IOTA/IOTA-ES occultation update for (494) Virtus / TYC 7361-00521-1 event on 2009 Sep 01, 18:22 UT Visible from Summary ------- On 2009 Sep 01 UT, the 86 km diameter asteroid (494) Virtus will occult a 10.8 mag star in the constellation Scorpius for observers along a path across . In the case of an occultation, the combined light of the asteroid and the star will drop by 3.5 mag to 14.2 mag (the magnitude of the asteroid) for at most 7.0 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: 71 * date and approx. time of event: 2009 Sep 01, 18:21 - 2009 Sep 01, 18:31 UT * magnitude of target star: 10.8 * magnitude drop [mag]: 3.5 * estimated maximum duration [s]: 7.0 * Moon: 92 % sunlit, 47° distance * Sun: 100° distance * rough path description: The occultation path -------------------- * approximate projected width [km]: 86 * 1 sigma uncertainty interval [path widths]: +/- 0.81 * 1 sigma uncertainty interval [seconds]: +/- 4.1 * 1 sigma uncertainty interval approx RA,DE ["]: (+/- .032 +/- .039) * 1 sigma uncertainty ellipse (major, minor, PA): ( .039", .032", 1° ) * approx speed of asteroid's shadow [km/s]: 12.2750 * website for maps: http://www.asteroidoccultation.com Path Coordinates: Occultation of TYC 7361-00521-1 by 494 Virtus on 2009 Sep 1 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 - 10 0 0 -31 12 44 18 21 10 79 88 0 -31 36 2 -30 49 26 -32 13 46 -30 11 42 - 9 0 0 -31 14 43 18 21 18 80 88 -1 -31 38 0 -30 51 25 -32 15 44 -30 13 42 - 8 0 0 -31 16 12 18 21 26 81 87 -2 -31 39 29 -30 52 55 -32 17 12 -30 15 12 - 7 0 0 -31 17 12 18 21 34 82 86 -3 -31 40 29 -30 53 56 -32 18 12 -30 16 13 - 6 0 0 -31 17 44 18 21 41 83 84 -4 -31 41 0 -30 54 27 -32 18 42 -30 16 45 - 5 0 0 -31 17 46 18 21 49 84 83 -5 -31 41 2 -30 54 29 -32 18 44 -30 16 47 - 4 0 0 -31 17 18 18 21 57 84 81 -5 -31 40 35 -30 54 2 -32 18 18 -30 16 20 - 3 0 0 -31 16 22 18 22 5 85 79 -6 -31 39 39 -30 53 5 -32 17 22 -30 15 23 - 2 0 0 -31 14 57 18 22 13 86 76 -7 -31 38 14 -30 51 39 -32 15 57 -30 13 56 - 1 0 0 -31 13 2 18 22 21 87 71 -8 -31 36 19 -30 49 44 -32 14 4 -30 12 0 0 0 0 -31 10 38 18 22 29 87 61 -9 -31 33 56 -30 47 20 -32 11 42 -30 9 35 1 0 0 -31 7 45 18 22 37 87 37 -10 -31 31 4 -30 44 26 -32 8 50 -30 6 39 2 0 0 -31 4 22 18 22 46 87 334 -11 -31 27 42 -30 41 2 -32 5 30 -30 3 15 3 0 0 -31 0 30 18 22 54 87 297 -12 -31 23 51 -30 37 10 -32 1 41 -29 59 20 4 0 0 -30 56 9 18 23 2 87 284 -12 -31 19 31 -30 32 47 -31 57 23 -29 54 56 5 0 0 -30 51 18 18 23 10 86 278 -13 -31 14 42 -30 27 55 -31 52 35 -29 50 2 6 0 0 -30 45 58 18 23 18 85 275 -14 -31 9 23 -30 22 34 -31 47 19 -29 44 38 7 0 0 -30 40 9 18 23 26 85 272 -15 -31 3 35 -30 16 43 -31 41 33 -29 38 45 8 0 0 -30 33 49 18 23 34 84 270 -16 -30 57 17 -30 10 22 -31 35 18 -29 32 21 9 0 0 -30 27 1 18 23 42 83 269 -17 -30 50 30 -30 3 31 -31 28 34 -29 25 28 10 0 0 -30 19 42 18 23 50 82 267 -18 -30 43 13 -29 56 11 -31 21 20 -29 18 4 11 0 0 -30 11 53 18 23 58 81 266 -19 -30 35 27 -29 48 20 -31 13 36 -29 10 11 12 0 0 -30 3 35 18 24 6 80 265 -20 -30 27 10 -29 40 0 -31 5 24 -29 1 47 13 0 0 -29 54 47 18 24 15 80 264 -20 -30 18 24 -29 31 9 -30 56 41 -28 52 53 14 0 0 -29 45 29 18 24 23 79 264 -21 -30 9 8 -29 21 49 -30 47 29 -28 43 29 15 0 0 -29 35 40 18 24 31 78 263 -22 -29 59 23 -29 11 58 -30 37 47 -28 33 34 16 0 0 -29 25 22 18 24 39 77 262 -23 -29 49 7 -29 1 37 -30 27 35 -28 23 9 17 0 0 -29 14 33 18 24 47 76 261 -24 -29 38 20 -28 50 46 -30 16 53 -28 12 13 18 0 0 -29 3 14 18 24 55 75 261 -25 -29 27 4 -28 39 24 -30 5 41 -28 0 47 19 0 0 -28 51 24 18 25 3 74 260 -26 -29 15 17 -28 27 31 -29 53 59 -27 48 50 20 0 0 -28 39 4 18 25 11 73 259 -27 -29 3 0 -28 15 8 -29 41 47 -27 36 22 21 0 0 -28 26 14 18 25 19 72 259 -28 -28 50 13 -28 2 15 -29 29 4 -27 23 24 22 0 0 -28 12 53 18 25 28 71 258 -29 -28 36 55 -27 48 50 -29 15 52 -27 9 54 23 0 0 -27 59 1 18 25 36 70 258 -30 -28 23 6 -27 34 55 -29 2 8 -26 55 54 24 0 0 -27 44 38 18 25 44 70 257 -31 -28 8 47 -27 20 29 -28 47 54 -26 41 23 25 0 0 -27 29 45 18 25 52 69 257 -32 -27 53 57 -27 5 33 -28 33 10 -26 26 20 26 0 0 -27 14 21 18 26 0 68 256 -32 -27 38 36 -26 50 5 -28 17 55 -26 10 47 27 0 0 -26 58 25 18 26 8 67 255 -33 -27 22 45 -26 34 6 -28 2 9 -25 54 42 28 0 0 -26 41 59 18 26 16 66 255 -34 -27 6 22 -26 17 36 -27 45 53 -25 38 7 29 0 0 -26 25 2 18 26 24 65 254 -35 -26 49 29 -26 0 36 -27 29 5 -25 21 0 30 0 0 -26 7 34 18 26 32 64 254 -36 -26 32 5 -25 43 4 -27 11 47 -25 3 22 31 0 0 -25 49 35 18 26 40 63 253 -37 -26 14 10 -25 25 1 -26 53 59 -24 45 13 32 0 0 -25 31 5 18 26 47 62 253 -38 -25 55 44 -25 6 27 -26 35 39 -24 26 32 33 0 0 -25 12 4 18 26 55 61 252 -39 -25 36 47 -24 47 22 -26 16 49 -24 7 21 34 0 0 -24 52 32 18 27 3 60 252 -40 -25 17 19 -24 27 46 -25 57 27 -23 47 38 35 0 0 -24 32 30 18 27 11 59 251 -41 -24 57 20 -24 7 39 -25 37 35 -23 27 25 36 0 0 -24 11 56 18 27 19 58 251 -42 -24 36 51 -23 47 2 -25 17 13 -23 6 40 37 0 0 -23 50 52 18 