Central Bureau for Astronomical Telegrams
IAUC 4794: V404 Cyg
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Read IAUC 4795
Circular No. 4794
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
V404 CYGNI
P. Szkody and B. Margon, University of Washington, report: "CCD
photometry fortuitously obtained at Kitt Peak National Observatory on
Apr. 13 gives B = 20.3, V = 18.3 and R = 16.9. These are brighter than
the estimates from the Palomar Sky Survey given on IAUC 4787, although
our estimate from the Survey E print gives a value nearer that of our R
photometry. It is possible that there was a brightening in the weeks
before the main outburst, as previously seen in x-rays in the nova KY
TrA (Kaluzienski et al. 1975, Ap.J. 201, L121)."
D. Jones and D. Carter, Observatorio del Roque de Los Muchachos,
report that nightly UBVRI observations were made during May 29-June 7
with the 1-m Kapteyn Telescope + CCD on La Palma. The star quickly rose
to a maximum of I = 9.63, V = 11.64 on May 30.1 UT. It then quickly
fell to a minimum of I = 12.36, V = 14.76 on June 2.1 and subsequently
rose uniformly in all bands to reach I = 11.72, V = 13.82 on June 7.1.
The other bands follow the behavior of V and I, with U and B being
particularly tightly correlated with an average value of U-B = +0.2.
These values are substantially different from those recorded by Wachmann
during the 1938 outburst and also unlike the visual lightcurve of V616 Mon.
P. Charles, B. Hassall and K. Sahu, Observatorio del Roque de Los
Muchachos; T. Broadhurst, A. Lawrence and A. Taylor, Queen Mary College,
London; and P. Hacking, California Institute of Technology, report:
"Low- and intermediate-dispersion spectroscopy obtained with the 2.5-m
Isaac Newton Telescope show that the spectrum is dominated by emission
lines, with H alpha, for example, having equivalent width 12 nm and FWHM
550 km/s on June 1.2 UT. We confirm all the features reported by Wagner
and Starrfield (IAUC 4786) but with much narrower widths. Also, our
spectra in no way resemble those of V616 Mon, because the emission lines
are so much stronger than the continuum. The Balmer and He II 469-nm
profiles vary from night to night, He II sometimes showing double-peaked
structure on a scale of 400 km/s. We see interstellar Na D and the 443
band, which imply a visual absorption of about 3 mag. In addition, the
389, 447 and 588 nm He I profiles show weak P-Cyg absorption, perhaps
due to an expanding shell surrounding the source. Because of the very
high x-ray luminosity and rapid variability, V404 Cyg is certainly not a
(white dwarf) recurrent nova and is unlike any previous x-ray transient.
The optical spectrum, however, is reminiscent of an extreme Sco X-1, so
it is likely to be an LMXB containing either a neutron star or
blackhole compact object."
1989 June 8 (4794) Brian G. Marsden
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