Electronic Telegram No. 5730
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


(8007) 1988 RU_6
     M. O'Connell, International Occultation Timing Association (IOTA), 
European Section, reports the discovery of an apparent satellite of the minor 
planet (8007), based on an occultation of the star UCAC4 354-170588 (which has 
Gaia catalogued magnitudes G = 12.07 and R = 11.07) on 2026 July 27.020 UT.  
This main-belt asteroid had a magnitude of 17.1, which was 5.0 magnitudes 
fainter than the target star.  The observation was made near Valdin, Spain, 
using a 35-cm telescope (+ Apollo-M Max Pro camera and a personal computer
synchronized by Network Time Protocol).  The recording, with a limiting 
magnitude of approximately G = 14.1, showed two consecutive occultations 
lasting 0.21 and 1.32 s, respectively, with a separation of 2.04 s.  This 
corresponds to chord lengths of 1.8 and 11.5 km, and a distance of 17.4 km 
between the chords.  The flux of each drop was lower than that of the 
comparison star, UCAC4 354-170722, which has Gaia magnitudes of 13.65 (G) 
and 12.90 (R).  The depths of these drops rule out a double star as the 
cause of the light curve.  The sky-plane configuration diagram showing the 
observed occultation chord is posted at the following website URL: 
http://www.cbat.eps.harvard.edu/iau/cbet/005700/CBET5730_Fig1.png.  The 
separation of the two bodies was 0".023 in p.a. 260 +/- 5 degrees, with 
a sky-plane separation of 24.1 km.
     Representative models of the system, as well as the observed and 
superimposed modeled light curves, are posted at the following website URL: 
http://www.cbat.eps.harvard.edu/iau/cbet/005700/CBET5730_Fig2.png.  The 
NEOWISE-catalogued diameter of (8007) is 9.0 +/- 0.8 km.  Assuming that the 
main body is spherical with a diameter of 11 km, Fresnel modeling of a central 
chord provides a good fit to the second drop in the light curve.  In the 
upper model (see Figure 2), the minimum size of the apparent satellite is 
modeled as an ellipse of 3.2 km x 1.9 km.  The lower model shows the apparent 
satellite's maximum size (assuming that it is circular) as having a diameter 
of 3.5 km.
     D. Herald (who forwarded this report to the Central Bureau) and 
D. Gault, Trans-Tasman Occultation Alliance; and C. Weber, European Section, 
International Occultation Timing Association, all aided in the analysis.  
The reader is also referred to the end notes on CBET 5679.


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

                         (C) Copyright 2026 CBAT
2026 August 26                   (CBET 5730)              Daniel W. E. Green