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IAUC 7113: U Sco; XTE J1550-564; 52P

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                                                  Circular No. 7113
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 617-495-7244/7440/7444 (for emergency use only)

     P. Schmeer, Bischmisheim, Germany, reports an outburst of this
recurrent nova, which last flared in 1987 (cf. IAUC 4395).  Confirmatory
observations have been received via E. Waagen at the AAVSO.  Visual
magnitudes: Feb. 25.194 UT, 9.5 (Schmeer); 25.562, 7.6 (L. Shaw, Pinole,
CA); 25.625, 8.0 (M. Mattiazzo, Wallaroo, South Australia).

XTE J1550-564
     J. Casares, Instituto de Astrofisica de Canarias; G. Dubus,
University of Amsterdam; and L. Homer, University of Oxford, report:
"We have obtained B, V and R images and medium-resolution spectroscopy
(0.38 nm) of the x-ray transient XTE J1550-564 (IAUC 7008) on Feb.
17-18 with the 3.5-m New Technology Telescope at the European Southern
Observatory, La Silla.  We measured B = 16.6 +/- 0.1, V = 16.3 +/- 0.1,
R = 15.5 +/- 0.1 on 1998 Sept. 19.4, so the transient has again reached
the optical brightness of the outburst last September (IAUC 7010) during
this current x-ray reflare (IAUC 7098, 7013).  Our spectra show a
reddened continuum dominated by strong interstellar features and broad
emission lines of H alpha (FWHM = 815 km/s, EW = 0.3 nm), He II 468.6-nm
(FWHM = 1150 km/s, EW = 0.2 nm) and the Bowen blend (FWHM = 1370 km/s,
EW = 0.3 nm), characteristic of x-ray transients in outburst.  We also
identify weak emission lines of He I 587.5-nm and 667.8-nm and H beta.
The H alpha and He II 468.6-nm lines are double-peaked with a separation
of about 380 km/s and exhibit a factor of 2-3 variability in their
equivalent widths between the two nights.  We measure equivalent widths
-3.6 for Na D (588.9-589.5 nm) and -0.30 for 661.3 nm, from which we
estimate an approximate E(B-V)= 1.0 +/- 0.1.  More optical observations
of this new blackhole candidate are very much required."

     Total visual magnitude estimates: Jan. 5.02 UT, 10.8 (J. Bortle,
Stormville, NY, 0.41-m reflector); 10.74, 10.8, (K. Hornoch, Lelekovice,
Czech Republic, 0.35-m reflector); 16.65, 11.5 (A. Pearce, Nedlands,
Western Australia, 0.41-m reflector); 23.95, 10.8 (M. Meyer, Frauenstein,
Germany, 0.25-m reflector); 27.58, 11.1 (N. Biver, Oahu, HI, 0.26-m
reflector); Feb. 5.79, 11.1 (R. J. Bouma, Groningen, The Netherlands,
0.25-m reflector); 9.89, 10.9 (A. Baransky, Kiev, Ukraine, 0.11-m
reflector); 13.74, 10.7 (S. Yoshida, Ibaraki, Japan, 0.25-m reflector);
16.91, 11.9 (J. Carvajal, Madrid, Spain, 0.21-m reflector); 22.74, 10.5
(M. Lehky, Hradec Kralove, Czech Republic, 25 x 100 binoculars).

                      (C) Copyright 1999 CBAT
1999 February 25               (7113)              Brian G. Marsden

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