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IAUC 2780: PRIME CANDIDATE FOR THE TRANSIENT X-RAY SOURCE A0535+26; Cen A; PERIODIC COMETS GIACOBINI (1896 V) AND METCALF (1906 VI)

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IAUC number 

                                                  Circular No. 2780
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


PRIME CANDIDATE FOR THE TRANSIENT X-RAY SOURCE A0535+26
     W. Liller, Center for Astrophysics, Harvard and Smithsonian
Observatories, reports that the peculiar B emission star BD +26 883
= HDE 245770 = SAO 077348, located 0m.1 west of the best position
for the transient x-ray source discovered by Eyles et al. (IAUC
2774), varies by at least 0.7 magnitude.  Normally its B magnitude
is 10.1 or 10.2, but it can be as bright as B = 9.6 +/- 0.1, according
to Harvard plates taken between 1933 and the present.  On the
most recent plate, taken on 1975 Feb. 2-3, it was at B = 9.9.
Three low-dispersion spectra taken in the 1920s confirm that HDE
245770 is a luminous OB star, but no trace of an emission feature
can be seen between 4900 and 3800 A.


CENTAURUS A
     R. C. Haymes, Rice University, writes: "In a 1974 Apr. 1 balloon
flight it was observed that Cen A had begun emitting much more
low-energy gamma radiation than previously.  A 1.1 E**-2 continuum was
detected, together with a broadened spectral line at 1.62 MeV."


PERIODIC COMETS GIACOBINI (1896 V) AND METCALF (1906 VI)
     Dr. N. A. Belyaev, Institute for Theoretical Astronomy, Leningrad,
provides the following predicted elements, calculated by
N. Yu. Goryamova, V. V. Emel'yanenko and himself:

             P/Giacobini          P/Metcalf
     Epoch = 1975 Dec. 14.0       1975 July 7.0 ET
         T = 1975 Nov. 6.7528     1975 June 20.9164 ET
     Peri. = 148.8587             207.9404
     Node  = 185.3450             187.2555  1950.0
     Incl. =  13.3392              13.0572
         q =   1.468177             1.594425 AU
         e =   0.583071             0.593381
         a =   3.521406             3.921177 AU
         n =   0.1491523            0.1269344
         P =   6.608                7.765 years

Ephemerides appear in Handb. Br. Astron. Assoc. for 1975.  The
predictions are necessarily somewhat uncertain, and neither comet is
expected to be brighter than magnitude 18.


1975 May 15                    (2780)              Brian G. Marsden

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