2008 OG19: A highly elongated Trans-Neptunian object

Abstract

From two observing runs during the 2014 summer at the Calar Alto Observatory in Almeŕa (Spain) and at the Sierra Nevada Observatory in Granada (Spain), we were able to derive CCD photometry of the Trans-Neptunian object 2008 OG19. We analysed the time series and obtained a double-peaked light curve with a peak-to-valley amplitude of 0.437 ± 0.011 mag and a rotational period of 8.727 ± 0.003 h. This implies that this object is very elongated closely resembling the case of Varuna. The photometry also allowed us to obtain an absolute magnitude in the R band of 4.39 ± 0.07 mag. From this result, we estimated an equivalent diameter of 2008 OG19 of 619-113+56 km using an average albedo for scattered disc objects. Finally, we interpreted the results under the assumption of hydrostatic equilibrium and found a lower limit for the density of 544-4+42 kg m-3. However, a more likely density is 609 ± 4 kg m-3 using an aspect angle of 60°, which corresponds to the most likely configuration for the spin axis with respect to the observer assuming random orientations.