Me 1-1: A PN containing a cool star

¹ Department of Astronomy, Peking University, Beijing 100871, PR China e-mail: shenzx@bac.pku.edu.cn
² Osservatorio Astronomico di Trieste, via GB Tiepolo 11, 1-34131 Trieste, Italy

Received: 4 February 2004
Accepted: 5 March 2004

Abstract

We report the detection of a cool stellar component at the center of the planetary nebula (PN) Me 1-1 and present optical spectra of the system. From measurements of nebular emission lines, we have derived electron temperature, density and chemical composition. Heavy elemental abundances deduced from collisionally excited lines (CELs) are compared with those derived from optical recombination lines (ORLs). The electron temperature and density deduced from the nebular analysis were used to calculate the nebular continuum emission, which was then subtracted from the observed spectrum in order to obtain the spectrum of the cool stellar component apparent in the observed spectrum. We calculate B and V magnitudes of the cool companion and obtain a color index of . By comparing the spectrum of the cool star with standard spectra in Pickles's 1998 Stellar Flux Library, we find that the cool component has the spectral type of a K3-4 bright giant. Our analysis suggests that Me 1-1 is probably a yellow symbiotic system.