Rotational properties of the binary and non-binary populations in the trans-Neptunian belt

Abstract

We present results for the short-term variability of binary trans-Neptunian objects (BTNOs). We performed CCD photometric observations using the 3.58 m Telescopio Nazionale Galileo (TNG), the 1.5 m Sierra Nevada Observatory (OSN) telescope, and the 1.23 m Centro Astronómico Hispano Alemán (CAHA) telescope at Calar Alto Observatory. We present results based on five years of observations and report the short-term variability of six BTNOs. Our sample contains three classical objects: (174567) We also derived some physical properties from their light curves, such as density, primary and secondary sizes, and albedo. We compiled and analyzed a vast light curve database for TNOs including centaurs to determine the light-curve amplitude and spin frequency distributions for the binary and non-binary populations. The mean rotational periods, from the Maxwellian fits to the frequency distributions, are 8.63 ± 0.52 h for the entire sample, 8.37 ± 0.58 h for the sample without the binary population, and 10.11 ± 1.19 h for the binary population alone. Because the centaurs are collisionally more evolved, their rotational periods might not be so primordial. We computed a mean rotational period, from the Maxwellian fit, of 8.86 ± 0.58 h for the sample without the centaur population, and of 8.64 ± 0.67 h considering a sample without the binary and the centaur populations. According to this analysis, regular TNOs spin faster than binaries, which is compatible with the tidal interaction of the binaries. Finally, we examined possible formation models for several systems studied in this work and by our team in previous papers.

Photometry of Centaurs and trans-Neptunian objects: 2060 Chiron (1977 UB), 10199 Chariklo (1997 CU26), 38628 Huya (2000 EB173), 28978 Ixion (2001 KX76), and 90482 Orcus (2004 DW)

“…Our best fit for the rotational period is P = 4.45±0.07 h (or a frequency of 0.225±0.003 rotations per hour). This is close to one of the aliases in Thirouin et al (2014), 4.31 h. The probability that there is no period with value P is 32.5±2.1% and that of the observations containing a period that is different from P is 1.0±0.4%. The light-curve of Huya in Fig.…”

“…Our sparse curve looks similar to that in fig. 11 of Thirouin et al (2014), its amplitude is ∼0.1 mag. For Huya, we found the following values of the colours: B − V = 1.00 ± 0.06, V − R = 0.58 ± 0.09, and R − I = 0.64 ± 0.20.…”

Taxonomy of trans-Neptunian objects and Centaurs as seen from spectroscopy

“…The three spectra are featureless between 0.6 and 0.9 µm and we expect that the surface observed during these three attempts was mainly devoid of any content related to aqueous alteration processes. Thirouin et al (2014) recently performed visible photometry to constrain the rotational period of this object and found different possibilities from their periodogram. Their best solution seems to be in agreement with a rotational period of 5.28 h, but three other peaks have been obtained and can not be ruled out.…”

“…We report in Fig. 4 the level of surface coverage for any relative rotational phase, considering the four possible rotational periods obtained by Thirouin et al (2014). For that, we considered that the 0 • corresponds to the longitude of the sub-earth point at the beginning of the first acquisition performed on 2013-07-13 and we decompose the sphere of Huya as 360 individual longitudinal-units.…”

The young Datura asteroid family

“…Relative photometry using 25 reference stars was carried out using Daophot routines (Stetson 1987). More details about our data reduction and analysis are available in Thirouin et al (2014Thirouin et al ( , 2016.…”