Brian Loader has observed a 2.9 second occultation from Darfield, South Island, New Zealand. However, part way through the event, the video records a single integration with the star plainly visible before disappearing again. No other reports were received.

View the prediction.

Observers:
  1    B Loader,Darfield                    
  2    B Loader,Darfield                    
  3(P) Prediction
       
       

Discussion:

The circle above is plotted at the expected 121 km diameter of Siwa. Brian's observed occultation duration of 2.9 seconds is well short of the expected maximum of 9.7 seconds suggesting that the observed chord is very close to the edge of the occultation path and that this is in fact a grazing occultation observation with a single flash event. With only one chord, it is not possible to be absolutely sure which limb of (140) Siwa has been observed but given the prediction precision and Brian's location, it is most likely the northern limb.

The figure below shows the Tangra light curve of the occultation.

Observational Data:

Observation details for MP ( 140 ) Siwa
By Star              UCAC2 40004100
On 2016-01-31  at 12:55:55.0

_______________________________

Observer   B. Loader
Location   Darfield
Longitude  +172:06
Latitude   -43:28
Altitude   210 m
Datum      WGS84
Telescope SCT including Cass and Mak
Aperture   20 cm
Seeing     Strong flickering Clear 
Camera Type  WAT910BD       AAV-PAL       
Camera Delay 
Timing     GPS - time inserted Video with frame analysis
Disappearance  12:55:55.11
Reappearance   12:55:56.43
Comments: AOTA times, (140) Siwa, FIRST event. Lightcurve from 12:55:29 to 12:56:31 by Tangra v3.5.5 using AperturePhotometry/AverageBackground. Analysis by AOTA v4.1.6.1. Report prepopulated by IOTA Reporting Add-in for OW ver.1.8

_______________________________

Observer   B. Loader
Location   Darfield
Longitude  +172:06
Latitude   -43:28
Altitude   210 m
Datum      WGS84
Telescope SCT including Cass and Mak
Aperture   20 cm
Seeing     Strong flickering Clear 
Camera Type  WAT910BD       AAV-PAL       
Camera Delay 
Timing     GPS - time inserted Video with frame analysis
Disappearance  12:55:56.75
Reappearance   12:55:57.99
Comments: AOTA times, (140) Siwa, SECOND event. Lightcurve from 12:55:29 to 12:56:31 by Tangra v3.5.5 using AperturePhotometry/AverageBackground. Analysis by AOTA v4.1.6.1. Report prepopulated by IOTA Reporting Add-in for OW ver.1.8