RASNZ Occultation Section - Erika Occultation Update

ASTROMETRIC UPDATE:
OCCULTATION BY (636) ERIKA - 2004 DEC 23

[Edwin Goffin's Prediction + Finder Charts]

UPDATE: 2004 NOV 21, 17:18 UT

THE UPDATED PATH

(Note: The duration given in the line below is the interval during which the occultation shadow sweeps across the Earth - please see the minute markers on the map to determine the approximate the time for your location)

On 2004 Dec 23 UT, the 74 km diameter asteroid (636) Erika will occult a 11.6 mag star in the constellation Aries for observers along a path across New Zealand.

In the case of an occultation, the combined light of the asteroid and the star will drop by 2.7 mag to 14.2 mag (the magnitude of the asteroid) for at most 34.8 seconds.

This update is based on UNSO/Flagstaff astrometry for the asteroid kindly provided by Ron Stone, historical astrometry from the MPC files (via AstDys), and the following catalogs for the star position: UCAC.

Additional details of this and other events are available at Steve Preston's website at http://www.asteroidoccultation.com/

EVENT DETAILS SUMMARY :

Event Rank : 88
(The event Rank is a measure of the likelihood of observing an event, and is equal to
the probability of at least one successful observation by a team of two observers spaced 1/8 path
width just inside opposite sides of the predicted path).
Date and approx. UT time of event : 2004 Dec 23, 09:47 - 2004 Dec 23, 10:55 UT
(Refer to map(s) for your own location)
Magnitude of target star : 11.6
Magnitude drop [mag] : 2.7
Estimated maximum duration [s] : 34.8
Phase of moon, angular distance : 91 % sunlit, 22° distance
Sun : 123° distance
Rough path description : New Zealand

Data for the target star :

Name : TYC 1207-01319-1
Constellation : Aries
J2000 position with proper motion to date of event [h,m,s ; °,',"]: RA: 02 06 23.5942 DE: +16 12 53.795
Position source : Pos: UCAC2, pm: UCAC2, pi:
Standard error : RA,DE ["]: ( .017, .022 )
V mag [mag] : 11.6
B mag [mag] : 12.6
Remarks : (none)

Data for the minor planet :

Number, name : (636) Erika
Approx. diameter [km] : 74
Approx. diameter [arcsec] : .049
Distance from Earth [AU] : 2.07000
Source of used astrometry : FASTT MPC (via Astdys)
Number of used observations : 551
Number of rejected observations : 34
Time covered by the observations : 1907 Mar 03 - 2004 Oct 30
1 sigma uncertainty ellipse (major, minor, PA) : 0.025, 0.014, 64°
Remarks : (none)
Orbital Elements for (636) Erika :
Update computed by : Steve Preston, Medina, Washington, USA. (OrbFit).

The Occultation Path :

Approximate projected width [km] : 105
Uncertainty interval [path widths] : +/- 0.56 (1 sigma)
Uncertainty interval [seconds] : +/- 19.9 (1 sigma)
Uncertainty interval approx RA,DE ["] : (+/- .030 +/- .026) (1 sigma)
Uncertainty ellipse (major, minor, PA) : ( .030", .026", 72° ) (1 sigma)
Approx speed of asteroid's shadow [km/s]: 2.1279
Important Note regarding Accuracy:
The uncertainty interval in path widths given above (and shown as a 1-sigma uncertainty ellipse on the plot) refers to RMS deviation and is applied as a +/- range. In other words, a path uncertainty of 1.0 path widths means that the actual center of the asteroid's shadow path should fall within plus or minus 1 path width of the plotted path center. However path errors larger than 1 sigma have been observed so observers should be alert for primary occultations within plus or minus 3 sigma of the updated path.
Further, almost all asteroidal satellites discovered so far have been found within 10 diameters of the asteroid (since this distance is deep enough within the gravitational well to be stable over long timescales). Therefore, if monitoring for secondary events, observing out to about 10 path-widths either side of the predicted track remains worthwhile.
We therefore recommend that you monitor for events if your observing location is up to +/- 10 path-widths from the predicted track. If not monitoring for occultations by secondary bodies you should observe from locations within 3 sigma of the nominal path.
In terms of time, the predictions are now usually accurate to about +/- 0.3 minute so you should be most attentive during the predicted minute of the event. However if intending to catch a potential satellite occultation you should start observing at least 10 times the predicted central duration before the predicted closest approach time for your location, and continue for a similar period afterwards.
Path Co-ordinates :

                  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
    178 32 23   -61  0  0    9 47  1    10   335    -1  179 29 32  177 35 58 -179 25 31  176 33 36
    177 58 14   -60  0  0    9 47 15    11   335    -2  178 53 10  177  3 59  179 55 33  176  3 57
    177 27 52   -59  0  0    9 47 31    12   335    -3  178 20 47  176 35 34  179 20 50  175 37 40
    177  0 52   -58  0  0    9 47 47    13   336    -3  177 51 57  176 10 21  178 49 53  175 14 24
    176 36 53   -57  0  0    9 48  5    14   336    -4  177 26 17  175 48  0  178 22 17  174 53 50

