2.2 Comments on stellar characteristics

The stellar emission-line fluxes presented in Table 3, are measured from a spectrum integrated over an aperture ( $3\hbox{$^{\prime\prime}$}\times 3\hbox{$^{\prime\prime}$}$) covering the central star in the WiFeS field. The emission line identification, wavelength, dereddened flux corrected for reddening using $c$(H$\beta$)$=0.99$, equivalent width $W_{\lambda }$ (Å), and FWHM (Å) are given in columns 1-5, respectively. All fluxes are given relative to CIV 5805, on a scale where CIV5805=100. We note that the width of CIV $\lambda$5805 is narrower than typical Wolf-Rayet central starts of PNe with the same stellar temperature (see e.g Crowther et al., 1998; Acker & Neiner, 2003), so it could be a wels as identified by DePew et al. (2011). Following the method used by Acker & Neiner (2003), a terminal wind velocity of 640kms$^{-1}$ is deduced from FWHM$($CIV$\lambda$5805$)=10.27$Å. However, we get a terminal velocity of 1560kms$^{-1}$ from FWHM$($CIV$\lambda$5805$)=25$Å reported by DePew et al. (2011). Although the CIII $\lambda$5696 line is not detected, the CIII/IV $\lambda$4650 is possibility identified. The HeII $\lambda$4686 line is fairly strong, but it could have a nebular origin. We see the presence of strong NIII $\lambda\lambda$4634,4641 lines and weak NV $\lambda\lambda$4603,4932 lines. Assuming that the HeII $\lambda$4686 line is a stellar emission line, M2-42 could have a stellar characteristics similar to WN8-type stars of van der Hucht (2001) based on $I($NIII$\lambda$4641 $)\gtrsim I($HeII$\lambda$4686) and $I($NIII$)\gg I($NV$)$. However, NII $\lambda$3995 and NIV $\lambda\lambda$3479-3484, 4058 lines are not in the wavelength coverage of our WiFeS observations, so we cannot certainly classify it as one of nitrogen sequences of Wolf-Rayet central stars of PNe.

Table: Stellar emission-line fluxes $I(\lambda )$ on a scale where CIV5805=100, equivalent width $W_{\lambda }$(Å), and FWHM (Å).

Line	$\lambda$(Å)	$I(\lambda )$	$W_{\lambda }$(Å)	FWHM(Å)
NV	4603	$33.58$:	$-1.16$	$3.14$
NIII	4634	$77.56$	$-3.15$	$1.25$
NIII	4641	$283.41$	$-10.91$	$3.08$
CIII/IV	4650	$220.38$	$-9.49$	$2.97$
CIII	4655	$42.05$	$-1.94$	$3.55$
CIV	4659	$63.19$	$-2.81$	$2.84$
HeII	4686	$139.46$	$-8.17$	$1.23$
NV	4932	$57.20$:	$-2.93$	$2.47$
CIV	5805	$100.00$	$-5.62$	$10.27$
CII	6462	$19.28$	$-1.11$	$2.09$
CIII	7037	$16.29$:	$-1.04$	$5.01$