Update for (44) Nysa - March 12/13, 2000

Jan Manek's update

                  IOTA/IOTA-ES occultation update for
       (44) Nysa / HIP 65531 = W Vir event on March 12/13, 2000
        visible from frm.Yugoslavia, Austria, SW Czech Republic, 
                      Germany, Denmark and Norway


Summary 

In the morning of night March 12/13, 2000 a ~9.9 mag star HIP 65531 = W Vir will be occulted by a 73 km asteroid (44) Nysa. This update is based on USNO/Flagstaff and TMO astrometry for the asteroid and Hipparcos star position.

The updated path shows no shift with time ~0.3 minutes earlier compared to Edwin Goffin's nominal prediction.

The path of this occultation runs over frm.Yugoslavia around 4:33 UT, Austria ~4:34 UT, SW Czech Republic ~4:34.5 UT, Germany ~4:35 UT, Denmark ~4:36 UT and finally SW Norway ~4:37 UT. Within expected errors is also very NE Italy, western Hungary, most of Czech Republic and NE Netherlands.

As was earlier mentioned by Roland Boninsegna on PLANOCCULT list, the target star is (prototype) variable W Virginis (subtype of delta Cephei variables). I have also tried to find how bright this star could be around the time of occultation and have estimated on basis of some AFOEV brightness estimates that it could be around 9.9 magnitude, which is slightly more optimistic than Roland's estimate. But even with my estimate the drop will be only around 0.8 magnitudes. This means that for accurate observation are preferred observation by means of video camera, IOTA occultation camera or CCD drift scans.

The event will take place on morning twilight sky, with best condition being in Germany, Denmark and Norway where the sun will be around 10 degrees below horizon. The accuracy of update should be fairly good so even expeditions to path with suitable equipment is possible. Good luck for everyone !!!!

The event at one glimpse:
 * date and approx. UT time of event: March 13, 2000 @ 04:35 UT
 * magnitude of target star: 9.9
 * magnitude drop [mag]: 0.8
 * estimated maximum duration [s]: 10.0
 * path description: given above
 * Goffin's original chart reference: A00_0311

The occultation path:
 * approximate ground width [km]: 200
 * uncertainty [path widths]: 1.0
 * uncertainty in time [s]: 15
 * map: below
 * remarks: Path uncertainities are given according to nominal star
    position errors and expected asteroid positional accuracy.
    !!!!!!!
    Thick line indicates the centerline for this event.
    !!!!!!!

Data for the target star:
 * name: HIP 65531 = SAO 139335 = PPM 196502 = W Vir
 * constellation: Virgo
 * J2000 position [h,m,s; o,',"]: 13h 26m 01.993s; -03o 22' 43.42"
 * position source: Hipparcos
 * estimated accuracy ["]: 0.01" (0.01", 0.01")
 * V mag [mag]: 9.9 approx.
 * B-V [mag]: +0.4 approx.
 * remarks: 
     Target star is in middle Virgo, 7.8 degrees almost exactly north of 
     1.1 mag star alpha Virginis = Spica or 3.5 degrees SW of 3.4 mag star
     zeta Virginis. There is 7.1 mag star SAO 139336 only 17' south of 
     target, but this one is much brighter. There is no convenient star 
     suitable as reference star for visual observations in close vicinity.

Close finding chart (prepared in GUIDE7):
 * occulted star is in center - labeled with cross
 * field is 3.0x3.0 degrees
 * limiting magnitude is 12.5
 * labeled stars have indicated SAO numbers





Data for the minor planet:
 * general information:
     number, name: (44) Nysa
     approx. diameter [km]: 73
 * orbital information
     orbit source: calculation Manek
     source of used astrometry: USNO/Flagstaff (Ron Stone), TMO (Bill Owen)
     number of used observations: 51 USNO, 69 TMO
     number of rejected observations: 5 USNO, 1 TMO
     time covered by the observations: 1997 05 10 - 2000 03 04
     rms residuals ["] (RA,DE): 0.07", 0.06"
     estimated positional accuracy at epoch of event ["]: 0.06"
     remarks: 

Data for the event:
 * UT date and time of least geocentric approach: 04:34.2  UT
 * approx. V mag of minor planet at event [mag]: 10.0
 * geocentric parallax of minor planet ["]: 6.461
 * magnitude drop [mag]: 0.8
 * estimated maximum duration [s]: 10.0
 * apparent motion of minor planet ["/h]: 26.52
 * angular distance to moon, phase of moon [deg,%]: 120, 48%
 * remarks: 

Calculator(s): Jan Manek








Path coordinates:
                                       Altitude
  E. Longitude    Latitude     U.T.    star  sun
   ........ shortened ..........................
     20 14 49    43  0  0    4 32 26    20    -5
     18 49 13    44  0  0    4 32 47    21    -6
     17 29 25    45  0  0    4 33  6    21    -7
     16 14 48    46  0  0    4 33 26    21    -7
     15  4 56    47  0  0    4 33 45    21    -8
     13 59 28    48  0  0    4 34  3    22    -9
     12 58  7    49  0  0    4 34 21    22    -9
     12  0 43    50  0  0    4 34 39    21   -10
     11  7  7    51  0  0    4 34 56    21   -10
     10 17 12    52  0  0    4 35 13    21   -10
      9 30 55    53  0  0    4 35 29    21   -11
      8 48 17    54  0  0    4 35 45    21   -11
      8  9 18    55  0  0    4 36  0    20   -11
      7 34  3    56  0  0    4 36 15    20   -11
      7  2 37    57  0  0    4 36 30    19   -11
      6 35  9    58  0  0    4 36 43    19   -11
      6 11 52    59  0  0    4 36 57    18   -11
      5 52 59    60  0  0    4 37 10    18   -11
      5 38 49    61  0  0    4 37 22    17   -11
      5 29 46    62  0  0    4 37 34    16   -11
      5 26 17    63  0  0    4 37 46    16   -10
      5 28 56    64  0  0    4 37 57    15   -10
      5 38 27    65  0  0    4 38  8    14   -10
      5 55 42    66  0  0    4 38 18    14    -9
      6 21 47    67  0  0    4 38 27    13    -9
      6 58  8    68  0  0    4 38 37    12    -8
      7 46 33    69  0  0    4 38 45    11    -8
      8 49 27    70  0  0    4 38 53    10    -7
     10 10  5    71  0  0    4 39  1     9    -7
     11 53  6    72  0  0    4 39  8     8    -6
     14  5 22    73  0  0    4 39 14     7    -5
   ........ 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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