## 5. The technical selection functionThe last unknown quantity in Eq. (18) is
, the selection function associated to the
probability of measuring orbital periods in novae as a function of
For periods detected through radial velocity measurements, the situation is not as clear. Using Kepler's third law, a secondary star mass - period relation such as that given by Patterson (1984) and basic geometry, it is possible to derive an equation for the radial velocity amplitude of the white dwarf which depends only on the orbital period and . At a fixed orbital inclination increases for a given primary mass roughly by a factor of 3 for periods between and , implying easier detection of longer periods. Moreover at very short periods, the time required to obtain spectra with a sufficiently high S/N ratio may not be short against the orbital period, hampering easy detection. On the other hand, a short period can be detected in shorter, more easily realizable sections of continuous observations. Currently, we cannot see an objective way to quantify the detection
probability for a given period due to these technical selection
effects. However, in view of the relatively few orbital periods
detected through radial velocity measurements, we expect this
probability to decrease with The parameter will probably be a small positive number. We expect . © European Southern Observatory (ESO) 1997 Online publication: June 5, 1998 |