Update for (640) Brambilla - November 17/18, 1999

Jan Manek's update

                     IOTA/IOTA-ES occultation update for
        (640) Brambilla / SAO 116455 event on November 17/18, 1999
    maybe visible from southern Portugal, Spain and Gibraltar in Europe,
                       and very east of South Africa


Summary 

In the night November 17/18, 1999 (yes, that's the night of Leonid's maximum) a 9.1 mag star SAO 116455 will be occulted by a 85 km asteroid (640) Brambilla. This update is based on USNO/Flagstaff astrometry for the asteroid and HIPPARCOS star position.

The updated path shows very large ~0.8" south-west shift with time ~3.2 minutes later compared to Edwin Goffin's nominal prediction.

The path now just barely miss south Portugal and runs over Gibraltar at ~23:28.5 UT. Then it runs over Africa to south and at ~23:43.5 UT the path runs over Maputo/Mosambique and along Indian coast of South Africa. However as the uncertainity is 3 path widths, also south Spain, whole southern half of Portugal and eastern part of South Africa still have a chance. Please check the attached charts for your local possibilities.

The event at one glimpse:
 * date and approx. UT time of event: November 17, 1999 @ 23:28 UT (Euro)
                                                          23:43 UT (S.A.)
 * magnitude of target star: 9.1
 * magnitude drop [mag]: 5.7
 * estimated maximum duration [s]: 10.5
 * path description: given above

The occultation path:
 * approximate ground width [km]: 110
 * uncertainty [path widths]: 3
 * uncertainty in time [s]: 30
 * maps: 2 (see below)
 * remarks: Path uncertainities are given according to nominal star position 
    errors and expected asteroid positional accuracy. 
    !!!!!!!
    Circles along the path are OCCULT exactly calculated centerline points. 
    !!!!!!!

Data for the target star:
 * name: SAO 116455 = PPM 154034 = HIP 40106 = TYC 0207 00445 1
 * constellation: Cancer
 * J2000 position [h,m,s; o,',"]: 08h 11m 32.231s; +07o 12' 51.31"
 * position source: HIPPARCOS
 * estimated accuracy ["]: 0.02" (0.01", 0.01")
 * V mag [mag]: 9.10
 * B-V [mag]: +1.37
 * remarks: 
     Target star is in very SW Cancer, about 2.3 degrees SW of 3.5 mag 
     star beta Cancri. About 17' SW of target is 8.6 mag star SAO 116438
     and just 3' west of target star is a nice triangle of 11-magnitude 
     stars.

Data for the minor planet:
 * general information:
     number, name: (640) Brambilla
     approx. diameter [km]: 85
 * orbital information
     orbit source: calculation Manek
     source of used astrometry: USNO/Flagstaff (Ron Stone)
     number of used observations: 29 USNO
     number of rejected observations: 4
     time covered by the observations: 1998 09 18 - 1999 11 06
     rms residuals ["] (RA,DE): 0.09", 0.09"
     estimated positional accuracy at epoch of event ["]: 0.11"
     remarks: Only 3 recent positions available.

Data for the event:
 * UT date and time of least geocentric approach: 23:38:07 UT
 * approx. V mag of minor planet at event [mag]: 14.8
 * geocentric parallax of minor planet ["]: 3.020
 * magnitude drop [mag]: 5.7
 * estimated maximum duration [s]: 10.5
 * apparent motion of minor planet ["/h]: 13.81
 * angular distance to moon, phase of moon [deg,%]: 138, 65%
 * remarks: 

Calculator(s): Jan Manek








Path coordinates:
                                       Altitude
  E. Longitude    Latitude     U.T.    star  sun
   ........ shortened ..........................
   - 17 00 00   + 36 25 29   23 28 14    3   -65
   - 15 00 00   + 36 29 37   23 28 16    5   -66
   - 13 00 00   + 36 29 21   23 28 19    6   -67
   - 11 00 00   + 36 24 40   23 28 23    8   -68
   -  9 00 00   + 36 15 31   23 28 27   10   -69
   -  7 00 00   + 36 01 46   23 28 33   11   -70
   -  5 00 00   + 35 43 19   23 28 39   13   -71
   -  3 00 00   + 35 19 57   23 28 47   15   -73
   -  1 00 00   + 34 51 28   23 28 55   16   -74
   +  1 00 00   + 34 17 34   23 29 05   18   -74
   +  3 00 00   + 33 37 53   23 29 15   20   -75
   +  5 00 00   + 32 52 01   23 29 27   22   -76
   +  7 00 00   + 31 59 24   23 29 41   23   -77
   +  9 00 00   + 30 59 25   23 29 56   25   -77
   + 11 00 00   + 29 51 15   23 30 13   27   -77
   ........ shortened ..........................

----------------------------------------------------------------------------
Jan Manek
Stefanik Observatory                Private :
Petrin 205                          Werichova 950
118 46  Praha 1                     152 00  Praha 5 - Barrandov     |_|_|
Czech Republic                      Czech Republic                  /   \
Internet : jmanek@mbox.vol.cz                                      |-O-O-|
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