In the course of our search for double degenerate ( DD ) binaries as potential progenitors of type Ia supernovae with the UVES spectrograph at the ESO VLT ( ESO S N Ia P rogenitor surve Y – SPY ) we discovered that the white dwarf HE 1414 - 0848 is a double-lined DA+DA binary with an orbital period of P = 12 ^ { \mathrm { h } } 25 ^ { \mathrm { m } } 39 ^ { \mathrm { s } } .
Semi-amplitudes of 128 km s ^ { -1 } and 100 km s ^ { -1 } are derived for the individual components .
The amplitude ratio and the measured difference in gravitational redshift is used to estimate the masses of the individual components : 0.55 M _ { \odot } and 0.71 M _ { \odot } .
Hence the total mass of the HE 1414 - 0848 system is 1.26 M _ { \odot } , only 10 % below the Chandrasekhar limit .
The results of a model atmosphere analysis are consistent with our mass estimated from the orbit .
Temperatures of the individual components are also determined .
Possible scenarios for the formation of this system are discussed .
The system will merge due to loss of angular momentum via gravitational wave radiation after two Hubble times .
HE 1414 - 0848 does not qualify as a SN Ia progenitor , but it is the most massive close DD known today .