IOTA/IOTA-ES occultation update for (206) Hersilia / HIP 42487 event on 2008 May 20, 21:37 UT Visible from W Africa Summary ------- On 2008 May 20 UT, the 95 km diameter asteroid (206) Hersilia will occult a 8.9 mag star in the constellation Cancer for observers along a path across W Africa. In the case of an occultation, the combined light of the asteroid and the star will drop by 5.2 mag to 14.1 mag (the magnitude of the asteroid) for at most 3.3 seconds. This update is based on UNSO/Flagstaff astrometry for the asteroid kindly provided by Alice Monet, TMO astrometry for the asteroid kindly provided by Bill Owen, historical astrometry from the MPC files (via AstDys), and the following catalogs for the star position: . The event at a glimpse ---------------------- * Rank: 95 * date and approx. time of event: 2008 May 20, 21:39 - 2008 May 20, 21:41 UT * magnitude of target star: 8.9 * magnitude drop [mag]: 5.2 * estimated maximum duration [s]: 3.3 * Moon: 99 % sunlit, 122° distance * Sun: 67° distance * rough path description: W Africa The occultation path -------------------- * approximate projected width [km]: 104 * 1 sigma uncertainty interval [path widths]: +/- 0.44 * 1 sigma uncertainty interval [seconds]: +/- 1.9 * 1 sigma uncertainty interval approx RA,DE ["]: (+/- .027 +/- .020) * 1 sigma uncertainty ellipse (major, minor, PA): ( .027", .020", 92° ) * approx speed of asteroid's shadow [km/s]: 28.4251 * website for maps: http://www.asteroidoccultation.com Path Coordinates: Occultation of HIP 42487 by 206 Hersilia on 2008 May 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 - 41 0 0 34 15 54 21 39 11 57 250 0 33 45 32 34 46 24 33 18 54 35 13 21 - 40 0 0 33 54 57 21 39 14 56 252 -1 33 24 32 34 25 29 32 57 52 34 52 28 - 39 0 0 33 33 44 21 39 17 56 253 -2 33 3 17 34 4 18 32 36 35 34 31 19 - 38 0 0 33 12 16 21 39 20 55 255 -3 32 41 46 33 42 53 32 15 3 34 9 56 - 37 0 0 32 50 33 21 39 24 54 256 -4 32 20 1 33 21 12 31 53 16 33 48 17 - 36 0 0 32 28 35 21 39 27 53 257 -5 31 58 2 32 59 17 31 31 14 33 26 24 - 35 0 0 32 6 24 21 39 30 53 258 -6 31 35 48 32 37 7 31 8 59 33 4 16 - 34 0 0 31 43 59 21 39 33 52 260 -7 31 13 21 32 14 44 30 46 30 32 41 55 - 33 0 0 31 21 20 21 39 36 51 261 -8 30 50 41 31 52 8 30 23 49 32 19 20 - 32 0 0 30 58 29 21 39 40 50 262 -9 30 27 48 31 29 18 30 0 54 31 56 32 - 31 0 0 30 35 26 21 39 43 49 263 -9 30 4 43 31 6 16 29 37 48 31 33 31 - 30 0 0 30 12 10 21 39 46 49 264 -10 29 41 26 30 43 2 29 14 30 31 10 19 - 29 0 0 29 48 44 21 39 49 48 265 -11 29 17 58 30 19 37 28 51 0 30 46 55 - 28 0 0 29 25 6 21 39 52 47 266 -12 28 54 19 29 56 1 28 27 20 30 23 20 - 27 0 0 29 1 18 21 39 55 46 267 -13 