Circular No. 2744 Central Bureau for Astronomical Telegrams INTERNATIONAL ASTRONOMICAL UNION Postal Address: Central Bureau for Astronomical Telegrams Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A. Cable Address: SATELLITES, NEWYORK Western Union: RAPID SATELLITE CAMBMASS MX 0513-40 N. V. Vidal and K. C. Freeman, Mount Stromlo and Siding Spring Observatories, write: "Following the identification by Markert and Clark of the x-ray source MX 0513-40 with the globular cluster NGC 1851 (IAUC 2735), we obtained short-exposure U, B and V photographs of the region with the 100-cm telescope at Siding Spring. These show that the only ultraviolet-bright star in the error box lies about 0'.5 from the center of the cluster. Using a photoelectric sequence of blue stars established around the cluster, we derived for this star the magnitude and colors V = 13.1 +/- 0.1, B-V = 0.0 +/- 0.2, U-B = -0.7 +/- 0.2. From image-tube spectra taken with the 190-cm telescope at Mount Stromlo, the spectral type is estimated as about B6III (based on H and He lines). Its radial velocity (320 km s**-1) is consistent with cluster membership and may be slightly variable. Weak H-beta emission blueward of the H-beta absorption is seen on some spectra. This ultraviolet-bright star seems to be a primary candidate for MX 0513-40. If the identification is correct, it will also have significant implications for the theory of ultraviolet-bright stars in globular clusters." COMET LOVAS (1974c) The following precise positions have been reported: 1974/75 UT R. A. (1950) Decl. m1 m2 Observer Apr. 22.08703 12 24 00.35 - 0 16 23.2 Torres 24.15638 12 22 40.62 - 0 18 31.2 " Jan. 8.56322 14 25 04.21 -35 59 40.4 16.3 Gilmore 9.84479 14 26 11.28 -36 19 16.3 15 Seki 9.86458 14 26 12.21 -36 19 31.3 " 12.54596 14 28 31.36 -37 01 01.4 Gilmore 12.63948 14 28 36.11 -37 02 30.2 16.2 " 13.84653 14 29 37.62 -37 21 11.9 15 Seki C. Torres and S. Barros (Department of Astronomy, University of Chile). Comet diffuse with central condensation. Cerro El Roble Station. Maksutov astrograph. Measurer: M. Wischnjewsky. A. C. Gilmore (Carter Observatory). 41-cm Cassegrain reflector. Measurer: Pamela M. Kilmartin. T. Seki (Kochi Observatory, Geisei Station). 1975 February 10 (2744) Brian G. Marsden
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