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)

Abstract

Both Centaurs and trans-Neptunian objects (TNOs) are minor bodies found in the outer Solar System. Centaurs are a transient population that moves between the orbits of Jupiter and Neptune, and they probably diffused out of the TNOs. TNOs move mainly beyond Neptune. Some of these objects display episodic cometary behaviour; a few percent of them are known to host binary companions. Here, we study the light-curves of two Centaurs—2060 Chiron (1977 UB) and 10199 Chariklo (1997 CU₂₆)—and three TNOs—38628 Huya (2000 EB₁₇₃), 28978 Ixion (2001 KX₇₆), and 90482 Orcus (2004 DW)—and the colours of the Centaurs and Huya. Precise, $\sim1~\%$, $R$-band absolute CCD photometry of these minor bodies acquired between 2006 and 2011 is presented; the new data are used to investigate the rotation rate of these objects. The colours of the Centaurs and Huya are determined using $\mathit{BVRI}$ photometry. The point spread function of the five minor bodies is analysed, searching for signs of a coma or close companions. Astrometry is also discussed. A periodogram analysis of the light-curves of these objects gives the following rotational periods: $5.5\pm0.4~\mbox{h}$ for Chiron, $7.0\pm 0.6~\mbox{h}$ for Chariklo, $4.45\pm0.07~\mbox{h}$ for Huya, $12.4\pm0.3~\mbox{h}$ for Ixion, and $11.9\pm0.5~\mbox{h}$ for Orcus. The colour indices of Chiron are found to be $B-V=0.53\pm0.05$, $V-R=0.37\pm0.08$, and $R-I=0.36\pm0.15$. The values computed for Chariklo are $V-R=0.62\pm0.07$ and $R-I=0.61\pm0.07$. For Huya, we find $V-R=0.58\pm0.09$ and $R-I=0.64\pm0.20$. Our rotation periods are similar to and our colour values are consistent with those already published for these objects. We find very low levels of cometary activity (if any) and no sign of close or wide binary companions for these minor bodies.

Appendix A: Astrometry of 2060 Chiron (1977 UB), 10199 Chariklo (1997 CU26), 38628 Huya (2000 EB173), 28978 Ixion (2001 KX76), and 90482 Orcus (2004 DW)

Table 9 Observations of 2060 Chiron (1977 UB) over interval 2006 June 26.298391–28.313276. During this observing run, Chiron was in Capricornus. See also Table 1

Table 10 Observations of 2060 Chiron (1977 UB) over interval 2011 July 30.217766–August 06.393033. During this observing run, Chiron was in Aquarius. All the observations in the $R$ filter. See also Table 2

Table 11 Observations of 2060 Chiron (1977 UB) over interval 2006 May 19.383990–22.438617. During this observing run, Chiron was in Aquarius

Table 12 Observations of Chariklo over interval 2006 June 27.950405–30.113403. See also Table 3. During this observing run, Chariklo was in Hydra

Table 13 Observations of Chariklo over interval 2011 July 30.043623–August 06.162685. During this observing run, Chariklo was in Lupus. All the observations in the $R$ filter. See also Table 4

Table 14 Observations of 38628 Huya (2000 EB₁₇₃) over interval 2006 June 27.994178–30.149815. During this observing run, Huya was in Virgo. See also Table 5

Table 15 Observations of 28978 Ixion (2001 KX₇₆) over interval 2010 May 9.267685–12.396771. During this observing run, Ixion was in Ophiuchus. See also Table 6

Table 16 Observations of 28978 Ixion (2001 KX₇₆) over interval 2006 June 28.031296–30.257153. During this observing run, Ixion was in Ophiuchus

Table 17 Observations of 90482 Orcus (2004 DW) over interval 2010 May 10.963438–12.100394. During this observing run, Orcus was in Sextans. See also Table 7

Table 18 Observations of 90482 Orcus (2004 DW) over interval 2011 January 04.31616–09.32441. During this observing run, Orcus was in Sextans. See also Table 8