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IAUC 8890: COMET 17P/HOLMES; C/2007 M5-M9

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IAUC number 

                                                  Circular No. 8890
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://www.cfa.harvard.edu/iau/cbat.html  ISSN 0081-0304
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COMET 17P/HOLMES
     C. Salyk and G. A. Blake, California Institute of Technology;
M. J. Mumma, B. P. Bonev, M. A. DiSanti, and G. L. Villanueva,
Goddard Space Flight Center; Y. Radeva, University of Maryland; K.
Magee-Sauer, Rowan University; and E. L. Gibb, University of
Missouri, St. Louis, report that they observed comet 17P/Holmes on
Oct. 29 and 30 UT (r = 2.46 AU) using NIRSPEC at the W. M. Keck
Observatory.  On Oct. 29, H_{2}O (eleven lines, 2.9-micron hot
bands), C_{2}H_{6} (eight Q-branches, 3.35-micron nu_{7} band),
C_{2}H_{2} (four lines, 3.0-micron nu_{3} band), HCN (nine lines,
3.0-micron nu_{3} band), and CH_{3}OH (3.52-micron P-, Q-, R-
branches, nu_{3} band) were detected.  Rotational temperatures for
H_{2}O, HCN, and C_{2}H_{6} were about 60 K.  All lines were
strongly peaked on the nucleus region, as expected for parent
volatiles.  Preliminary production rates (x 10**27} molecules/s)
are:  H_{2}O, 275; C_{2}H_{6}, 5.9; C_{2}H_{2}, 1.5; HCN, 1.5; and
CH_{3}OH, 11.  The abundance ratios are:  H_{2}O : C_{2}H_{6} :
C_{2}H_{2} : HCN : CH_{3}OH = 100 : 2.2 : 0.54 : 0.54 : 4.0.
Comet 17P seems to be enriched in organics, like C/2001 A2.  On
Oct. 30, abundance ratios for H_{2}O, C_{2}H_{2}, and HCN were
similar to those on Oct. 29.  The R0 and P2 lines of CO (4.7-
micron 1-0 band) were detected; if T_{rot} = 60 K, the formal CO
abundance is 14 (+/- 4) relative to water (100).


COMETS C/2007 M5-M9 (SOHO)
     Further to IAUC 8889, additional near-sun comets have been
found on SOHO website images -- C/2007 M5 and C/2007 M8 being non-
group, and the rest being Kreutz sungrazers.  C/2007 M5, which has
the smallest perihelion distance on record (q = 0.0011 AU), entered
the C2 field-of-view at peak brightness (mag about 6.5) and faded
rapidly, disappearing from view before it reached the occulting
disk.  C/2007 M6 was stellar in appearance (mag about 7) in C3
images, but diffuse with no tail in C2 images.  C/2007 M7 and
C/2007 M9 were faint (mag about 8) and diffuse.  C/2007 M8 was very
small, circular (nearly stellar in appearance), and faint (mag
about 7.5-8), appearing to be marginally diffuse.

 Comet        2007 UT      R.A.(2000)Decl.   Inst.  F    MPEC
 C/2007 M5    June 25.229   6 06.0  +22 37   C2     BZ   2007-U15
 C/2007 M6         25.346   6 05.4  +21 38   C3/2   BZ   2007-U15
 C/2007 M7         25.413   6 07.9  +21 39   C2     BZ   2007-U16
 C/2007 M8         25.564   6 17.8  +22 32   C2     HS   2007-U16
 C/2007 M9         27.604   6 16.5  +21 44   C2     BZ   2007-U16

                      (C) Copyright 2007 CBAT
2007 November 6                (8890)            Daniel W. E. Green

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