Discovery of an optical cocoon tail behind the runaway HD 185806. (arXiv:2206.14806v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Spetsieri_Z/0/1/0/all/0/1">Z.T. Spetsieri</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Boumis_P/0/1/0/all/0/1">P. Boumis</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Chiotellis_A/0/1/0/all/0/1">A. Chiotellis</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Akras_S/0/1/0/all/0/1">S. Akras</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Derlopa_S/0/1/0/all/0/1">S. Derlopa</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Shetye_S/0/1/0/all/0/1">S. Shetye</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Meyer_D/0/1/0/all/0/1">D.M.A. Meyer</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bowman_D/0/1/0/all/0/1">D.M. Bowman</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gvaramadze_V/0/1/0/all/0/1">V.V. Gvaramadze</a>
Studies on the circumstellar structures around evolved stars provide vital
information on the evolution of the parent star and the properties of the local
interstellar medium. In this work, we present the discovery and
characterization of an optical cocoon tail behind the star HD 185806. The
cocoon apex emission is puzzling, as it is detected in the infrared but shows
no signal in the optical wavelength. The H-alpha and [OIII] fluxes of the
nebular structure vary from 2.7 to 8.5×10^{-12} erg s^{-1} cm^ {-2} and from
0.9 to 7.0×10^{-13} erg s^{-1} cm^{-2}, respectively. Through high-resolution
spectroscopy, we derive the spectral type of the star, construct the
position-velocity diagrams of the cocoon tail for the H-alpha, [OIII] and [NII]
emission lines, and determine its velocity in the range of -100 to 40 km s
^{-1} . Furthermore, we use SED fitting and MESA evolutionary models adopting a
distance of 900 pc, and classify HD 185806 as a 1.3 M star, in the transition
phase between the RGB and early AGB stages. Finally, we study the
morpho-kinematic structure of the cocoon tail using the astronomical software
SHAPE. An ellipsoidal structure, with an inclination of 19 degrees with respect
to the plane of sky is found to better reproduce the observed cocoon tail of HD
185806.
Studies on the circumstellar structures around evolved stars provide vital
information on the evolution of the parent star and the properties of the local
interstellar medium. In this work, we present the discovery and
characterization of an optical cocoon tail behind the star HD 185806. The
cocoon apex emission is puzzling, as it is detected in the infrared but shows
no signal in the optical wavelength. The H-alpha and [OIII] fluxes of the
nebular structure vary from 2.7 to 8.5×10^{-12} erg s^{-1} cm^ {-2} and from
0.9 to 7.0×10^{-13} erg s^{-1} cm^{-2}, respectively. Through high-resolution
spectroscopy, we derive the spectral type of the star, construct the
position-velocity diagrams of the cocoon tail for the H-alpha, [OIII] and [NII]
emission lines, and determine its velocity in the range of -100 to 40 km s
^{-1} . Furthermore, we use SED fitting and MESA evolutionary models adopting a
distance of 900 pc, and classify HD 185806 as a 1.3 M star, in the transition
phase between the RGB and early AGB stages. Finally, we study the
morpho-kinematic structure of the cocoon tail using the astronomical software
SHAPE. An ellipsoidal structure, with an inclination of 19 degrees with respect
to the plane of sky is found to better reproduce the observed cocoon tail of HD
185806.
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