Electronic Telegram No. 5679
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


(12148) CARAVAGGIO
     J.-F. Gout, International Occultation Timing Association (IOTA), reports 
the discovery of an apparent satellite of minor planet (12148) based on an
occultation of the star UCAC4 549-045196 (which has catalogued Gaia magnitudes
G = 11.97 and R = 11.48) on 2026 Jan. 27.395 UT.  The magnitude of (12148) was 
17.9 (or six magnitudes fainter than the target star).  Gout observed from 
Starkville, MS, USA using a 28-cm telescope, a CMOS camera, and a Linux 
computer synchronized by Network Time Protocol (in which the accuracy of his
time synchronization has been tested multiple times with a GPS-triggered
flasher and found it to be always better than 10 ms).  The recording showed 
two consecutive occultations of durations 0.09 and 0.7 s, separated by 5.5 s, 
corresponding to chord lengths of 1.1 and 8.75 km.  Allowing for possible 
ellipticity of the asteroid profile, the length of the longer chord is 
consistent with the 7.8 km diameter listed in the Asteroid Lightcurve Data 
Exchange Format (ALCDEF) database.  The flux during both occultations dropped 
below that of comparison stars UCAC4 549-045199 (Gaia magnitudes G = 12.9 and 
R = 12.1) and UCAC4 549-045202 (Gaia magnitudes G = 12.9 and R = 12.4), ruling 
out the possibility of a binary star.  While the flux for the longer event 
dropped below the limiting magnitude of the recording (approximately G = 14.0 
and R = 13.5), the flux for the shorter event bottomed at a level comparable 
to that of comparison star UCAC4 549-045197 (Gaia magnitudes G = 13.4 and R = 
12.9).  Modeling, which incorporated the effects of Fresnel diffraction, 
indicated that the occultation by the main body was near-central, while the 
diameter of the presumed satellite, assuming it is substantially spherical, 
was between 0.7 and 3.0 km.  The observed light curve, together with the 
modeled light curve, is posted at the following website URL:
http://www.cbat.eps.harvard.edu/iau/cbet/005600/CBET5679_Fig1.png.  The 
sky-plane configuration diagram showing the observed occultation chords, 
together with the Fresnel diffraction model for the main body, and two for 
the satellite showing the chord locations for the minimum and maximum 
probable diameter of the satellite, is posted at the following website URL:
http://www.cbat.eps.harvard.edu/iau/cbet/005600/CBET5679_Fig2.png.  The red 
circle in those plots represents the physical size of the body.  The 
separation of the satellite was 0".0548 in p.a. 288.9 +/- 0.5 degrees, 
with a separation of 73.9 km. 
     D. Herald and D. Gault of the Trans-Tasman Occultation Alliance and C. 
Weber of the European Section of the IOTA aided in the analysis; B. Anderson 
(IOTA) provided the Fresnel diffraction software.  Herald has also provided a 
supplemental article that was prepared at the request of the Central Bureau to 
describe how these teams rule out potential problem cases with regard to the 
observation and analysis of these occultations, and it accessible via URL 
http://www.cbat.eps.harvard.edu/iau/cbet/005600/CBET5679_supplement.pdf.


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

                         (C) Copyright 2026 CBAT
2026 April 6                     (CBET 5679)              Daniel W. E. Green