Central Bureau for Astronomical Telegrams
IAUC 2839: N Cyg 1975
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Circular No. 2839
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
Cable Address: SATELLITES, NEWYORK
Western Union: RAPID SATELLITE CAMBMASS
NOVA CYGNI 1975
The following early independent discoveries have been reported:
Aug. 29.64 UT, mv = 2.5 (V. Harevich, Eniseysk, U.S.S.R.); 29.69,
2.5 (A. N. Bocharov, Gophitskoye, U.S.S.R.); 29.72, 2.8 (S. Yu.
Shugarov, Sternberg Astronomical Institute; correction to IAUC
2826); 29.73, 2 (S. K. Vsekhsvyatskij, Kiev Observatory); 29.78, 3
(Y. Shefer, Kfar-Saba, Israel; correction to IAUC 2826).
B. V. Kukarkin and E. P. Aksenov, Sternberg Astronomical Institute,
report further prediscovery observations: Aug. 5.91 UT, V
= 15.95 (Z. Alksne and I. Platais, Radioastrophysica1 Observatory,
Riga); 8.01, B = 17.6 (Alksne and Platais); 12.98, B = 17.0 (N. N.
Samus, Sternberg Astronomical Institute); 24.94, R = 13.5 (Alksne
and Platais). N. V. Vidal and W. Liller, Center for Astrophysics,
report that inspection of Harvard patrol plates taken between 1898
and 1975 Aug. 10 did not show any object down to about magnitude
15.5 within +/- 0'.5 of the position of the nova.
The following photoelectric observations have been reported:
1975 UT V B - V U - B Observer
Sept. 6.368 5.60 +0.45 -0.58 Margrave & Doolittle
6.405 5.67 +0.44 -0.60 "
6.431 5.63 +0.44 -0.57 "
8.383 6.09 +0.42 -0.60 "
9 6.21 +0.38 -0.60 French
10 6.35 +0.35 -0.63 "
10.330 6.41 +0.36 -0.56 Margrave & Doolittle
11.304 6.47 +0.37 -0.56 "
12.264 6.51 +0.33 -0.48 "
13.264 6.63 +0.32 -0.48 "
14.283 6.80 +0.31 -0.48 "
15.415 6.86 +0.27 -0.47 "
T. E. Margrave and J. H. Doolittle (Blue Mountain Observatory,
University of Montana). Accuracy 0.03 in V, 0.02 in B-V, 0.04 in
U-B. Comparison stars HR 7949 and 8162 and other UBV standards.
Eight B and V measures during Sept. 6.358-6.434 UT are consistent
to 0.01 with a periodic variation of amplitude 0.06 magnitude
and period 3.2 hr (Tempesti, IAUC 2834). A corresponding
series of U measures gave no conclusive evidence of variation.
H. French (Kitt Peak National Observatory). Accuracy 0.06 in V,
0.01 in B-V and U-B. Communicated by R. Kirshner.
P. Maley, Houston, Texas, provides the following recent visual
magnitude estimates: Sept. 17.17 UT, 6.8; 18.07, 7.0; 19.12, 7.1;
20.08, 7.0; 21.12, 7.1; 22.12, 7.1; 23.14, 7.2; 24.12, 7.2.
R. H. Koch and C. W. Ambruster, Flower and Cook Observatory,
report that they observed further light minima on Sept. 14.173,
15.142 and 15.292 UT and light maxima on Sept. 14.237 and 15.20.
The amplitudes are 0.11 magnitude in yellow, 0.13 magnitude in blue.
Preliminary ephemeris: primary light minimum = 1975 Sept. 10.0705
UT + 0.2738E. A 'bump' before primary minimum developed between
Sept. 14.30 and 15.08 and caused an apparent momentary lengthening
of the period to 0.2797 day. A. B. Hull finds no polarization
variations greater than 0.05 percent and 1o during the cycle (in
three bandpasses).
G. de Vaucouleurs, Department of Astronomy, University of
Texas at Austin, writes that the visual maximum was magnitude 1.80
+/- 0.05 on Aug. 30.85 UT and that extrapolation of the light curve
indicates that the nova may be expected to reach V = 8.0, 9.0 and
10.0 on or about Sept. 30, Oct. 30 and Dec. 15, respectively. From
the rate of decay he finds (m-M)_V = 12.05 and MV_ = -10.25 (at maximum).
He suggests that (m-M) should be corrected by -3.2E = -1.45
+/- 0.3 for absorption [where the color excess E(B-V) was inferred
from interstellar line intensities measured by J. Tomkin at McDonald
Observatory near maximum light]; thus the distance is 1.3 +/- 0.2 kpc.
B. Campbell, David Dunlap Observatory, reports that spectrum
scans on Sept. 5.2-5.3 UT show variations in all four emission
peaks of H-alpha on a timescale of 1 hr. The total intensity of H-alpha was
found to vary on a similar timescale during Sept. 7.2-7.3. In the
range 6000-7000 A on both dates the continuum was about 3.7 magnitudes
below the peaks of H-alpha and was also variable.
S. Jeffers and W. Weller, Physics Department, York University,
Downsview, Ontario, report: "Low-resolution time-resolved (Delta-t = 2
min) spectra (instrumental full width at half height 16 A) obtained
with an intensifier silicon vidicon spectrometer on a 60-cm reflector
on Sept. 3.1, 4.1, 5.1, 7.3 and 8.2 UT show striking night-to-night
and short-term variability. Both line strengths and profiles
are affected, especially the Balmer lines and C III 4650 A.
Night-to-night changes in the Balmer lines appear to be in the relative
strengths of at least three and possibly four components, possibly
associated with various shell ejections. Time-resolved spectra on
Sept. 5.1 show variations in the peak intensity of H-beta and H-gamma of
about 6 percent on timescales of 2-6 min. The growth of C III
4650 A can be seen relative to the Fe II spectrum on timescales of
15-30 min. The line blend at 5010 A shows no measurable variation
on the same spectra."
1975 September 25 (2839) Brian G. Marsden
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