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IAUC 8884: C/2007 U1; V5558 Sgr

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IAUC number

                                                  Circular No. 8884
Central Bureau for Astronomical Telegrams
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
URL http://www.cfa.harvard.edu/iau/cbat.html  ISSN 0081-0304
Phone 617-495-7440/7244/7444 (for emergency use only)

     An apparently asteroidal object reported by the LINEAR survey
(discovery observation tabulated below) that was posted on the
Minor Planet Center's 'NEOCP' webpage has been found to show
cometary appearance by several CCD observers.  G. Sostero, E.
Guido, and V. Gonano (Remanzacco, Italy, 0.45-m reflector) write
that their co-adding of 73 unfiltered 60-s exposures obtained on
Oct. 21.1 UT reveals a tiny coma nearly 18" in diameter of mag
about 18.6, elongated toward the northwest.  K. Sarneczky and L. L.
Kiss report that their co-added 900-s R-band image taken with the
2.3-m reflector at Siding Spring on Oct. 21.8 shows a 6" coma and
12"-long tail in p.a. 150 deg.  L. Buzzi (Varese, Italy, 0.60-m
reflector) notes that his exposures from Oct. 21.1 and 22.1 show
that the object appears slightly diffuse with a central
condensation and a 10" round coma, but no tail.

     2007 UT             R.A. (2000) Decl.       Mag.
     Oct. 19.40678    7 43 54.42   + 2 29 27.5   19.4

The available astrometry, the following preliminary parabolic
orbital elements, and an ephemeris appear on MPEC 2007-U53.

     T = 2008 Aug.  7.291 TT          Peri. =   1.431
                                      Node  =  50.142   2000.0
     q = 3.30999 AU                   Incl. = 157.756

     R. J. Rudy, D. K. Lynch, R. W. Russell, The Aerospace
Corporation; and C. E. Woodward, University of Minnesota, report
0.8- to 5.5-micron spectroscopy of V5558 Sgr on Oct. 10 and 11 UT
using the Infrared Telescope Facility (+ SpeX).  The bright,
narrow-lined, slowly evolving nova V5558 Sgr (cf. IAUC 8874) showed
a spectrum dominated by low-excitation emission lines.  The P-Cyg
profiles have disappeared from the hydrogen lines but were present
on the He I triplet at 1.0830 microns and the singlet at 2.0581
microns, which were both weak.  N I lines were strong, but C I
features are weak or absent entirely.  Fe II features were strong,
and the infrared complexes at 1, 1.6, and 2 microns were present.
Line widths (FWHM) were about 1600 km/s.  The O I lines, which
included a large contribution from continuum fluorescence, indicate
a reddening of E(B-V) about 0.8.  No dust formation was detected.

                      (C) Copyright 2007 CBAT
2007 October 22                (8884)            Daniel W. E. Green

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