Central Bureau for Astronomical Telegrams
IAUC 4826: V745 Sco; V1521 Cyg (CYGNUS X-3); NOTICE TO SUBSCRIBERS
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Read IAUC 4827
Circular No. 4826
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
V745 SCORPII
S. Shore, Computer Sciences Corporation; G. Sonneborn, Laboratory
for Astronomy and Solar Physics, Goddard Space Flight Center; and S.
Starrfield, Institute of Geophysics and Planetary Physics, Los Alamos
National Laboratory, report: "Low-dispersion ultraviolet spectra (range
115-335 nm, resolution 0.6 nm) of the recurrent nova V745 Sco were
obtained with the International Ultraviolet Explorer satellite on Aug.
3.2-3.35 and 4.55-4.7 UT. The ultraviolet spectrum is dominated by
high-temperature emission lines. A weak continuum is also present
longward of 250 nm. Visual magnitude estimates were derived from IUE
Fine-Error Sensor data (400-700 nm): Aug. 3.3 UT, 10.9; 4.7, 11.5.
There was no discernible change in the spectrum between the two
observing sessions, even though the optical brightness decreased by
about 0.6 mag. The detected emission lines are: N V 124.0 nm, Si IV
140.0, N IV] 148.6, C IV 155.0, He II 164.0, O III] 166.6, N III]
175.0, C III] 190.9 blended with Si III] 189.2, Mg II 280.0, O III 313
and [Ne III] 335 nm. C IV, N III] and Mg II, the strongest lines in
the spectrum, are extremely broad with FWHM about 4000 km/s. Similar
lines and blends can be seen in the ultraviolet spectrum of the
recurrent nova U Sco obtained on 1979 June 28 near maximum (Williams et
al. 1981, Ap.J. 251, 221)."
Magnitude estimates by W. Liller, Vina del Mar, Chile (2415 film,
minus UV filter): Aug. 1.03 UT, 9.9; 2.97, 10.2; 4.04, 10.4; 5.01, 10.7.
V1521 CYGNI (CYGNUS X-3)
V. Kotov, Crimean Astrophysical Observatory, reports that the
recent flare (cf. IAUC 4817) was independently detected by N. S.
Nesterov, who found the 8.2-mm flux to increase from < 0.5 Jy on
July 19 to 11.32 +/- 0.1 Jy on July 21.
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1989 August 5 (4826) Brian G. Marsden
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