IOTA/IOTA-ES occultation update for (24) Themis / 2UCAC 38739336 event on 2012 Jul 12, 11:05 UT Visible from SW USA, Mexico Summary ------- On 2012 Jul 12 UT, the 177 km diameter asteroid (24) Themis will occult a 12.0 mag star in the constellation Taurus for observers along a path across SW USA, Mexico. In the case of an occultation, the combined light of the asteroid and the star will drop by 1.5 mag to 13.2 mag (the magnitude of the asteroid) for at most 5.1 seconds. This update is based on UNSO/Flagstaff astrometry for the asteroid kindly provided by Alice Monet, historical astrometry from the MPC files (via AstDys), and the following catalogs for the star position: UCAC. The event at a glimpse ---------------------- * Rank: 91 * date and approx. time of event: 2012 Jul 12, 11:02 - 2012 Jul 12, 11:03 UT * geocentric midpoint of event [JD]: 2456120.96199583 * magnitude of target star: 12.0 * magnitude drop [mag]: 1.5 * estimated maximum duration [s]: 5.1 * Moon: 37 % sunlit, 24° distance * Sun: 52° distance * rough path description: SW USA, Mexico The occultation path -------------------- * approximate projected width [km]: 212 * 1 sigma uncertainty interval [path widths]: +/- 0.51 * 1 sigma uncertainty interval [seconds]: +/- 2.4 * 1 sigma uncertainty interval approx RA,DE ["]: (+/- .032 +/- .034) * 1 sigma uncertainty ellipse (major, minor, PA): ( .034", .032", 360° ) * approx speed of asteroid's shadow [km/s]: 34.6296 * website for maps: http://www.asteroidoccultation.com Path Coordinates: Occultation of 2UCAC 38739336 by 24 Themis on 2012 Jul 12 Centre Star Star Sun Path Limits Error Limits E. Longitude Latitude U.T. Alt Az Alt Limit 1 Limit 2 Limit 3 Limit 4 o ' " o ' " h m s o o o o ' " o ' " o ' " o ' " Latitude Latitude Latitude Latitude -137 0 0 19 21 0 11 2 43 0 69 -41 .. .. .. 20 23 27 .. .. .. 21 28 1 -136 0 0 19 43 22 11 2 43 1 69 -40 18 41 34 20 45 58 .. .. .. 21 50 42 -135 0 0 20 6 4 11 2 43 2 70 -39 19 4 7 21 8 49 .. .. .. 22 13 42 -134 0 0 20 29 6 11 2 43 3 70 -38 19 27 0 21 32 0 18 24 28 22 37 3 -133 0 0 20 52 27 11 2 44 4 70 -38 19 50 13 21 55 30 18 47 32 23 0 43 -132 0 0 21 16 7 11 2 44 5 71 -37 20 13 45 22 19 20 19 10 55 23 24 42 -131 0 0 21 40 6 11 2 44 6 71 -36 20 37 34 22 43 27 19 34 36 23 49 0 -130 0 0 22 4 22 11 2 45 7 71 -35 21 1 42 23 7 52 19 58 35 24 13 34 -129 0 0 22 28 55 11 2 46 8 72 -34 21 26 7 23 32 35 20 22 52 24 38 26 -128 0 0 22 53 45 11 2 46 9 72 -33 21 50 48 23 57 33 20 47 25 25 3 34 -127 0 0 23 18 51 11 2 47 10 73 -32 22 15 45 24 22 48 21 12 14 25 28 58 -126 0 0 23 44 12 11 2 48 11 73 -31 22 40 58 24 48 17 21 37 18 25 54 37 -125 0 0 24 9 47 11 2 48 12 74 -30 23 6 25 25 14 1 22 2 37 26 20 30 -124 0 0 24 35 36 11 2 49 13 74 -29 23 32 6 25 39 59 22 28 10 26 46 36 -123 0 0 25 1 38 11 2 50 14 74 -28 23 58 0 26 6 9 22 53 56 27 12 56 -122 0 0 25 27 53 11 2 51 15 75 -27 24 24 6 26 32 32 23 19 55 27 39 27 -121 0 0 25 54 19 11 2 52 16 75 -27 24 50 25 26 59 6 23 46 6 28 6 9 -120 0 0 26 20 55 11 2 53 17 76 -26 25 16 54 27 25 50 24 12 28 28 33 2 -119 0 0 26 47 42 11 2 55 18 76 -25 25 43 34 27 52 45 24 39 0 29 0 5 -118 0 0 27 14 39 11 2 56 19 77 -24 26 10 23 28 19 48 25 5 43 29 27 16 -117 0 0 27 41 43 11 2 57 20 78 -23 26 37 21 28 47 0 25 32 34 29 54 36 -116 0 0 28 8 56 11 2 59 21 78 -22 27 4 27 29 14 20 25 59 33 30 22 2 -115 0 0 28 36 15 11 3 0 22 79 -21 27 31 39 29 41 45 26 26 39 30 49 35 -114 0 0 29 3 40 11 3 1 23 79 -20 27 58 59 30 9 17 26 53 53 31 17 