The puzzling properties of the magnetic O star Tr16-22

Autores
Nazé, Yaël; Barbá, Rodolfo Héctor; Bagnulo, Stefano; Morrell, Nidia Irene; Gamen, Roberto Claudio; Petit, Véronique; Neiner, Coralie
Año de publicación
2016
Idioma
inglés
Tipo de recurso
artículo
Estado
versión publicada
Descripción
Context. The detection of bright, hard, and variable X-ray emission in Tr16-22 prompted spectropolarimetric observations of this star, which in turn led to the discovery of a surface magnetic field. Aims. We want to further constrain the properties of this star, in particular to verify whether X-ray variations are correlated to changes in optical emission lines and magnetic field strength, as expected from the oblique rotator model that is widely accepted for magnetic O stars. Methods. We have obtained new low-resolution spectropolarimetric and long-term high-resolution spectroscopic monitoring of Tr16-22, and we also analyse new, serendipitous X-ray data. Results. The new X-ray observations are consistent with previous data, but their addition does not help to solve the ambiguity in the variation timescale because of numerous aliases. No obvious periodicity or any large variations are detected in the spectropolarimetric data of Tr16-22 obtained over three months. The derived field values appear to be in line with previous measurements, suggesting constancy of the field (though the possibility of small, short-term field variations cannot be excluded). Variations in the equivalent widths of Hα are very small, and they do not appear to be related to the X-ray timescale; the overall lack of large variations in optical emission lines is consistent with the magnetic field constancy. In addition, variations of the radial velocities indicate that Tr16-22 is probably a SB1 binary with a very long period. Conclusions. Our new measurements of optical emission lines and magnetic field strength do not show an obvious correlation with X-ray variations. Our current data thus cannot be interpreted in terms of the common model, which assumes the electromagnetic emission associated with a wind confined by a dipolar field tilted with respect to the rotation axis. However, the sampling is imperfect and new data are needed to further constrain the actual periodicity of the various observed phenomena. If inconsistencies are confirmed, then we will need to consider alternative scenarios.
Instituto de Astrofísica de La Plata
Facultad de Ciencias Astronómicas y Geofísicas
Materia
Ciencias Astronómicas
Stars: early-type
Stars: individual: Tr16-22
Stars: magnetic field
X-rays: stars
Nivel de accesibilidad
acceso abierto
Condiciones de uso
http://creativecommons.org/licenses/by-nc-sa/4.0/
Repositorio
SEDICI (UNLP)
Institución
Universidad Nacional de La Plata
OAI Identificador
oai:sedici.unlp.edu.ar:10915/85816

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network_name_str SEDICI (UNLP)
spelling The puzzling properties of the magnetic O star Tr16-22Nazé, YaëlBarbá, Rodolfo HéctorBagnulo, StefanoMorrell, Nidia IreneGamen, Roberto ClaudioPetit, VéroniqueNeiner, CoralieCiencias AstronómicasStars: early-typeStars: individual: Tr16-22Stars: magnetic fieldX-rays: starsContext. The detection of bright, hard, and variable X-ray emission in Tr16-22 prompted spectropolarimetric observations of this star, which in turn led to the discovery of a surface magnetic field. Aims. We want to further constrain the properties of this star, in particular to verify whether X-ray variations are correlated to changes in optical emission lines and magnetic field strength, as expected from the oblique rotator model that is widely accepted for magnetic O stars. Methods. We have obtained new low-resolution spectropolarimetric and long-term high-resolution spectroscopic monitoring of Tr16-22, and we also analyse new, serendipitous X-ray data. Results. The new X-ray observations are consistent with previous data, but their addition does not help to solve the ambiguity in the variation timescale because of numerous aliases. No obvious periodicity or any large variations are detected in the spectropolarimetric data of Tr16-22 obtained over three months. The derived field values appear to be in line with previous measurements, suggesting constancy of the field (though the possibility of small, short-term field variations cannot be excluded). Variations in the equivalent widths of Hα are very small, and they do not appear to be related to the X-ray timescale; the overall lack of large variations in optical emission lines is consistent with the magnetic field constancy. In addition, variations of the radial velocities indicate that Tr16-22 is probably a SB1 binary with a very long period. Conclusions. Our new measurements of optical emission lines and magnetic field strength do not show an obvious correlation with X-ray variations. Our current data thus cannot be interpreted in terms of the common model, which assumes the electromagnetic emission associated with a wind confined by a dipolar field tilted with respect to the rotation axis. However, the sampling is imperfect and new data are needed to further constrain the actual periodicity of the various observed phenomena. If inconsistencies are confirmed, then we will need to consider alternative scenarios.Instituto de Astrofísica de La PlataFacultad de Ciencias Astronómicas y Geofísicas2016info:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionArticulohttp://purl.org/coar/resource_type/c_6501info:ar-repo/semantics/articuloapplication/pdfhttp://sedici.unlp.edu.ar/handle/10915/85816enginfo:eu-repo/semantics/altIdentifier/issn/0004-6361info:eu-repo/semantics/altIdentifier/doi/10.1051/0004-6361/201629320info:eu-repo/semantics/openAccesshttp://creativecommons.org/licenses/by-nc-sa/4.0/Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International (CC BY-NC-SA 4.0)reponame:SEDICI (UNLP)instname:Universidad Nacional de La Platainstacron:UNLP2025-09-29T11:16:44Zoai:sedici.unlp.edu.ar:10915/85816Institucionalhttp://sedici.unlp.edu.ar/Universidad públicaNo correspondehttp://sedici.unlp.edu.ar/oai/snrdalira@sedici.unlp.edu.arArgentinaNo correspondeNo correspondeNo correspondeopendoar:13292025-09-29 11:16:44.531SEDICI (UNLP) - Universidad Nacional de La Platafalse
