Circular No. 6704

Central Bureau for Astronomical Telegrams INTERNATIONAL ASTRONOMICAL UNION

Mailstop 18, 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)

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Phone 617-495-7244/7440/7444 (for emergency use only)

COMET P/1997 N2 (HELIN-ROMAN-ALU 2) Comet P/1989 U1 (= 1989y = 1989 XVI) has been recovered on CCD

frames obtained by C. W. Hergenrother with the Smithsonian Astrophysical Observatory’s 1.2-m reflector on Mt. Hopkins. Candidate images among several measured by T. B. Spahr and motion-checked by G. V. Williams show some possible very slight diffuseness on July 13, and this is more evident on a coaddition of the two-night total exposure of 12 min, a short tail then also being evident in p.a. 250^{o}. The indicated correction to the prediction by B. G. Marsden on MPC 23483 (ephemeris on MPC 29154) is ΔT = −0.6 day.

1997 UT  α_{2000}  δ_{2000}  m_{2}
July 13.45823  1^{h}00^{m}00.^{s}27  +7^{o}36′20′′.4
13.46002  1 00 00.43  +7 36 20.9
13.46183  1 00 00.59  +7 36 21.8
14.43271  1 01 26.89  +7 43 01.7  19.6
14.43450  1 01 27.06  +7 43 02.7
14.43628  1 01 27.21  +7 43 03.3

The following orbital elements by Williams satisfy 16 observations 1989–1997 with mean residual 1′′.0:

Epoch = 1997 Nov. 8.0 TT

T = 1997 Nov. 10.0833 TT  ω = 220.^{o}9513
e = 0.531645  Ω = 178.4818 }2000.0
q = 1.910084 AU  i = 5.7751

a = 4.078279 AU n^{o} = 0.1196709 P = 8.236 years

1997 TT α_{2000}  δ_{2000}  Δ  r  ϵ  β  m_{2}
July 21 1^{h}11.^{m}00 + 8^{o}25.^{′}7 1.752 2.154 98.^{o}7 27.^{o}8 20.1
31 1 24.92 + 9 21.1 1.616 2.116 104.8 27.6 19.9
Aug. 10 1 37.79 +10 03.1 1.487 2.080 111.1 27.0 19.7
20 1 49.28 +10 29.3 1.368 2.047 117.9 25.9 19.4
30 1 59.01 +10 37.6 1.258 2.017 125.3 24.1 19.1
Sept. 9 2 06.53 +10 26.2 1.160 1.990 133.3 21.6 18.9
19 2 11.52 + 9 54.4 1.076 1.967 142.0 18.3 18.6
29 2 13.78 + 9 03.5 1.008 1.948 151.4 14.3 18.3
Oct. 9 2 13.40 + 7 57.3 0.959 1.932 161.2  9.6 18.0
19 2 10.99 + 6 43.6 0.931 1.921 170.6  4.9 17.7
29 2 07.52 + 5 32.3 0.925 1.913 172.0  4.1 17.6
1997 July 21  \begin{matrix}c \\ ◯ \end{matrix} Copyright 1997 CBAT  Brian G. Marsden