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IAUC 2881: theta1 Ori A; CI Cyg; omicron And; 1975p

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IAUC number

                                                  Circular No. 2881
Central Bureau for Astronomical Telegrams
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.

theta1 ORIONIS A
     The following visual magnitude estimates indicate that the
expected primary minimum on Dec. 5 did occur but that the duration
may have been significantly shorter than 24 hours (cf. IAUC 2859):
Dec. 5.24 UT, 6.7 (D. di Cicco, Waltham, Massachusetts); 5.577, 8.0
(V. L. Matchett, Indooroopilly, Queensland); 6.23, 6.7 (di Cicco).

     Recent observations indicate that this star is having another
outburst (cf. IAUC 2788, 2804).  Selected visual magnitude estimates:
Nov. 6.0 UT, 11.4 (J. Bortle, Brooks Observatory); 21.84,
11.0 (G. M. Hurst, Northampton, England); 24.1, 11.2 (Bortle);
26.88, 10.5 (Hurst); 29.89, 10.0 (Hurst); Dec. 2.0, 10.2 (Bortle)

     M. Fracassini and L. E. Pasinetti, Merate Observatory, Milan,
communicate: "Two spectrograms of omicron And obtained on Dec. 4.7 UT
with the Zeiss prism spectrograph (dispersion 35 A/mm at H-gamma) of the
137-cm telescope at the Merate Observatory show that H-beta, H-gamma, H-delta
and H-epsilon have absorption cores sharper and deeper than those observed
during the whole month of November and in particular on Nov. 28 and 29.
Sharp absorption metallic lines have appeared or are enhanced, and
it may be that the major shell is developing."

     J. Hers, Randburg, near Johannesburg, provides the following
additional precise position, obtained with a 20-cm reflector:

     1975 UT             R. A. (1950) Decl.
     Nov. 17.08507    11 35 15.43   -42 14 38.3

     J. B. Trainor, South Caulfield, Victoria (using 12 x 50 binoculars),
and T. B. Tregaskis, Mount Eliza, Victoria (instrument not
specified), each reported the total magnitude as 8, on Nov. 27.72
and 27.74 UT, respectively.

1975 December 8                (2881)              Brian G. Marsden

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