IOTA/IOTA-ES occultation update for (140) Siwa / TYC 5553-01190-1 event on 2012 Dec 20, 05:32 UT Visible from E Brazil Summary ------- On 2012 Dec 20 UT, the 121 km diameter asteroid (140) Siwa will occult a 9.8 mag star in the constellation Virgo for observers along a path across E Brazil. In the case of an occultation, the combined light of the asteroid and the star will drop by 4.2 mag to 14.0 mag (the magnitude of the asteroid) for at most 3.7 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: 93 * date and approx. time of event: 2012 Dec 20, 05:29 - 2012 Dec 20, 05:30 UT * geocentric midpoint of event [JD]: 2456281.73054167 * magnitude of target star: 9.8 * magnitude drop [mag]: 4.2 * estimated maximum duration [s]: 3.7 * Moon: 50 % sunlit, 148° distance * Sun: 59° distance * rough path description: E Brazil The occultation path -------------------- * approximate projected width [km]: 149 * 1 sigma uncertainty interval [path widths]: +/- 0.47 * 1 sigma uncertainty interval [seconds]: +/- 1.8 * 1 sigma uncertainty interval approx RA,DE ["]: (+/- .025 +/- .024) * 1 sigma uncertainty ellipse (major, minor, PA): ( .025", .024", 95° ) * approx speed of asteroid's shadow [km/s]: 32.9172 * website for maps: http://www.asteroidoccultation.com Path Coordinates: Occultation of TYC 5553-01190-1 by 140 Siwa on 2012 Dec 20 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 - 55 0 0 -17 10 45 5 29 22 0 99 -41 -17 52 2 -16 29 49 -18 31 11 .. .. .. - 54 0 0 -17 20 32 5 29 22 1 99 -40 -18 1 52 -16 39 33 -18 41 4 .. .. .. - 53 0 0 -17 30 43 5 29 22 2 99 -40 -18 12 7 -16 49 41 -18 51 22 .. .. .. - 52 0 0 -17 41 19 5 29 22 3 98 -39 -18 22 46 -17 0 14 -19 2 5 -16 21 56 - 51 0 0 -17 52 20 5 29 23 4 98 -38 -18 33 50 -17 11 11 -19 13 12 -16 32 50 - 50 0 0 -18 3 44 5 29 23 5 98 -38 -18 45 18 -17 22 32 -19 24 44 -16 44 8 - 49 0 0 -18 15 33 5 29 23 6 97 -37 -18 57 11 -17 34 17 -19 36 40 -16 55 50 - 48 0 0 -18 27 46 5 29 24 7 97 -36 -19 9 27 -17 46 26 -19 49 0 -17 7 55 - 47 0 0 -18 40 22 5 29 24 8 97 -35 -19 22 8 -17 58 59 -20 1 44 -17 20 24 - 46 0 0 -18 53 22 5 29 25 9 96 -34 -19 35 11 -18 11 55 -20 14 52 -17 33 17 - 45 0 0 -19 6 45 5 29 26 10 96 -34 -19 48 38 -18 25 14 -20 28 23 -17 46 32 - 44 0 0 -19 20 31 5 29 26 11 96 -33 -20 2 29 -18 38 56 -20 42 17 -18 0 10 - 43 0 0 -19 34 40 5 29 27 12 95 -32 -20 16 42 -18 53 0 -20 56 34 -18 14 11 - 42 0 0 -19 49 11 5 29 28 13 95 -31 -20 31 17 -19 7 27 -21 11 13 -18 28 34 - 41 0 0 -20 4 4 5 29 29 14 94 -30 -20 46 15 -19 22 17 -21 26 15 -18 43 19 - 40 0 0 -20 19 20 5 29 30 15 94 -30 -21 1 35 -19 37 28 -21 41 40 -18 58 27 - 39 0 0 -20 34 57 5 29 31 16 94 -29 -21 17 16 -19 53 0 -21 57 25 -19 13 55 - 38 0 0 -20 50 55 5 29 32 17 93 -28 -21 33 19 -20 8 54 -22 13 33 -19 29 45 - 37 0 0 -21 7 14 5 29 34 18 93 -27 -21 49 43 -20 25 9 -22 30 1 -19 45 56 - 36 0 0 -21 23 54 5 29 35 19 92 -26 -22 6 28 -20 41 44 -22 46 50 -20 2 27 - 35 0 0 -21 40 54 5 29 36 20 92 -25 -22 23 33 -20 58 40 -23 4 0 -20 19 18 - 34 0 0 -21 58 15 5 29 38 21 92 -24 -22 40 58 -21 15 56 -23 21 29 -20 36 30 - 33 0 0 -22 15 55 5 29 39 22 91 -23 -22 58 42 -21 33 31 -23 39 19 -20 54 1 - 32 0 0 -22 33 54 5 29 41 22 91 -22 -23 16 46 -21 51 25 -23 57 27 -21 11 51 - 31 0 0 -22 52 11 5 29 42 23 90 -22 -23 35 9 -22 9 38 -24 15 54 -21 29 59 - 30 0 0 -23 10 47 5 29 44 24 89 -21 -23 53 50 -22 28 10 -24 34 40 -21 48 27 - 29 0 0 -23 29 42 5 29 46 25 89 -20 -24 12 49 -22 46 59 -24 53 44 -22 7 12 - 28 0 0 -23 48 53 5 29 47 26 88 -19 -24 32 5 -23 6 6 -25 13 