Electronic Telegram No. 5522
Central Bureau for Astronomical Telegrams
Mailing address:  Hoffman Lab 209; Harvard University;
 20 Oxford St.; Cambridge, MA  02138; U.S.A.
e-mail:  cbatiau@eps.harvard.edu (alternate cbat@iau.org)
URL http://www.cbat.eps.harvard.edu/index.html
Prepared using the Tamkin Foundation Computer Network


(61784) 2000 QL_178
     D. Herald (Murrumbateman, Australia) on behalf of the International
Occultation Timing Association (IOTA), writes that N. Carlson (observing near
Tucson, AZ, USA) and J. Bardecker (IOTA; observing near Gardnerville, NV, USA)
reported the discovery of a satellite of minor planet (61784) from
occultation observations made on 2024 Apr. 29.285 UT of the 12.0-magnitude
star UCAC4 393-057338.  Carlson observed two consecutive occultations of 0.18
and 0.44 s, with an interval of 0.40 s, resulting in chord lengths of 2.2 and
5.3 km (respectively), with a mid-chord separation of 5.3 km (light curve
posted at http://www.cbat.eps.harvard.edu/iau/cbet/005500/CBET5522_Fig1.png;
see CBET 5521 for explanation of graph).  The limiting red magnitude was
estimated to be 13.0 and the limiting green magnitude 13.5.  The minor
planet was at ephemeris V magnitude 19.0 (red mag 18.2).  Both light drops
were greater than 1.3 magnitudes, thereby excluding a double-star hypothesis.
Bardecker observed but did not detect an occultation.  The NEOWISE catalogue
diameter for this minor planet is 5.2 km, and the separation of the two light
drops is too large to be explained by an occultation by the two ends of an
elongate body having a size consistent with the NEOWISE diameter.  The
position of the satellite relative to the main body is 0".0067 in p.a. 302
degrees.  The sky-plane plot conveys the light curves (posted at website URL
http://www.cbat.eps.harvard.edu/iau/cbet/005500/CBET5522_Fig2.png) of Carlson
(bottom chord), and the constraining "miss" chord of Bardecker (top chord).
The star is moving right to left.  The size of the satellite is set to a
circle with a diameter matching the chord length of 2.2 km.  The chord length
for the main body is the same as the NEOWISE diameter for this minor planet,
with the constraining "miss" chord suggesting that the main body may have an
elliptic profile.  Carlson used a 24-cm Schmidt-Casssegrain reflector (+
RunCam Night Eagle Astro camera).  D. Gault, Trans-Tasman Occultation
Alliance (TTOA), and Herald (IOTA and TTOA) aided in the analysis of these
observations.


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

                         (C) Copyright 2025 CBAT
2025 March 12                    (CBET 5522)              Daniel W. E. Green