14 -113 0 0 29 31 11 11 3 3 24 80 -19 28 26 23 30 36 54 27 21 11 31 44 57 -112 0 0 29 58 45 11 3 5 25 81 -18 28 53 52 31 4 34 27 48 35 32 12 44 -111 0 0 30 26 24 11 3 6 26 81 -17 29 21 26 31 32 18 28 16 3 32 40 34 -110 0 0 30 54 5 11 3 8 27 82 -16 29 49 2 32 0 5 28 43 35 33 8 26 -109 0 0 31 21 48 11 3 10 28 83 -15 30 16 40 32 27 53 29 11 8 33 36 19 -108 0 0 31 49 32 11 3 11 29 83 -14 30 44 20 32 55 41 29 38 44 34 4 12 -107 0 0 32 17 16 11 3 13 30 84 -13 31 12 0 33 23 30 30 6 20 34 32 5 -106 0 0 32 45 0 11 3 15 31 85 -12 31 39 40 33 51 17 30 33 56 34 59 56 -105 0 0 33 12 42 11 3 17 31 86 -11 32 7 19 34 19 3 31 1 32 35 27 46 -104 0 0 33 40 22 11 3 19 32 86 -10 32 34 56 34 46 46 31 29 6 35 55 32 -103 0 0 34 7 59 11 3 21 33 87 -9 33 2 30 35 14 25 31 56 37 36 23 14 -102 0 0 34 35 31 11 3 23 34 88 -8 33 30 0 35 42 0 32 24 6 36 50 52 -101 0 0 35 3 0 11 3 25 35 89 -7 33 57 26 36 9 30 32 51 30 37 18 24 -100 0 0 35 30 22 11 3 27 36 90 -6 34 24 47 36 36 54 33 18 49 37 45 50 - 99 0 0 35 57 38 11 3 29 37 91 -5 34 52 2 37 4 12 33 46 3 38 13 8 - 98 0 0 36 24 47 11 3 32 37 92 -5 35 19 11 37 31 21 34 13 11 38 40 19 - 97 0 0 36 51 49 11 3 34 38 93 -4 35 46 12 37 58 23 34 40 12 39 7 21 - 96 0 0 37 18 41 11 3 36 39 94 -3 36 13 4 38 25 16 35 7 4 39 34 14 - 95 0 0 37 45 25 11 3 38 40 95 -2 36 39 48 38 51 59 35 33 49 40 0 56 - 94 0 0 38 11 58 11 3 40 40 96 -1 37 6 23 39 18 31 36 0 24 40 27 28 Uncertainty in time = +/- 3 secs Prediction of 2012 Jun 6.0 Data for the target star ------------------------ * name: 2UCAC 38739336 * constellation : Taurus * J2000 position with proper motion to date of event [h,m,s ; °,',"] RA: 03 44 28.1812 DE: +19 52 53.764 * position source: mpos:UCAC4 pm:UCAC4 * standard error: RA,DE ["]: ( .031, .033 ) * V mag [mag]: 12.0 * B mag [mag]: 0.0 * Diameter [mas]: 0 * remarks: Data for the minor planet ------------------------- * general information: (number) name: (24) Themis approx. diameter [km]: 177 approx. diameter ["]: .066 distance from Earth [AU]: 3.67500 * orbital information: orbit source: Preston date of fit: 2012 Jun 06 source of used astrometry: FASTT MPC (via Astdys) number of used observations: 1807 number of rejected observations: 194 time covered by the observations: 1900 Aug 26 - 2012 Jan 03 1 sigma uncertainty ellipse (major, minor, PA): 0.008, 0.005, 76° remarks: * orbital elements for (24) Themis : Mean anomaly = 275.61996703 deg Arg. of pericenter = 106.62746484 deg Long. of node = 36.12789710 deg Inclination = 0.75577868 deg Eccentricity = 0.12834394 Semimajor axis = 3.13871061 AU Perihelion dist = 2.73587613 AU Mag: H = 7.21, G = 0.19 Epoch of elements : MJD 56120.46200000 TDT (2012 Jul 12.462) ------ occelmnt file for Occult BEGIN ----------------------------------- 2012 Jul 12 24 Themis 11h 5.3m UT 12.0 3 44 28.181 19 52 53.762UCAC 38739336 0.0 13.2 177 5.1 3.675 3.228 10.69 -40.9509 19.879 15.11 21.87 11.0879 -0.12648 0.53838 19.02825 4.46849 -0.00432 -0.00098 2000 275.5380792012 712.00000106.627465 36.127897 0.7557790.12834394 3.1387106 2.7358761 7.1 5.00.19 RATE 1.7724630 0.000000 0.000000 0.000000 0.0000000 0.0000000 0.0000000 Meas 0.034 0.032 360 1.51 0.034 0 0 2 4 056084.0020120712_739336 ------ occelmnt file for Occult END ----------------------------------- ============================================ Calculator (s): Steve Preston Date of update: 2012 Jun 06, 02:35 UT Steve Preston 7640 NE 32nd St Medina, WA 98039 425-688-9965 mailto: stevepr@acm.org