Context :

Aims : We announce the discovery of two new transiting planets , and provide their accurate initial characterization .

Methods : First identified from the HATNet wide-field photometric survey , these candidate transiting planets were then followed-up with a variety of photometric observations .
Determining the planetary nature of the objects and characterizing the parameters of the systems were mainly done with the SOPHIE spectrograph at the 1.93 m telescope at OHP and the TRES spectrograph at the 1.5 m telescope at FLWO .

Results : HAT-P-42b and HAT-P-43b are typical hot Jupiters on circular orbits around early-G/late-F main sequence host stars , with periods of 4.641876 \pm 0.000032 and 3.332688 \pm 0.000016 days , masses of 0.975 \pm 0.126 and 0.660 \pm 0.083 M _ { J } , and radii of 1.277 \pm 0.149 and 1.283 _ { -0.034 } ^ { +0.057 } R _ { J } , respectively .
These discoveries increase the sample of planets with measured mean densities , which is needed to constrain theories of planetary interiors and atmospheres .
Moreover , their hosts are relatively bright ( V < 13.5 ) facilitating further follow-up studies .

Conclusions :