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1 aa graphicx txfonts natbib ();a, M yr 1 dkms 1 Hβ H + He + C +++ N +++ O + O ++ O +++ [N ii][o iii][sii][ar iv] [O ii] λ37, 379 [O ii] λ73, 733 O ii λ51 [O iii] λ5 µm [Oiii] λ88 µm Oiii] λ11 C ii] λ3 C iii] λ199 C ii λ7 [N ii] λ58 N iii] λ58 [O i] λ3 [O ii] λ377 [O iii] λ57 [O iii] λ33 [Ne iii] λ389 [S ii] λ717, 731 [S ii] λ9, 7 [N ii] λ5755/58 [O iii] λ33/57 [S ii] λ731/717 [Ar iv] λ71/713 Q(H ) cm 3 erg s 1 erg s 1 cm Å 1 erg cm 3 s 1 M yr-1t eff v Z M M L R M R L Z Q(He ) Q(He + ) T T [O III]33/57 L M T eff T equiv M up M low M neb Ṁ M v exp Hα H ih iihe iihe iiλ8 [C iii][o ][Oii] [Ne iii] [S ii]λ75 [S iii]λ953 [S iii]λ31 [S iii][ar iii]λ7135 [Ar iii][ar iv]λ H He He ++ C ++ N N + N ++ O Ne ++ S + S ++ Ar +++ document Comprehensive modelling of the planetary nebula LMC-SMP 1andits[WC] typecentralstar The planetary nebula LMC-SMP 1andits[WC] typecentralstar G. Stasińska1 G. Gräfener M. Peña3 W.-R. Hamann L. Koesterke R. Szczerba5 LUTH, Observatoire de Meudon, 5 Place Jules Janssen, F-9195 Meudon Cedex, France G. Stasińska Received ; Accepted We present a comprehensive study of the Magellanic Cloud planetary nebula SMP 1andofitsnucleus, aw olf Rayettypestarclassified[WC5 ].T heobservationalmaterialconsistsofhst ST ISspectroscopyandimaging, togetherwitho LT E.Forthecentralstarwedeterminethefollowingparameters :L =1 3.9 L, R =. R, T =87.5kK, Ṁ =1.1, v = 1, and a clumping factor of D =. The elemental abundances by mass are X He =.5, X C =.5, X N < 51 5, X O =.3, and X Fe < 11. The fluxes from the model stellar atmosphere were used to compute photoionization models of the nebula. All the available observations, within their error bars, were used to constrain these models. We find that the ionizing fluxes predicted by the stellar model are basically consistent with the fluxes needed by the photoionization model to reproduce the nebular emission, within the error margins. However, there are indications that the stellar model overestimates the number and hardness of Lyman continuum photons. The photoionization models imply a clumped density structure of the nebular material. The observed / line ratio implies the existence of carbon-rich clumps in the nebula. Such clumps are likely produced by stellar wind ejecta, possibly mixed with the nebular material. We discuss our results with regard to the stellar and nebular post-agb evolution. The observed Fe-deficiency for the central star indicates that the material which is now visible on the stellar surface has been exposed to s-process nucleosynthesis during previous thermal pulses. The absence of nitrogen allows to set an upper limit to the remaining H-envelope mass after a possible AGB final thermal pulse. Finally, we infer from the total amount of carbon detected in the nebula that the strong [WC] mass-loss may have been active only for a limited period during the post-agb evolution. stars: Wolf-Rayet stars: atmospheres stars: mass-loss ISM: abundances ISM: planetary nebulae: individual: SMP 1 planetarynebulae(general):ism : abundances Introduction sec:intro Only a few studies have been devoted so far to a consistent modelling of a planetary nebula and of its central star. Such studies are useful to get a better insight into the relation between the nebula and its progenitor. Another, very important aspect is that this is the only way to test model atmosphere predictions 1

