Central Bureau for Astronomical Telegrams
IAUC 2931: 1975n; 1976d
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Read IAUC 2932
Circular No. 2931
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
COMET WEST (1975n)
Further precise positions have been reported as follows:
1976 UT R. A. (1950) Decl. m1 Observer
Mar. 20.50990 21 04 16.87 +11 29 39.2 Giclas
21.81681 21 02 17.04 +11 45 29.5 4 Tomita
22.78501 21 00 52.71 +11 56 46.5 4 "
H. L. Giclas (Lowell Observatory). Measurer: M. L. Kantz. The
positions by this observer (see also IAUC 2928) evidently refer to
nucleus B, although that on Mar. 6.54 possibly refers to A or D.
The positions by B. Milet (IAUC 2928) probably refer to A, possibly
to D (but not to the object observed on Mar. 6.54).
K. Tomita (Tokyo Astronomical Observatory, Dodaira Station). 91-cm
reflector. These positions definitely refer to nucleus A.
The following orbital elements, by the undersigned, were derived
from 40 observations 1975 Aug. 10 to 1976 Mar. 22 (with the
probable positions of nucleus A after perihelion). Perturbations
by all nine planets were taken into account. The somewhat less
satisfactory residuals in other attempted solutions suggest that
nucleus A is probably the most massive component of the comet.
Epoch 1976 Mar. 3.0 ET
T = 1976 Feb. 25.2212 ET Peri. = 358.4186
e = 0.999955 Node = 118.2332 1950.0
q = 0.196630 AU Incl. = 43.0710
Further photographic observations of the separations and
position angles of the additional nuclei (relative to nucleus A):
Nucleus B. Mar. 14.49 UT, 9".7, 332o (C. Knuckles and S. Murrell,
New Mexico State University; measured by E. J. Reese); 18.51,
12".7, 326o (Knuckles et al.); 19.50, 11".9, 318o (D. A. Ketelsen,
D. Dee and J. S. Neff, University of Iowa); 21.82, 15".5, 320o
(Tomita); 22.46, 15".3, 322o (Ketelsen et al.); 22.79, 14".6, 321o
(Tomita); 24.50, 16".3, 319o (Knuckles et al.).
Nucleus C. Mar. 14.49 UT, 4".2, 300o (Knuckles et al.); 18.51, 7".7,
295o (Knuckles et al.); 19.50, 8".9, 286o (Ketelsen et al.);
22.46, 11".7, 293o (Ketelsen et al.); 24.50, 14".5, 291o (Knuckles
et al.).
Nucleus D. Mar. 14.49 UT, 4".6, 358o (Knuckles et al.); 18.51, 6".1,
344o (Knuckles et al.); 19.50, 6".5, 330o (Ketelsen et al.);
21.82, 5".4, 348o (Tomita); 22.46, 7".2, 337o (Ketelsen et al.):
22.79, 6".6, 342o (Tomita); 24.50, 7".1, 338o (Knuckles et al.).
The origin of position angle on Mar. 19.50 is uncertain. J. Bortle,
Brooks Observatory, reports that nuclei B, C and D were all some
1.5-2.0 magnitudes fainter than A on Mar. 20.4; B was perhaps only
0.5-1.0 magnitude fainter than A on Mar. 22.4 and 23.4 but 2 magnitudes
fainter (as was D) and difficult to observe on Mar. 24.4. Nucleus
C was not observed on Mar. 22-24 and evidently then at least
3 magnitudes fainter than nucleus A.
It is possible that some of the early observations tentatively
attributed to nucleus B [notably those on Mar. 5.23 (IAUC 2924) and
8.53 (IAUC 2927) but probably not that on Mar. 8.40 (IAUC 2924);
see also the note above about the Mar. 6.54 observation] refer in
fact to nucleus D. Z. Sekanina, Center for Astrophysics, remarks
that, while the situation is still not entirely clear, it is at
least as possible that D separated from A as from B (cf. IAUC 2930).
Further observations by J. C. Webber et al. (cf. IAUC 2928)
show that the peak intensity of the OH emission at 1667 MHz had
more than doubled (to > 0.30 Jy) on Mar. 19, 20 and 21.
S. Wyckoff and P. A. Wehinger, Royal Greenwich Observatory,
report that spectrograms (range 3300-8000 A, dispersions 40 and 210
A/mm) obtained with the 250-cm reflector on Mar. 21.2, 23.2 and
24.2 UT revealed emission features due to CN (red and blue systems),
C2 (Swan system), CH, C3, NH, NH2 (7-0 through 12-0 bands), and in
the tail CO+, H2O+ and possibly CO2+.
Further selected total visual magnitude estimates and tail
information: Mar. 14.15 UT, 2.2, 5o.3 in p.a. 290o (F. Popperl, Bad
Reichenhall, Germany, 12.5-cm refractor); 16.43, 2.3, 1o.5 in 300o
(W. I. Nissen, Bradenton, Florida, naked eye); 19.43, 2.4, 1o.5 in
290o (Nissen); 20.40, 3.7, 4o in 286o (Bortle, 10 x 50 binoculars);
21.46, 3.9, - (P. Maley, Houston, Texas, 7 x 35 binoculars); 22.41,
3.8, 6o.5 in 290o (Bortle); 24.40, 4.1, ~ 7o (Bortle).
COMET BRADFIELD (1976d)
Extension of the ephemeris on IAUC 2926:
1976 ET R. A. (1950) Decl. Delta r m1
Apr. 2 4 36.81 - 7 12.6 1.031 1.004 11.6
7 4 49.47 - 2 57.2
12 4 59.08 + 0 13.9 1.376 1.147 12.8
17 5 06.85 + 2 42.0
22 5 13.45 + 4 40.1 1.710 1.293 13.8
27 5 19.29 + 6 16.4
May 2 5 24.61 + 7 36.5 2.022 1.441 14.6
B. Sumner, Pallarenda, Queensland, sends the following visual
magnitude estimate (15-cm reflector): Mar. 17.41 UT, 10 or fainter.
1976 March 26 (2931) Brian G. Marsden
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