We combine the CfA3 supernovae Type Ia (SN Ia) sample with samples from the literature to calculate improved constraints on the dark energy equation of state parameter, w. The CfA3 sample is added to the Union set of Kowalski et al. (2008, Cat. J/ApJ/686/749) to form the Constitution set and, combined with a baryonic acoustic oscillations (BAO) prior, produces 1+w=0.013^+0.066^-0.068 (0.11syst), consistent with the cosmological constant. The CfA3 addition makes the cosmologically useful sample of nearby SN Ia between 2.6 and 2.9 times larger than before, reducing the statistical uncertainty to the point where systematics play the largest role. We use four light-curve fitters to test for systematic differences: SALT, SALT2, MLCS2k2 (RV=3.1), and MLCS2k2 (RV=1.7).

Cone search capability for table J/ApJ/700/1097/table1 (SALT light curve fit parameters and distances. Constitution set)

Cone search capability for table J/ApJ/700/1097/table2 (SALT2 light curve fit parameters and distances)

Cone search capability for table J/ApJ/700/1097/table3 (MLCS31 light curve fit parameters)

Cone search capability for table J/ApJ/700/1097/table4 (MLCS17 light curve fit parameters)