2 in the Lyman continuum and thus to validate the model atmospheres. The works of Rauch, Köppen & Werner (199, 199), Peña et al. (1998), De Marco & Crowther (1998, 1999), De Marco et al. (1) are examples of such studies, while Crowther et al. (1999) have performed a similar study on a Population I Wolf-Rayet ring nebula. Such investigations are particularly important in the case of planetary nebulae with Wolf-Rayet type central stars (which represent about 1% of all planetary nebulae), since recent work (e.g. Górny & Tylenda, De Marco & Soker ) have completely changed previous views on the evolutionary status of these objects. In general, Wolf-Rayet central stars of PNe belong to the [WC] sequence. In our galaxy most of these objects have been classified as [WC-early] or [WC-late] types, with only few objects of intermediate types (Tylenda, Acker & Stenholm 1993). In the Magellanic Clouds, the WR central stars are also of [WC] type (except for the extraordinary central star of LMC-N, e.g. Peña et al. 1997b), but in this case they have been classified in the intermediate [WC] types. Peña et al. (1997a) suggested that such a difference might be a consequence of the differences in metallicity between the Milky Way and the Magellanic Clouds. In any case, [WC] central stars show spectral features identical to those of massive WC stars but at much lower luminosity, and they can be analyzed with the tools developed for massive WR stars (e.g. Hamann 1997). In the present paper, we concentrate on the planetary nebula SMP 1(alsoknownasN 3,WSandLM 1 37)whichisamongthebrightestplanetarynebulaeintheLargeMagellanicCloud.T hisisagoodcaseforadetailedstudy : T heobjectisataknowndistancemodulusof18.5 magben1:, equivalentto5.1 kpc.t hecentralstarisoneofthebrightest[wc] ]type(monk, Barlow&Clegg1988; Peña, Ruiz&T orres P eimbert1997a), thereforethenebularspectrumcontainsmanylines Using HST STIS, we have secured high signal-to-noise spectra of SMP 1inawidespectralrange.T hisprovidedstrongconstr New Observations and Previous Data sec:obs Observations HST STIS spectroscopic data were obtained on 1998/1/3 (HST Cycle 7, program ID 733). MAMA and CCD detectors were employed to cover the broadest spectral range possible. Prior to the spectroscopic observations, STIS images were obtained to acquire the target. The log of the observations is presented in Table 1. table*[htbp]log of observations tabular llcrcl Instrument Image ID Date λ Range t exp Remarks [-1mm]mm.5mm CTIO m Ret. a 31/1/ and 1slit width HST STIS G1Lo57n17/1/ FUV-MAMA (a) CTIO m with Reticon detector and grating KPGL [mm]mm.5mm Direct images with HST WFPC were searched in the archives. Apart from our own STIS images for target acquisition (see Table 1), weretrievedthef OCimageW 1ID1T, obtainedon1993/11/8, withexposuretimeof3minthrou Hα,Hβ and lines. We also considered ground-based spectrophotometric data for SMP 1obtainedbyMonk, Barlow, &Clegg(1988),Meatheri All the available spectroscopic data are presented in Table neb : fluxes, whichliststhereddeningcorrectedfluxesfortheobs 1)obtainedbythedifferentauthors.W ealsolistthetotalhβ flux observed in the slit, F (), the logarithmic extinction at, C(), and the slit dimensions, when available. All the spectra mentioned above have good signalto-noise, and the differences among observations by different authors are, in general, small. Note that observations by Peña et al. (1997a) were made both with a slit of and a slit of 1and, as noted by these authors, the line ratios are very similar in both slits. The flux reported in column of Table neb : fluxesistheoneobtainedwiththe1slit. SMP 1isoneofthetwelveplanetarynebulaeintheLMCdetectedbyIRAS.T hefluxesretrievedfromtheirasdatabaseare : F (1µm) =.8 Jy (flux density quality = ) F(5µm) =.13 Jy (flux density quality = 3), F(µm).1 Jy (flux density quality = 1). table*[hbt] Nebular dereddened fluxes from different authors tabular llrrrrr lambda ion 5cDereddened fluxes relative to Hβ [-1mm]mm.5mm Preliminary analysis of the observational data In HST images the nebula appears perfectly spherical and shows no small-scale structure. The surface flux distribution, as derived from the image o57niuq, is shown in Fig. fig : distribution.t heionizingstardominatestheemiss figure[htbp] [width=.5]stasinska-smp1-fig1.eps Radial distribution of the surface brightness. The STIS image 57niuq, obtained for target acquisition, was employed to prepare this graphic. The radius is measured in pixels. Each pixel is equivalent to.5. fig:distribution

3 .1 F λ /F(H β ) [A o -1 ].5 F λ /F(H β )..5. 3

4 x O IV 3d D - 3p P o O III 3d 3 D o - 3p 3 P C IV 9 - O IV 3d F o - 3p D O VI 3p P o - 3s S O III 3p 3 D - 3s 3 P o O III 3d 1 F o - 3p 1 D 5 - He II 11 - He II 1 - He II 9 - C IV - 5 3p 3 P o - 3s 3 S He II - 3 He II 8 - C IV s S - 5p P o O V 3p 1 P o - 3s 1 S O III 3d 1 P o - 3p 1 S O VI x s 3 S - 3p 3 P o C IV 9p P o - 5d D p 3 1 D - p 1 P o C II Neb. C IV 8-5 O IV 5g G - f F o C IV 5 - He II - 3 O V 3p 3 P - 3s 3 S O IV 3p S - 3s P C IV 7-5 O IV 3d D o - 3p P 1 o x - iron forest - p 3 P - p 3 P o p 1 S - p 1 P o O IV (not calc.) C IV 7 - O V p 1 D - p 1 P o Si IV 3p P o - 3s S 3p 3 P - 3p 3 P o C IV p P o - s S 3d 3 F o - 3d 3 D d 3 D - 3p 3 P o He II 3 - C IV - f F o C IV - d D

5 X Fe =1 - O IV C IV O V Si IV - iron forest - X Fe =1 1 - X Fe =