IOTA/IOTA-ES occultation update for (162) Laurentia / 2UCAC 20929601 event on 2008 Mar 01, 13:48 UT Visible from Canada in twilight Summary ------- On 2008 Mar 01 UT, the 99 km diameter asteroid (162) Laurentia will occult a 12.5 mag star in the constellation Sagittarius for observers along a path across Canada in twilight. In the case of an occultation, the combined light of the asteroid and the star will drop by 2.4 mag to 14.8 mag (the magnitude of the asteroid) for at most 3.8 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: 56 * date and approx. time of event: 2008 Mar 01, 13:46 - 2008 Mar 01, 13:47 UT * magnitude of target star: 12.5 * magnitude drop [mag]: 2.4 * estimated maximum duration [s]: 3.8 * Moon: 36 % sunlit, 5° distance * Sun: 69° distance * rough path description: Canada in twilight The occultation path -------------------- * approximate projected width [km]: 286 * 1 sigma uncertainty interval [path widths]: +/- 1.12 * 1 sigma uncertainty interval [seconds]: +/- 3.8 * 1 sigma uncertainty interval approx RA,DE ["]: (+/- .047 +/- .046) * 1 sigma uncertainty ellipse (major, minor, PA): ( .047", .046", 90° ) * approx speed of asteroid's shadow [km/s]: 26.4063 * website for maps: http://lunar-occultations.com/iota/asteroids/astrndx.htm http://www.asteroidoccultation.com Path Coordinates: Occultation of 2UCAC 20929601 by 162 Laurentia on 2008 Mar 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 ' " Longitude Longitude Longitude Longitude -123 10 11 59 0 0 13 46 36 1 154 -11 -125 56 43 -120 13 37 ... .. .. -112 45 53 -122 6 51 58 0 0 13 46 36 2 155 -11 -124 52 6 -119 11 18 ... .. .. -111 44 8 -120 59 23 57 0 0 13 46 37 3 155 -10 -123 43 55 -118 4 14 ... .. .. -110 35 23 -119 47 40 56 0 0 13 46 38 4 156 -9 -122 32 2 -116 52 11 ... .. .. -109 19 9 -118 31 27 55 0 0 13 46 39 5 158 -9 -121 16 16 -115 34 52 ... .. .. -107 54 40 -117 10 25 54 0 0 13 46 41 7 159 -8 -119 56 21 -114 11 52 ... .. .. -106 20 51 -115 44 8 53 0 0 13 46 43 8 160 -7 -118 31 59 -112 42 35 ... .. .. -104 36 3 -114 12 3 52 0 0 13 46 45 9 161 -6 -117 2 42 -111 6 14 ... .. .. -102 37 40 -112 33 24 51 0 0 13 46 48 10 163 -5 -115 27 57 -109 21 43 ... .. .. -100 21 29 -110 47 8 50 0 0 13 46 52 12 164 -4 -113 47 1 -107 27 28 -119 42 22 - 97 39 40 -108 51 52 49 0 0 13 46 56 13 166 -2 -111 58 54 -105 21 10 -118 3 25 - 94 14 32 -106 45 31 48 0 0 13 47 1 14 168 -1 -110 2 17 -102 59 12 -116 18 58 - 88 59 40 Latitude Latitude Latitude Latitude -106 0 0 47 39 48 13 47 3 15 168 0 46 10 15 49 17 46 43 11 21 53 47 30 Uncertainty in time = +/- 4 secs [Prediction of 2008 Feb 14.0] Data for the target star ------------------------ * name: 2UCAC 20929601 * constellation : Sagittarius * J2000 position with proper motion to date of event [h,m,s ; °,',"] RA: 18 11 48.3539 DE: -26 58 30.798 * position source: mpos:UCAC2 pm:UCAC2 * standard error: RA,DE ["]: ( .045, .045 ) * V mag [mag]: 12.5 * B mag [mag]: 0.0 * remarks: Data for the minor planet ------------------------- * general information: (number) name: (162) Laurentia approx. diameter [km]: 99 approx. diameter ["]: .041 distance from Earth [AU]: 3.30700 * orbital information: orbit source: Preston date of fit: 2008 Feb 13 source of used astrometry: FASTT MPC (via Astdys) number of used observations: 849 number of rejected observations: 82 time covered by the observations: 1902 Apr 07 - 2007 Aug 07 1 sigma uncertainty ellipse (major, minor, PA): 0.014, 0.009, 93° remarks: * orbital elements for (162) Laurentia : Mean anomaly = 86.57280629 deg Arg. of pericenter = 112.70267020 deg Long. of node = 36.43554376 deg Inclination = 6.08064214 deg Eccentricity = 0.17295756 Semimajor axis = 3.02802344 AU Perihelion dist = 2.50430389 AU Mag: H = 8.86, G = 0.15 Epoch of elements : MJD 54526.57500000 TDT (2008 Mar 01.575) ------ occelmnt file for Occult BEGIN ----------------------------------- 2008 Mar 1 162 Laurentia 13h 48.0m UT 12.5 18 11 48.354-26 58 30.802UCAC 20929601 0.0 14.8 99 3.8 3.307 2.954 -3.41 -93.7785 -26.974 -23.92 -7.30 13.7995 0.08142 0.93457 14.84931 -1.28108 -0.00552 -0.00025 2000 85.3429312008 224.00000112.702670 36.435544 6.0806420.17295756 3.0280234 2.5043039 8.8 5.00.15 RATE 1.8705320 0.000000 0.000000 0.000000 0.0000000 0.0000000 0.0000000 Meas 0.047 0.046 90 2.12 0.046 0 54510.5020080301_929601 ------ occelmnt file for Occult END ----------------------------------- ============================================ Calculator (s): Steve Preston Date of update: 2008 Feb 14, 02:28 UT Steve Preston 7640 NE 32nd St Medina, WA 98039 425-688-9965 mailto: stevepr@acm.org