IOTA/IOTA-ES occultation update for (1838) Ursa / TYC 2404-00415-1 event on 2012 Aug 19, 10:55 UT Visible from Mexico Summary ------- On 2012 Aug 19 UT, the 40 km diameter asteroid (1838) Ursa will occult a 10.5 mag star in the constellation Auriga for observers along a path across Mexico. In the case of an occultation, the combined light of the asteroid and the star will drop by 6.2 mag to 16.7 mag (the magnitude of the asteroid) for at most 1.3 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: 38 * date and approx. time of event: 2012 Aug 19, 10:52 - 2012 Aug 19, 10:54 UT * geocentric midpoint of event [JD]: 2456158.9553 * magnitude of target star: 10.5 * magnitude drop [mag]: 6.2 * estimated maximum duration [s]: 1.3 * Moon: 4 % sunlit, 84° distance * Sun: 62° distance * rough path description: Mexico The occultation path -------------------- * approximate projected width [km]: 41 * 1 sigma uncertainty interval [path widths]: +/- 1.75 * 1 sigma uncertainty interval [seconds]: +/- 2.8 * 1 sigma uncertainty interval approx RA,DE ["]: (+/- .038 +/- .029) * 1 sigma uncertainty ellipse (major, minor, PA): ( .039", .028", 74° ) * approx speed of asteroid's shadow [km/s]: 30.5219 * website for maps: http://www.asteroidoccultation.com Path Coordinates: Occultation of TYC 2404-00415-1 by 1838 Ursa on 2012 Aug 19 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 -133 0 0 - 5 53 12 10 52 15 0 58 -60 - 6 6 19 - 5 40 4 .. .. .. - 4 54 0 -132 0 0 - 5 15 18 10 52 15 1 58 -59 - 5 28 29 - 5 2 7 - 6 14 29 - 4 15 51 -131 0 0 - 4 36 50 10 52 15 3 58 -58 - 4 50 4 - 4 23 36 - 5 36 15 - 3 37 8 -130 0 0 - 3 57 48 10 52 15 4 58 -57 - 4 11 5 - 3 44 31 - 4 57 27 - 2 57 53 -129 0 0 - 3 18 14 10 52 15 5 58 -56 - 3 31 34 - 3 4 54 - 4 18 7 - 2 18 4 -128 0 0 - 2 38 9 10 52 16 6 58 -55 - 2 51 31 - 2 24 45 - 3 38 15 - 1 37 45 -127 0 0 - 1 57 32 10 52 16 7 58 -54 - 2 10 58 - 1 44 6 - 2 57 52 - 0 56 55 -126 0 0 - 1 16 26 10 52 17 9 58 -52 - 1 29 55 - 1 2 57 - 2 16 59 - 0 15 36 -125 0 0 - 0 34 52 10 52 18 10 58 -51 - 0 48 24 - 0 21 19 - 1 35 38 0 26 12 -124 0 0 0 7 10 10 52 19 11 58 -50 - 0 6 25 0 20 45 - 0 53 49 1 8 26 -123 0 0 0 49 38 10 52 20 12 58 -49 0 36 0 1 3 16 - 0 11 33 1 51 7 -122 0 0 1 32 30 10 52 21 13 58 -48 1 18 50 1 46 11 0 31 8 2 34 11 -121 0 0 2 15 46 10 52 22 15 58 -46 2 2 4 2 29 30 1 14 12 3 17 39 -120 0 0 2 59 24 10 52 23 16 58 -45 2 45 39 3 13 10 1 57 39 4 1 28 -119 0 0 3 43 23 10 52 24 17 58 -44 3 29 35 3 57 11 2 41 27 4 45 37 -118 0 0 4 27 40 10 52 26 18 58 -43 4 13 51 4 41 31 3 25 35 5 30 5 -117 0 0 5 12 15 10 52 27 20 58 -42 4 58 24 5 26 8 4 10 0 6 14 50 -116 0 0 5 57 6 10 52 29 21 58 -40 5 43 12 6 11 1 4 54 42 6 59 49 -115 0 0 6 42 11 10 52 30 22 58 -39 6 28 15 6 56 7 5 39 38 7 45 3 -114 0 0 7 27 28 10 52 32 23 58 -38 7 13 31 7 41 26 6 24 47 8 30 28 -113 0 0 8 12 56 10 52 34 25 59 -37 7 58 57 8 26 55 7 10 8 9 16 3 -112 0 0 8 58 32 10 52 36 26 59 -36 8 44 32 9 12 33 7 55 37 10 1 46 -111 0 0 9 44 15 10 52 38 27 59 -34 9 30 14 9 58 18 8 41 15 10 47 36 -110 0 0 10 30 4 10 52 40 28 59 -33 10 16 1 10 44 8 9 26 58 11 33 30 -109 0 0 11 15 56 10 52 43 30 60 -32 11 1 52 11 30 1 10 12 45 12 19 26 -108 0 0 12 1 49 10 52 45 31 60 -31 11 47 44 12 15 54 10 58 34 13 5 23 -107 0 0 12 47 41 10 52 47 32 60 -30 12 33 35 13 1 48 11 44 23 13 51 18 -106 0 0 13 33 31 10 52 50 33 61 -28 13 19 25 13 47 38 12 30 11 14 37 11 -105 0 0 14 19 16 10 52 52 34 61 -27 14 5 10 14 33 24 13 15 55 15 22 58 -104 0 0 15 4 56 10 52 55 36 61 -26 14 50 49 15 19 3 14 1 33 16 8 38 -103 0 0 15 50 27 10 52 58 37 62 -25 15 36 20 16 4 34 14 47 4 16 54 9 -102 0 0 16 35 48 