28 30 30 29 32 14 28 3 30 29 59 34 - 26 0 0 28 37 20 21 39 58 45 268 -14 28 6 31 29 8 17 27 39 31 29 35 38 - 25 0 0 28 13 13 21 40 1 44 269 -15 27 42 23 28 44 11 27 15 22 29 11 33 - 24 0 0 27 48 58 21 40 4 43 270 -16 27 18 7 28 19 56 26 51 5 28 47 18 - 23 0 0 27 24 34 21 40 7 43 271 -17 26 53 42 27 55 33 26 26 39 28 22 56 - 22 0 0 27 0 2 21 40 9 42 271 -18 26 29 10 27 31 2 26 2 7 27 58 25 - 21 0 0 26 35 24 21 40 12 41 272 -19 26 4 32 27 6 24 25 37 28 27 33 48 - 20 0 0 26 10 39 21 40 15 40 273 -20 25 39 47 26 41 40 25 12 43 27 9 4 - 19 0 0 25 45 49 21 40 18 39 274 -21 25 14 56 26 16 49 24 47 52 26 44 14 - 18 0 0 25 20 53 21 40 20 38 274 -22 24 50 0 25 51 54 24 22 56 26 19 18 - 17 0 0 24 55 53 21 40 23 37 275 -23 24 25 0 25 26 54 23 57 56 25 54 18 - 16 0 0 24 30 49 21 40 25 36 276 -24 23 59 57 25 1 50 23 32 53 25 29 14 - 15 0 0 24 5 42 21 40 28 35 276 -25 23 34 50 24 36 43 23 7 47 25 4 6 - 14 0 0 23 40 33 21 40 30 34 277 -26 23 9 41 24 11 33 22 42 38 24 38 56 - 13 0 0 23 15 22 21 40 33 33 278 -27 22 44 31 23 46 21 22 17 28 24 13 44 - 12 0 0 22 50 9 21 40 35 32 278 -28 22 19 19 23 21 8 21 52 17 23 48 30 - 11 0 0 22 24 56 21 40 38 31 279 -29 21 54 7 22 55 54 21 27 6 23 23 16 - 10 0 0 21 59 44 21 40 40 30 279 -30 21 28 55 22 30 40 21 1 55 22 58 1 - 9 0 0 21 34 32 21 40 42 29 280 -31 21 3 44 22 5 27 20 36 45 22 32 47 - 8 0 0 21 9 22 21 40 44 28 280 -32 20 38 35 21 40 16 20 11 37 22 7 35 - 7 0 0 20 44 14 21 40 46 27 281 -33 20 13 28 21 15 7 19 46 31 21 42 24 - 6 0 0 20 19 8 21 40 48 26 281 -34 19 48 25 20 50 0 19 21 28 21 17 16 - 5 0 0 19 54 7 21 40 50 25 282 -35 19 23 24 20 24 57 18 56 29 20 52 12 - 4 0 0 19 29 9 21 40 52 24 282 -36 18 58 29 19 59 58 18 31 35 20 27 11 - 3 0 0 19 4 17 21 40 54 23 283 -37 18 33 38 19 35 4 18 6 46 20 2 16 - 2 0 0 18 39 30 21 40 55 22 283 -38 18 8 53 19 10 15 17 42 2 19 37 25 - 1 0 0 18 14 49 21 40 57 21 283 -39 17 44 14 18 45 32 17 17 25 19 12 41 0 0 0 17 50 15 21 40 59 20 284 -40 17 19 42 18 20 56 16 52 55 18 48 3 1 0 0 17 25 49 21 41 0 19 284 -40 16 55 18 17 56 28 16 28 33 18 23 33 2 0 0 17 1 31 21 41 1 18 284 -41 16 31 2 17 32 8 16 4 18 17 59 11 3 0 0 16 37 22 21 41 3 17 285 -42 16 6 55 17 7 56 15 40 13 17 34 57 4 0 0 16 13 22 21 41 4 16 285 -43 15 42 57 16 43 54 15 16 18 17 10 53 5 0 0 15 49 32 21 41 5 15 285 -44 15 19 10 16 20 2 14 52 32 16 46 58 6 0 0 15 25 52 21 41 6 14 286 -45 14 55 33 15 56 20 14 28 57 16 23 14 7 0 0 15 2 24 21 41 7 13 286 -46 14 32 7 15 32 49 14 5 34 15 59 41 8 0 0 14 39 8 21 41 8 12 286 -47 14 8 53 15 9 30 13 42 22 15 36 20 9 0 0 14 16 4 21 41 9 11 287 -48 13 45 52 14 46 23 13 19 23 15 13 11 10 0 0 13 53 13 21 41 10 10 287 -49 13 23 4 14 23 30 12 56 37 14 