IOTA/IOTA-ES occultation update for (987) Wallia / TYC 1395-01556-1 event on 2008 May 16, 01:08 UT Visible from Chile, Argentina Summary ------- On 2008 May 16 UT, the 44 km diameter asteroid (987) Wallia will occult a 9.8 mag star in the constellation Cancer for observers along a path across Chile, Argentina. In the case of an occultation, the combined light of the asteroid and the star will drop by 6.2 mag to 16.0 mag (the magnitude of the asteroid) for at most 1.9 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: 33 * date and approx. time of event: 2008 May 16, 01:10 - 2008 May 16, 01:12 UT * magnitude of target star: 9.8 * magnitude drop [mag]: 6.2 * estimated maximum duration [s]: 1.9 * Moon: 85 % sunlit, 64° distance * Sun: 71° distance * rough path description: Chile, Argentina The occultation path -------------------- * approximate projected width [km]: 47 * 1 sigma uncertainty interval [path widths]: +/- 2.00 * 1 sigma uncertainty interval [seconds]: +/- 2.9 * 1 sigma uncertainty interval approx RA,DE ["]: (+/- .023 +/- .030) * 1 sigma uncertainty ellipse (major, minor, PA): ( .030", .023", 3° ) * approx speed of asteroid's shadow [km/s]: 22.4366 * website for maps: http://www.asteroidoccultation.com Path Coordinates: Occultation of TYC 1395-01556-1 by 987 Wallia on 2008 May 16 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 -111 0 0 - 9 41 20 1 10 13 59 338 -1 - 9 55 38 - 9 27 3 -10 53 7 - 8 30 12 -110 0 0 -10 10 22 1 10 18 59 337 -2 -10 24 42 - 9 56 3 -11 22 19 - 8 59 4 -109 0 0 -10 39 42 1 10 23 58 336 -3 -10 54 4 -10 25 21 -11 51 49 - 9 28 15 -108 0 0 -11 9 20 1 10 28 57 334 -4 -11 23 44 -10 54 57 -12 21 36 - 9 57 43 -107 0 0 -11 39 14 1 10 33 56 333 -5 -11 53 40 -11 24 50 -12 51 39 -10 27 29 -106 0 0 -12 9 24 1 10 38 55 332 -6 -12 23 51 -11 54 58 -13 21 58 -10 57 30 -105 0 0 -12 39 49 1 10 43 54 331 -7 -12 54 18 -12 25 21 -13 52 32 -11 27 46 -104 0 0 -13 10 28 1 10 48 53 330 -9 -13 24 59 -12 55 58 -14 23 20 -11 58 17 -103 0 0 -13 41 20 1 10 52 52 329 -10 -13 55 52 -13 26 49 -14 54 20 -12 29 1 -102 0 0 -14 12 24 1 10 57 51 328 -11 -14 26 58 -13 57 51 -15 25 32 -12 59 57 -101 0 0 -14 43 39 1 11 2 50 327 -12 -14 58 15 -14 29 5 -15 56 55 -13 31 5 -100 0 0 -15 15 5 1 11 6 49 326 -13 -15 29 42 -15 0 30 -16 28 28 -14 2 24 - 99 0 0 -15 46 40 1 11 11 48 325 -14 -16 1 18 -15 32 3 -17 0 9 -14 33 52 - 98 0 0 -16 18 23 1 11 15 47 324 -15 -16 33 3 -16 3 45 -17 31 59 -15 5 29 - 97 0 0 -16 50 14 1 11 19 46 323 -16 -17 4 55 -16 35 34 -18 3 56 -15 37 14 - 96 0 0 -17 22 10 1 11 24 45 323 -17 -17 36 53 -17 7 30 -18 35 58 -16 9 5 - 95 0 0 -17 54 13 1 11 28 44 322 -18 -18 8 56 -17 39 31 -19 8 6 -16 41 2 - 94 0 0 -18 26 19 1 11 32 43 321 -19 -18 41 