Before analysing the geometrical and radiative properties of the
system we have corrected the magnitudes and indices of
the effect of interstellar extinction,
by using the comparison stars as local reddening indicators.
The intrinsic magnitudes and colours of the comparison stars have been
computed by using the calibration for F-type stars of Crawford (1975).
This calibration is based on the fact that, although 
and (b-y) are
indices related to the effective temperature, is free of interstellar
reddening while (b-y) is affected. Latterly, Reglero et al. (1990),
proved that the index can be used also for later-type star
reddening estimations, in the range G5-K2 and luminosity classes V-III.
We found E(b-y) 0.003 and 0.010
for the comparison and check star respectively.
Because the comparison stars are at close angular separation from the binary
system and also at approximately the same distance, and are of similar
spectral types, it is safe to assume for ZZ UMa the mean of their reddening
values (0.006), that is within the calibration errors.
The intrinsic values for V, m1, and c1 are calculated using the equations of Crawford & Mandewewala (1976). In Table 2 (click here) we list the standard intrinsic photometric indices for the comparison stars. The magnitudes and indices listed are the mean of the values obtained in the nights where we observed standard stars (42 measurements for the comparison and 38 for the check spread over the different observational campaigns). Errors are the rms of the values to the mean.
Absolute magnitudes, Mv, visual surface brightness, 
, metal
contents, [Fe/H], and effective temperatures, 
, were derived from
the semiempirical calibrations of Crawford (1975),
Moon (1984), Nissen (1981)
and Saxner & Hammarback (1985), respectively. Both comparisons appear
to be main sequence stars with solar metal abundances. They can be
classified as G0 V and G1 V.
Table 3 (click here) list the radiative parameters for the comparisons.
Errors in the table are the values given for the calibrations. For the
distance, d, bolometric magnitude, 
and radius, R/R0, the
errors listed are the propagation of errors through the formula.
| star | y0 | (b-y)0 | m0 | c0 | | ||||
| HD 15242 | 10.115 | 0.365 | 0.177 | 0.306 | 2.597 | ||||
 | 0.013 | 0.005 | 0.010 | 0.021 | 0.014 | ||||
| HD 15251 | 9.956 | 0.386 | 0.230 | 0.323 | 2.598 | ||||
|
| 0.012 | 0.005 | 0.014 | 0.021 | 0.017 |
| name | Mv | | [Fe/H] | | d | | R/R0 |
| HD 15242 | 4.53 | 3.754 | -0.21 | 5837 | 130 | 4.42 | 1.09 |
|
| 0.28 | 0.026 | 0.20 | 60 | 17 | 0.38 | 0.19 |
| HD 15251 | 4.32 | 3.751 | 0.27 | 5848 | 135 | 4.16 | 1.22 |
|
| 0.28 | 0.026 | 0.20 | 60 | 17 | 0.38 | 0.21 |