Photoionization model analysis of the planetary nebula Hu1-2^*

¹ School of Science Education (Astronomy), Chungbuk National University, 48 Gaeshin-dong Heungduk-gu, CheongJu, ChungBuk 361-763, South Korea e-mail: hyung@chungbuk.ac.kr
² Kapteyn Astronomical Institute, PO Box 800, 9700 AV Groningen, The Netherlands
³ Laboratory for Astronomy and Solar Physics, Code 681, Goddard Space Flight Center, Greenbelt, MD 20771, USA

Received: 1 April 2004
Accepted: 9 June 2004

Abstract

We have obtained high resolution optical spectra of the planetary nebula Hu 1-2 in the wavelength region of 3700 Å–10 050 Å, with the Hamilton Echelle Spectrograph (HES) at Lick Observatory. Diagnostic analysis indicates that the nebular gas can be represented by inhomogeneous shells of electron density 4000–10 000 cm^-3, and a gas temperature of 12 000–18 000 K. Using the spherically symmetric photoionization model with appropriate abundances, we tried to accommodate the observed physical conditions and high electron temperatures. The chemical composition of the nebula was derived from calculations using a photoionization model which predicts the observed IUE, HES and ISO line intensities; and the composition was then compared to previous determinations. Model analysis confirms the semi-empirically determined abundance derivations carried out in earlier studies. He and N abundances are high, but those of C, O, Ne and S are very low.