Asteroid (2009) Voloshina occults 5.5 mag star xi Ari on Dec. 1/2

There will be occultation of the brightest star this year (5.46 mag. xi Ari) by asteroid (2009) Voloshina visible from Northern Russia, Scandinavia and probably Britain. Diameter of asteroid is 34 km (0.023") and the current uncertainty is about 0.07" (3 path widths). New (as of Nov. 25) map is available here. Steve Preston also provided details of occultation.

Target star: xi Ari (24 Ari, ZC 354, HD 14951, HIP 11249, HR 702, SAO 92932)

The problem is that xi Ari is a spectroscopic binary, but parameters of this double star are not known well. J.Bourgeois in Belgium determined 0.05" separation in PA=46 during Jan 16, 1997 lunar occultation. Parallax is 0.0054" and if separation is 0.05", the orbital radius is about 10 A.U. Since the spectral class of stars is B7IV, masses of components must be about 5 solar ones. This gives the orbital period of the order of 10 years which means the positions of components have changed significantly since 1997.

Series of lunar occultations of xi Ari

Probably the only way to find out actual separation in this system is to observe another lunar occultation of it. There will be several of them till the end of 2001. Below are the maps generated by Occult software for the events on Oct. 4, Nov. 1 and Nov. 28.

Oct. 4

Nov. 1

Nov. 28

Useful links

Denis Denissenko (denis@hea.iki.rssi.ru)

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