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تسجيل مستخدم جديدThe Complex Rotational Light Curve of (385446) Manwe-Thorondor, a Multi-Component Eclipsing System in the Kuiper Belt
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Kuiper Belt Object (385446) Manwe-Thorondor is a multi-object system with mutual events predicted to occur from 2014 to 2019. To detect the events, we observed the system at 4 epochs (UT 2016 Aug 25 and 26, 2017 Jul 22 and 25, 2017 Nov 9, and 2018 Oct 6) in g, r, and VR bands using the 4-m SOAR and the 8.1-m Gemini South telescopes at Cerro Pachon, Chile and Lowell Observatory s 4.3-m Discovery Channel Telescope at Happy Jack, Arizona. These dates overlap the uncertainty range (+/- 0.5 d) for four inferior events (Thorondor eclipsing Manwe). We clearly observe variability for the unresolved system with a double-peaked period 11.88190 +/- 0.00005 h and ~0.5 mag amplitude together with much longer-term variability. Using a multi-component model, we simultaneously fit our observations and earlier photometry measured separately for Manwe and Thorondor with the Hubble Space Telescope. Our fit suggests Manwe is bi-lobed, close to the barbell shape expected for a strengthless body with density ~0.8 g/cm3 in hydrostatic equilibrium. For Manwe, we thereby derive maximum width to length ratio ~0.30, surface area equivalent to a sphere of diameter 190 km, geometric albedo 0.06, mass 1.4x1018 kg, and spin axis oriented ~75 deg from Earth s line of sight. Changes in Thorondor s brightness by ~0.6 mag with ~300-d period may account for the system s long-term variability. Mutual events with unexpectedly shallow depth and short duration may account for residuals to the fit. The system is complex, providing a challenging puzzle for future modeling efforts.
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