-point values into quantized scaled integers which are compressed using the Rice algorithm. The compressed data stream is stored in FITS format using the tiled-image compression convention. This is technically a lossy compression method, since the pixel values are not exactly reproduced, however all the significant photometric and astrometric information content of the image can be preserved while still achieving file compression ratios in the range of 4 to 8. We also show that introducing dithering, or randomization, when assigning the quantized pixel-values can significantly improve the photometric and astrometric precision in the stellar images in the compressed file without adding additional noise. We quantify our results by comparing the stellar magnitudes and positions as measured in the original uncompressed image to those derived from the same image after applying successively greater amounts of compression.
    Keywords: Astronomy
    Type: Astronomical Data Analysis Software and Systems XIX (ADASS 2009); Oct 04, 2009 - Oct 08, 2009; Sapporo; Japan
    Format: text
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