SIMBAD references

Spectroscopic analysis of the classical Cepheid FN Aql from three high-resolution CCD spectra near minimum and maximum light gives the following results: 1) Mean T_eff=5483K; logg=1.25 and V_t=4.0km/s; 2) Metallicities derived for each phase are consistent with each other and close to the solar value; 3) The Cepheid is crossing the instability strip for at least the third time. 4) It has anomalously low carbon ([C/H]=-0.93dex) and nitrogen ([N/H]=+0.09dex) abundances, which is unusual for a Cepheid not crossing the instability strip for the first time. Since FN Aql is an IRAS object and candidate protoplanetary nebulae according to Volk & Kwok (1989ApJ...342..345V), we assume that the star's peculiarities are caused either by envelope loss after the second dredge-up or that it is an unusual Cepheid for which existing nucleosynthesis and mixing models are unable to reproduce the CNO abundance pattern.