## A Consistent Spectral Model of WR 136 and its Associated Bubble NGC 6888

**J. Reyes-Pérez(1), C. Morisset(1), M. Peña(1), A. Mesa-Delgado(2)**

(1)Instituto de Astronomía, Universidad Nacional Autónoma de México; (2)Instituto de Astrofísica, Facultad de Física, Ponticia Universidad Católica de Chile

We analyse whether a stellar atmosphere model computed with the code CMFGEN

provides an optimal description of the stellar observations of WR 136 and

simultaneously reproduces the nebular observations of NGC 6888, such as the

ionization degree, which is modelled with the pyCloudy code. All the

observational material available (far and near UV and optical spectra) were

used to constrain such models. We found that even when the stellar luminosity

and the mass-loss rate were well constrained, the stellar temperature T_* at

tau = 20, can be in a range between 70 000 and 110 000 K. When using the nebula

as an additional restriction we found that the stellar models with T_* sim 70

000 K represent the best solution for both, the star and the nebula. Results

from the photoionization model show that if we consider a chemically

homogeneous nebula, the observed N+/O+ ratios found in different nebular

zones can be reproduced, therefore it is not necessary to assume a chemical

inhomogeneous nebula. Our work shows the importance of calculating coherent

models including stellar and nebular constraints. This allowed us to determine,

in a consistent way, all the physical parameters of both the star and its

associated nebula. The chemical abundances derived are 12 + log(N/H) = 9.95, 12

+ log(C/H) = 7.84 and 12 + log(O/H) = 8.76 for the star and 12 + log(N/H) =

8.40, 12 + log(C/H) = 8.86 and 12 + log(O/H) = 8.20. Thus the star and the

nebula are largely N- and C- enriched and O-depleted.

**Reference: **accepted by MNRAS

Status: Manuscript has been accepted

**Weblink: **http://arxiv.org/abs/1507.00051

**Comments: **

**Email: **jperez@astro.unam.mx