  We report the discovery of WASP-38b, a long period transiting planet in an
eccentric 6.871815 day orbit. The transit epoch is 2455335.92050 +/- 0.00074
(HJD) and the transit duration is 4.663 hours. WASP-38b's discovery was enabled
due to an upgrade to the SuperWASP-North cameras. We performed a spectral
analysis of the host star HD 146389/BD+10 2980 that yielded Teff = 6150 +/-
80K, logg =4.3 +/- 0.1, vsini=8.6 +/- 0.4 km/s, M*=1.16 +/- 0.04 Msun and R*
=1.33 +/- 0.03 Rsun, consistent with a dwarf of spectral type F8. Assuming a
main-sequence mass-radius relation for the star, we fitted simultaneously the
radial velocity variations and the transit light curves to estimate the orbital
and planetary parameters. The planet has a mass of 2.69 +/- 0.06 Mjup and a
radius of 1.09 +/-0.03 Rjup giving a density, rho_p = 2.1 +/-0.1 rho_jup. The
high precision of the eccentricity e=0.0314 +/- 0.0044 is due to the relative
transit timing from the light curves and the RV shape. The planet equilibrium
temperature is estimated at 1292 +/- 33K. WASP-38b is the longest period planet
found by SuperWASP-North and with a bright host star (V =9.4 mag), is a good
candidate for followup atmospheric studies.
