Electronic Telegram No. 5521
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


(127418) 2002 NB_19
     D. Herald (Murrumbateman, Australia), on behalf of the Trans-Tasman
Occultation Alliance (TTOA), writes that S. Kerr (observing at Glenlee, Qld.,
Australia) reported the discovery of a satellite of minor planet (127418) from
an occultation observation made on 2024 Aug. 17.3534 UT of the 11.8-magnitude
star UCAC4 355-159264.  With a limiting V magnitude of about 14.0, Kerr
observed two consecutive occultations of 2.08 and 0.58 s, with an interval of
1.99 s, resulting in chord lengths of 6.0 and 1.7 km, respectivelly, with a
mid-chord separation of 5.7 km (light curve posted at the following website
URL:  http://www.cbat.eps.harvard.edu/iau/cbet/005500/CBET5521_Fig1.png).  The
red line in Figure 1 is the zero line arising from the background subtraction;
because of the noise associated with the very short exposures used, the signal
at the bottom of the light curve will typically straddle that zero line,
rather than lie entirely on or above it (note that in these magnitude-drop
assessments, the authors rely on using comparison stars of known color
magnitudes, and not the zero point in the signal-background light-curve
presentation).  The vertical scale is a plot of ADU as a representation of the
relative brightness of the star over time (cf. CBET 5511).  The light curve
for the second occultation is consistent with Fresnel diffraction by a small
body.  Both light drops were greater than 1.9 mag, thereby excluding a double-
star hypothesis.  The ephemeris V magnitude for (127418) at the time of
occultation was 19.5, and the NEOWISE catalogue diameter for (127418) is 5.3
km.  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".0066 in p.a. 81 degrees.  The sky-plane plot depicts the light curve
(cf. URL http://www.cbat.eps.harvard.edu/iau/cbet/005500/CBET5521_Fig2.png)
from Kerr's data, in which the star is moving from right to left.  The size of
the satellite is set to a circle with a diameter matching the chord length of
1.7 km; the size of the main body is depicted using the NEOWISE diameter.
Kerr used a 30-cm Schmidt-Cassegrain reflector (+ Watec 910BD video camera).
D. Gault (TTOA) and Herald aided in the analysis of this observation.


NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
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                         (C) Copyright 2025 CBAT
2025 March 12                    (CBET 5521)              Daniel W. E. Green