Electronic Telegram No. 5569
Central Bureau for Astronomical Telegrams
Mailing address:  Hoffman Lab 209; Harvard University;
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e-mail:  cbatiau@eps.harvard.edu (alternate cbat@iau.org)
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Prepared using the Tamkin Foundation Computer Network


(60050) 1999 TJ_106
     D. Gault and P. Nosworthy, Trans-Tasman Occultation Alliance (TTOA),
report the discovery of an apparent satellite of minor planet (60050).  On
2025 Apr. 21.4129 UT, (60050) was observed to occult the 11.1-magnitude star
UCAC4 452-046117 from two sites in the Blue Mountains, west of Sydney,
Australia.  Nosworthy used a 28-cm telescope (+ Watec WAT-910BD video camera)
and observed a 0.38-s occultation corresponding to a chord length of 3.9 km.
Gault used a 30-cm telescope (+ Watec WAT-910BD video camera) and observed a
0.14-s occultation corresponding to a chord length of 1.4 km.  The light
curves from both observations are posted at the following website URL:
http://www.cbat.eps.harvard.edu/iau/cbet/005500/CBET5569_Fig1.png.  Both
observers recorded flux drops that reached magnitude approximately 13, being
2 mag fainter than the star, thereby eliminating any likelihood that a double
star was involved in these observations.  This minor planet is listed in the
Asteroid Light Curve Database (ALCD) with a peak-to-peak maximum brightness
variation of 0.22 mag and a rotation period of 16 hours.  Analysis of the Gaia
green-magnitude measurements of (60050) for the six instances where the
measurements extended over a period of either 2.5 or 5 hours showed a
variation of between 0.01 and 0.25 magnitude over those periods.  The analysis
of the data from various sky surveys that was undertaken by B. Carry et al.
(2024, A.Ap. 687, A38) derived the oblateness as 0.94 +/-0.08.  None of these
data suggest that (60050) is highly elongate.  The magnitude variation of 0.25
is indicative of a body that has an axis ratio of 1.26:1.  Two configuration
diagrams showing the observed chords (1 = Nosworthy, 2 = Gault), with the star
"moving" from top-left to bottom-right, is posted at the following URL:
http://www.cbat.eps.harvard.edu/iau/cbet/005500/CBET5569_Fig2.png.  The
configuration diagrams locate the main body on alternative sides of chord 1.
The main body is drawn with an area consistent with the NEOWISE-catalogue
diameter of 7.2 +/- 0.8 km, with an axis ratio of 1.26:1.  While the
orientation of the main body is not determined by the observation, the
diagrams are drawn with the major axis aligned with the satellite to
illustrate the minimum separation of the bodies consistent with the data of
NEOWISE, ALCD, Gaia, and Carry et al. for (60050).  The separation of the
bodies in both configurations excludes the possibility of a single body being
responsible for both occultations.  The separations of the presumed satellite
from the main body in the two configurations shown in Fig. 2 are 0".0045 in
p.a. 94 degrees (with a sky-plane separation of 9.9 km) and 0".0072 in p.a.
103 degrees (with a sky-plane separation of 15.9 km).  D. Herald (TTOA)
contributed to the analysis.


NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2025 CBAT
2025 June 13                     (CBET 5569)              Daniel W. E. Green