IOTA/IOTA-ES occultation update for (24) Themis / TYC 1395-00885-1 event on 2008 May 12, 17:48 UT Visible from Africa Summary ------- On 2008 May 12 UT, the 161 km diameter asteroid (24) Themis will occult a 12.2 mag star in the constellation Cancer for observers along a path across Africa. In the case of an occultation, the combined light of the asteroid and the star will drop by 0.9 mag to 12.5 mag (the magnitude of the asteroid) for at most 6.4 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: 98 * date and approx. time of event: 2008 May 12, 17:49 - 2008 May 12, 17:52 UT * magnitude of target star: 12.2 * magnitude drop [mag]: 0.9 * estimated maximum duration [s]: 6.4 * Moon: 56 % sunlit, 22° distance * Sun: 75° distance * rough path description: Africa The occultation path -------------------- * approximate projected width [km]: 171 * 1 sigma uncertainty interval [path widths]: +/- 0.37 * 1 sigma uncertainty interval [seconds]: +/- 1.9 * 1 sigma uncertainty interval approx RA,DE ["]: (+/- .024 +/- .030) * 1 sigma uncertainty ellipse (major, minor, PA): ( .030", .024", 1° ) * approx speed of asteroid's shadow [km/s]: 25.0406 * website for maps: http://www.asteroidoccultation.com Path Coordinates: Occultation of TYC 1395-00885-1 by 24 Themis on 2008 May 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 1 0 0 - 4 29 1 17 49 15 65 340 -1 - 5 18 30 - 3 39 48 - 5 55 18 - 3 3 32 2 0 0 - 4 51 2 17 49 20 64 338 -2 - 5 40 37 - 4 1 44 - 6 17 30 - 3 25 24 3 0 0 - 5 13 25 17 49 25 64 337 -3 - 6 3 6 - 4 24 1 - 6 40 3 - 3 47 37 4 0 0 - 5 36 9 17 49 29 63 335 -4 - 6 25 55 - 4 46 39 - 7 2 56 - 4 10 11 5 0 0 - 5 59 13 17 49 34 62 333 -5 - 6 49 5 - 5 9 37 - 7 26 10 - 4 33 5 6 0 0 - 6 22 36 17 49 38 61 332 -6 - 7 12 34 - 5 32 55 - 7 49 43 - 4 56 19 7 0 0 - 6 46 19 17 49 43 60 331 -7 - 7 36 22 - 5 56 32 - 8 13 35 - 5 19 52 8 0 0 - 7 10 20 17 49 47 60 329 -8 - 8 0 28 - 6 20 28 - 8 37 46 - 5 43 44 9 0 0 - 7 34 39 17 49 52 59 328 -9 - 8 24 53 - 6 44 41 - 9 2 15 - 6 7 54 10 0 0 - 7 59 15 17 49 56 58 327 -10 - 8 49 35 - 7 9 13 - 9 27 1 - 6 32 21 11 0 0 - 8 24 9 17 50 0 57 326 -11 - 9 14 34 - 7 34 1 - 9 52 3 - 6 57 5 12 0 0 - 8 49 19 17 50 5 56 325 -13 - 9 39 48 - 7 59 6 -10 17 22 - 7 22 6 13 0 0 - 9 14 44 17 50 9 55 324 -14 -10 5 19 - 8 24 26 -10 42 56 - 7 47 23 14 0 0 - 9 40 24 17 50 13 54 323 -15 -10 31 4 - 8 50 1 -11 8 45 - 8 12 55 15 0 0 -10 6 19 17 50 17 53 322 -16 -10 57 4 - 9 15 51 -11 34 48 - 8 38 41 16 0 0 -10 32 27 17 50 21 52 321 -17 -11 23 17 - 9 41 55 -12 1 5 - 9 4 41 17 0 0 -10 58 48 17 50 25 51 320 -18 -11 49 42 -10 8 11 -12 27 34 - 9 30 55 18 0 0 -11 25 22 17 50 29 50 319 -19 -12 16 20 -10 34 41 -12 54 15 - 9 57 21 19 0 0 -11 52 7 17 50 33 49 319 -20 -12 43 10 -11 1 21 -13 21 8 -10 23 58 20 0 0 -12 19 3 17 50 37 48 318 -21 -13 10 10 -11 28 13 -13 48 11 -10 50 