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    Understanding the Radio Variability of Sagittarius A*

    Access Status
    Open access via publisher
    Authors
    Macquart, Jean-pierre
    Bower, G.
    Date
    2006
    Type
    Journal Article
    
    Metadata
    Show full item record
    Citation
    Macquart, Jean-pierre and Bower, G. 2006. Understanding the Radio Variability of Sagittarius A*. The Astrophysical Journal. 641: pp. 302-318.
    Source Title
    The Astrophysical Journal
    DOI
    10.1086/500317
    ISSN
    0004637X
    Faculty
    Faculty of Science and Engineering
    Curtin Institute of Radio Astronomy
    Remarks

    Copyright © 2006 The American Astronomical Society ("AAS")-[The Astrophysical Journal (ApJ) Macquart, Jean-pierre, 2006 ApJS 641-302-318.]

    URI
    http://hdl.handle.net/20.500.11937/15990
    Collection
    • Curtin Research Publications
    Abstract

    We determine the characteristics of the 7 mm to 20 cm wavelength radio variability in Sgr A on timescales from days to three decades. The amplitude of the intensity modulation is between 30% and 39% at all wavelengths. Analysis of uniformly sampled data with proper accounting of the sampling errors associated with the light curves shows that Sgr A exhibits no 57 day or 106 day quasi-periodic oscillations, contrary to previous claims. The cause of the variability is investigated by examining a number of plausible scintillation models, enabling those variations that could be attributed to interstellar scintillation to be isolated from those that must be intrinsic to the source. Thinscreen scattering models do not account for the variability amplitude on most timescales. However, models in which the scattering region is extended out to a radius of 50-500 pc from the Galactic center account well for the broad characteristics of the variability on >4 day timescales. The 10% variability on <4 day timescales at 0.7-3 cm appears to be intrinsic to the source. The degree of scintillation variability expected at millimeter wavelengths depends sensitively on the intrinsic source size; the variations, if due to scintillation, would require an intrinsic source size smaller than that expected.

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