Weak emission-line central stars of planetary nebulae

We present new spectroscopic data of 14 candidates for the weak emission-line type of central stars of planetary nebulae ([WELS]). With a medium resolution of about 2 Angstrom, we confirmed the main spectral characteristics of these stars but found that two objects of our sample are in fact early-type [WC] ([WCE]) stars. The lambda4650 and C IV lambdalambda5801, 5812 features are resolved, and they were used in a tentative classification. Based on the C IV lines the [WELS] stars of our sample can be divided qualitatively into two main groups: clear emission and very weak or no emission. We compared mean equivalent widths of carbon and oxygen lines of the [WELS] stars with those of the [WCE] and [WCL] types. The results are not conclusive but point in favor of an increase in temperature from [WCL] to [WCE], followed perhaps by a decrease from [WCE] to [WELS].