Letter | Published:

Observations of X rays from near NGC6440

Naturevolume 257pages3233 (1975) | Download Citation



ON nine separate occasions between October 27, 1971, and January 6, 1973, the MIT instrument aboard OSO-7 scanned the region of sky within about 10° of the galactic centre. Subsequent analysis of this data, in the form of all-sky maps, led to the discovery of several previously unreported X-ray sources1. The most intense of these, MX1746–20, was found at α = 17 h 46.0 min.δ = −20° 22.2′ (1950.0) or, in galactic coordinates lII = 7.73°, bII = 3.76°. The 90% confidence contour for this position is a circle of radius approximately 0.26°. This uncertainty includes an estimate of the probable aspect error as well as statistical uncertainty.

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    Markert, T. H., et al., IAU Circ., No. 2765 (1975).

  2. 2

    Clark, G. W., et al., Astrophys. J., 179, 263 (1973).

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    Arp, H. C., in Galactic Structure (edit. by Blaauw, A., and Schmidt, M.), 401 (University of Chicago Press, 1965).

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    Clark, G. W., Astrophys. J. Lett. (in the press).

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    Bahcall, J. N., and Ostriker, J. P., Nature, 256, 23–24 (1975).

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  1. Center for Space Research, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139

    • T. H. MARKERT
    • , D. E. BACKMAN
    • , C. R. CANIZARES
    • , G. W. CLARK
    •  & A. M. LEVINE


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