Bibcode
                                    
                            DOI
                                    
                            García-Lario, Pedro; Riera, Angels; Manchado, A.
    Referencia bibliográfica
                                    The Astrophysical Journal, Volume 526, Issue 2, pp. 854-861.
Fecha de publicación:
    
                        12
            
                        1999
            
  Revista
                                    
                            Número de citas
                                    29
                            Número de citas referidas
                                    24
                            Descripción
                                    Based on optical and near-infrared ground-based spectroscopy and optical
and near-infrared Hubble Space Telescope (HST) images, we confirm the
classification of Hen 401 as a bipolar proto-planetary nebula. HST
images reveal a highly elongated morphology, consisting of two main
bipolar lobes of unequal surface brightness separated by a dark lane of
dust with a total extension of 28''x3'',
superimposed on a much fainter background emission of elliptical shape
extending over ~10''x5''. The simultaneous
detection of spectral lines formed under very different density
conditions, together with the strong obscuration observed along the
equatorial plane, is interpreted as the signature of a circumstellar
disk, which would be responsible for the strong collimation observed. We
conclude that the emission observed is mainly due to scattering of the
light originated in the fluorescence-excited inner region of the
circumstellar disk. In addition, we also report the detection of strong
molecular H2 emission in the near infrared, confirming that
the onset of the H2 emission occurs in proto-PNs after the
bipolar structure has developed, but before photoionization takes place.