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IAUC 7187: 1999cf; XTE J1550-564

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IAUC number

                                                  Circular No. 7187
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
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SUPERNOVA 1999cf IN UGC 8539
     S. Benetti, Telescopio Nazionale Galileo, communicates:
"Inspection of a preliminarily reduced CCD spectrogram (range
330-756 nm, resolution 0.25 nm) obtained on June 4.04 UT with the
William Herschel Telescope (+ ISIS) at La Palma confirms that SN
1999cf (cf. IAUC 7178) is a type-Ia supernova at maximum light.
The spectrum is dominated by P-Cyg lines of intermediate-mass
elements superimposed on a blue continuum.  Visible lines include
Ca II (H and K), Si II (597.2 and 635.5 nm), and S II (546.8,
561.2, 565.4 nm).  The expansion velocities deduced from the minima
of Si II 635.5-nm and Ca II H and K lines, corrected by the
redshift (7353 km/s, from NED) of the parent galaxy, are about
12 000 and 15 800 km/s, respectively."

XTE J1550-564
     R. Jain, C. Bailyn, and J. Greene, Yale University; J. Orosz,
Pennsylvania State University; J. McClintock, Harvard-Smithsonian
Center for Astrophysics; and R. Remillard, Massachusetts Institute
of Technology, report YALO consortium observations of XTE
J1550-564:  "We have obtained data from May 14.40 to June 1.3 UT
using the YALO 1-m telescope at Cerro Tololo.  The uncalibrated
R-band data, with relative precision of 0.02 mag, show a 1-mag
decrease during this period; hence the optical light curve has not
yet reached the true quiescent level.  Between May 14.4 and 23.28,
we obtained on average three 1200-s Johnson R exposures per night;
each was separated by several hours.  We detrended the lightcurve
by removing a linear decay of 0.05 mag/day and find clear evidence
for a modulation of 0.1 mag (full amplitude).  Using the CLEAN
algorithm and performing a fourier transform, we find a period of
1.5 +/- 0.1 days.  Similarly, by using the phase-dispersion-
minimization technique, we find a clear period at 1.5 days.  If
this period of about 1.5 days (which was suggested earlier by Soria
and Wu, IAUC 7184) is correct, then the modulation we see may be
due to a 'superhump' or to an illumination effect.  On the other
hand, if the light from the secondary dominates the light from the
accretion disk (as suggested by the strong absorption lines
reported by Soria and Wu), then the modulation we observe could be
an ellipsoidal modulation.  In this case, the orbital period would
be near 3 days.  Further spectroscopic observations will be needed
to definitively determine the orbital period."

                      (C) Copyright 1999 CBAT
1999 June 4                    (7187)            Daniel W. E. Green

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