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IAUC 8788: V2362 Cyg; C/2003 G5; C/2006 W3

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IAUC number 

                                                  Circular No. 8788
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)


V2362 CYGNI
     J. Rayner, Institute for Astronomy, Univeristy of Hawaii; R. J.
Rudy, D. K. Lynch, R. W. Russell, and C. C. Venturini, Aerospace
Corporation; and C. E. Woodward, University of Minnesota, report
that 0.8- to 5-micron spectroscopy of V2362 Cyg was obtained from
Nov. 30 and Dec. 20 UT using the SPEX instrument on the 3-m
reflector of the Infrared Telescope Facility.  The Nov. 30 data
were obtained at the visual peak of the nova's second outburst.
That outburst rejuvenated its spectrum, erasing the higher
excitation lines and most of the He I emission features -- and
replacing them with strong lines of neutral carbon, nitrogen, and
oxygen and singly ionized iron.  There were no signs of dust local
to the nova.  In contrast, the Dec. 20 measurement revealed a
spectrum completely transformed through the formation of hot dust.
Beyond 2 microns, the spectrum is well fitted by a Planck function
with the single temperature of 1410 K.  In retrospect, it is clear
that the precipitous drop in the visible light curve beginning in
early December was due to dust formation, and that emission from
this hot dust accounted for the unexpectedly bright fluxes between
3 and 13 microns measured on Dec. 12 and reported on IAUC 8785.
The failure to recognize the dust at that time was a consequence of
its high temperature, which placed the characteristic turnover of
the Planck function outside of the measurement range.  The
underlying emission-line spectrum also changed significantly since
Nov. 30, showing both a narrowing of the lines and an increase in
excitation marked by the appearance of He II emission.


COMET C/2003 G5 (SOHO)
     Another Kreutz sungrazing comet (cf. IAUC 8786) found on
archival SOHO website images, being very faint and diffuse with no
tail:

 Comet        2003 UT      R.A.(2000)Decl.   Inst.  F    MPEC
 C/2003 G5    Apr.  6.518   1 07.8  + 5 46   C2     HS   2006-X25


COMET C/2006 W3 (CHRISTENSEN)
     Improved orbital elements (cf. IAUC 8780) from MPEC 2006-Y63:

     T = 2009 July  6.6610 TT         Peri. = 133.4836
                                      Node  = 113.5485  2000.0
     q = 3.126610 AU                  Incl. = 127.0481

                      (C) Copyright 2006 CBAT
2006 December 30               (8788)            Daniel W. E. Green

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