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IAUC 5172: 1991 BA; 4U 0115+63; 1990c

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                                                  Circular No. 5172
Central Bureau for Astronomical Telegrams
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
Telephone 617-495-7244/7440/7444 (for emergency use only)
TWX 710-320-6842 ASTROGRAM CAM     EASYLINK 62794505

1991 BA
     An asteroidal object of V = 17.5 was discovered in Cancer on
Jan. 18.23 UT by D. Rabinowitz with Spacewatch, Kitt Peak, and
followed by him and J. V. Scotti for 5 hr, during which time it moved
7.1 deg to the east and south.  From seven measurements by Scotti,
B. G. Marsden established that this was an Apollo object with the
following approximate orbital elements: T = 1991 Mar. 2.06 ET, Peri.
= 70.58, Node = 118.34, i = 1.96 (equinox 1950.0), q = 0.713 AU, e =
0.682, a = 2.24 AU.  All the observations are satisfied within 1",
so there is no possibility that this was an artificial object in a
geocentric orbit.  With H = 28.5, the object was presumably some ten
times smaller than 1990 UN (cf. IAUC 5130), until now the celestial
object of smallest known size, and 1991 BA is thus estimated to be
only 5-10 m across.  During the observed arc, the topocentric distance
of 1991 BA decreased from 0.0052 to 0.0033 AU, the latter distance
being closer than any natural object outside the atmosphere
has been known to come.  It passed the earth at a record (geocentric)
miss distance of 0.0011 AU (170 000 km) on Jan. 18.72 UT and
moved into the daytime sky.

4U 0115+63
     H. Mendelson and T. Mazeh, Wise Observatory, report:  "The
optical counterpart of the x-ray pulsar 4U 0115+63 is going through
another eruption.  On Jan. 12 and 13 the stellar I magnitude was
12.3 +/- 0.1, typical of the previous eruptions (cf. IAUC 4555).
Last November the star was still found to be faint, I = 13.4 +/-
0.2, suggesting that the present eruption might have a short timescale,
contrary to the previous 1990 long outburst.  During the last
short eruption in 1988, no x-ray output was detected.  Spectroscopic
and x-ray observations are, therefore, urged."

COMET LEVY (1990c)
     Total visual magnitude estimates (cf. IAUC 5157):  Jan. 7.51
UT, 7.6 (A. Hale, Kitt Peak, AZ, 10x50 binoculars); 9.83, 8.1 (M.
Ohkuma, Doudaira, Saitama, Japan, 20x100 binoculars); 13.54, 7.0 (C.
S. Morris, Pine Mountain Club, CA, 20x80 binoculars); 18.75, 7.6
(Ohkuma, Shirahama, Chiba, Japan, 10x70 binoculars); 19.53, 7.0

1991 January 21                (5172)             Daniel W. E. Green

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