47 21 0 0 -12 46 9 17 50 41 47 317 -22 -13 37 20 -11 55 15 -14 15 24 -11 17 46 22 0 0 -13 13 24 17 50 45 46 317 -23 -14 4 39 -12 22 27 -14 42 46 -11 44 55 23 0 0 -13 40 48 17 50 48 45 316 -24 -14 32 6 -12 49 47 -15 10 16 -12 12 13 24 0 0 -14 8 19 17 50 52 44 315 -26 -14 59 41 -13 17 15 -15 37 54 -12 39 39 25 0 0 -14 35 58 17 50 55 43 315 -27 -15 27 23 -13 44 51 -16 5 38 -13 7 12 26 0 0 -15 3 43 17 50 59 42 314 -28 -15 55 11 -14 12 32 -16 33 28 -13 34 51 27 0 0 -15 31 33 17 51 2 41 314 -29 -16 23 4 -14 40 20 -17 1 23 -14 2 37 28 0 0 -15 59 28 17 51 6 40 313 -30 -16 51 2 -15 8 12 -17 29 23 -14 30 27 29 0 0 -16 27 27 17 51 9 39 312 -31 -17 19 3 -15 36 9 -17 57 26 -14 58 22 30 0 0 -16 55 29 17 51 12 38 312 -32 -17 47 7 -16 4 9 -18 25 32 -15 26 20 31 0 0 -17 23 33 17 51 15 37 311 -33 -18 15 13 -16 32 11 -18 53 40 -15 54 21 32 0 0 -17 51 39 17 51 18 36 311 -34 -18 43 21 -17 0 15 -19 21 48 -16 22 24 33 0 0 -18 19 45 17 51 21 35 310 -35 -19 11 29 -17 28 20 -19 49 57 -16 50 28 34 0 0 -18 47 51 17 51 24 34 310 -36 -19 39 36 -17 56 25 -20 18 6 -17 18 32 35 0 0 -19 15 57 17 51 27 33 309 -37 -20 7 43 -18 24 29 -20 46 13 -17 46 35 36 0 0 -19 44 0 17 51 29 32 309 -38 -20 35 47 -18 52 32 -21 14 18 -18 14 37 37 0 0 -20 12 2 17 51 32 31 308 -39 -21 3 49 -19 20 32 -21 42 20 -18 42 37 38 0 0 -20 40 0 17 51 34 30 308 -40 -21 31 47 -19 48 30 -22 10 19 -19 10 35 39 0 0 -21 7 53 17 51 37 29 307 -41 -21 59 41 -20 16 24 -22 38 13 -19 38 29 40 0 0 -21 35 43 17 51 39 28 307 -42 -22 27 30 -20 44 13 -23 6 2 -20 6 18 41 0 0 -22 3 26 17 51 41 27 307 -43 -22 55 14 -21 11 57 -23 33 45 -20 34 2 42 0 0 -22 31 4 17 51 44 26 306 -44 -23 22 51 -21 39 35 -24 1 22 -21 1 41 43 0 0 -22 58 35 17 51 46 25 306 -45 -23 50 21 -22 7 7 -24 28 51 -21 29 13 44 0 0 -23 25 57 17 51 48 24 305 -46 -24 17 42 -22 34 31 -24 56 12 -21 56 37 45 0 0 -23 53 12 17 51 50 23 305 -47 -24 44 56 -23 1 46 -25 23 25 -22 23 54 46 0 0 -24 20 18 17 51 51 22 304 -48 -25 12 0 -23 28 54 -25 50 28 -22 51 2 47 0 0 -24 47 14 17 51 53 21 304 -49 -25 38 54 -23 55 51 -26 17 21 -23 18 1 48 0 0 -25 13 59 17 51 55 20 303 -50 -26 5 38 -24 22 39 -26 44 3 -23 44 50 49 0 0 -25 40 34 17 51 56 19 303 -50 -26 32 10 -24 49 16 -27 10 34 -24 11 28 50 0 0 -26 6 57 17 51 58 18 302 -51 -26 58 31 -25 15 41 -27 36 53 -24 37 56 51 0 0 -26 33 8 17 51 59 17 302 -52 -27 24 40 -25 41 55 -28 3 0 -25 4 11 52 0 0 -26 59 7 17 52 1 16 301 -53 -27 50 35 -26 7 56 -28 28 53 -25 30 14 53 0 0 -27 24 52 17 52 2 15 301 -54 -28 16 18 -26 33 44 -28 54 33 -25 56 4 54 0 0 -27 50 23 17 52 3 14 300 -55 -28 41 46 -26 59 18 -29 19 59 -26 21 41 55 0 0 -28 15 40 17 52 4 13 300 -56 -29 7 0 -27 24 38 -29 45 10 -26 47 4 56 0 0 -28 40 42 17 52 5 12 299 -56 -29 31 58 -27 49 44 -30 10 6 -27 12 12 57 0 0 -29 5 29 17 52 6 11 299 -57 -29 56 42 -28 14 35 -30 34 47 -27 37 5 58 0 0 -29 30 1 17 52 7 10 