Electronic Telegram No. 5693
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)
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Prepared using the Tamkin Foundation Computer Network


(44) NYSA
     A. Berdeu, European Southern Observatory (ESO) and Laboratoire
d'Instrumentation et de Recherche en Astrophysique (LIRA), Vitacura, Chile; 
K. Minker, Lowell Observatory, Flagstaff; G. Li Causi, Istituto Nazionale di 
Astrofisica (INAF), Rome; A. Conrad, Large Binocular Telescope Observatory, 
Tucson; F. Pedichini and S. Antoniucci, INAF; M. Marsset, ESO, Garching; B. 
Carry, Observatoire de la Cote d'Azur, Nice; and F. Vachier, Observatoire de 
Paris, report the discovery of an apparent satellite in the (44) Nysa system. 
The presumed satellite was detected in optical-wavelength adaptive-optics 
images from the SHARK-VIS instrument on the Large Binocular Telescope on 2026 
Feb. 15 and Mar. 21 UT.  Each observation consisted of a series of short-
exposure images lasting three hours in total.  The apparent satellite was 
detected with two different methods:  (a) in the remaining residuals after 
subtracting the light of the primary from these images with a dedicated 
deconvolution algorithm modeling the bright halo, and (b) through PCA-ADI 
analysis adapted from exoplanet detection using the fact that acquisitions 
were made in pupil stabilized mode.  The on-sky motion of the asteroid is too 
rapid for this object to be a background star, and only one other minor planet
was detected within 5' radius of (44) on 2026 Feb. 15:  2026 BU_4, which has 
too large of a differential motion relative to Nysa (> 7"/hr) to be the
observed object; thus, the probability of this object resulting from
background contamination is very low.  The apparent satellite was located at a 
distance of 180 km (0".215) in p.a. 39 degrees on Feb. 15.3 UT and 160 km 
(0".175) in p.a. 138 degrees on Mar. 21.2, corresponding to the mid-time of 
these observations.  A magnitude difference of about 9 is detected between the 
primary and the presumed satellite, implying a satellite diameter of
approximately 0.5 km when assuming consistent albedo between the components.  
This presumed satellite is distinct from the unusual morphology reported on 
CBET 5664.  No evidence of this satellite has been previously reported.  The 
potential evidence for binarity presented by Cellino et al. (1985, A.Ap. 144, 
355) clearly originates from the object’s unusual morphology, not this small 
new presumed satellite.



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                         (C) Copyright 2026 CBAT
2026 May 26                      (CBET 5693)              Daniel W. E. Green