    176 15 37   -56  0  0    9 48 24    15   336    -5  177  3 28  175 28 14  177 57 41  174 35 43
    175 56 48   -55  0  0    9 48 44    16   336    -6  176 43 14  175 10 48  177 35 50  174 19 48
    175 40 12   -54  0  0    9 49  5    17   336    -6  176 25 20  174 55 30  177 16 26  174  5 54
    175 25 39   -53  0  0    9 49 28    18   336    -7  176  9 35  174 42  7  176 59 17  173 53 50
    175 12 57   -52  0  0    9 49 51    19   336    -8  175 55 46  174 30 32  176 44 11  173 43 27

    175  1 58   -51  0  0    9 50 16    20   336    -9  175 43 44  174 20 34  176 30 58  173 34 36
    174 52 34   -50  0  0    9 50 42    21   336   -10  175 33 22  174 12  7  176 19 29  173 27 12
    174 44 38   -49  0  0    9 51  9    22   336   -10  175 24 31  174  5  4  176  9 37  173 21  7
    174 38  3   -48  0  0    9 51 37    23   336   -11  175 17  6  173 59 18  176  1 14  173 16 16
    174 32 44   -47  0  0    9 52  6    24   336   -12  175 11  0  173 54 45  175 54 15  173 12 35

    174 28 36   -46  0  0    9 52 36    24   335   -13  175  6  8  173 51 21  175 48 33  173  9 58
    174 25 35   -45  0  0    9 53  8    25   335   -14  175  2 27  173 49  0  175 44  5  173  8 22
    174 23 37   -44  0  0    9 53 40    26   335   -15  174 59 51  173 47 40  175 40 46  173  7 44
    174 22 40   -43  0  0    9 54 14    27   334   -16  174 58 17  173 47 18  175 38 32  173  8  0
    174 22 39   -42  0  0    9 54 48    28   334   -16  174 57 43  173 47 50  175 37 20  173  9  8

    174 23 32   -41  0  0    9 55 24    29   334   -17  174 58  6  173 49 14  175 37  7  173 11  6
    174 25 18   -40  0  0    9 56  0    30   333   -18  174 59 22  173 51 28  175 37 51  173 13 52
    174 27 53   -39  0  0    9 56 38    30   333   -19  175  1 31  173 54 31  175 39 29  173 17 24
    174 31 18   -38  0  0    9 57 17    31   332   -20  175  4 30  173 58 20  175 42  0  173 21 41
    174 35 29   -37  0  0    9 57 56    32   332   -21  175  8 18  174  2 54  175 45 22  173 26 41

    174 40 26   -36  0  0    9 58 37    33   331   -22  175 12 54  174  8 13  175 49 33  173 32 23
    174 46  8   -35  0  0    9 59 18    34   331   -23  175 18 16  174 14 14  175 54 33  173 38 47
    174 52 35   -34  0  0   10  0  1    34   330   -24  175 24 24  174 20 59  176  0 20  173 45 52
    174 59 45   -33  0  0   10  0 45    35   329   -25  175 31 18  174 28 26  176  6 55  173 53 37
    175  7 38   -32  0  0   10  1 29    36   329   -26  175 38 56  174 36 34  176 14 16  174  2  2

    175 16 14   -31  0  0   10  2 15    36   328   -27  175 47 18  174 45 24  176 22 23  174 11  8
    175 25 34   -30  0  0   10  3  1    37   327   -28  175 56 25  174 54 56  176 31 17  174 20 53
    175 35 36   -29  0  0   10  3 49    38   326   -29  176  6 17  175  5  9  176 40 56  174 31 19
    175 46 22   -28  0  0   10  4 37    38   325   -30  176 16 54  175 16  5  176 51 22  174 42 25
    175 57 52   -27  0  0   10  5 26    39   325   -31  176 28 16  175 27 43  177  2 35  174 54 13

    176 10  7   -26  0  0   10  6 17    40   324   -32  176 40 24  175 40  5  177 14 36  175  6 42
    176 23  7   -25  0  0   10  7  8    40   323   -33  176 53 19  175 53 10  177 27 25  175 19 55
    176 36 54   -24  0  0   10  8  0    41   322   -34  177  7  1  176  7  1  177 41  3  175 33 50
    176 51 28   -23  0  0   10  8 53    41   321   -35  177 21 33  176 21 38  177 55 32  175 48 31
    177  6 51   -22  0  0   10  9 47    42   320   -36  177 36 55  176 37  3  178 10 54  176  3 57

    177 23  5   -21  0  0   10 10 41    42   319   -37  177 53  9  176 53 17  178 27  8  176 20 12
    177 40 11   -20  0  0   10 11 37    43   317   -38  178 10 17  177 10 22  178 44 18  176 37 15
    177 58 12   -19  0  0   10 12 34    43   316   -39  178 28 20  177 28 19  179  2 26  176 55 10
    178 17  8   -18  0  0   10 13 31    43   315   -40  178 47 22  177 47 11  179 21 34  177 13 57
    178 37  4   -17  0  0   10 14 29    44   314   -41  179  7 24  178  7  1  179 41 44  177 33 41

    178 58  1   -16  0  0   10 15 29    44   313   -43  179 28 29  178 27 50 -179 57  1  177 54 22
    179 20  2   -15  0  0   10 16 29    44   311   -44  179 50 41  178 49 42 -179 34 37  178 16  4
    179 43 12   -14  0  0   10 17 30    44   310   -45 -179 45 57  179 12 40 -179 11  1  178 38 50

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