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Table 5

Precise Pluto positions based on 20052013 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 20052013 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 (OC)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.

(a)

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).

(b)

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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