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IAUC 7749: 2001 QW_322; U Sco; 1RXS J232953.9+062814

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                                                  Circular No. 7749
Central Bureau for Astronomical Telegrams
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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2001 QW_322
     J. J. Kavelaars, McMaster University; J.-M. Petit,
Observatoire de Besancon; B. Gladman, Observatoire de la Cote
d'Azur; and M. Holman, Harvard-Smithsonian Center for Astrophysics,
report the discovery of another putative binary transneptunian
system, with available astrometry, orbital elements, and an
ephemeris given on MPEC 2001-V34.  Images acquired on Aug. 24 by
Kavelaars at the Canada-France-Hawaii Telescope and analyzed by
Petit revealed the presence of two transneptunian objects with
identical sky motions and nearly identical magnitudes (R = 24.0 +/-
0.1).  The system has an angular separation of 4", several times
larger than that of the other known cubewano binary system (cf.
IAUC 7610) and the two other known plutino binary systems (cf. IAUC
3241, 3509; IAUC 7733).  A gradual separation of 0".2 +/- 0".1 per
month is detected at the limit of the astrometric precision.  An
assumed 4-percent albedo implies that both components have radii of
about 100 km; assuming a circular orbit and a density of 1 g/cm**3
indicates an orbital period of approximately 4 yr, consistent with
the measured change in angular separation.  The very small
variation in position angle implies that the system is seen nearly

     B. E. Schaefer, University of Texas, Austin, writes:  "An
eruption of the recurrent nova U Sco was discovered on 29 archival
photographs at the Harvard College Observatory dating from mid-1945.
The observed peak magnitude was at B = 9.57 on May 31, although the
lack of plates over the previous 24 days allows for a somewhat
brighter maximum.  Representative B magnitudes:  June 5, 11.56; 11,
13.74; July 2, 15.15; 7, 16.98; 16, 17.37.  The 1945 event suggests
that the average recurrence timescale is fairly uniform at around
11 years, with outbursts missed (perhaps due to conjunction with
the sun) around 1956 and 1967."

1RXS J232953.9+062814
     J. Biggs, Perth Observatory, reports that four exposures were
taken of this object (cf. IAUC 7747) by Biggs and S. Walsh with the
Mike Candy Telescope on Nov. 8.62, yielding magnitude R = 14.8 +/-
0.5 and the following position:  R.A. = 23h29m54s.2, Decl. =
+6 28'12" (equinox 2000.0); the uncertainty of +/- 1" is within the
11" uncertainty of its x-ray position (cf. Voges et al. 1999, A.Ap.
349, 389).  Biggs adds that a star in the USNO-A2.0 catalogue at R
= 15.6 has position end figures 54s.36, 10".4.

                      (C) Copyright 2001 CBAT
2001 November 9                (7749)            Daniel W. E. Green

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