High resolution linear spectropolarimetry: a study of the potentiality in probing stellar atmospheres and circumstellar environments
type: CreativeWork
description: Polarimetry is considered as an important searching tool in Astronomy and it deserves to be a standard observational technique for a variety of astrophysical environments. Many phenomena, in fact, can contribute to the polarisation of radiation and so, its observation can potentially provide information about their basic causes. In particular, in a stellar context high resolution spectropolarimetry can potentially: (i) investigate the physics of the shaping mechanisms of the protoplanetary nebulae (PNe) and the possible interaction between the central star and the very close surrounding, (ii) investigate stellar photospheric inhomogeneities (e.g. pulsations, granulations, hot spots and magnetic activity), (iii) play a key role in the exoplanet research. Despite this, however, the difficulties involved in the measurements and in the theoretical interpretation made this technique not as widespread as it deserves. The main goal of this work is to demonstrate the diagnostic potential of high resolution linear spectropolarimetry. At this purpose, we studied the polarised spectrum of the post-AGB binary system 89 Herculis on the basis of data collected with the high resolution \emph{Catania Astrophysical Observatory Spectropolarimeter} (CAOS) and \emph{HArps-North POlarimeter} (HANPO), in addition to archive data taken with the \emph{Echelle SpectroPolarimtric Device for the Observation of Stars} (ESPaDOnS). We found the existence of linear polarisation in the metal lines in absorption and in some of the metal lines in emission: this is the first \emph{Second Solar Spectrum} ever observed in a star different than the Sun. We have then analyzed the observed polarisation properties. Firstly, regarding the polarisation measured across the absorption lines, we found that the complex Stokes $Q$ and $U$ morphologies vary with the orbital period of the system. We then rule out magnetic field, continuum depolarisation due to pulsations and hot spots as a possible origin. We found…
abstract: Polarimetry is considered as an important searching tool in Astronomy and it deserves to be a standard observational technique for a variety of astrophysical environments. Many phenomena, in fact, can contribute to the polarisation of radiation and so, its observation can potentially provide information about their basic causes. In particular, in a stellar context high resolution spectropolarimetry can potentially: (i) investigate the physics of the shaping mechanisms of the protoplanetary nebulae (PNe) and the possible interaction between the central star and the very close surrounding, (ii) investigate stellar photospheric inhomogeneities (e.g. pulsations, granulations, hot spots and magnetic activity), (iii) play a key role in the exoplanet research. Despite this, however, the difficulties involved in the measurements and in the theoretical interpretation made this technique not as widespread as it deserves. The main goal of this work is to demonstrate the diagnostic potential of high resolution linear spectropolarimetry. At this purpose, we studied the polarised spectrum of the post-AGB binary system 89 Herculis on the basis of data collected with the high resolution \emph{Catania Astrophysical Observatory Spectropolarimeter} (CAOS) and \emph{HArps-North POlarimeter} (HANPO), in addition to archive data taken with the \emph{Echelle SpectroPolarimtric Device for the Observation of Stars} (ESPaDOnS). We found the existence of linear polarisation in the metal lines in absorption and in some of the metal lines in emission: this is the first \emph{Second Solar Spectrum} ever observed in a star different than the Sun. We have then analyzed the observed polarisation properties. Firstly, regarding the polarisation measured across the absorption lines, we found that the complex Stokes $Q$ and $U$ morphologies vary with the orbital period of the system. We then rule out magnetic field, continuum depolarisation due to pulsations and hot spots as a possible origin. We found…
author: GANGI, MANUELE ETTORE MICHEL
language: eng
keywords: spectropolarimetry, stars, post-AGB
date published: 2018-10-23
date modified: 2026-07-24T01:34:56Z
provider: Università degli Studi di Catania
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Università degli studi di Catania

PropertyValue
property ID: Handle
value: https://hdl.handle.net/20.500.11769/581925