27 26 57 251 -43 -24 15 51 -23 25 53 -24 56 19 -22 45 25 38 0 0 -23 29 17 18 27 34 56 250 -44 -23 54 20 -23 4 14 -24 34 55 -22 23 39 39 0 0 -23 7 11 18 27 42 55 250 -45 -23 32 19 -22 42 4 -24 13 1 -22 1 22 40 0 0 -22 44 35 18 27 49 54 249 -46 -23 9 47 -22 19 24 -23 50 36 -21 38 35 41 0 0 -22 21 29 18 27 57 53 249 -47 -22 46 45 -21 56 13 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0 0 -16 7 35 18 29 33 38 244 -62 -16 33 49 -15 41 21 -17 16 19 -14 58 52 56 0 0 -15 37 31 18 29 39 37 244 -63 -16 3 49 -15 11 14 -16 46 26 -14 28 38 57 0 0 -15 7 4 18 29 45 36 243 -64 -15 33 25 -14 40 43 -16 16 8 -13 58 2 58 0 0 -14 36 13 18 29 51 35 243 -65 -15 2 38 -14 9 48 -15 45 27 -13 27 2 59 0 0 -14 5 0 18 29 56 33 243 -66 -14 31 28 -13 38 32 -15 14 23 -12 55 39 60 0 0 -13 33 25 18 30 2 32 243 -67 -13 59 56 -13 6 53 -14 42 56 -12 23 55 61 0 0 -13 1 28 18 30 7 31 242 -68 -13 28 3 -12 34 53 -14 11 8 -11 51 51 62 0 0 -12 29 11 18 30 12 30 242 -69 -12 55 49 -12 2 34 -13 38 59 -11 19 26 63 0 0 -11 56 35 18 30 18 29 242 -70 -12 23 16 -11 29 54 -13 6 31 -10 46 42 64 0 0 -11 23 40 18 30 22 28 242 -72 -11 50 24 -10 56 56 -12 33 43 -10 13 39 65 0 0 -10 50 27 18 30 27 27 241 -73 -11 17 14 -10 23 41 -12 0 37 - 9 40 19 66 0 0 -10 16 57 18 30 32 26 241 -74 -10 43 46 - 9 50 8 -11 27 14 - 9 6 43 67 0 0 - 9 43 11 18 30 36 24 241 -75 -10 10 3 - 9 16 20 -10 53 35 - 8 32 51 68 0 0 - 9 9 11 18 30 40 23 241 -76 - 9 36 4 - 8 42 17 -10 19 40 - 7 58 44 69 0 0 - 8 34 56 18 30 44 22 241 -77 - 9 1 52 - 8 8 1 - 9 45 30 - 7 24 24 70 0 0 - 8 0 28 18 30 48 21 241 -78 - 8 27 26 - 7 33 31 - 9 11 8 - 6 49 52 71 0 0 - 7 25 48 18 30 52 20 240 -79 - 7 52 48 - 6 58 50 - 8 36 32 - 6 15 7 72 0 0 - 6 50 58 18 30 55 19 240 -80 - 7 17 59 - 6 23 57 - 8 1 46 - 5 40 13 73 0 0 - 6 15 57 18 30 59 17 240 -81 - 6 43 0 - 5 48 56 - 7 26 49 - 5 5 9 74 0 0 - 5 40 48 18 31 2 16 240 -81 - 6 7 52 - 5 13 45 - 6 51 43 - 4 29 56 75 0 0 - 5 5 32 18 31 5 15 240 -82 - 5 32 36 - 4 38 27 - 6 16 29 - 3 54 37 76 0 0 - 4 30 8 18 31 7 14 240 -83 - 4 57 14 - 4 3 3 - 5 41 8 - 3 19 12 77 0 0 - 3 54 39 18 31 10 13 240 -83 - 4 21 46 - 3 27 34 - 5 5 41 - 2 43 41 78 0 0 - 3 19 6 18 31 12 12 240 -84 - 3 46 13 - 2 52 0 - 4 30 9 - 2 8 7 79 0 0 - 2 43 30 18 31 14 10 240 -84 - 3 10 37 - 2 16 24 - 3 54 34 - 1 32 30 80 0 0 - 2 7 52 18 31 16 9 240 -84 - 2 34 59 - 1 40 46 - 3 18 56 - 0 56 52 81 0 0 - 1 32 13 18 31 17 8 240 -83 - 1 59 20 - 1 5 7 - 2 43 17 - 0 21 13 82 0 0 - 0 