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IAUC 8704: 73P; P/1999 RE_70 =

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                                                  Circular No. 8704
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)
CBAT@CFA.HARVARD.EDU (science)
URL http://cfa-www.harvard.edu/iau/cbat.html  ISSN 0081-0304
Phone 617-495-7440/7244/7444 (for emergency use only)


COMET 73P/SCHWASSMANN-WACHMANN
    G. A. Blake and C. Salyk, California Institute of Technology;
B. P. Bonev, G. L. Villanueva, M. A. DiSanti, and M. J. Mumma,
Goddard Space Flight Center; K. Magee-Sauer, Rowan University; and
E. L. Gibb, University Missouri at St. Louis, report that component
'C' was observed on Apr. 7 and 16 UT using NIRSPEC at the W. M.
Keck Observatory.  On Apr. 7, H_2O (twelve lines, 2.9-micron hot-
bands), C_2H_6 ({**R}Q_0 and {**P}Q_1 near 3.35 microns, nu_7 band),
and HCN (six lines near 3.0 microns, nu_3 band) were detected.
Sensitive upper limits for CH_4 (R0 and R1 near 3.3 microns, nu_3
band), CH_3OH (3.52-micron Q-branch, nu_2 band), and H_2CO (3.59-
micron Q-branch, nu_1 band) were also obtained.  H_2O (eight lines)
yielded a rotational temperature of 55 +/- 6 K; for HCN (six lines)
the value was 52 K, and a rotational temperature of 55 K was
assumed for other species.  Production rates (10**25 molecules/s)
or upper limits (3-sigma) for Apr. 7 are as follows:  H_2O (590 +/-
60), C_2H_6 (0.9 +/- 0.2), HCN (1 +/- 0.1), CH_4 (< 1.5), CH_3OH (<
3), H_2CO (< 3).  The preliminary abundance ratios are then H_2O :
C_2H_6 : HCN : CH_4 : CH_3OH : H_2CO = 100 : 0.15 : 0.2 : < 0.25 :
< 0.5 : < 0.5.  On Apr. 16, the abundance ratios were:  H_2O : HCN
: CH_4 : H_2CO = 100 : 0.2 : < 0.25 : 0.5 +/- 0.13, respectively.
The abundance ratios (relative to H_2O) of C_2H_6, HCN, CH_4, and
CH_3OH in component 'C' of 73P are similar to those seen in C/1999
S4 (LINEAR), and are much lower than those of most other comets.
     Further to IAUC 8703, three additional components to 73P have
been observed on three or more nights and thus given designations
('AN', 'AO', and 'AP') and first announced on MPEC 2006-H26.


COMET P/1999 RE_70 = (118401)
     H. H. Hsieh and D. Jewitt, University of Hawaii (UH), report
that two 120-s R-band images of this object (with a = 3.20 AU, e =
0.19), obtained on 2005 Nov. 26, show a tail < 7" long in p.a. 90
deg; the images were made at the Gemini North Telescope during
their survey of Themis-family objects under the suspicion that
(118401) might show cometary activity along with other objects
having similar main-asteroid-belt orbital elements [133P/Elst-
Pizarro = (7968) and P/2005 U1].  Confirming observations from 2005
Dec. 22, 24, 25, 26, and 27 with the UH 2.2-m telescope also show
the cometary appearance of (118401) -- the Dec. 22 observation
being made by J. Pittichova, and the rest by Hsieh; a co-added
9900-s image from Dec. 27 shows a faint coma with a fan-shaped tail
about 9" long in p.a. 90 deg.

                      (C) Copyright 2006 CBAT
2006 April 24                  (8704)            Daniel W. E. Green

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