Central Bureau for Astronomical Telegrams
IAUC 2779: Cyg X-1; 1974f; 1973l; P/ENCKE
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Read IAUC 2780
Circular No. 2779
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
CYGNUS X-1
C. C. Wu, P. R. Wesselius, R. J. van Duinen, K. S. de Boer and
J. W. G. Aalders, Space Research Department, Kapteyn Institute,
University of Groningen, communicate: "Ultraviolet observations by
the University of Groningen instrument on board the Astronomical
Netherlands Satellite (ANS) show that the flux of Cyg X-1 (HDE
226868) between 1550 and 3300 A was 5.8 x 10**-10 erg cm**-2 s**-1 on May
3.16 UT. There was no significant variation 34 hours later. The
energy distribution is consistent with a reddened early B-type star."
J. Heise, A. C. Brinkman, R. Mewe, J. Schrijver, A. G. F. den
Boggende and E. Gronenschild, Laboratory for Space Research,
Utrecht, communicate: "Since the upward transition of Cyg X-1
(Gursky et al. IAUC 2778) a soft x-ray flux of 0.38 +/- 0.04 cts/s
has been observed between 0.2 and 0.53 keV with the soft x-ray
detector on board the ANS spacecraft. The measured flux can be
accounted for by assuming a power law (photon number) spectrum with
index -3.5 and a column density of 7 x 10**21 in the range 0.5 to 6
keV, in agreement with the spectrum derived from our 1-6 keV detector.
The main part of the soft flux is coming from the range 0.4-0.53
keV. The flux at 0.50 keV then corresponds to 13 +/- 3 ph cm**-2
s**-1 keV**-1. This suggests that the power spectrum is valid over the
entire range 0.5 to 6 keV, which leads with a distance of 2.5 kpc
to an intensity of Cyg X-1 of 9.6 x 10**27 erg s**-1 in that energy
range."
R. M. Hjellming, D. M. Gibson and F. N. Owen, National Radio
Astronomy Observatory, write: "On hearing of the report by Gursky
et al. (IAUC 2778), we found that radio observations of Cyg X-1
with the N.R.A.O. interferometer showed increased levels of radio
emission. Cyg X-1 had been at roughly 0.015 Jy since the initial
radio 'turn-on' and associated x-ray decrease in Mar. 1971. On
1975 May 9 the radio source, still coincident in position with the
star HDE 226868, was at a level of 0.024 Jy at 2695 Hz and showed
time variation between 0.044 and 0.030 Jy at 8085 MHz. At its peak
the source was about three times its previous level at 8085 MHz."
C. T. Bolton, David Dunlap Observatory, reports: "Spectrograms
(12 A/mm) of the blue-violet region of HDE 226868 taken at the
David Dunlap Observatory on May 9-11 at spectroscopic phases 0.957
and 0.135 (near maximum velocity) and 0.312 (superior conjunction
of the x-ray source) show no significant changes from spectrograms
obtained at the same phases prior to the recent x-ray change of
state of Cyg X-1."
Corrigendum: On IAUC 2778, line 9, for 575 cts/s, read 790
cts/s.
PERIODIC COMET HONDA-MRKOS-PAJDUSAKOVA (1974f)
Dr. Elizabeth Roemer, Lunar and Planetary Laboratory, communicates
the following precise positions, obtained with the 154-cm
reflector at the Catalina Station. Measurer: Carolyn C. McCarthy.
1974/75 UT R. A. (1950) Decl.
Nov. 17.08333 18 49 26.37 -13 04 51.5
Mar. 13.33958 9 36 43.71 -24 00 11.6
PERIODIC COMET SCHWASSMANN-WACHMANN 2 (1973l)
The following precise positions have been reported:
1975 UT R. A. (1950) Decl. m1 m2 Observer
Mar. 18.52513 12 46 47.72 + 0 40 02.6 16.1 Gilmore
21.73681 12 44 30.77 + 0 58 31.5 13 Seki
A. C. Gilmore (Carter Observatory). 41-cm f/13.5 Cassegrain
reflector. Measurer: Pamela M. Kilmartin.
T. Seki (Kochi Observatory, Geisei Station). From Orient. Astron.
Assoc. Comet Bull. No. 101.
PERIODIC COMET ENCKE
Extension of the ephemeris on IAUC 2547:
1975 ET R. A. (1950) Decl. Delta r m2
June 17 23 10.68 - 6 04.8 3.538 3.824 20.6
27 23 09.77 - 6 04.5
July 7 23 07.08 - 6 14.9 3.289 3.879 20.4
17 23 02.54 - 6 36.2
27 22 56.20 - 7 07.8 3.091 3.928 20.2
Aug. 6 22 48.24 - 7 48.2
16 22 39.02 - 8 35.1 2.987 3.970 20.0
26 22 29.06 - 9 25.0
Sept. 5 22 18.99 -10 14.5 3.007 4.007 20.0
15 22 09.45 -10 59.8
25 22 01.05 -11 38.3 3.156 4.036 20.3
Oct. 5 21 54.18 -12 08.1
15 21 49.14 -12 28.5 3.410 4.060 20.6
m2 = 14.5 + 5 log Delta + 5 log r + 0.03 (phase angle)
1975 May 15 (2779) Brian G. Marsden
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