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IAUC 3343: U Sco; PLUTO; GX 326.3-1.8; NOTICE TO SUBSCRIBERS

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IAUC number 

                                                  Circular No. 3343
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 617-864-5758


U SCORPII
     C.-Y. Shao, Center for Astrophysics, informs us that an
exposure on Mar. 2.33 UT by J. H. Bulger with the 41-cm astrograph
at Harvard College Observatory's Agassiz Station shows no trace of
this object (cf. IAUC 3341) down to magnitude 15 or fainter.  F. M.
Bateson, Royal Astronomical Society of New Zealand, reported on Mar.
28 that observers in Auckland had not detected the object.


PLUTO
     Observers with access to large telescopes are reminded that
Pluto will be at opposition on Apr. 8 and that the reported satellite
1978 P 1 (IAUC 3241; Christy and Harrington 1978, Astron. J.
83, 1005) has not been unequivocally confirmed.  Direct observation
in conditions of excellent seeing could separate the satellite
from the primary.  R. S. Harrington, U.S. Naval Observatory, provides
the following approximate ephemeris for greatest northern
elongation (separation ~ 0".9, p.a. ~ 350o): 1979 Apr. 2.8 +/- 6.3867E
Greatest southern elongation (separation ~ 0.9, p.a. ~ 170o) occurs
midway between the greatest northern elongations.


GX 326.3-1.8
     P. C. Agrawal and G. R. Riegler, Jet Propulsion Laboratory,
report the detection of soft x-ray emission from the supernova remnant
MSH 15-56 = GX 326.3-1.8 with the low-energy detector 1 of the
HEAO-A2 experiment.  Assuming a thermal spectrum of temperature 10**7
K and a column density of 10**22 H cm**-2, the energy flux is estimated
to be (5.4 +/- 1.5) x 10**-11 erg cm**-2 s**-1.  The source was observed in
the 0.7-2.0-keV band.  No flux was detected in the 0.15-0.4-keV
band, consistent with a column density of ~ 10**-22 H cm**-2 deduced
from 21-cm measurements.  The ecliptic latitude of the soft x-ray
source agrees to within 0o.1 of that of the supernova remnant.


NOTICE TO SUBSCRIBERS
     Subscribers are advised that, owing to the recent change in
the computing system at the Smithsonian Astrophysical Observatory,
the Apr. 1 bills for the IAU Circulars will be delayed, probably
until around May 1.  For the same reason, it is not immediately
possible for us to make address changes or otherwise update
accounts.


1979 April 6                   (3343)              Brian G. Marsden

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