Central Bureau for Astronomical Telegrams
IAUC 6703: V723 Cas; BL Lac
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Circular No. 6703
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
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Phone 617-495-7244/7440/7444 (for emergency use only)
V723 CASSIOPEIAE
T. Iijima and L. Rosino, Asiago Astrophysical Observatory,
report: "A spectrogram (range 460-710 nm, resolution 0.06 nm) of
V723 Cas (N Cas 1995) was taken at Asiago Observatory on July 1.09
UT using the 1.82-m reflector (+ echelle spectrograph). Prominent
emission lines of [Fe VII] at 572.1 nm (equivalent width -2.76 nm)
and at 608.6 nm (EW = -7.04 nm) were detected in the spectrum.
These lines were not seen in a spectrum taken on May 30.1 with the
same instruments. The intensity of the emission line He II 468.6-
nm relative to H-beta increased from 0.16 to 0.54 during the same
period, while [O III] 500.7-nm was nearly stable and its intensity
was about 0.15 of H-beta in both spectra. Prominent emission lines
in the last spectrum, in order of decreasing intensity, are as
follows (line positions given in nm): H-alpha, H-beta, He II 468.6,
He I 587.6, He I 706.5, [N II] 575.5, [Fe VII] 608.6, [O III]
500.7, He I 667.8, [Fe VII] 572.1, Si II 504.1, He II 541.2, [Fe
VI] 517.7, [Fe II] 464.0, [Fe III] 527.0, He I 501.6, [S III]
631.0, [Ca V] 530.9, [Fe II] 497.3, [O III] 495.5, Si II 505.6, Si
II 637.1, and [Fe VII] 515.8. About two years after the explosion,
this slowest classical nova seems to have entered the nebular
stage. The high intensities of Si II lines, however, are fairly
unusual for spectra of classical novae in this stage."
BL LACERTAE
R. Hartman, D. Bertsch, S. Bloom, P. Sreekumar, and D.
Thompson, Goddard Space Flight Center, report: "The EGRET
instrument on the Compton Gamma Ray Observatory detects a
significant increase in BL Lac at gamma-ray energies above 100 MeV,
in observations made during a target of opportunity following the
announcement of an increase of over 1 mag in the optical emission
of this source (IAUC 6693, 6700). The average gamma-ray flux above
100 MeV is 1.3 x 10E-6 photons cmE-2 sE-1, based on data for 2.3
days. The significance level of the detections is 6.6 sigma. The
current flux level is 3.5 times that of the only other weak
detection in January 1995. Prior to 1995, EGRET only detected
upper limits from BL Lac."
F. Ma and D. Barry, University of Texas, report that UBVRI
images of the field of BL Lac were made with the McDonald
Observatory 0.76-m telescope between July 19.21 and 21.46 UT. The
preliminary lightcurve shows that it might have peaked on July
19.220 with R = 12.62 +/- 0.05. Between July 19.454 and 19.467, it
faded about 0.3 mag, from R = 13.08 +/- 0.05 to 13.37 +/- 0.05, in
19 min. Additional R magnitudes: July 20.2243, 13.2; 20.4694,
12.86; 21.238, 13.69; 21.455, 13.07.
(C) Copyright 1997 CBAT
1997 July 21 (6703) Daniel W. E. Green
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