Circular No. 6281

Central Bureau for Astronomical Telegrams INTERNATIONAL ASTRONOMICAL UNION

Postal Address: Central Bureau for Astronomical Telegrams Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A. IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)

BMARSDEN@CFA.HARVARD.EDU or DGREEN@CFA.HARVARD.EDU (science) Phone 617-495-7244/7440/7444 (for emergency use only)

COMET C/1995 Y1 (HYAKUTAKE) Additional positions, from G. Garradd (Loomberah, N.S.W.; 0.25-m

f/4.1 reflector + CCD):

1995 UT  α_{2000}  δ_{2000}
Dec. 28.66561  14^{h}28^{m}10.^{s}94  −24^{o}22′57′′.6
28.68005  14 28 14.22  −24 22 49.3
28.68786  14 28 16.06  −24 22 43.9
28.70090  14 28 18.96  −24 22 35.4
28.70584  14 28 20.03  −24 22 32.0

Garradd adds that a 300-s exposure showed a coma diameter of 2′.5 with a broad, 2′.5-long extension in p.a. 250^{o}. The coma lacked a distinct central condensation in 5- and 10-s images; rather there was a region of diameter ∼ 10′′ of relatively uniform brightness.

The following preliminary parabolic orbital elements, by the undersigned, are from 18 observations, Dec. 26–28:

T = 1996 Feb. 23.938 TT  ω = 45.^{o}516
Ω = 195.863 }2000.0
q = 1.06376 AU  i = 54.220
1995/96 α_{2000}  δ_{2000}  Δ  r  ϵ  β  m_{1}
Dec. 19 13^{h}53.^{m}16 −25^{o}39.^{′}9 1.897 1.514 52.^{o}4 31.^{o}0 10.7
24 14 10.86 −25 06.5 1.812 1.461 53.5 32.8 10.4
29 14 29.45 −24 19.4 1.730 1.409 54.5 34.6 10.2
Jan. 3 14 48.96 −23 16.5 1.650 1.359 55.4 36.6  9.9
8 15 09.44 −21 55.6 1.574 1.312 56.2 38.5  9.7
13 15 30.88 −20 14.4 1.503 1.267 56.8 40.5  9.4
18 15 53.25 −18 11.2 1.437 1.225 57.2 42.4  9.2
23 16 16.48 −15 44.6 1.379 1.187 57.4 44.3  8.9
28 16 40.47 −12 54.5 1.330 1.154 57.5 46.0  8.7
Feb. 2 17 05.08 − 9 42.6 1.290 1.124 57.4 47.5  8.6
7 17 30.14 − 6 12.1 1.262 1.100 57.0 48.7  8.4

Total visual magnitude estimates: Dec. 26.86 UT, 10.5 (Y. Hyakutake, Hayato, Japan, 25×150 binoculars); 27.52, 10.2 (A. Hale, Cloudcroft, NM, 0.41-m reflector; coma diameter ∼ 4′).

1995 December 28 Daniel W. E. Green