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IAUC 4790: V404 Cyg = GS 2023+338; 1988k; Occn OF 28 SGR BY SATURN ON 1989 JULY 2-3

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                                                  Circular No. 4790
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

V404 CYGNI = GS 2023+338
     R. M. Hjellming, National Radio Astronomy Observatory; X.-h. Han,
NRAO and Beijing Observatory; and F. A. Cordova, Los Alamos National
Laboratory, communicate: "VLA observations show a strong, variable
radio source at R.A. = 20 22 06.30, Decl. = +33 42 16.3 (equinox
1950.0, uncertainty 1"), coincident with the optical position of Nova
V404 Cyg 1938.  Preliminary analysis shows that on May 30.19 UT the
flux was 1.6, 1.2 and 1.1 Jy at frequencies of 4.9, 8.4 and 14.9 GHz,
respectively.  By June 1.33 UT the first two had changed to 0.098 and
0.08 Jy.  These data may indicate the rapid decay stage of an
expanding synchrotron-radiating source that is much stronger than the
radio counterparts of the x-ray transients A0620-00, GS2000+25 and Cen
X-4 (Hjellming et al. 1988, Ap.J. 335, L75).  However, the apparent
radio spectra are unusual for x-ray transients, so there could be
sparse sampling of more erratic variability of a complex source.  In
any case, the radio position and variability indicate that our object
is the radio counterpart of the current outburst of V404 Cyg = GS
2023+338.  VLA observations will continue every few to several days
for at least the next few weeks."

     G. M. Hurst, Basingstoke, England, reports the following preliminary
photometry from photographs by M. Mobberley, Chelmsford: May 26.99 UT,
12.8 (revision to IAUC 4783); 27.96, 12.5; 28.98, 11.9; 29.96, 12.5.

     With reference to IAUC 4787, H. E. Bond, Space Telescope Science
Institute, reports that two R-band CCD images obtained with the 0.9-m
reflector at Cerro Tololo on June 2.00 UT showed an extended coma of
about 14" x 9".

     With reference to the upcoming occultation of 28 Sgr by Saturn's
rings (IAUC 4746; Dunham et al. 1989, Sky Telescope 77, 638), B.
Wallis and L. Lane, Jet Propulsion Laboratory, remark that the use of
methane-band filters at 0.89 or (particularly) 2.2 microns would
reduce contamination of the stellar signature by the scattered light
from Saturn.

1989 June 2                    (4790)              Brian G. Marsden

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