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Occultation of UCAC4 597-003782 by (54598) Bienor
30th December 2014
Update 29th of December
From the RIO Team: It was made with a new NIMA orbit fit, that also uses
positions from recent Bienor images provided by José Luis. For a detailed map have a look down on the page!
Update 28th of December
Images taken by the Granada Team (Jose Luis Ortiz Team) with the 1.2m at CAHA and the 0.77m La Hita telescope showed a move of the track towards east.
After the discovery of a ring system by Felipe Braga-Ribas, et al. Nature 13155(2014) around Chariklo, the upcoming occultation may draw your attention. The star is very bright (12m4 in R-Band) and the area of visibility spans around large parts of Europe and Marocco as well. Occultation astronomy is the most powerful technique to gain further knowledge about these objects. Bienor, just like Chariklo, belongs to the Centaur group of objects.
The area of a possible occultation is considerably larger than just the path of the shadow of the Bienor itself, because of the search for a ring and or satellites around Bienor. Therefore all observatories from Central Europe down to Marocco and further should observe. Felipe Brage-Ribas maintains a special website with actual updates for the event. There you can get many informations and possible updates as soon as say come up. He also has finder charts for the field including a DSS image.
More finder charts with different fields of view you can download from here:
The star is easy to find, its just below M33!
For Italy the event will take place around 22h 18min UTC. Please record a minium of 10min before and after this time, better more!
Some informations about Bienor
Bienor was discovered by M. W. Buie, S. D. Kern, R. L. Millis and L. H. Wasserman on August 27th, 2000. It has an approximate diameter of 207km, determined by constrains from observations with the Spitzer telescope [1]. Its albedo can be estimated around 0.03 to 0.05 [1]. The apparent magnitude is around 20m, the absolute one is 7m6 [2].
The semi-major axis of its orbit is 16.5 AU, the excentricity of the orbit is 0.201. It has an orbital period of 66.85 years. The surface temperature is assumed to be about 69 K
[1] Stansberry, Grundy, Brown, Spencer, Trilling, Cruikshank, Luc Margot Physical Properties of Kuiper Belt and Centaur Objects: Constraints from Spitzer Space Telescope (2007)
[2] AstDyS (54598) Bienor Ephemerides". Department of Mathematics, University of Pisa, Italy.
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A detailed map of the path of the shadow across Northern Africa and Europe is given below. Please keep in mind, that the prediction may contain errors reasonable larger than the diameter of the body, and that possible rings and/or satellites may be detected even further away from Bienor.
Here you find the updates Granda Team, J.L. Ortiz First from the 1.2m Instrument at CAHA:
Second from the 0.77m La Hita Telescope
Comment by J.L.Ortiz
Note that for the size of Bienor I used the most recent and accurate determination shown in Duffard et al. (2014) which is 198km +/- 6km based on Herschel Space Observatory data. This effective diameter is larger than "default" estimates used in other predictions, but the actual shadow width could be even larger if the object is very elongated (which we think it is) but this will depend on the orientation of the body, which we do not know.
Also note that if Bienor has rings, these could be up to 2 or 3 Bienor radii away from the main body, so the shadow path width of the rings could be up to 6 times larger than the one depicted in the maps for Bienor. So a large area in Europe could potentially observe the rings, if they exist.
Detailed map of last update (29th of December), provided by Felipe Brage-Ribas:
The dashed lines delimits the
estimated error bar, from the ephemeris and star position
uncertainties.
Observations should be made from 22:10 to 22:30 UTC
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