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Publications Relating to the 2002 YE25 Binary Asteroid Discovery

Central Bureau for Astronomical Telegrams

The discovery was announced via the Central Bureau for Astronomical Telegrams on July 18, 2022 as Electronic Telegram No 5151. Note that a subscription may be required to access the published document.

                                                 Electronic Telegram No. 5151
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

(172376) 2002 YE_25
    P. Nosworthy, Hazelbrook, NSW, Australia (longitude 150d27'06".5, latitude -33d42'26".6, elevation 648 m), and D. Gault, Hawkesbury Heights, NSW, Australia (150d38'27".9, -33d39'51".9, 286 m), report the discovery of the likely binary nature of the minor planet (172376) from the occultation of 11th-magnitude star TYC 6854-01090-1 on 2022 May 16.447 UT. The minor planet was about 9 magnitudes fainter than the star. An occultation at both locations was not expected due to the small diameter of the occulting object. Both observers video-recorded an occultation, with the light level dropping to the limiting magnitudes (about 14.0 and 13.9) of the two recordings. The corresponding magnitude drop of about 3.0 as recorded at both locations excludes the possibility of the star being a double star with different components of the star being occulted at the two locations. The NEOWISE diameter of (172376), as determined at two epochs in 2010, is 5.7 +/- 0.6 km, giving an equivalent cross-sectional area of between 20 and 31 sq km. The two occultation chords were of length 3.8 and 3.3 km, with a mid-chord separation of 15.3 km. Assuming a highly elongate cylindrical object similar to that of minor planets (433) Eros or (216) Kleopatra, the minimal apparent cross- sectional area would be greater than 55 sq km (i.e., much larger than that expected from the NEOWISE diameter. However, if the two occultation chords were caused by spherical bodies 10 percent larger than the respective chords, the combined cross-sectional area of those bodies would be 24 sq km, fully consistent with that expected from the NEOWISE diameter. Accordingly, the observation is fully consistent with (172376) being a binary system. D. Herald (who with Nosworthy and Gault are part of the Trans-Tasman Occultation Alliance) aided in the analyses. P. Pravec adds that if (172376) is a (nearly) equal-sized binary, the prospects for its detection in the Gaia data are weak (cf. Pravec and Scheirich 2012, Planet. Space Sci. 73, 55).

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

                         (C) Copyright 2022 CBAT
2022 July 18                     (CBET 5151)              Daniel W. E. Green