10 53 1 38 62 -24 16 21 41 16 49 55 15 32 25 17 39 30 -101 0 0 17 20 57 10 53 3 39 63 -22 17 6 51 17 35 4 16 17 36 18 24 38 -100 0 0 18 5 52 10 53 6 40 63 -21 17 51 47 18 19 59 17 2 33 19 9 31 - 99 0 0 18 50 33 10 53 9 42 64 -20 18 36 27 19 4 39 17 47 16 19 54 9 - 98 0 0 19 34 56 10 53 12 43 64 -19 19 20 51 19 49 1 18 31 43 20 38 28 - 97 0 0 20 19 0 10 53 16 44 65 -18 20 4 56 20 33 5 19 15 51 21 22 28 - 96 0 0 21 2 44 10 53 19 45 65 -17 20 48 42 21 16 47 19 59 40 22 6 7 - 95 0 0 21 46 6 10 53 22 46 66 -16 21 32 5 22 0 8 20 43 8 22 49 23 - 94 0 0 22 29 5 10 53 25 47 67 -14 22 15 5 22 43 5 21 26 13 23 32 16 - 93 0 0 23 11 38 10 53 28 49 67 -13 22 57 40 23 25 38 22 8 53 24 14 42 - 92 0 0 23 53 46 10 53 32 50 68 -12 23 39 49 24 7 43 22 51 9 24 56 42 - 91 0 0 24 35 26 10 53 35 51 69 -11 24 21 31 24 49 22 23 32 57 25 38 14 - 90 0 0 25 16 37 10 53 38 52 70 -10 25 2 45 25 30 31 24 14 17 26 19 16 - 89 0 0 25 57 19 10 53 42 53 71 -9 25 43 28 26 11 10 24 55 8 26 59 48 - 88 0 0 26 37 29 10 53 45 54 72 -8 26 23 41 26 51 19 25 35 29 27 39 48 - 87 0 0 27 17 8 10 53 48 55 73 -7 27 3 22 27 30 55 26 15 18 28 19 16 - 86 0 0 27 56 14 10 53 52 56 74 -6 27 42 30 28 9 58 26 54 34 28 58 11 - 85 0 0 28 34 46 10 53 55 57 75 -5 28 21 5 28 48 27 27 33 18 29 36 31 - 84 0 0 29 12 43 10 53 59 58 76 -4 28 59 5 29 26 22 28 11 27 30 14 16 - 83 0 0 29 50 5 10 54 2 59 77 -3 29 36 29 30 3 41 28 49 1 30 51 26 - 82 0 0 30 26 51 10 54 6 60 78 -2 30 13 18 30 40 25 29 26 0 31 27 59 - 81 0 0 31 3 1 10 54 9 61 79 -1 30 49 31 31 16 32 30 2 23 32 3 56 Uncertainty in time = +/- 3 secs Prediction of 2012 Jun 21.0 Data for the target star ------------------------ * name: TYC 2404-00415-1 * constellation : Auriga * J2000 position with proper motion to date of event [h,m,s ; °,',"] RA: 05 36 56.7219 DE: +31 48 39.970 * position source: mpos:UCAC2 pm:UCAC2 * standard error: RA,DE ["]: ( .017, .020 ) * V mag [mag]: 10.5 * B mag [mag]: 10.9 * Diameter [mas]: 0 * remarks: Data for the minor planet ------------------------- * general information: (number) name: (1838) Ursa approx. diameter [km]: 40 approx. diameter ["]: .016 distance from Earth [AU]: 3.51600 * orbital information: orbit source: Preston date of fit: 2012 Jun 21 source of used astrometry: FASTT MPC (via Astdys) number of used observations: 908 number of rejected observations: 12 time covered by the observations: 1951 Apr 09 - 2012 Feb 02 1 sigma uncertainty ellipse (major, minor, PA): 0.035, 0.020, 70° remarks: * orbital elements for (1838) Ursa : Mean anomaly = 332.72656246 deg Arg. of pericenter = 54.15026330 deg Long. of node = 44.27387415 deg Inclination = 21.98690896 deg Eccentricity = 0.01845058 Semimajor axis = 3.22108978 AU Perihelion dist = 3.16165881 AU Mag: H = 10.69, G = 0.15 Epoch of elements : MJD 56158.45500000 TDT (2012 Aug 19.455) ------ occelmnt file for Occult BEGIN ----------------------------------- 2012 Aug 19 1838 Ursa 10h 55.6m UT 10.5 5 36 56.722 31 48 39.97TYC 2404-00415-1 10.9 16.7 40 1.3 3.516 3.190 14.26 -47.8691 31.807 16.98 12.56 10.9272 -0.07484 0.20029 16.25725 5.69954 -0.00506 0.00020 2000 331.2850662012 811.00000 54.150263 44.273874 21.9869090.01845058 3.2210898 3.161658810.6 5.00.15 RATE 1.7049040 0.000000 0.000000 0.000000 0.0000000 0.0000000 0.0000000 Meas 0.039 0.028 74 2.75 0.027 0 0-1 0 056099.0020120819_0415-1 ------ occelmnt file for Occult END ----------------------------------- ============================================ Calculator (s): Steve Preston Date of update: 2012 Jun 21, 01:34 UT Steve Preston 7640 NE 32nd St Medina, WA 98039 425-688-9965 mailto: stevepr@acm.org