298 -58 -30 21 9 -28 39 10 -30 59 11 -28 1 43 59 0 0 -29 54 16 17 52 7 9 298 -59 -30 45 20 -29 3 29 -31 23 20 -28 26 5 60 0 0 -30 18 15 17 52 8 8 297 -59 -31 9 15 -29 27 32 -31 47 11 -28 50 11 61 0 0 -30 41 56 17 52 9 7 297 -60 -31 32 52 -29 51 18 -32 10 45 -29 14 0 62 0 0 -31 5 21 17 52 9 6 296 -61 -31 56 12 -30 14 47 -32 34 2 -29 37 32 63 0 0 -31 28 27 17 52 9 5 296 -61 -32 19 14 -30 37 58 -32 57 1 -30 0 46 64 0 0 -31 51 16 17 52 10 4 295 -62 -32 41 58 -31 0 51 -33 19 41 -30 23 43 65 0 0 -32 13 47 17 52 10 3 295 -63 -33 4 24 -31 23 26 -33 42 3 -30 46 22 66 0 0 -32 35 59 17 52 10 2 294 -63 -33 26 31 -31 45 43 -34 4 6 -31 8 42 67 0 0 -32 57 52 17 52 10 1 294 -64 -33 48 19 -32 7 41 -34 25 51 -31 30 43 68 0 0 -33 19 25 17 52 10 0 293 -64 -34 9 48 -32 29 20 .. .. .. -31 52 26 Uncertainty in time = +/- 2 secs [Prediction of 2008 May 8.0] Data for the target star ------------------------ * name: TYC 1395-00885-1 * constellation : Cancer * J2000 position with proper motion to date of event [h,m,s ; °,',"] RA: 08 41 10.3567 DE: +19 00 16.165 * position source: mpos:UCAC2 pm:UCAC2 * standard error: RA,DE ["]: ( .022, .029 ) * V mag [mag]: 12.2 * B mag [mag]: 12.2 * remarks: Data for the minor planet ------------------------- * general information: (number) name: (24) Themis approx. diameter [km]: 161 approx. diameter ["]: .080 distance from Earth [AU]: 2.79000 * orbital information: orbit source: Preston date of fit: 2008 May 07 source of used astrometry: FASTT MPC (via Astdys) number of used observations: 1480 number of rejected observations: 193 time covered by the observations: 1900 Aug 26 - 2008 Apr 07 1 sigma uncertainty ellipse (major, minor, PA): 0.010, 0.007, 105° remarks: * orbital elements for (24) Themis : Mean anomaly = 3.73075860 deg Arg. of pericenter = 107.88459381 deg Long. of node = 35.99292171 deg Inclination = 0.75951972 deg Eccentricity = 0.13176395 Semimajor axis = 3.13036467 AU Perihelion dist = 2.71789546 AU Mag: H = 7.21, G = 0.19 Epoch of elements : MJD 54598.74200000 TDT (2008 May 12.742) ------ occelmnt file for Occult BEGIN ----------------------------------- 2008 May 12 24 Themis 17h 48.2m UT 12.2 8 41 10.357 19 0 16.16TYC 1395-00885-1 12.2 12.5 161 6.4 2.790 3.023 -12.07 -7.6204 19.008 -87.95 18.36 17.8030 -0.09235 -0.32501 13.60446 -3.83105 0.00523 -0.00137 2000 2.1750712008 5 4.00000107.884594 35.992922 0.7595200.13176395 3.1303647 2.7178955 7.1 5.00.19 RATE 1.7795560 0.000000 0.000000 0.000000 0.0000000 0.0000000 0.0000000 Meas 0.030 0.024 1 1.37 0.030 0 54594.5020080512_0885-1 ------ occelmnt file for Occult END ----------------------------------- ============================================ Calculator (s): Steve Preston Date of update: 2008 May 08, 03:07 UT Steve Preston 7640 NE 32nd St Medina, WA 98039 425-688-9965 mailto: stevepr@acm.org