14 research outputs found
A Single-chord Stellar Occultation by the Extreme Trans-Neptunian Object (541132) Leleākūhonua
A stellar occultation by the extreme large-perihelion trans-Neptunian object (541132) Leleākūhonua (also known by the provisional designation of 2015 TG387) was predicted by the Lucky Star project and observed with the Research and Education Collaborative Occultation Network on 2018 October 20 UT. A single detection and a nearby nondetection provide constraints for the size and albedo. When a circular profile is assumed, the radius is r = 110+14-10 km, corresponding to a geometric albedo Pv = 0.21+0.03-0.05, for an adopted absolute magnitude of HV = 5.6, typical of other objects in dynamically similar orbits. The occultation also provides a high-precision astrometric constraint
The Sizes and Albedos of Centaurs 2014 YY and 2013 NL from Stellar Occultation Measurements by RECON
In 2019, the Research and Education Collaborative Occultation Network (RECON)
obtained multiple-chord occultation measurements of two centaur objects: 2014
YY on 2019 January 28 and 2013 NL on 2019 September 4. RECON is a
citizen-science telescope network designed to observe high-uncertainty
occultations by outer solar system objects. Adopting circular models for the
object profiles, we derive a radius km and a geometric albedo
for 2014 YY, and a radius km and geometric albedo for 2013
NL. To the precision of these measurements, no atmosphere or rings are
detected for either object. The two objects measured here are among the
smallest distant objects measured with the stellar occultation technique. In
addition to these geometric constraints, the occultation measurements provide
astrometric constraints for these two centaurs at a higher precision than has
been feasible by direct imaging. To supplement the occultation results, we also
present an analysis of color photometry from the Pan-STARRS surveys to
constrain the rotational light curve amplitudes and spectral colors of these
two centaurs. We recommend that future work focus on photometry to more
deliberately constrain the objects' colors and light curve amplitudes, and on
follow-on occultation efforts informed by this astrometry
Physical properties of Hi'iaka from stellar occultation data
Two very bright stellar occultations by Hi'iaka, the largest satellite of the dwarf planet Haumea, were predicted to take place during in April 2021. Since the uncertainty on Hi'iaka's shadow path was large due to uncertainty on Hi'iaka's position with respect to Haumea, we performed an observational campaign using medium-sized telescopes to obtain high accuracy astrometric data of Hi'iaka's orbit around Haumea. The astrometric data allowed us to successfully observe the first stellar occultation on April 6[SUP]th[/SUP], with final path crossing North Africa. We only obtained one positive chord in this event from the TRAPPIST-North telescope at Oukaïmeden Observatory (Morocco), but thanks to this detection, we were able to obtain a more accurate path for the second event on April 16[SUP]th[/SUP]. The second shadow path was predicted to cross the continental US from East to West. We carried out a huge observational campaign involving more than 50 professional and amateur observatories across the US and southern Canada. The final path of this second stellar occultation moved slightly to the North of the predicted path and, as a result, we were able to obtain 5 positive chords and negative chords only from the south of the shadow. We also collected photometric data in order to obtain Hi'iaka's rotational light-curve and calculate its three-dimensional shape. The rotational light-curve was obtained by observing the unresolved system of Haumea-Hi'iaka and removing Haumea's rotational light-curve from the data. Using Hi'iaka's rotational light-curve we obtained the rotational phase at which each stellar occultation took place, which allowed us to obtain a three-dimensional model of the satellite. Preliminary results from the stellar occultation show that Hi'iaka, with a triaxial shape as suggested in previous publications, is larger than what has been thought before and with a similar albedo to that of Haumea. In this talk we will present our analysis and preliminary results of some of Hi'iaka's physical properties
Size and Shape Constraints of (486958) Arrokoth from Stellar Occultations
International audienceWe present the results from four stellar occultations by (486958) Arrokoth, the flyby target of the New Horizons extended mission. Three of the four efforts led to positive detections of the body, and all constrained the presence of rings and other debris, finding none. Twenty-five mobile stations were deployed for 2017 June 3 and augmented by fixed telescopes. There were no positive detections from this effort. The event on 2017 July 10 was observed by the Stratospheric Observatory for Infrared Astronomy with one very short chord. Twenty-four deployed stations on 2017 July 17 resulted in five chords that clearly showed a complicated shape consistent with a contact binary with rough dimensions of 20 by 30 km for the overall outline. A visible albedo of 10% was derived from these data. Twenty-two systems were deployed for the fourth event on 2018 August 4 and resulted in two chords. The combination of the occultation data and the flyby results provides a significant refinement of the rotation period, now estimated to be 15.9380 ± 0.0005 hr. The occultation data also provided high-precision astrometric constraints on the position of the object that were crucial for supporting the navigation for the New Horizons flyby. This work demonstrates an effective method for obtaining detailed size and shape information and probing for rings and dust on distant Kuiper Belt objects as well as being an important source of positional data that can aid in spacecraft navigation that is particularly useful for small and distant bodies