50 15 11 0 0 13 30 35 21 41 11 9 287 -50 13 0 29 14 0 49 12 34 5 14 27 32 12 0 0 13 8 11 21 41 11 8 287 -50 12 38 8 13 38 23 12 11 46 14 5 3 13 0 0 12 46 2 21 41 12 7 288 -51 12 16 1 13 16 11 11 49 42 13 42 48 14 0 0 12 24 8 21 41 12 6 288 -52 11 54 10 12 54 14 11 27 53 13 20 49 15 0 0 12 2 29 21 41 13 5 288 -53 11 32 34 12 32 32 11 6 20 12 59 4 16 0 0 11 41 7 21 41 13 4 288 -54 11 11 14 12 11 6 10 45 3 12 37 36 17 0 0 11 20 0 21 41 13 2 288 -54 10 50 11 11 49 57 10 24 2 12 16 24 18 0 0 10 59 11 21 41 14 1 289 -55 10 29 24 11 29 4 10 3 18 11 55 29 19 0 0 10 38 38 21 41 14 0 289 -56 10 8 55 11 8 29 9 42 51 11 34 51 Uncertainty in time = +/- 2 secs [Prediction of 2008 May 17.0] Data for the target star ------------------------ * name: HIP 42487 * constellation : Cancer * J2000 position with proper motion to date of event [h,m,s ; °,',"] RA: 08 39 42.9495 DE: +18 33 10.503 * position source: mpos:HIP pm:HIP plx:HIP * standard error: RA,DE ["]: ( .025, .018 ) * V mag [mag]: 8.9 * B mag [mag]: 9.1 * remarks: Data for the minor planet ------------------------- * general information: (number) name: (206) Hersilia approx. diameter [km]: 95 approx. diameter ["]: .045 distance from Earth [AU]: 2.90400 * orbital information: orbit source: Preston date of fit: 2008 May 17 source of used astrometry: FASTT TMO MPC (via Astdys) number of used observations: 876 number of rejected observations: 141 time covered by the observations: 1902 Nov 21 - 2008 May 14 1 sigma uncertainty ellipse (major, minor, PA): 0.012, 0.008, 100° remarks: * orbital elements for (206) Hersilia : Mean anomaly = 57.04772453 deg Arg. of pericenter = 301.51807236 deg Long. of node = 145.26703462 deg Inclination = 3.78066708 deg Eccentricity = 0.04081644 Semimajor axis = 2.74044991 AU Perihelion dist = 2.62859449 AU Mag: H = 8.64, G = 0.15 Epoch of elements : MJD 54606.90100000 TDT (2008 May 20.901) ------ occelmnt file for Occult BEGIN ----------------------------------- 2008 May 20 206 Hersilia 21h 37.8m UT 8.9 8 39 42.950 18 33 10.50HIP 42487 9.1 14.1 95 3.3 2.904 3.336 -10.49 -73.4303 18.556 -145.30 20.20 21.6299 0.08493 0.38948 15.66551 -3.46388 0.00494 -0.00130 2000 55.5484432008 514.00000301.518072145.267035 3.7806670.04081644 2.7404499 2.6285945 8.7 5.00.15 RATE 2.1725580 0.000000 0.000000 0.000000 0.0000000 0.0000000 0.0000000 Meas 0.027 0.020 92 1.44 0.020 0 54603.5020080520__42487 ------ occelmnt file for Occult END ----------------------------------- ============================================ Calculator (s): Steve Preston Date of update: 2008 May 17, 17:16 UT Steve Preston 7640 NE 32nd St Medina, WA 98039 425-688-9965 mailto: stevepr@acm.org