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IAUC 2551: Cyg X-1; 1973h; 1973 EC

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IAUC number 

                                                  Circular No. 2551
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


CYGNUS X-1
     Dr. E. N. Walker, Royal Greenwich Observatory, reports: "The
blue light curve of Cyg X-1 = HDE 226868 has changed since 1972.
Observations on 18 nights between 1973 May 26 and June 18 at the
Spanish Sierra Nevada show symmetrical and very regular primary
minima and variable secondary minima.  The secondary minima that
should have occurred on June 1 to 2 and June 12 to 13 did not occur.
This possibly indicates that secondary minima are not occurring on
alternate cycles.  Changes in the optical spectra and x-ray behavior
should be looked for."


COMET HUCHRA (1973h)
     The following precise positions have been reported:

     1973 UT             R.A. (1950) Decl.       Mag.   Observer
     May   5.60833   14 21 16.5    +29 53 14     14     Seki
           5.64931   14 21 13.4    +29 52 15              "
          14.03616   14 10 17.77   +26 32 39.4   13.5   Antal
          14.05417   14 10 16.47   +26 32 12.9            "
     June  2.00300   13 53 12.99   +18 11 09.9   15     Wood

T. Seki (Kochi Observatory).  Correction to IAUC 2536.  From Orient.
   Astron. Assoc. COmet Bull. No. 66.
M. Antal (Skalnate Pleso Observatory).  30-cm f/5 astrograph.
N. Wood and R. L. Waterfield (Woolston Observatory).  Measurer:
   Waterfield.  Inner coma 15" in diameter, very faint outer coma
   1'.5 in diamter.


1973 EC
     Mr. J. Gibson, Observatorio Austral Yale Columbia, El Leoncito,
communicates the following precise positin, obtained with the
51-cm double astrograph.  Measurer: Mrs. Ursula Gibson.

     1973 UT             R.A. (1950) Decl.
     May  28.32986   19 58 10.56   -12 43 23.7


1973 June 29                   (2551)              Brian G. Marsden

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