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Title: A Method to Measure the Transverse Magnetic Field and Orient the Rotational Axis of Stars

Abstract

Direct measurements of stellar magnetic fields are based on the splitting of spectral lines into polarized Zeeman components. With a few exceptions, Zeeman signatures are hidden in data noise, and a number of methods have been developed to measure the average, over the visible stellar disk, of longitudinal components of the magnetic field. At present, faint stars are only observable via low-resolution spectropolarimetry, which is a method based on the regression of the Stokes V signal against the first derivative of Stokes I . Here, we present an extension of this method to obtain a direct measurement of the transverse component of stellar magnetic fields by the regression of high-resolution Stokes Q and U as a function of the second derivative of Stokes I . We also show that it is possible to determine the orientation in the sky of the rotation axis of a star on the basis of the periodic variability of the transverse component due to its rotation. The method is applied to data, obtained with the Catania Astrophysical Observatory Spectropolarimeter along the rotational period of the well known magnetic star β CrB.

Authors:
; ; ;  [1]; ; ;  [2];  [3]
  1. Università di Catania, Dipartimento di Fisica e Astronomia, Sezione Astrofisica, Via S. Sofia 78, I-95123 Catania (Italy)
  2. INAF—Osservatorio Astrofisico di Catania, Via S. Sofia 78, I-95123 Catania (Italy)
  3. Armagh Observatory, College Hill, Armagh BT61 9DG. Northern Ireland (United Kingdom)
Publication Date:
OSTI Identifier:
22679738
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 848; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASTROPHYSICS; EXCEPTIONS; MAGNETIC FIELDS; MAGNETIC STARS; NOISE; ORIENTATION; PERIODICITY; POLARIZATION; RESOLUTION; ROTATION; ZEEMAN EFFECT

Citation Formats

Leone, Francesco, Scalia, Cesare, Gangi, Manuele, Giarrusso, Marina, Munari, Matteo, Scuderi, Salvatore, Trigilio, Corrado, and Stift, Martin J. A Method to Measure the Transverse Magnetic Field and Orient the Rotational Axis of Stars. United States: N. p., 2017. Web. doi:10.3847/1538-4357/AA8D72.
Leone, Francesco, Scalia, Cesare, Gangi, Manuele, Giarrusso, Marina, Munari, Matteo, Scuderi, Salvatore, Trigilio, Corrado, & Stift, Martin J. A Method to Measure the Transverse Magnetic Field and Orient the Rotational Axis of Stars. United States. doi:10.3847/1538-4357/AA8D72.
Leone, Francesco, Scalia, Cesare, Gangi, Manuele, Giarrusso, Marina, Munari, Matteo, Scuderi, Salvatore, Trigilio, Corrado, and Stift, Martin J. Fri . "A Method to Measure the Transverse Magnetic Field and Orient the Rotational Axis of Stars". United States. doi:10.3847/1538-4357/AA8D72.
@article{osti_22679738,
title = {A Method to Measure the Transverse Magnetic Field and Orient the Rotational Axis of Stars},
author = {Leone, Francesco and Scalia, Cesare and Gangi, Manuele and Giarrusso, Marina and Munari, Matteo and Scuderi, Salvatore and Trigilio, Corrado and Stift, Martin J.},
abstractNote = {Direct measurements of stellar magnetic fields are based on the splitting of spectral lines into polarized Zeeman components. With a few exceptions, Zeeman signatures are hidden in data noise, and a number of methods have been developed to measure the average, over the visible stellar disk, of longitudinal components of the magnetic field. At present, faint stars are only observable via low-resolution spectropolarimetry, which is a method based on the regression of the Stokes V signal against the first derivative of Stokes I . Here, we present an extension of this method to obtain a direct measurement of the transverse component of stellar magnetic fields by the regression of high-resolution Stokes Q and U as a function of the second derivative of Stokes I . We also show that it is possible to determine the orientation in the sky of the rotation axis of a star on the basis of the periodic variability of the transverse component due to its rotation. The method is applied to data, obtained with the Catania Astrophysical Observatory Spectropolarimeter along the rotational period of the well known magnetic star β CrB.},
doi = {10.3847/1538-4357/AA8D72},
journal = {Astrophysical Journal},
issn = {0004-637X},
number = 2,
volume = 848,
place = {United States},
year = {2017},
month = {10}
}