Circular No. 7542
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
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XTE J1118+480
     J. McClintock, M. Garcia, P. Zhao, N. Caldwell, and E. Falco,
Harvard-Smithsonian Center for Astrophysics, write:  "Spectroscopic
observations of this x-ray nova were made with the new 6.5-m MMT on
Dec. 1 (two spectra) and 4 (six spectra).  As expected, the spectra
contain both broad Balmer emission lines and the numerous
absorption features characteristic of a late-type dwarf.  Robust
velocity measurements were obtained by cross-correlating the
individual spectra (range 490-650 nm) against the spectra of
several bright dwarfs (K5-M2).  The eight velocities provide good
an orbital period P = 0.1701 +/- 0.0003 day (IAUC 7412, 7418), and
a time of maximum velocity on 2000 Dec. 1.4776 +/- 0.0005 UT.  The
large value of the mass function, f(M) = 6.0 +/- 0.3 solar masses,
is rivaled only by that of V404 Cyg.  Our Oct. 26 observations (V =
18.8; Whipple Observatory 1.2-m telescope) showed that the nova was
near its pre-outburst brightness (IAUC 7390).  See also the
simultaneous Nov. 30-Dec. 1 photometry given below."