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IAUC 4735: SUB-Millisec OPTICAL PULSAR IN 1987A; 1989B

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                                                  Circular No. 4735
Central Bureau for Astronomical Telegrams
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

     J. Middleditch, Los Alamos National Laboratory; C. Pennypacker,
D. E. Morris, R. A. Muller, S. Perlmutter, and T. Sasseen, Lawrence
Berkeley Laboratory; J. A. Kristian and W.E. Kunkel, Mount Wilson and
Las Campanas Observatories; M. A. Hamuy, Cerro Tololo Interamerican
Observatory; J. N. Imamura, University of Oregon; T. Y. Steiman-Cameron,
Ames Research Center, NASA; I. K. Shelton, University of Toronto;
and I. R. Tuohy and S. Rawlings, Mt. Stromlo and Siding Spring
Observatories, communicate:   "We report observation of an
optical pulsar in the supernova 1987A in the Large Magellanic Cloud.
Detection was made at the Cerro Tololo 4-m telescope on Jan. 18,
using a silicon photodiode with a sampling rate of 5 kHz.  The
magnitude of the pulsed light from the supernova changed continuously
from mag 19 to 18 during a 7-hr period Jan. 18.1-18.3 UT.  No
pulsations were detected during a subsequent observation taken
at the Las Campanas 2.5-m telescope on Jan. 31 in two 100-min runs
with an upper limit of mag 20.  The frequency of the pulsar during
the Jan. 18 observation was tracked by dividing the data into
independent half-hour runs; the statistical significance during these
runs ranged from 11 to 37 standard deviations.  The frequency exhibits
a sinusoidal modulation; the 15 frequency measurements were within
5 percent (rms) of a sine function with a central value of 1968.629
Hz (barycentric), amplitude 3 x 10E-3 Hz (peak-to-peak)
and period of 8 hr.  Significant power was observed with the
same sinusoidal modulation at the aliased frequencies for both the
first and second harmonics."

     Visual magnitude estimates (visual unless otherwise indicated):
Jan. 28.20 UT, 13.5: (S. H. Lucas, Midlothian, IL; independent
discovery, not confirmed at the time); 29.11, 13.0 (A. Kane, Exeter,
England; independent discovery); 29.63, 13: (T. Yumine, Wakayama City,
Japan; prediscovery photograph on Fujicolor Super HG400 film);
31.46, 12.5 (D. Patchick, Culver City, CA); Feb. 1.96, 12.4 (G. M.
Hurst, Basingstoke, England); 2.29, 12.3 (R. Royer, Wrightwood, CA);
3.28, 12.1 (A. Hale, Las Cruces, NM); 4.64, 12.5 (A. Pearce,
Woodlands, W. Australia); 5.03, 12.2 (S. Korth, Duesseldorf, W.
Germany); 6.78, 12.1 (Pearce); 8.00, 12.3 (A. Boattini, Florence,
Italy); 8.97, 12.1 (J. D. Shanklin, Cambridge, England).

1989 February 8                (4735)             Daniel W. E. Green

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