Context : This paper is framed within a large project devoted to studying the presence of circumstellar material around main sequence stars , and looking for exocometary events .
The work concentrates on HR 10 ( A2 IV/V ) , known for its conspicuous variability in the circumstellar narrow absorption features of Ca ii K and other lines , so far interpreted as \beta Pic-like phenomena , within the falling evaporating body scenario .

Aims : The main goal of this paper is to carry out a thorough study of HR 10 to find the origin of the observed variability , determine the nature of the star , its absolute parameters , and evolutionary status .

Methods : Interferometric near-infrared ( NIR ) observations , multi-epoch high-resolution optical spectra spanning a time baseline of more than 32 years , and optical and NIR photometry , together with theoretical modelling , were used to tackle the above objectives .

Results : Our results reveal that HR 10 is a binary .
The narrow circumstellar absorption features superimposed on the photospheric Ca ii K lines – and lines of other species – can be decomposed into two or more components , the two deep ones tracing the radial velocity of the individual stars , which implies that their origin can not be ascribed to transient exocometary events , their variability being fully explained by the binarity of the object .
There does not appear to be transient events associated with potential exocomets .
Each individual star holds its own circumstellar shell and there are no traces of a circumbinary envelope .
Finally , the combined use of the interferometric and radial velocity data leads to a complete spectrometric and orbital solution for the binary , the main parameters being : an orbital period of 747.6 days , eccentricities of the orbits around the centre of mass 0.25 ( HR 10-A ) , 0.21 ( HR 10-B ) and a mass ratio of q = M _ { B } / M _ { A } = 0.72 - 0.84 .
The stars are slightly off the main sequence , the binary being \sim 530 Myr old .

Conclusions :