Central Bureau for Astronomical Telegrams
IAUC 4817: V1521 Cyg (CYGNUS X-3); 1987A
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Circular No. 4817
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
V1521 CYGNI (CYGNUS X-3)
E. B. Waltman, R. L. Fiedler and K. J. Johnston report: "The second
flare anticipated on IAUC 4798 has occurred, following the return of Cyg
X-3 to its quiescent level by late June. Observations with the Green
Bank interferometer, operated by the National Radio Astronomy
Observatory for the Naval Research Laboratory and the U.S. Naval
Observatory, show that on July 21.362 UT the flux again reached 18.0 Jy
at 8.085 GHz and 5.9 Jy at 2.7 GHz. Eight hours later the flux was
still rising. Flares in Cyg X-3 typically last a few days at a level
exceeding 5 Jy."
SUPERNOVA 1987A IN THE LARGE MAGELLANIC CLOUD
B. E. Schaefer, NASA Goddard Space Flight Center, reports:
"Observations made on July 16 with the CCD camera on the 0.91-m
reflector at Cerro Tololo show that three small bright knots have
appeared in the light echo around SN 1987A. Their distances and
position angles from the supernova are for knot 1, 53".0, 17.1 deg; knot
2, 52".0, 20.0 deg; and knot 3, 51".5, 20.7 deg. The knots appear where
the inner ring intersects a ridge of nebulosity seen on pre-eruption
plates. The three knots are diffuse (with a FWHM estimated as 2",
corresponding to a radius of 0.24 pc) and out of round (knots 1 and 3
have an eccentricity of roughly 0.30). The core of knot 1 has V = 18.0
(corresponding to an absolute magnitude of -1) and colors B-V = +1.2,
V-R = +0.4, R-I = +0.2. Knots 2 and 3 have similar colors and are both
0.4 mag fainter. These knots are likely to remain visible for less than
a month or so. The inner ring has a uniform radius of 52" and a width
from 5" to 12"; this ring is brightest between p.a. 10-60 deg and
280-330 deg, with the same distribution as the nebulosity visible before
the eruption, thus associating this nebulosity with the inner ring; the
brightest location has a V brightness of 20.4 mag arcsec-2. The outer
ring has a bright section (20.0 mag arcsec-2 in V) over p.a. 320-350
deg; over p.a. 290-360 deg the radius is 86" with a typical width of
11", and for p.a. 0-150 deg the radius is significantly larger at 90".
The colors of the brightest portion of the outer ring are U-B = -0.70,
B-V = +0.98, V-R = +0.37, R-I = +0.34. The surface brightness of the
echo is considerably brighter than in previous reports, and the total
brightness of the entire echo is estimated to be V = 13."
1989 July 21 (4817) Brian G. Marsden
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