A QSO survey via optical variability and zero proper motion in the M92 field - II. Follow-up spectroscopy and properties of the QSO sample

The combination of variability and proper motion constraints (VPM search) i s believed to provide an efficient yet unconventional search strategy for Q SOs with selection effects quite different from conventional optical QSO su rveys. We performed a VPM QSO search in a 10 square degrees field around M9 2 on 162 selected digitised Schmidt plates in the Johnson B band with a tim e-baseline of more than three decades. In Paper I, we constructed a sample of VPM QSO candidates with B less than or equal to 19.7. The spectroscopic follow-up observations revealed 58 QSOs and 7 Seyfert 1 galaxies as well as 27 narrow-emission line galaxies. We present the low-resolution spectra an d the data for the QSOs and Seyfert galaxies: AGN types, accurate positions , redshifts, mean B magnitudes, and colour indices, along with the selectio n parameters of the VPM search, i.e., indices for variability, proper motio n, and image structure. The redshifts cover the interval 0 less than or sim ilar to z less than or similar to 3; absolute magnitudes are in the range - 21 less than or similar to M-B less than or similar to - 29. The statistica l properties of the resulting QSO sample are studied in detail. No signific ant differences were found between our VPM QSO sample and published QSO sam ples from multicolour or spectroscopic surveys. The fraction of QSOs with u nusual colours is estimated to be less than 5 per cent within the magnitude range B less than or equal to 19.7.