Time variation of the water maser in ON2 E. E. Lekht, M. A. Trinidad, J. E. Mendoza–Torres, G. M. Rudnitskij and A. M. Tolmachev A&A, 456 1 (2006) 145-150 Published online: 23 August 2006 DOI: 10.1051/0004-6361:20053495