Central Bureau for Astronomical Telegrams
IAUC 4747: CAL 87; 1987A
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Circular No. 4747
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
Telephone 617-495-7244/7440/7444 (for emergency use only)
TWX 710-320-6842 ASTROGRAM CAM EASYLINK 62794505
MARSDEN or GREEN@CFA.BITNET MARSDEN or GREEN@CFAPS2.SPAN
CAL 87
T. Naylor, IUE Observatory, European Space Agency; P. Callanan
and G. Machin, Oxford University; and P. A. Charles, Royal Greenwich
Observatory, La Palma, write: "We have discovered the orbital
period of the eclipsing low-mass x-ray binary CAL 87 in the Large
Magellanic Cloud (cf. Cowley et al. 1984, Ap.J. 286, 196) to be 10.6 hr.
The data were taken using CCD cameras on the South African Astronomical
Observatory 1.0-m and European Southern Observatory 1.5-m Danish
telescopes between Jan. 1 and 8. Combining three eclipse timings from
the ESO lightcurves with five estimates of phase zero from visual
examination of the SAAO images yields the following ephemeris: HJD of
eclipse minimum = 2447531.5919(76) + 0.4434(20)E, where the figures in
parentheses refer to formal 90-percent confidence limits for the last
two digits, assuming the lightcurve to be identical for each cycle.
However, since the eclipse duration is greater than that which is
expected if the eclipse is due to the secondary alone (see Pakull et
al. 1988, A.Ap. 203, L27), we suggest that the eclipse is partially
caused by vertical structure in the accretion disk, as in X0921-63.
For this reason, our errors should be treated as lower limits. The
eclipse is approximately 0.9 mag in the V band and 1.2 mag in the B band."
SUPERNOVA 1987A IN THE LARGE MAGELLANIC CLOUD
D. Allen, Anglo-Australian Observatory; and P. Meikle and J.
Spyromilio, Imperial College, London, communicate: "We obtained
observations, using an infrared spectrometer (FIGS) on the
Anglo-Australian Telescope, of the 1083.0-nm He I line in SN 1987A.
A narrow component, unresolved at resolution 300 km/s, has been
present since at least 1988 Sept. with little change in intensity,
and it now accounts for almost half the total line flux. On Feb. 28
the narrow component was found to arise predominently in a compact
blob about 0".8 from the supernova at position angle 200 +/- 15 deg.
A weaker, more diffuse component is also suspected to the north
of the supernova. The narrow line most plausibly arises from
excitation by the initial ultraviolet flash of a highly asymmetric
progenitor wind. The position angle agrees with that of the
velocity gradient measured in similar optical lines (IAUC 4739)."
Visual magnitude estimates (cf. IAUC 4726): Jan. 30.45 UT, 11.8
(P. Williams, Heathcote, N.S.W.); Feb. 2.58, 11.7 (Williams);
6.53, 12.1 (A. Pearce, Woodlands, W. Australia).
1989 March 1 (4747) Daniel W. E. Green
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