IOTA/IOTA-ES occultation update for (140) Siwa / UCAC2 34287590 event on 2008 Apr 03, 12:02 UT Visible from Japan, China Summary ------- On 2008 Apr 03 UT, the 110 km diameter asteroid (140) Siwa will occult a 11.8 mag star in the constellation Leo for observers along a path across Japan, China. In the case of an occultation, the combined light of the asteroid and the star will drop by 1.4 mag to 12.8 mag (the magnitude of the asteroid) for at most 9.0 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: 99 * date and approx. time of event: 2008 Apr 03, 11:53 - 2008 Apr 03, 12:10 UT * magnitude of target star: 11.8 * magnitude drop [mag]: 1.4 * estimated maximum duration [s]: 9.0 * Moon: 10 % sunlit, 166° distance * Sun: 157° distance * rough path description: Japan, China The occultation path -------------------- * approximate projected width [km]: 113 * 1 sigma uncertainty interval [path widths]: +/- 0.31 * 1 sigma uncertainty interval [seconds]: +/- 3.2 * 1 sigma uncertainty interval approx RA,DE ["]: (+/- .026 +/- .023) * 1 sigma uncertainty ellipse (major, minor, PA): ( .026", .023", 99° ) * approx speed of asteroid's shadow [km/s]: 12.1338 * website for maps: http://www.asteroidoccultation.com Path Coordinates: Occultation of UCAC2 34287590 by 140 Siwa on 2008 Apr 3 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 93 0 0 37 10 9 12 10 12 23 99 0 37 40 54 36 39 28 38 0 0 36 20 29 94 0 0 37 8 1 12 10 9 24 99 -1 37 38 47 36 37 20 37 57 53 36 18 20 95 0 0 37 5 34 12 10 6 25 100 -2 37 36 21 36 34 52 37 55 27 36 15 52 96 0 0 37 2 47 12 10 2 26 100 -3 37 33 35 36 32 4 37 52 42 36 13 4 97 0 0 36 59 41 12 9 59 27 101 -4 37 30 29 36 28 57 37 49 37 36 9 56 98 0 0 36 56 15 12 9 56 27 102 -4 37 27 4 36 25 30 37 46 12 36 6 28 99 0 0 36 52 29 12 9 52 28 102 -5 37 23 19 36 21 43 37 42 28 36 2 40 100 0 0 36 48 23 12 9 49 29 103 -6 37 19 14 36 17 36 37 38 24 35 58 33 101 0 0 36 43 58 12 9 45 30 104 -7 37 14 50 36 13 10 37 34 1 35 54 6 102 0 0 36 39 13 12 9 41 30 104 -8 37 10 7 36 8 24 37 29 18 35 49 19 103 0 0 36 34 9 12 9 37 31 105 -8 37 5 4 36 3 18 37 24 16 35 44 12 104 0 0 36 28 45 12 9 33 32 106 -9 36 59 41 35 57 52 37 18 55 35 38 46 105 0 0 36 23 1 12 9 29 33 106 -10 36 53 59 35 52 7 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4 12 10 -154 0 0 4 42 25 11 56 50 47 276 -64 5 15 17 4 9 37 5 35 42 3 49 20 -153 0 0 4 19 43 11 56 43 46 276 -63 4 52 33 3 46 58 5 12 57 3 26 42 -152 0 0 3 57 13 11 56 36 45 277 -62 4 30 0 3 24 30 4 50 23 3 4 15 -151 0 0 3 34 55 11 56 29 44 277 -61 4 7 40 3 2 14 4 28 1 2 42 1 -150 0 0 3 12 50 11 56 23 43 277 -60 3 45 32 2 40 11 4 5 52 2 20 0 -149 0 0 2 50 58 11 56 16 42 277 -60 3 23 38 2 18 22 3 43 56 1 58 12 -148 0 0 2 29 19 11 56 10 41 278 -59 3 1 57 1 56 46 3 22 13 1 36 37 -147 0 0 2 7 55 11 56 3 40 278 -58 2 40 30 1 35 24 3 0 45 1 15 17 -146 0 0 1 46 45 11 55 57 39 278 -57 2 19 18 1 14 17 2 39 31 0 54 11 -145 0 0 1 25 50 11 55 51 38 278 -56 1 58 20 0 53 25 2 18 32 0 33 21 -144 0 0 1 5 11 11 55 45 37 278 -55 1 37 38 0 32 48 1 57 48 0 12 45 -143 0 0 0 44 47 11 55 39 36 279 -54 1 17 12 0 12 27 1 37 20 - 0 7 34 -142 0 0 0 24 39 11 55 34 35 279 -53 0 57 2 - 0 7 38 1 17 8 - 0 27 37 -141 0 0 0 4 48 11 55 28 34 279 -53 0 37 8 - 0 27 27 0 57 13 - 0 47 24 -140 0 0 - 0 14 46 11 55 23 33 279 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20 - 4 32 40 - 3 9 39 - 4 52 14 -126 0 0 - 4 16 6 11 54 25 18 279 -38 - 3 44 27 - 4 47 41 - 3 24 47 - 5 7 14 -125 0 0 - 4 30 49 11 54 22 17 279 -37 - 3 59 12 - 5 2 22 - 3 39 34 - 5 21 53 -124 0 0 - 4 45 10 11 54 19 16 279 -36 - 4 13 36 - 5 16 40 - 3 53 59 - 5 36 10 -123 0 0 - 4 59 9 11 54 17 15 279 -35 - 4 27 37 - 5 30 37 - 4 8 2 - 5 50 5 -122 0 0 - 5 12 47 11 54 14 14 279 -35 - 4 41 17 - 5 44 12 - 4 21 43 - 6 3 39 -121 0 0 - 5 26 2 11 54 12 13 279 -34 - 4 54 35 - 5 57 25 - 4 35 3 - 6 16 50 -120 0 0 - 5 38 55 11 54 10 12 279 -33 - 5 7 30 - 6 10 16 - 4 47 59 - 6 29 40 -119 0 0 - 5 51 25 11 54 8 11 279 -32 - 5 20 3 - 6 22 44 - 5 0 33 - 6 42 6 -118 0 0 - 6 3 33 11 54 6 10 279 -31 - 5 32 12 - 6 34 49 - 5 12 44 - 6 54 10 -117 0 0 - 6 15 18 11 54 4 9 279 -30 - 5 43 59 - 6 46 32 - 5 24 33 - 7 5 51 -116 0 0 - 6 26 39 11 54 3 8 279 -29 - 5 55 23 - 6 57 51 - 5 35 58 - 7 17 10 -115 0 0 - 6 37 37 11 54 2 7 278 -28 - 6 6 23 - 7 8 47 - 5 46 59 - 7 28 5 -114 0 0 - 6 48 12 11 54 1 6 278 -27 - 6 17 0 - 7 19 20 - 5 57 37 - 7 38 36 -113 0 0 - 6 58 24 11 54 0 5 278 -26 - 6 27 14 - 7 29 30 - 6 7 52 - 7 48 45 -112 0 0 - 7 8 12 11 53 59 4 278 -25 - 6 37 3 - 7 39 16 - 6 17 43 - 7 58 29 -111 0 0 - 7 17 36 11 53 58 3 278 -24 - 6 46 29 - 7 48 38 - 6 27 10 - 8 7 51 -110 0 0 - 7 26 36 11 53 58 2 278 -23 - 6 55 31 - 7 57 36 - 6 36 13 - 8 16 48 -109 0 0 - 7 35 12 11 53 57 1 278 -22 - 7 4 8 - 8 6 11 - 6 44 51 - 8 25 21 -108 0 0 - 7 43 23 11 53 57 0 278 -21 - 7 12 22 - 8 14 21 - 6 53 6 - 8 33 30 Uncertainty in time = +/- 3 secs [Prediction of 2008 Mar 28.0] Data for the target star ------------------------ * name: UCAC2 34287590 * constellation : Leo * J2000 position with proper motion to date of event [h,m,s ; °,',"] RA: 11 35 20.0110 DE: +07 29 29.048 * position source: mpos:UCAC2 pm:UCAC2 * standard error: RA,DE ["]: ( .020, .020 ) * V mag [mag]: 11.8 * B mag [mag]: 0.0 * remarks: Data for the minor planet ------------------------- * general information: (number) name: (140) Siwa approx. diameter [km]: 110 approx. diameter ["]: .075 distance from Earth [AU]: 2.03500 * orbital information: orbit source: Preston date of fit: 2008 Mar 27 source of used astrometry: FASTT MPC (via Astdys) number of used observations: 1225 number of rejected observations: 178 time covered by the observations: 1900 Apr 26 - 2008 Mar 10 1 sigma uncertainty ellipse (major, minor, PA): 0.017, 0.011, 111° remarks: * orbital elements for (140) Siwa : Mean anomaly = 256.37550135 deg Arg. of pericenter = 197.28665133 deg Long. of node = 107.29495625 deg Inclination = 3.18754840 deg Eccentricity = 0.21675935 Semimajor axis = 2.73173900 AU Perihelion dist = 2.13960902 AU Mag: H = 8.47, G = 0.15 Epoch of elements : MJD 54559.50200000 TDT (2008 Apr 03.502) ------ occelmnt file for Occult BEGIN ----------------------------------- 2008 Apr 3 140 Siwa 12h 2.5m UT 11.8 11 35 20.011 7 29 29.05UCAC2 34287590 0.0 12.8 110 9.0 2.035 -1.847 11.00 161.0278 7.489 0.18 5.57 12.0409 0.09020 0.22554 -6.35750 2.54676 0.00187 -0.00126 2000 254.3012552008 325.00000197.286651107.294956 3.1875480.21675935 2.7317390 2.1396090 8.3 5.00.15 RATE 2.1829570 0.000000 0.000000 0.000000 0.0000000 0.0000000 0.0000000 Meas 0.026 0.023 99 1.31 0.023 0 54553.5020080403_287590 ------ occelmnt file for Occult END ----------------------------------- ============================================ Calculator (s): Steve Preston Date of update: 2008 Mar 28, 06:38 UT Steve Preston 7640 NE 32nd St Medina, WA 98039 425-688-9965 mailto: stevepr@acm.org