* Astronomy

Title: CoRoT 102699796, the first metal-poor Herbig Ae pulsator: a hybrid delta Sct-gamma Dor variable?
Authors: V. Ripepi, F. Cusano, M. Di Criscienzo, G. Catanzaro, F. Palla, M. Marconi, P. Ventura, C. Neiner, C. Catala, S. Bernabei

We present the analysis of the time series observations of CoRoT 102699796 obtained by the CoRoT satellite that show the presence of five independent oscillation frequencies in the range 3.6-5 c/d. Using spectra acquired with FLAMES@VLT, we derive the following stellar parameters: spectral type F1V, T_eff=7000 ±200 K, log(g)=3.8 ±0.4, [M/H]=$-1.1 ±0.2, v sin i=50 ±5 km/s, L/L_odot=21^{+21}_{-11}. Thus, for the first time we report the existence of a metal poor, intermediate-mass PMS pulsating star. Ground-based and satellite data are used to derive the spectral energy distribution of CoRoT 102699796 extending from the optical to mid-infrared wavelengths. The SED shows a significant IR excess at wavelengths greater than ~5 mu. We conclude that CoRoT 102699796 is a young Herbig Ae (F1Ve) star with a transitional disk, likely associated to the HII region [FT96]213.1-2.2.
The pulsation frequencies have been interpreted in the light of the non-radial pulsation theory, using the LOSC code in conjunction with static and rotational evolutionary tracks. A minimisation algorithm was used to find the best-fit model with M=1.84 solar masses, T_eff=6900 K which imply an isochronal age of t ~2.5 Myr. This result is based on the interpretation of the detected frequencies as g-modes of low-moderate n-value. To our knowledge, this is the first time that such modes are identified in a intermediate-mass PMS pulsating star. Since CoRoT 102699796 lies in the region of the HR diagram where the delta Sct and gamma Dor instability strips intersect, we argue that the observed pulsation characteristics are intermediate between these classes of variables, i.e. CoRoT 102699796 is likely the first PMS hybrid gamma Dor-delta Sct pulsator ever studied.

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