Central Bureau for Astronomical Telegrams
IAUC 4272: 4U 2129+12; 0754+101; PLUTO
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Circular No. 4272
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
TWX 710-320-6842 ASTROGRAM CAM Telephone 617-495-7244/7440/7444
4U 2129+12
P. Hertz, Naval Research Laboratory, writes: "I have searched
the HEAO A-1 data base for variability of 4U 2129+12, the M15 x-ray
source, at the 8.54-hr period reported by Naylor et al. and Ilovaisky
et al. (IAUC 4263) for AC 211, the proposed optical counterpart.
For 58 detections obtained during 1977 Nov. 19.3-23.3 I
find an approximately sinusoidal modulation at a period of 8.77 +
0.19 hr. The peak-to-peak amplitude is ~ 45 percent of the mean
flux at this epoch. The probability of a spurious periodicity
being detected in this data set is < 8 percent; the probability of
detecting such a spurious periodicity with a period consistent with
the proposed optical period is < 0.15 percent. The detection of
x-ray modulations at the optical period confirms the optical
identification of AC 211 with the M15 x-ray source."
0754+101
H. R. Miller, Georgia State University, writes that the BL
Lac object 0754+101 (OI 090.4) was observed with the Lowell
Observatory's 1.07-m telescope on Sept. 30 and found to be undergoing
a mild outburst. At V = 14.78, it was 1.0-2.0 mag brighter
than the typical minimum brightness for the object.
PLUTO
K. Reinsch and M. W. Pakull, Institut fur Astronomie und
Astrophysik, Technische Universitat Berlin, report: "CCD observations
on 1986 Apr. 2 and 18 with the 2.2-m and Danish 1.5-m telescopes
at the European Southern Observatory revealed mutual eclipses
of Pluto and its satellite with depths of 0.20 and 0.13 mag,
respectively. Combining these results with our nondetection of
events (depths < 0.01 mag) on 1985 Apr. 19 and 22 and the earlier
shallow eclipses (Binzel et al. 1985, Science 228, 1193), we
determined the radii of Pluto and Charon to be 1100 +/- 70 and 580 +/-
50 km, respectively. We find the mean density of the system to be
2.1 +/- 0.5 g cm**-3, the sidereal orbital period 6.38718 +/- 0.00013 d
(within 0.003 percent of Pluto's rotational period) and the plane-
of-sky orbital inclination 92.84 +/- 0.09 deg (on 1986 Apr. 18.125 UT)."
1986 November 17 (4272) Brian G. Marsden
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