Central Bureau for Astronomical Telegrams
IAUC 3107: 1977m; HD 193793; HD 77581 (VELA X-1); RY Sgr
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Read IAUC 3108
Circular No. 3107
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 Telex: 921428
Telephone: (617) 864-5758
COMET KOHLER (1977m)
Further total visual magnitude estimates indicate that this
comet is brighter than shown on IAUC 3105: Sept. 7.21 UT, 9.1 (D.
Machholz, Los Gatos, California, 25-cm reflector); 9.05, 9.9 (J.
Bortle, Brooks Observatory, 32-cm reflector); 11.05, 9.0 (Bortle,
10 x 50 binoculars); 11.12, 10.1 (R. Hill, Greensboro, North Carolina,
15-cm reflector); 12.05, 9.6 (Bortle, 32-cm reflector); 12.07,
9.1 (S. O'Meara, Harvard Observatory, 23-cm refractor).
HD 193793
P. M. Williams, M. J. Stewart, D. H. Beattie and T. J. Lee,
Royal Observatory, Edinburgh, report that observations with the 150-cm
Tenerife flux collector show that the WC6 + 06 star HD 193793 =
BD +43 3571 has brightened by about two magnitudes in the near
infrared. Observations on three occasions during Sept. 4-11 yield
the magnitudes now to be J = 5.5, H = 5.0, K = 4.0, L' (3.8 um) =
2.5. Photometry in the 10 um window and a spectrogram in the visible
would help confirm the interpretation that an optically thick
circumstellar dust shell of temperature ~ 1250 K has formed.
HD 77581 (VELA X-1)
J. E. Steiner, Instituto Astronomico e Geofisico, Universidade
de Sao Paulo, writes that an optical pulsation of period 283 seconds
has been discovered. Observations made at the Porto Alegre
Observatory with a narrow-band filter centered at H-beta show a pulsation
with the same period as the x-ray pulsation. A modulation of
up to 2 percent is present at all binary phases.
RY SAGITTARII
F. M. Bateson, Variable Star Section, Royal Astronomical Society
of New Zealand, writes that the recent decline (cf. IAUC 3098)
was independently detected by members of the Section. Photoelectric
observations at the Auckland Observatory yield: Aug. 18.432 UT,
V = 7.03, B-V = +0.81, U-B = +0.49; 19.501, 7.15, +0.81, +0.51.
Recent visual magnitude estimates: Aug. 30.50, 7.9 (B. Sumner,
Townsville, Queensland); Sept. 3.18, 8.4 (P. Collins, Steward Obs.);
5.49, 8.7 (Sumner); 8.18, 8.8 (Collins); 12.1, 9.6 (Bortle).
1977 September 13 (3107) Brian G. Marsden
Read IAUC 3108
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