dc.title.none.fl_str_mv The puzzling properties of the magnetic O star Tr16-22
title The puzzling properties of the magnetic O star Tr16-22
spellingShingle The puzzling properties of the magnetic O star Tr16-22
Nazé, Yaël
Ciencias Astronómicas
Stars: early-type
Stars: individual: Tr16-22
Stars: magnetic field
X-rays: stars
title_short The puzzling properties of the magnetic O star Tr16-22
title_full The puzzling properties of the magnetic O star Tr16-22
title_fullStr The puzzling properties of the magnetic O star Tr16-22
title_full_unstemmed The puzzling properties of the magnetic O star Tr16-22
title_sort The puzzling properties of the magnetic O star Tr16-22
dc.creator.none.fl_str_mv Nazé, Yaël
Barbá, Rodolfo Héctor
Bagnulo, Stefano
Morrell, Nidia Irene
Gamen, Roberto Claudio
Petit, Véronique
Neiner, Coralie
author Nazé, Yaël
author_facet Nazé, Yaël
Barbá, Rodolfo Héctor
Bagnulo, Stefano
Morrell, Nidia Irene
Gamen, Roberto Claudio
Petit, Véronique
Neiner, Coralie
author_role author
author2 Barbá, Rodolfo Héctor
Bagnulo, Stefano
Morrell, Nidia Irene
Gamen, Roberto Claudio
Petit, Véronique
Neiner, Coralie
author2_role author
author
author
author
author
author
dc.subject.none.fl_str_mv Ciencias Astronómicas
Stars: early-type
Stars: individual: Tr16-22
Stars: magnetic field
X-rays: stars
topic Ciencias Astronómicas
Stars: early-type
Stars: individual: Tr16-22
Stars: magnetic field
X-rays: stars
dc.description.none.fl_txt_mv Context. The detection of bright, hard, and variable X-ray emission in Tr16-22 prompted spectropolarimetric observations of this star, which in turn led to the discovery of a surface magnetic field. Aims. We want to further constrain the properties of this star, in particular to verify whether X-ray variations are correlated to changes in optical emission lines and magnetic field strength, as expected from the oblique rotator model that is widely accepted for magnetic O stars. Methods. We have obtained new low-resolution spectropolarimetric and long-term high-resolution spectroscopic monitoring of Tr16-22, and we also analyse new, serendipitous X-ray data. Results. The new X-ray observations are consistent with previous data, but their addition does not help to solve the ambiguity in the variation timescale because of numerous aliases. No obvious periodicity or any large variations are detected in the spectropolarimetric data of Tr16-22 obtained over three months. The derived field values appear to be in line with previous measurements, suggesting constancy of the field (though the possibility of small, short-term field variations cannot be excluded). Variations in the equivalent widths of Hα are very small, and they do not appear to be related to the X-ray timescale; the overall lack of large variations in optical emission lines is consistent with the magnetic field constancy. In addition, variations of the radial velocities indicate that Tr16-22 is probably a SB1 binary with a very long period. Conclusions. Our new measurements of optical emission lines and magnetic field strength do not show an obvious correlation with X-ray variations. Our current data thus cannot be interpreted in terms of the common model, which assumes the electromagnetic emission associated with a wind confined by a dipolar field tilted with respect to the rotation axis. However, the sampling is imperfect and new data are needed to further constrain the actual periodicity of the various observed phenomena. If inconsistencies are confirmed, then we will need to consider alternative scenarios.
Instituto de Astrofísica de La Plata
Facultad de Ciencias Astronómicas y Geofísicas
description Context. The detection of bright, hard, and variable X-ray emission in Tr16-22 prompted spectropolarimetric observations of this star, which in turn led to the discovery of a surface magnetic field. Aims. We want to further constrain the properties of this star, in particular to verify whether X-ray variations are correlated to changes in optical emission lines and magnetic field strength, as expected from the oblique rotator model that is widely accepted for magnetic O stars. Methods. We have obtained new low-resolution spectropolarimetric and long-term high-resolution spectroscopic monitoring of Tr16-22, and we also analyse new, serendipitous X-ray data. Results. The new X-ray observations are consistent with previous data, but their addition does not help to solve the ambiguity in the variation timescale because of numerous aliases. No obvious periodicity or any large variations are detected in the spectropolarimetric data of Tr16-22 obtained over three months. The derived field values appear to be in line with previous measurements, suggesting constancy of the field (though the possibility of small, short-term field variations cannot be excluded). Variations in the equivalent widths of Hα are very small, and they do not appear to be related to the X-ray timescale; the overall lack of large variations in optical emission lines is consistent with the magnetic field constancy. In addition, variations of the radial velocities indicate that Tr16-22 is probably a SB1 binary with a very long period. Conclusions. Our new measurements of optical emission lines and magnetic field strength do not show an obvious correlation with X-ray variations. Our current data thus cannot be interpreted in terms of the common model, which assumes the electromagnetic emission associated with a wind confined by a dipolar field tilted with respect to the rotation axis. However, the sampling is imperfect and new data are needed to further constrain the actual periodicity of the various observed phenomena. If inconsistencies are confirmed, then we will need to consider alternative scenarios.
publishDate 2016
dc.date.none.fl_str_mv 2016
dc.type.none.fl_str_mv info:eu-repo/semantics/article
info:eu-repo/semantics/publishedVersion
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http://creativecommons.org/licenses/by-nc-sa/4.0/
Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International (CC BY-NC-SA 4.0)
eu_rights_str_mv openAccess
rights_invalid_str_mv http://creativecommons.org/licenses/by-nc-sa/4.0/
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