We have used spectra of hot stars from the RAVE Survey in order to investigate the visibility and properties of five diffuse interstellar bands previously reported in the literature. The RAVE spectroscopic survey for Galactic structure and kinematics
records CCD spectra covering the 8400-8800 Ang wavelength region at 7500 resolving power. The spectra are obtained with the UK Schmidt at the AAO, equipped with the 6dF multi-fiber positioner. The DIB at 8620.4 Ang is by far the strongest and cleanest of all DIBs occurring within the RAVE wavelength range, with no interference by underlying absorption stellar lines in hot stars. It correlates so tightly with reddening that it turns out to be a reliable tool to measure it, following the relation E(B-V) = 2.72 (+/- 0.03) x E.W.(Ang), valid throughout the general interstellar medium of our Galaxy. The presence of a DIB at 8648 Ang is confirmed. Its intensity appears unrelated to reddening, in agreement with scanty and preliminary reports available in the literature, and its measurability is strongly compromised by severe blending with underlying stellar HeI doublet at 8649 Ang. The two weak DIBS at 8531 and 8572 Ang do not appear real and should actually be blends of underlying stellar lines. The very weak DIB at 8439 Ang cannot be resolved within the profile of the much stronger underlying hydrogen Paschen 18 stellar line.
The orbit and physical parameters of the previously unsolved SB2 EB V570 Per are derived using high resolution Asiago Echelle spectroscopy and B, V photo-electric photometry. The metallicity from chi^2 analysis is [M/H]=+0.02 +/- 0.03, and reddening
from interstellar NaI and KI absorption lines is E(B-V) =0.023 +/- 0.007. The two components have masses of 1.449 +/- 0.006 and 1.350 +/- 0.006 Msun and spectral types F3 and F5, respectively. They are both still within the Main Sequence band (T_1 =6842 +/- 25 K, T_2 =6562 +/- 25 K from chi^2 analysis, R_1 =1.523 +/- 0.030, R_2 =1.388 +/- 0.019 Rsun) and are dynamically relaxed to co-rotation with the orbital motion (Vrot sin i_{1,2} =40 and 36 (+/-1) km/sec). The distance to V570 Per obtained from the orbital solution is 123 +/- 2 pc, in excellent agreement with the revised Hipparcos distance of 123 +/- 11 pc. The observed properties of V570 Per components are compared to BaSTI models computed on purpose for exactly the observed masses and varied chemical compositions. This system is interesting since both components have their masses in the range where the efficiency of convective core overshooting has to decrease with the total mass as a consequence of the decreasing size of the convective core during the central H-burning stage. Our numerical simulations show that, a small but not null overshooting is required, with efficiencies lambda_{OV} =0.14 and 0.11 for the 1.449 and 1.350 Msun components, respectively. This confirms the finding of Paper II on the similar system V505 Per. At the approx 0.8 Gyr age of the system, the element diffusion has reduced the surface metallicity of the models from the initial [M/H]=+0.17 to [M/H]=+0.02, in perfect agreement with the spectroscopically derived [M/H]=+0.02 +/- 0.03 value.
The orbit and fundamental physical parameters of the double-lined eclipsing binary V505 Per are derived by means of Echelle high resolution, high S/N spectroscopy and B, V photometry. Effective temperatures, gravities, rotational velocities and metal
licities are obtained from atmospheric chi^2 analysis. An E(B-V)<=0.01 mag reddening is derived from interstellar NaI and KI lines. The distance to the system computed from orbital parameters (60.6 +/- 1 pc) is identical to the newly re-reduced Hipparcos parallax (61.5 +/- 1.9 pc). The masses of the two components (M(1) = 1.2693 +/- 0.0011 and M(2) = 1.2514 +/- 0.0012 Msun) place them in the transition region between convective and radiative stellar cores of the HR diagram, with the more massive of the two showing already the effect of evolution within the Main Sequence band (T(1) = 6512 +/- 21 K, T(2) = 6462 +/- 12 K, R(1) = 1.287 +/- 0.014, R(2) = 1.266 +/- 0.013 Rsun). This makes this system of particular relevance to theoretical stellar models, as a test on the overshooting. We compare the firm observational results for V505 Per component stars with the predictions of various libraries of theoretical stellar models (BaSTI, Padova, Granada, Yonsei-Yale, Victoria-Regina) as well as BaSTI models computed specifically for the masses and chemical abundances of V505 Per. We found that the overshooting at the masses of V505 Per component stars is already pretty low, but not null, and described by efficiencies lambda(OV)=0.093 and 0.087 for the 1.27 and 1.25 Msun components, respectively. According to the computed BaSTI models, the age of the system is about 0.9 Gyr and the element diffusion during this time has reduced the surface metallicity from the initial [M/H]=-0.03 to the current [M/H]=-0.13, in excellent agreement with observed [M/H]=-0.12 +/- 0.03.
