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IAUC 7609: V4334 Sgr; 1998 SF_36

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                                                  Circular No. 7609
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://cfa-www.harvard.edu/iau/cbat.html  ISSN 0081-0304
Phone 617-495-7440/7244/7444 (for emergency use only)

     K. Hinkle and R. Joyce, Kitt Peak National Observatory (KPNO),
report infrared photometry of V4334 Sgr (cf. IAUC 6322) obtained on
two different telescopes and instruments on Mar. 13.6 UT:
"Observers Hinkle and Joyce at the KPNO 4-m telescope (using the
Phoenix spectrograph in imaging mode) report [1.083 microns] = 13.6,
[1.205 microns] = 13.0, [1.647 microns] = 9.4, [2.230 microns] =
6.1, and [3.226 microns] = 3.3.  Observers M. Brown and G. Tiede at
the KPNO 2.1-m telescope (using SQIID) report J = 12.60, H = 9.36,
and K = 6.42.  This confirms the reported brightening (cf. IAUC
7592).  The infrared photometry, except for [1.083 microns], is
consistent with a 680-K blackbody that is unchanged over the last
year (cf. IAUC 7422)."
     T. R. Geballe, Gemini Observatory; B. Smalley, V. H. Tyne, and
A. Evans, Keele University; and S. P. S. Eyres, University of
Central Lancashire, obtained medium-resolution J and K-band spectra
of V4334 Sgr on Mar. 21.6 UT at the U.K. Infrared Telescope:  "We
estimate J = 13.2 and K = 6.7 from the spectra, confirming the
brightening in the J band observed by Lederle and Kimeswenger (IAUC
7592), but possibly indicating some fading since their measurement.
The brightening at J is due to a stronger continuum; the flux in
the He line at 1.083 microns has decreased markedly since our
previous observation in Aug. 2000.  We urge continued monitoring of
this object."

1998 SF_36
     R. P. Binzel, Massachusetts Institute of Technology, reports
obtaining 0.8- to 2.5-micron spectroscopic measurements of 1998
SF_36 on Feb. 19.5 and Mar. 28.6 UT using the NASA Infrared
Telescope Facility 3-m reflector on Mauna Kea:  "Combined with Kitt
Peak 4-m visible spectrum measurements (cf. IAUC 7598), complete
coverage is available over 0.5-2.5 microns.  These data fully
reveal the features of an S-type minor-planet spectrum whose 1-
micron-feature center is at 0.99 +/- 0.01 microns and 2- to
1-micron 'band area ratio' is 0.40 +/- 0.02, placing it within the
S(IV) category of Gaffey et al. (1993, Icarus 106, 573).   The
minor-planet reflectance spectrum resembles that of laboratory
measurements of LL chondrite meteorites (Gaffey 1976, J. Geophys.
Res. 81, 905; all spectra normalized to unity at 0.55 microns),
although it appears more steeply red-sloped by an average
reflectance of 0.20 per micron.  1998 SF_36 appears to have the
surface composition of a reddened ordinary chondrite meteorite."

                      (C) Copyright 2001 CBAT
2001 April 11                  (7609)            Daniel W. E. Green

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