Central Bureau for Astronomical Telegrams

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IAUC 6085: 1993 SB; RE J1255+266; 1994l

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IAUC number

                                                  Circular No. 6085
Central Bureau for Astronomical Telegrams
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
Phone 617-495-7244/7440/7444     TWX 710-320-6842 ASTROGRAM CAM

1993 SB
     A tentative recovery of this object by J. Luu and D. Jewitt
with the University of Hawaii's 2.2-m reflector on Sept. 10 has
been confirmed by Jewitt and J. Chen on Sept. 29 and by M. R.
Kidger and G. V. Williams on images obtained with the 2.5-m
Isaac Newton reflector on Aug. 15 and 16.  Computations by B. G.
Marsden show that this is the first of the transneptunian objects
found during the past two years actually known to have a Neptune-
crossing orbit, a general solution yielding an obviously unstable
result with a = 42.9 AU, e = 0.42, q = 25.0 AU, i = 2 deg.  However,
the uncertainty is such that the available observations can be
represented almost equally well by an orbit with a = 39.4 AU,
e = 0.32, q = 26.8 AU, i = 2 deg, which is in 2:3 resonance with
Neptune and prevents the object from approaching within 21 AU of
Neptune.  Further details are on MPEC 1994-S06.  As with 1993 RO
and SC (cf. IAUC 6076), further observations, at this and future
oppositions, will be required before it can be proven whether there
can be close encounters with Neptune or not.

RE J1255+266
     M. Dahlem, Johns Hopkins University; and H.-C. Kreysing,
Astronomical Institute, University of Tubingen, report the
serendipitous detection with the ROSAT WFC of an extremely bright
EUV source at R.A. = 12h55m07s.6, Decl. = +26d41'21" (equinox
2000.0, uncertainty +/- 20").  The observations started on
June 25.51 UT, when the measured countrate was about 14 cts/s.
This temporarily made RE J1255+266 the brightest EUV source in
the sky.  During the observing run, which ended on July 7.19 UT,
the lightcurve showed an exponential decrease in flux with a decay
time of about 1 day.  At the time of the detection the source
was more than 3000 times brighter than the sensitivity limit of the
ROSAT WFC all-sky survey, during which it was not detected.  The
Palomar Sky Survey plates show no obvious optical counterpart.  A few
faint objects close to the source position might belong to the
cluster Abell 1656.

     Total visual magnitude estimates: Sept. 11.43 UT, 10.7 (C. S.
Morris, Pine Mountain Club, CA, 0.26-m reflector); 17.15, 10.5 (A.
Diepvens, Balen, Belgium, 0.15-m refractor); 24.46, 10.1 (Morris);
27.12, 10.6 (J. Lancashire, Cambridge, England, 0.30-m refractor).

1994 October 1                 (6085)              Brian G. Marsden

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