56 34 18 31 19 7 240 -83 - 1 23 41 - 0 29 28 - 2 7 37 0 14 25 83 0 0 - 0 20 57 18 31 20 6 240 -82 - 0 48 3 0 6 9 - 1 31 59 0 50 2 84 0 0 0 14 38 18 31 21 5 240 -82 - 0 12 28 0 41 43 - 0 56 22 1 25 35 85 0 0 0 50 9 18 31 21 3 240 -81 0 23 4 1 17 13 - 0 20 49 2 1 4 86 0 0 1 25 36 18 31 22 2 240 -80 0 58 32 1 52 39 0 14 40 2 36 28 87 0 0 2 0 56 18 31 22 1 240 -79 1 33 54 2 27 59 0 50 4 3 11 46 Uncertainty in time = +/- 6 secs [Prediction of 2008 Mar 20.0] Data for the target star ------------------------ * name: TYC 7361-00521-1 * constellation : Scorpius * J2000 position with proper motion to date of event [h,m,s ; °,',"] RA: 17 12 45.0537 DE: -30 11 31.645 * position source: mpos:UCAC2 pm:UCAC2 * standard error: RA,DE ["]: ( .026, .038 ) * V mag [mag]: 10.8 * B mag [mag]: 12.0 * remarks: Data for the minor planet ------------------------- * general information: (number) name: (494) Virtus approx. diameter [km]: 86 approx. diameter ["]: .048 distance from Earth [AU]: 2.46900 * orbital information: orbit source: Preston date of fit: 2008 Mar 20 source of used astrometry: FASTT MPC (via Astdys) number of used observations: 1137 number of rejected observations: 110 time covered by the observations: 1902 Oct 07 - 2008 Feb 13 1 sigma uncertainty ellipse (major, minor, PA): 0.019, 0.010, 101° remarks: * orbital elements for (494) Virtus : Mean anomaly = 21.85487661 deg Arg. of pericenter = 217.72892250 deg Long. of node = 38.36663428 deg Inclination = 7.07531143 deg Eccentricity = 0.05723036 Semimajor axis = 2.98781387 AU Perihelion dist = 2.81682021 AU Mag: H = 9.07, G = 0.15 Epoch of elements : MJD 55075.76600000 TDT (2009 Sep 01.766) ------ occelmnt file for Occult BEGIN ----------------------------------- 2009 Sep 1 494 Virtus 18h 22.7m UT 10.8 17 12 45.054-30 11 31.65TYC 7361-00521-1 12.0 14.2 86 7.0 2.469 1.900 1.58 1.4636 -30.193 -95.70 8.03 18.3784 -0.00051 -0.01258 6.91404 0.44497 0.00553 -0.00033 2000 20.7544832009 827.00000217.728923 38.366634 7.0753110.05723036 2.9878139 2.8168202 9.0 5.00.15 RATE 1.9084190 0.000000 0.000000 0.000000 0.0000000 0.0000000 0.0000000 Meas 0.039 0.032 1 1.81 0.039 0 54545.5020090901_0521-1 ------ occelmnt file for Occult END ----------------------------------- ============================================ Calculator (s): Steve Preston Date of update: 2008 Mar 20, 12:46 UT Steve Preston 7640 NE 32nd St Medina, WA 98039 425-688-9965 mailto: stevepr@acm.org