1 Introduction

Among the galactic Luminous Blue Variables (LBV), the supergiant P Cyg (HD 193237, B1Ia+) is both a historical prototype since its famous XVIIth century eruptions, and an intriguing paradigm in many aspects. In their exhaustive study of P Cyg's fundamental parameters, mass loss physics and evolution, Nota et al. ([Nota et al. 1995]) have claimed this star as being the unique case of the so-called "Peculiar Nebulae'' class LBVs. Indeed, the 22 arcseconds (arcsec) faint and spherical nebulae around P Cyg, were only recently discovered by Barlow et al. ([Barlow et al. 1994]) who estimate its mass as $0.01\ M_\odot$. This value differs significantly from those of more regular LBVs, ranging from 1 $M_{\odot}$ to 4.2 $M_{\odot}$(e.g. for AG Car) which also present more asymmetric nebula.

Figure 1: H$_{\alpha }$ long exposures of P Cyg (top) and the reference star 59 Cyg (bottom) recorded with the CP20 camera at OHP during October 4th 1997 using the AO system BOA from ONERA through a filter ( $\Delta \lambda$ = 10 nm). The images are smoothed using a moving average window of 4$\times$4 pixels. Note that the theoretical angular resolution of the 1.52 m telescope at 6563 Å  ( $1.22\lambda /D=0.110$ arcsec) is closely reached (broken first Airy ring is visible on 59 Cyg) whilst for P Cyg a more complex and resolved structure can be suspected

Evolutive tracks suggest an initial mass of 48 $\pm$ 6 $M_{\odot}$, and its present mass is estimated to be at the most 40 $M_{\odot}$, but lower masses ($\sim$ 30 $M_{\odot}$) are also reported in literature ([Lamers et al. 1983]; [Lamers et al. 1985]; [Turner et al. 1999]). However, the fine spatial structure of this large amount of excreted matter remains to be detailed. P Cyg's relative proximity ($\sim$ 1.8 kpc, [Lamers et al. 1983]) represents an opportunity to observe its radiatively driven mass loss from the starting point out to the interstellar medium. Indeed, at 1.8 kpc, the central star radius ( $76~R_{\odot}$) corresponds to a tiny angle of 0.2 milliarcsecond (mas) but the H$_{\alpha }$emitting region extends over several tens of arcsecs, and radio emission seems to attain even larger scales ([Meaburn et al. 1999]). The optical and radio observations reported to date, depict an essentially clumpy distribution of matter, both at large ([Taylor et al. 1991]; [Nota et al. 1995]) and small scales ([Skinner et al. 1998]; [Vakili et al. 1997]), with temporally variable emission ([Skinner et al. 1997]). These imaging observations remain sparse and can loosely constrain the spatial and/or temporal evolution of the clumps in the nebula. Moreover, in the optical wavelengths, the star to envelope brightness ratio remains an obstacle for studying the immediate environment of the central star. In this paper we report an attempt to observe the H$_{\alpha }$ circumstellar environment of P Cyg during an AO run at the OHP observatory on October 1997 using short exposures collected with a photon-counting camera.

Figure 2: Synthetic representation of the H$_{\alpha }$ region of P Cyg multiplied by the filter transmission used for the adaptive optics imaging of P Cyg. The same filter was used for 59 Cyg. About 45.6% of the transmitted light originates from the line continuum

The paper is organized as follows. In Sect. 2, we describe the AO+imaging instrumentation used for this study as well as data reduction and calibration procedures. Section 3 describes the image reconstruction in which particular efforts have been made to test the validity of the PSF. The last section makes a critical discussion of our findings, and attention is given on the perspectives opened by the emergencies of new high angular resolution techniques. A need arises for a coordinated campaign for a global approach of P Cyg, and LBVs environment.