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IAUC 3533: Prob. N IN Sgr; Q0957+561; P/ENCKE

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                                                  Circular No. 3533
Central Bureau for Astronomical Telegrams
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

     H. Kosai, Tokyo Astronomical Observatory, telexes that Minoru
Honda has discovered a stellar object in Sagittarius, at R.A =
18h16m.5, Decl. = -24o45' (equinox 1950.0).  The object was of mv = 9.0
on Oct. 28.42 UT and comparable in brightness on Oct. 29 and 30.

     I. M. Kopylov, Director of the Special Astrophysical Observatory,
Zelenchukskaya, communicates: "G. M. Beskin, S. I. Neizvestnyj
and V. F. Shvartsman report that the components of the double quasar
Q0957+561 have 'switched roles' as a result of their slow variability.
Component B is now brighter than component A, whereas during
1979 and the first half of 1980 component A was the brighter (cf.
IAUC 3481).  Electrophotometric observations with the 6-m telescope
on Oct. 12.05 UT give for component A: U = 16.75, B = 17.69, V =
17.51, R = 16.96; for component B: U = 16.75, B = 17.65, V = 17.35,
R = 16.74.  On Oct. 13.05 UT they give for component A: U = 16.76,
B = 17.71, V = 17.51, R = 16.98; for component B: U = 16.73, B =
17.64, V = 17.34, R = 16.70.  These figures are appreciably different
from previous values.  For example, on 1979 Dec. 22.06 UT
observations with the same telescope gave for component A: U =
16.61, B = 17.56, V = 17.39, R = 16.89; for component B: U = 16.93,
B = 17.84, V = 17.51, R = 16.86.  If components A and B represent
the same physical object that has been split into two images by a
gravitational lens, then the time delay between the two light paths
is greater than 1.5 years."

     P. D. Feldman, Department of Physics, The Johns Hopkins University,
writes that he, M. C. Festou, H. A. Weaver and H. U. Keller
observed P/Encke with the International Ultraviolet Explorer on Oct.
24 when the comet was at a heliocentric distance of 1.015 AU.
Strong emission was detected at L-alpha (7.5 kR averaged in aperture 10"
x 20") and the OH (0,0) band (3.5 kR).  The CS (0,0) band at 257.5
nm also appeared but was very weak.  The above numbers translate
into an estimated water-production rate of the order of 10**28 mol s**-1.
Detection of the OH 0.18-m lines in absorption should be possible in
early November.  Further IUE observations will be made on Nov. 3-5.

1980 November 3                (3533)              Brian G. Marsden

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