3 -18 11 37 -19 40 17 -17 13 3 - 93 0 0 -18 58 29 1 11 36 42 321 -20 -19 13 14 -18 43 45 -20 12 31 -17 45 8 - 92 0 0 -19 30 40 1 11 40 41 320 -22 -19 45 26 -19 15 56 -20 44 47 -18 17 16 - 91 0 0 -20 2 54 1 11 44 40 319 -23 -20 17 40 -19 48 9 -21 17 4 -18 49 26 - 90 0 0 -20 35 7 1 11 47 39 319 -24 -20 49 54 -20 20 21 -21 49 21 -19 21 36 - 89 0 0 -21 7 19 1 11 51 38 318 -25 -21 22 7 -20 52 33 -22 21 36 -19 53 45 - 88 0 0 -21 39 30 1 11 55 37 317 -26 -21 54 18 -21 24 43 -22 53 49 -20 25 54 - 87 0 0 -22 11 38 1 11 58 36 317 -27 -22 26 26 -21 56 51 -23 25 59 -20 58 0 - 86 0 0 -22 43 42 1 12 1 35 316 -28 -22 58 30 -22 28 54 -23 58 4 -21 30 2 - 85 0 0 -23 15 41 1 12 5 34 315 -29 -23 30 30 -23 0 53 -24 30 4 -22 2 0 - 84 0 0 -23 47 34 1 12 8 33 315 -30 -24 2 23 -23 32 46 -25 1 58 -22 33 53 - 83 0 0 -24 19 21 1 12 11 32 314 -31 -24 34 10 -24 4 33 -25 33 45 -23 5 40 - 82 0 0 -24 51 0 1 12 14 31 314 -32 -25 5 49 -24 36 12 -26 5 23 -23 37 19 - 81 0 0 -25 22 30 1 12 17 30 313 -33 -25 37 19 -25 7 43 -26 36 53 -24 8 50 - 80 0 0 -25 53 51 1 12 19 29 313 -34 -26 8 40 -25 39 4 -27 8 13 -24 40 12 - 79 0 0 -26 25 2 1 12 22 28 312 -35 -26 39 50 -26 10 15 -27 39 21 -25 11 25 - 78 0 0 -26 56 1 1 12 25 27 311 -36 -27 10 49 -26 41 15 -28 10 19 -25 42 26 - 77 0 0 -27 26 48 1 12 27 26 311 -37 -27 41 36 -27 12 2 -28 41 3 -26 13 16 - 76 0 0 -27 57 23 1 12 29 25 310 -37 -28 12 10 -27 42 38 -29 11 35 -26 43 54 - 75 0 0 -28 27 44 1 12 32 24 310 -38 -28 42 30 -28 12 59 -29 41 52 -27 14 18 - 74 0 0 -28 57 50 1 12 34 23 309 -39 -29 12 35 -28 43 6 -30 11 55 -27 44 28 - 73 0 0 -29 27 41 1 12 36 22 309 -40 -29 42 26 -29 12 59 -30 41 42 -28 14 24 - 72 0 0 -29 57 17 1 12 38 21 308 -41 -30 12 1 -29 42 35 -31 11 12 -28 44 4 - 71 0 0 -30 26 36 1 12 40 20 307 -42 -30 41 19 -30 11 55 -31 40 26 -29 13 28 - 70 0 0 -30 55 38 1 12 41 19 307 -43 -31 10 20 -30 40 58 -32 9 23 -29 42 35 - 69 0 0 -31 24 22 1 12 43 18 306 -44 -31 39 3 -31 9 44 -32 38 1 -30 11 25 - 68 0 0 -31 52 48 1 12 45 17 306 -44 -32 7 27 -31 38 11 -33 6 21 -30 39 57 - 67 0 0 -32 20 55 1 12 46 16 305 -45 -32 35 33 -32 6 19 -33 34 21 -31 8 11 - 66 0 0 -32 48 43 1 12 47 15 305 -46 -33 3 19 -32 34 8 -34 2 2 -31 36 5 - 65 0 0 -33 16 11 1 12 49 14 304 -47 -33 30 46 -33 1 37 -34 29 23 -32 3 40 - 64 0 0 -33 43 18 1 12 50 13 303 -48 -33 57 52 -33 28 46 -34 56 23 -32 30 55 - 63 0 0 -34 10 5 1 12 51 12 303 -48 -34 24 37 -33 55 34 -35 23 1 -32 57 49 - 62 0 0 -34 36 30 1 12 52 11 302 -49 -34 51 1 -34 22 1 -35 49 19 -33 24 22 - 61 0 0 -35 2 34 1 12 53 10 302 -50 -35 17 3 -34 48 7 -36 15 14 -33 50 34 - 60 0 0 -35 28 16 1 12 54 9 301 -51 -35 42 43 -35 13 51 -36 40 48 -34 16 25 - 59 0 0 -35 53 36 1 12 55 8 301 -51 -36 8 1 -35 39 12 -37 5 58 -34 41 53 - 58 