Presentation #307.12 in the session “Centaur/KBO/Pluto Gathertown”.
(119951) 2002 KX14 is a low-inclination (i ~ 0.4°), low-eccentricity (e ~ 0.04) cold classical TNO, orbiting the Sun at an average distance of a ~ 39 au. The Spitzer radiometric diameter is given as 455 ± 27 km. Spin parameters are yet unknown. To date three stellar occultations by this TNO were successfully observed: (1) a single-chord observation on Apr 26, 2012, constraining the area-equivalent diameter to at least 365 (+30, -21) km, (2) a double-chord recording on Sep 19, 2018, and (3) a multi-chord observation on May 26, 2020. Occultation events (2) & (3) in 2018 and 2020 were predicted, updated and announced by the Lucky Star* project and collaboration. Astrometric observations contributing to prediction updates were derived from observatories in Brazil and Chile used by the LS teams. Here we report the prediction, observation and analysis of events (2) and (3), namely the occultation of the star Gaia DR2 4113743899728632704 (G = 15.8 mag) on Sep 19, 2018 and of the star Gaia DR2 4111560308371475840 (G = 14.6 mag) on May 26, 2020, and provide first results on the size and profile shape of this object. The shadow of the 2018 event crossed Australia and was recorded by two stations. The shadow of event (3) was predicted to cross eastern Europe. As this event was suitable to be observed by smaller telescopes, the amateur community was also informed. Ten stations recorded the occultation with apertures between 20 cm and 80 cm. 14 stations reported a non-detection of the occultation event within their observing windows. For both events we fitted the positive chords to an ellipse (circle in case of event (2)) to derive the instantaneous limb of 2002 KX14. From the fit parameters we derived the size of the 2D projected profile as well as a high-accurate astrometric position for the time of occultation. Photometric observations to derive the light curve amplitude and the rotational period, also with the aim to put constraints on the albedo as well as on the 3D size and shape of 2002 KX14, are in preparation. While planning these photometric observations we recognized that 2002 KX14 will have a very low phase angle opposition on 2021 June 14.3 UT (α ~0.004°). Thus we carried out several photometric measurements at small phase angles (0.04° < α < 0.22°) with the 4.2-m William Herschel telescope at the Roque de los Muchachos observatory, La Palma, Spain, and will present first results on this as well.
(*) Lucky Star (LS) is an EU-funded research activity to obtain physical properties of distant Solar System objects using stellar occultations. LS collaboration agglomerates the efforts of the Paris, Granada, and Rio teams.