Table 5
Precise Pluto positions based on 2005−2013 stellar occultations and on UCAC4-based star positions observed at OPD.
Star central | ICRS star positions | Mean error | Repeatability | Pluto’s offsets from | Geocentric positions of Pluto from occultations | |||||||||
observation | stellar occultations | JD | RA | Declination | ||||||||||
Occultation | epoch | RA | Declination | Mag | σ α | σ δ | E α | E δ | No. of | Δαcosδ | Δδ | |||
date | years | h | degrees | R | mas | mas | mas | mas | frames | mas | mas | UTC | h | degrees |
|
||||||||||||||
2005 Jul. 11a | 2013.532 | 17.481948800 | –15.01518791 | 15.1 | 51 | 47 | 14 | 8 | 40 | 14.7 | 18.5 | 2 453 562.650983796 | 17.481944643 | –15.01496958 |
2006 Apr. 10b | 2006.162 | 17.768578025 | –15.76946559 | 15.6 | 53 | 52 | 18 | 9 | 179 | –34.2 | 25.9 | 2 453 835.713437500 | 17.768573370 | –15.76963836 |
2006 Jun. 12 | 2013.532 | 17.686688372 | –15.69289891 | 15.0 | 53 | 55 | 43 | 26 | 70 | 80.4 | 65.9 | 2 453 899.184375000 | 17.686688380 | –15.69293003 |
2007 Mar. 18 | 2007.281 | 17.918248760 | –16.47620446 | 15.2 | 54 | 53 | 15 | 14 | 663 | –37.5 | 55.9 | 2 454 177.957812500 | 17.918247276 | –16.47612781 |
2007 Jun. 09 | 2009.540 | 17.847403865 | –16.37480759 | 16.4 | 55 | 56 | 37 | 18 | 73 | 14.0 | 48.7 | 2 454 260.900428241 | 17.847403854 | –16.37482619 |
2007 Jun. 14 | 2006.646 | 17.839094971 | –16.37838923 | 15.7 | 54 | 53 | 16 | 13 | 452 | –23.2 | 56.8 | 2 454 265.560034722 | 17.839095024 | –16.37838867 |
2007 Jul. 31 | 2006.715 | 17.761664371 | –16.49212569 | 15.2 | 57 | 52 | 10 | 16 | 184 | 73.7 | 44.5 | 2 454 313.075752315 | 17.761665201 | –16.49217792 |
2008 Jun. 22 | 2008.519 | 17.975837402 | –17.04398606 | 12.5 | 57 | 49 | 17 | 23 | 93 | 37.1 | 79.2 | 2 454 640.299305555 | 17.975837607 | –17.04403300 |
2008 Jun. 24 | 2008.519 | 17.972886881 | –17.04703340 | 15.9 | 56 | 51 | 4 | 9 | 94 | 55.0 | 82.1 | 2 454 641.942928241 | 17.972886732 | –17.04698831 |
2008 Aug. 25 | 2008.519 | 17.890861945 | –17.25764839 | 16.0 | 53 | 54 | 11 | 8 | 68 | –10.3 | 53.1 | 2 454 703.691099537 | 17.890860411 | –17.25761219 |
2010 Feb. 14 | 2010.507 | 18.320660911 | –18.27841969 | 10.6 | 58 | 58 | 21 | 8 | 71 | 34.0 | 82.1 | 2 455 241.700393518 | 18.320660719 | –18.27836469 |
2010 May 19 | 2013.587 | 18.338000723 | –18.19669245 | 17.1 | 57 | 58 | 78 | 9 | 164 | 96.9 | 47.2 | 2 455 335.745856482 | 18.338000944 | –18.19672189 |
2010 Jun. 04 | 2010.479 | 18.313314917 | –18.21438647 | 14.9 | 60 | 59 | 23 | 8 | 283 | 78.1 | 80.7 | 2 455 352.150752315 | 18.313314995 | –18.21442508 |
2011 Jun. 23 | 2011.457 | 18.432076650 | –18.80195362 | 14.5 | 58 | 56 | 2 | 2 | 76 | –15.6 | 105.5 | 2 455 735.975115741 | 18.432076445 | –18.80191986 |
2012 Jul. 18 | 2013.587 | 18.537408929 | –19.40536793 | 14.6 | 59 | 58 | 8 | 13 | 214 | 9.3 | 65.5 | 2 456 126.676215278 | 18.537408960 | –19.40537236 |
2013 May 04 | 2013.346 | 18.797926508 | –19.69009352 | 14.3 | 57 | 54 | 10 | 15 | 86 | 83.1 | 110.7 | 2 456 416.849201389 | 18.797926607 | –19.69010286 |
Notes. Precise star positions and geocentric Pluto positions for 16 stellar occultation dates between 2005−2013 are listed. The ICRS positions of the stars are given at noon of the occultation date in Col. 1. The mean error refers to the standard deviations of the (O−C)s from the (α, δ) star reductions. The repeatability is the standard deviation of the star position. All star positions were obtained using the UCAC4 as reference star catalog. The number of UCAC4 stars in each frame varies typically between 100 (for Perkin-Elmer) and 500 (for Zeiss and Boller & Chivens), depending on the size of the FOV. The epoch of the observation of the stars are given. The positions were corrected by UCAC4 proper motions, when available, to place the star positions at the occultation epochs given in the table. Proper motions from other catalogs were used otherwise (see text). Magnitudes in the R band were taken from the catalogs that provided the proper motions to the respective stars. The offsets on Pluto’s positions, as obtained from the stellar occultations, are given with respect to DE421 and are in the sense observation minus DE421 (see Fig. 12). The positions of Pluto in the two last columns are geocentric astrometric positions in the ICRS, as obtained from stellar occultations (that is, corrected for the respective offsets). The associated JD is close (about 1s) to the geocentric closest approach. The relative geocentric distance of Pluto with respect to the star is determined with mas accuracy from the fitting of the light curves of stellar occultations. Adding our star positions to these distances allowed us to obtain the listed 16 Pluto positions for these occultations. These Pluto positions are as precise as the positions derived for the stars themselves.
This refers to an occultation by Charon. However, since the offset is mostly due to the planetary ephemeris DE421, rather than an offset in the orbit of Charon around Pluto as given by plu021, the same offset obtained for Charon can be applied to Pluto’s position (see also Sicardy et al. 2006).
We note that there was no occultation on 2006 April 10 and this was actually predicted. The offsets could be derived due to high resolution adaptative optics observations of Pluto and the star made at the ESO-VLT 8 m Telescope UT4 (Paranal, Chile) – see Assafin et al. (2010).
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