5 -22 26 14 - 27 0 0 -24 8 22 5 29 49 27 88 -18 -24 51 39 -23 25 30 -25 32 43 -22 45 34 - 26 0 0 -24 28 7 5 29 51 28 87 -17 -25 11 29 -23 45 10 -25 52 38 -23 5 10 - 25 0 0 -24 48 8 5 29 53 29 87 -16 -25 31 35 -24 5 7 -26 12 49 -23 25 2 - 24 0 0 -25 8 25 5 29 55 30 86 -15 -25 51 56 -24 25 19 -26 33 15 -23 45 10 - 23 0 0 -25 28 57 5 29 57 31 85 -14 -26 12 33 -24 45 46 -26 53 56 -24 5 33 - 22 0 0 -25 49 43 5 29 59 32 85 -13 -26 33 24 -25 6 28 -27 14 52 -24 26 11 - 21 0 0 -26 10 44 5 30 1 32 84 -12 -26 54 29 -25 27 24 -27 36 2 -24 47 3 - 20 0 0 -26 31 58 5 30 3 33 83 -11 -27 15 48 -25 48 34 -27 57 25 -25 8 8 - 19 0 0 -26 53 25 5 30 6 34 82 -10 -27 37 20 -26 9 56 -28 19 1 -25 29 26 - 18 0 0 -27 15 4 5 30 8 35 82 -9 -27 59 3 -26 31 31 -28 40 49 -25 50 57 - 17 0 0 -27 36 55 5 30 10 36 81 -8 -28 20 59 -26 53 18 -29 2 49 -26 12 40 - 16 0 0 -27 58 57 5 30 13 37 80 -7 -28 43 5 -27 15 15 -29 24 59 -26 34 34 - 15 0 0 -28 21 10 5 30 15 37 79 -7 -29 5 22 -27 37 24 -29 47 21 -26 56 39 - 14 0 0 -28 43 33 5 30 18 38 78 -6 -29 27 49 -27 59 43 -30 9 51 -27 18 53 - 13 0 0 -29 6 5 5 30 20 39 77 -5 -29 50 25 -28 22 11 -30 32 32 -27 41 18 - 12 0 0 -29 28 45 5 30 23 40 76 -4 -30 13 10 -28 44 48 -30 55 20 -28 3 51 - 11 0 0 -29 51 34 5 30 25 40 75 -3 -30 36 3 -29 7 33 -31 18 17 -28 26 33 - 10 0 0 -30 14 31 5 30 28 41 74 -2 -30 59 3 -29 30 25 -31 41 20 -28 49 22 - 9 0 0 -30 37 34 5 30 30 42 73 -1 -31 22 9 -29 53 25 -32 4 30 -29 12 19 Uncertainty in time = +/- 2 secs Prediction of 2012 Dec 17.0 Data for the target star ------------------------ * name: TYC 5553-01190-1 * constellation : Virgo * J2000 position with proper motion to date of event [h,m,s ; °,',"] RA: 13 54 50.8932 DE: -08 46 43.393 * position source: mpos:UCAC2 pm:UCAC2 * standard error: RA,DE ["]: ( .022, .024 ) * V mag [mag]: 9.8 * B mag [mag]: 11.4 * Diameter [mas]: 0 * remarks: Data for the minor planet ------------------------- * general information: (number) name: (140) Siwa approx. diameter [km]: 121 approx. diameter ["]: .052 distance from Earth [AU]: 3.21300 * orbital information: orbit source: Preston date of fit: 2012 Jul 10 source of used astrometry: FASTT MPC (via Astdys) number of used observations: 1609 number of rejected observations: 180 time covered by the observations: 1900 Apr 26 - 2012 May 16 1 sigma uncertainty ellipse (major, minor, PA): 0.012, 0.006, 111° remarks: * orbital elements for (140) Siwa : Mean anomaly = 272.68052603 deg Arg. of pericenter = 196.89083126 deg Long. of node = 107.26896691 deg Inclination = 3.18652286 deg Eccentricity = 0.21654501 Semimajor axis = 2.73231494 AU Perihelion dist = 2.14064577 AU Mag: H = 8.42, G = 0.15 Epoch of elements : MJD 56281.23100000 TDT (2012 Dec 20.231) ------ occelmnt file for Occult BEGIN ----------------------------------- 2012 Dec 20 140 Siwa 5h 32.0m UT 9.8 13 54 50.893- 8 46 43.39TYC 5553-01190-1 11.4 14.0 121 3.7 3.213 3.252 -16.21 36.5071 -8.775 96.43 -23.43 5.5330 -0.18791 -0.55389 17.61025 -5.92221 -0.00474 0.00192 2000 272.41188920121219.00000196.890831107.268967 3.1865230.21654501 2.7323149 2.1406458 8.3 5.00.15 RATE 2.1822670 0.000000 0.000000 0.000000 0.0000000 0.0000000 0.0000000 Meas 0.025 0.024 95 1.47 0.024 0 0 2-3 056278.0020121220_1190-1 ------ occelmnt file for Occult END ----------------------------------- ============================================ Calculator (s): Steve Preston Date of update: 2012 Jul 10, 06:05 UT Steve Preston 7640 NE 32nd St Medina, WA 98039 425-688-9965 mailto: stevepr@acm.org