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IAUC 3858: 4U 1543-45; A0538-66

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                                                  Circular No. 3858
Central Bureau for Astronomical Telegrams
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
TWX 710-320-6842 ASTROGRAM CAM     Telephone 617-864-5758

4U 1543-45
     R. J. Blissett and the EXOSAT Observatory Team report that a
3-hr EXOSAT observation on Aug. 28 located the transient x-ray
source 4U 1543-45 (IAUC 3854) at a position preliminarily determined
as R.A. = 15h43m34s, Decl. = -47deg31'1 (equinox 1950.0; maximum
error radius 30").  This is 3' northwest of the 50" region of
uncertainty previously quoted.  The 2-10-keV spectrum is unusually
soft with a characteristic temperature of ~ 1.7 keV, similar to
that previously reported from A0620-00 (V616 Mon) after maximum.

     With the help of the above report, H. Pedersen, M. Veron, P.
Veron and H.-E. Schuster, European Southern Observatory, communicate
that comparison of a red plate taken with the 1.0-m Schmidt
telescope on Aug. 31.0 UT with the red ESO Sky Survey shows a star
at R.A. = 15h43m33s9,  Decl. = -47deg30'54" (equinox 1950.0) that has
increased in brightness by ~ 1 mag.  The position is 8" northwest of
the mag 12 star that appears 13 mm northwest of the northwest
corner of the error box shown by Matilsky et al. (1972, Ap.J. 174,
L53).  CCD observations on Sept. 2.0 with the 1.54-m Danish telescope
give V = 14.9, B-V = +0.7.  Low-dispersion spectra obtained
on Sept. 2.0 and 3.0 with the 3.6-m telescope show emission lines
from N III 463.4 and 464.2 nm, He II 469 nm and He I 668 nm; H-alpha
emission, if present, is weak; absorption lines include Na D
(equivalent width 0.25 nm) and 628.4 nm (interstellar).

     J. Menzies, South African Astronomical Observatory, telexes
that the LMC recurrent transient A0538-66, which has been quiescent
in the optical region since late 1982 (IAUC 3757), appears to
have become active again.  Spectrograms obtained by M. Feast
around Aug. 9.17 UT (phase 0.02) show weak emission lines at H-beta
and H-gamma and a strong, double-peaked line with equivalent width 1.7
+/- 0.1 nm at He II 469 nm.  On the previous night there were very
weak H lines and no sign of He II.  The spectral change was accompanied
by a change in brightness in the blue continuum of ~ 1 mag.

     I. Howarth, University College, London, reports that an IUE
observation on Aug. 26.9 UT (phase 0.1) shows emission lines at
N V 124 nm, C IV 155 nm and He II 164 nm.

1983 September 6               (3858)              Brian G. Marsden

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