RASNZ Occultation Section - Yamamoto Occultation Update

ASTROMETRIC UPDATE:
OCCULTATION BY (2249) YAMAMOTO - 2021 May 04

Event Rank : 99

(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. An event rank of 100 indicates that the prediction is expected to be very accurate).

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 time for your location.

On 2021 May 04 UT, the 40.6 km diameter asteroid (2249) Yamamoto will occult a 8.7 mag star in the constellation Leo for observers along a path acrosstnio New Zealand, from Hicks Bay tp Auckland, and across Australia from Tweed Heads across southern Queensland and into southern Northern Territory in evening twilight.

In the case of an occultation, the combined light of the asteroid and the star will drop by 8.19 mag to 16.89 mag (the magnitude of the asteroid) for at most 5.8 seconds.

This update is based on, astrometry for the asteroid kindly provided by the IAU Minor Planet Center.

This work has made use of data from the European Space Agency (ESA)mission Gaia (http://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, http://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, inparticular the institutions participating in the Gaia Multilateral Agreement.

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

EVENT DETAILS SUMMARY :

Event Rank : 99
Date and approx. UT time of event : 2021 May 04, 08:14 - 2021 May 04, 08:37
(Refer to map(s) for your own location)
Magnitude of target star : 8.70
Magnitude drop [mag] : 8.19
Estimated maximum duration [s] : 5.8
Phase of moon, angular distance : 45 % sunlit, 170° distance
Sun : 106° distance
Rough path description : New Zealand, Australia

Data for the target star :

Name : TYC 0836-00918-1
Constellation : Leo
J2000 position with proper motion to date of event [h,m,s ; °,',"]: RA: 10 08 36.3568 DE: +13 07 34.761
Position source : Gaia EDR3
Standard error : RA,DE [mas]: (0.100,0.100)
V mag [mag] : 8.70
B mag [mag] : IOTA/IOTA-ES occultation update for
Remarks : (none)

Data for the minor planet :

Number, name : (2249) Yamamoto
Approx. diameter [km] : 41
Approx. diameter [arcsec] : 0.020
Distance from Earth [AU] : 2.76190
Source of used astrometry : MPC, JPL
Number of used observations : 0
Number of rejected observations : 0
Time covered by the observations : 1800 Jan 01 - 1800 Jan 01
1 sigma uncertainty ellipse (major, minor, PA) : 0.009", 0.003", 107.691°
Remarks : (none)
Orbital Elements for (2249) Yamamoto :
Update computed by : Steve Preston, Medina, Washington, USA. (OrbFit).

The Occultation Path :

Approximate projected width [km] : 55
Uncertainty interval [path widths] : +/- 0.14 (1 sigma)
Uncertainty interval [seconds] : +/- 2.6 (1 sigma)
Uncertainty interval approx RA,DE ["] : (+/- 0.009, +/- 0.004) (1 sigma)
Uncertainty ellipse (major, minor, PA) : (0.009", 0.003", 108°) (1 sigma)
Approx speed of asteroid's shadow [km/s]: 7.0185
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 :

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