DETECTION OF FLUORINE IN THE HALO PLANETARY NEBULA BoBn 1: EVIDENCE FOR A BINARY PROGENITOR STAR

摘要

We have found the fluorine lines [F IV] λλ3996.92, 4059.90 in the extremely metal-poor ([Ar/H] = -2.10 ± 0.21) halo planetary nebula (PN) BoBn 1 in high-dispersion spectra from the 8.2 m VLT UVES archive. Chemical abundance analysis shows that the fluorine abundance is [F/H] = +1.06 ± 0.08, making BoBn 1 the most fluorine-enhanced and metal-poor PN among fluorine-detected PNe and providing new evidence that fluorine is enhanced by nucleosynthesis in low-mass metal-poor stars. A comparison with the abundances of carbon-enhanced metal-poor (CEMP) stars suggests that BoBn 1 shares their origin and evolution with CEMP- s stars such as HE 1305+0132. BoBn 1 might have evolved from a binary consisting of ～2 M_☉ primary and ～0.8 M_☉ secondary stars.