0 0 -36 18 33 1 12 55 8 300 -52 -36 32 56 -36 4 11 -37 30 46 -35 6 59 - 57 0 0 -36 43 7 1 12 56 7 299 -53 -36 57 29 -36 28 47 -37 55 12 -35 31 42 - 56 0 0 -37 7 18 1 12 56 6 299 -53 -37 21 38 -36 53 0 -38 19 13 -35 56 3 - 55 0 0 -37 31 6 1 12 57 5 298 -54 -37 45 24 -37 16 50 -38 42 52 -36 20 0 - 54 0 0 -37 54 31 1 12 57 4 298 -54 -38 8 47 -37 40 16 -39 6 6 -36 43 34 - 53 0 0 -38 17 32 1 12 57 3 297 -55 -38 31 45 -38 3 19 -39 28 57 -37 6 45 - 52 0 0 -38 40 9 1 12 58 2 296 -56 -38 54 20 -38 25 58 -39 51 24 .. .. .. - 51 0 0 -39 2 22 1 12 58 1 296 -56 -39 16 31 -38 48 13 -40 13 27 .. .. .. - 50 0 0 -39 24 10 1 12 58 1 295 -57 -39 38 18 -39 10 4 -40 35 6 .. .. .. Uncertainty in time = +/- 4 secs [Prediction of 2008 May 8.0] Data for the target star ------------------------ * name: TYC 1395-01556-1 * constellation : Cancer * J2000 position with proper motion to date of event [h,m,s ; °,',"] RA: 08 36 34.5326 DE: +18 51 13.153 * position source: mpos:UCAC2 pm:UCAC2 * standard error: RA,DE ["]: ( .018, .028 ) * V mag [mag]: 9.8 * B mag [mag]: 11.0 * remarks: Data for the minor planet ------------------------- * general information: (number) name: (987) Wallia approx. diameter [km]: 44 approx. diameter ["]: .015 distance from Earth [AU]: 4.01900 * orbital information: orbit source: Preston date of fit: 2008 May 07 source of used astrometry: FASTT MPC (via Astdys) number of used observations: 869 number of rejected observations: 52 time covered by the observations: 1937 May 01 - 2008 Mar 25 1 sigma uncertainty ellipse (major, minor, PA): 0.015, 0.012, 112° remarks: * orbital elements for (987) Wallia : Mean anomaly = 152.14706581 deg Arg. of pericenter = 16.33242255 deg Long. of node = 322.96524798 deg Inclination = 8.88511391 deg Eccentricity = 0.22970964 Semimajor axis = 3.14942564 AU Perihelion dist = 2.42597221 AU Mag: H = 9.41, G = 0.15 Epoch of elements : MJD 54602.04800000 TDT (2008 May 16.048) ------ occelmnt file for Occult BEGIN ----------------------------------- 2008 May 16 987 Wallia 1h 8.6m UT 9.8 8 36 34.533 18 51 13.15TYC 1395-01556-1 11.0 16.0 44 1.9 4.019 1.833 -9.55 -122.1262 18.856 161.95 19.15 1.1429 -0.12955 -0.35091 11.88852 -4.36299 0.00528 -0.00136 2000 151.7859172008 514.00000 16.332423322.965248 8.8851140.22970964 3.1494256 2.4259722 9.3 5.00.15 RATE 1.7634250 0.000000 0.000000 0.000000 0.0000000 0.0000000 0.0000000 Meas 0.030 0.023 3 3.00 0.030 0 54594.5020080516_1556-1 ------ occelmnt file for Occult END ----------------------------------- ============================================ Calculator (s): Steve Preston Date of update: 2008 May 08, 03:23 UT Steve Preston 7640 NE 32nd St Medina, WA 98039 425-688-9965 mailto: stevepr@acm.org