Central Bureau for Astronomical Telegrams
IAUC 4797: V404 Cyg; V1819 Cyg
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Read IAUC 4798
Circular No. 4797
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
R. M. Wagner, Ohio State University; T. J. Kreidl, Lowell
Observatory; S. B. Howell, Planetary Science Institute; G. W.
Collins, Ohio State University; and S. Starrfield, Arizona
State University, write: "Time-resolved CCD photometry of
V404 Cyg was obtained during June 2.37-2.46 UT using the
Lowell Observatory RCA CCD camera attached to the Perkins
1.8-m telescope. Time series analysis of these data has
revealed the presence of a periodic photometric variation in
R-band continuum light with a period of 10.0 +/- 0.1 min. The
peak-to-peak amplitude of this variation is about 0.06 mag.
The variation is present in the raw data at a statistical
significance greater than the 95-percent confidence level
and increases to greater than the 99-percent confidence level
when the effects of major flares are removed. The modulation
is present in two separate subsets of the data and is not
present in the photometry of anonymous field stars. Stochastic
flickering superposed on the periodic modulation prevented any
better determination of the accuracy of the period. Our
observations may have been obtained during the low optical state
reported by Jones and Carter (IAUC 4794), which could have
increased the probability of the detection of any periodic
variation. If confirmed, the observed photometric period could
originate from orbital motion. The early presence of strong He
emission lines in the optical (IAUC 4783) suggests that the
secondary star is evolved. However, the great strength of
He II (468.6 nm) is also reminiscent of that observed in some
intermediate polars or AM Her stars. Thus the periodic
photometric modulation could also arise from the rotation of
a magnetic white dwarf or magnetized neutron star. We agree
with Charles et al. (IAUC 4794) that the recent temporal
evolution of the object is unlike that observed for V616 Mon
and that the source is more similar to a low-mass x-ray binary.
These differences could be understood if we are observing
accretion onto a neutron star instead of a black hole, as may
be the case in V616 Mon. High-time-resolution radial
velocity studies and polarimetric observations, as well as
searches for analogous periods at x-ray wavelengths, will be
required to distinguish between these cases."
V1819 CYGNI
Visual magnitude estimates (cf. IAUC 4690): Jan. 2.74 UT,
14.5 (A. Boattini, Florence, Italy); May 17.10, 14.9 (M.
Verdenet, Bourbon-Lancy, France); June 5.17, 15.3: (J. E. Bortle,
Stormville, NY).
1989 June 13 (4797) Daniel W. E. Green
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