Central Bureau for Astronomical Telegrams
IAUC 5819: YY Her; 1993 KA2
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Circular No. 5819
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@CFA or GREEN@CFA (.SPAN, .BITNET or .HARVARD.EDU)
YY HERCULIS
U. Munari and L. M. Buson, Asiago and Padova Observatories;
R. J. Ivison, University of Toronto; and G. Sostero and A. Lepardo,
Associazione Friulana di Astronomia e Meteorologia (AFAM), Udine,
Italy, communicate: "Near-simultaneous ultraviolet, optical, and
near-infrared observations have been performed on the symbiotic
star YY Her, which is currently experiencing a bright phase (cf.
IAUC 5805). Photoelectric photometry with the AFAM 0.45-m reflector
on June 15.94 and 18.03 UT gives, respectively, V = 11.67, B-V
= +0.30 and V = 11.68, B-V = +0.20, U-B = -0.58 (+/- 0.04 in all
colors), compared to V about 14.2 and B-V about +1.5 in the fall of
1992. Flux calibrated CCD spectra (ranges 400-620 nm with the
echelle spectrograph and 350-1050 nm with the Boller & Chivens
spectrograph) were secured on June 6 and 10 at the Asiago Observatory's
1.82-m telescope. Additional spectra were obtained on June
11 with the Manchester echelle spectrograph on the 2.5-m Isaac
Newton Telescope in the Canary Islands. Finally, International
Ultraviolet Explorer SWP and LWP low-resolution spectra were collected
on June 14 at the VILSPA station of the European Space Agency.
The optical region, dominated by TiO bands in 1992, is now dominated
by hot continuum emission (extending well into the red) and also
by an intense Balmer continuum in emission. Compared to the fall
of 1992, the absolute intensity of H I, He I, and He II show an
approximately 10-fold increase, while the H-beta/H-gamma ratio
stayed fixed. [O III] and [N III] are now detected in emission.
Preliminary inspection of the Asiago high-resolution spectra does
not show signs of relevant mass loss or significant changes in the
line profiles. The IUE spectra show 5-fold and 4-fold increases in
the continuum at 145.0 and 250.0 nm compared with 1980 May archival
data. The He II 164.0-nm line is now by far the strongest emission
feature. Other strong emission lines are N V at 124.0 nm, O IV +
Si IV at 140.0 nm, N IV at 148.5 nm, C IV at 155.0 nm, O III at
166.5 nm, N III at 175.0 nm, Si III at 189.2 nm, and C III at 190.8
nm. The observed behavior is quite different from classical
symbiotic outbursts, and close monitoring seems in order."
1993 KA2
Corrigendum. On IAUC 5817, the observer on both dates was T.
Gehrels, not D. Rabinowitz.
1993 June 21 (5819) Daniel W. E. Green
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