Critical study of the distribution of rotational velocities of Be stars : II: Differential rotation and some hidden effects interfering with the interpretation of the V sin i param...

Autores
Zorec, Juan; Frémat, Y.; Domiciano de Souza, A.; Royer, F.; Cidale, Lydia Sonia; Hubert, A. M.; Semaan, T.; Martayan, C.; Cochetti, Yanina Roxana; Arias, María Laura; Aidelman, Yael Judith; Stee, P.
Año de publicación
2017
Idioma
inglés
Tipo de recurso
artículo
Estado
versión publicada
Descripción
Aims. We assume that stars may undergo surface differential rotation to study its impact on the interpretation of Vsin i and on the observed distribution Φ(u) of ratios of true rotational velocities u = V/Vc (Vc is the equatorial critical velocity). We discuss some phenomena affecting the formation of spectral lines and their broadening, which can obliterate the information carried by Vsin i concerning the actual stellar rotation. Methods. We studied the line broadening produced by several differential rotational laws, but adopted Maunder's expression Ω(0) = Ω0(1 + α cos2 0) as an attempt to account for all of these laws with the lowest possible number of free parameters. We studied the effect of the differential rotation parameter a on the measured Vsin i parameter and on the distribution Φ(u) of ratios u = V/Vc. Results. We conclude that the inferred Vsin i is smaller than implied by the actual equatorial linear rotation velocity Veq if the stars rotate with α < 0, but is larger if the stars have a α > 0. For a given |α| the deviations of Vsin i are larger when α < 0. If the studied Be stars have on average α < 0, the number of rotators with Veq 0.9Vc is larger than expected from the observed distribution Φ(u); if these stars have on average α > 0, this number is lower than expected. We discuss seven phenomena that contribute either to narrow or broaden spectral lines, which blur the information on the rotation carried by Vsin i and, in particular, to decide whether the Be phenomenon mostly rely on the critical rotation. We show that two-dimensional radiation transfer calculations are needed in rapid rotators to diagnose the stellar rotation more reliably.
Facultad de Ciencias Astronómicas y Geofísicas
Materia
Astronomía
stars: emission-line
Be - stars: rotation
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:10915/77716

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network_name_str SEDICI (UNLP)
spelling Critical study of the distribution of rotational velocities of Be stars : II: Differential rotation and some hidden effects interfering with the interpretation of the V sin i parameterZorec, JuanFrémat, Y.Domiciano de Souza, A.Royer, F.Cidale, Lydia SoniaHubert, A. M.Semaan, T.Martayan, C.Cochetti, Yanina RoxanaArias, María LauraAidelman, Yael JudithStee, P.Astronomíastars: emission-lineBe - stars: rotationAims. We assume that stars may undergo surface differential rotation to study its impact on the interpretation of Vsin i and on the observed distribution Φ(u) of ratios of true rotational velocities u = V/Vc (Vc is the equatorial critical velocity). We discuss some phenomena affecting the formation of spectral lines and their broadening, which can obliterate the information carried by Vsin i concerning the actual stellar rotation. Methods. We studied the line broadening produced by several differential rotational laws, but adopted Maunder's expression Ω(0) = Ω0(1 + α cos2 0) as an attempt to account for all of these laws with the lowest possible number of free parameters. We studied the effect of the differential rotation parameter a on the measured Vsin i parameter and on the distribution Φ(u) of ratios u = V/Vc. Results. We conclude that the inferred Vsin i is smaller than implied by the actual equatorial linear rotation velocity Veq if the stars rotate with α < 0, but is larger if the stars have a α > 0. For a given |α| the deviations of Vsin i are larger when α < 0. If the studied Be stars have on average α < 0, the number of rotators with Veq 0.9Vc is larger than expected from the observed distribution Φ(u); if these stars have on average α > 0, this number is lower than expected. We discuss seven phenomena that contribute either to narrow or broaden spectral lines, which blur the information on the rotation carried by Vsin i and, in particular, to decide whether the Be phenomenon mostly rely on the critical rotation. We show that two-dimensional radiation transfer calculations are needed in rapid rotators to diagnose the stellar rotation more reliably.Facultad de Ciencias Astronómicas y Geofísicas2017-06info: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/10915/77716enginfo:eu-repo/semantics/altIdentifier/issn/1432-0746info:eu-repo/semantics/altIdentifier/doi/10.1051/0004-6361/201628761info: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:UNLP2025-10-15T11:05:50Zoai:sedici.unlp.edu.ar:10915/77716Institucionalhttp://sedici.unlp.edu.ar/Universidad públicaNo correspondehttp://sedici.unlp.edu.ar/oai/snrdalira@sedici.unlp.edu.arArgentinaNo correspondeNo correspondeNo correspondeopendoar:13292025-10-15 11:05:50.863SEDICI (UNLP) - Universidad Nacional de La Platafalse
dc.title.none.fl_str_mv Critical study of the distribution of rotational velocities of Be stars : II: Differential rotation and some hidden effects interfering with the interpretation of the V sin i parameter
title Critical study of the distribution of rotational velocities of Be stars : II: Differential rotation and some hidden effects interfering with the interpretation of the V sin i parameter
spellingShingle Critical study of the distribution of rotational velocities of Be stars : II: Differential rotation and some hidden effects interfering with the interpretation of the V sin i parameter
Zorec, Juan
Astronomía
stars: emission-line
Be - stars: rotation
title_short Critical study of the distribution of rotational velocities of Be stars : II: Differential rotation and some hidden effects interfering with the interpretation of the V sin i parameter
title_full Critical study of the distribution of rotational velocities of Be stars : II: Differential rotation and some hidden effects interfering with the interpretation of the V sin i parameter
title_fullStr Critical study of the distribution of rotational velocities of Be stars : II: Differential rotation and some hidden effects interfering with the interpretation of the V sin i parameter
title_full_unstemmed Critical study of the distribution of rotational velocities of Be stars : II: Differential rotation and some hidden effects interfering with the interpretation of the V sin i parameter
title_sort Critical study of the distribution of rotational velocities of Be stars : II: Differential rotation and some hidden effects interfering with the interpretation of the V sin i parameter
dc.creator.none.fl_str_mv Zorec, Juan
Frémat, Y.
Domiciano de Souza, A.
Royer, F.
Cidale, Lydia Sonia
Hubert, A. M.
Semaan, T.
Martayan, C.
Cochetti, Yanina Roxana
Arias, María Laura
Aidelman, Yael Judith
Stee, P.
author Zorec, Juan
author_facet Zorec, Juan
Frémat, Y.
Domiciano de Souza, A.
Royer, F.
Cidale, Lydia Sonia
Hubert, A. M.
Semaan, T.
Martayan, C.
Cochetti, Yanina Roxana
Arias, María Laura
Aidelman, Yael Judith
Stee, P.
author_role author
author2 Frémat, Y.
Domiciano de Souza, A.
Royer, F.
Cidale, Lydia Sonia
Hubert, A. M.
Semaan, T.
Martayan, C.
Cochetti, Yanina Roxana
Arias, María Laura
Aidelman, Yael Judith
Stee, P.
author2_role author
author
author
author
author
author
author
author
author
author
author
dc.subject.none.fl_str_mv Astronomía
stars: emission-line
Be - stars: rotation
topic Astronomía
stars: emission-line
Be - stars: rotation
dc.description.none.fl_txt_mv Aims. We assume that stars may undergo surface differential rotation to study its impact on the interpretation of Vsin i and on the observed distribution Φ(u) of ratios of true rotational velocities u = V/Vc (Vc is the equatorial critical velocity). We discuss some phenomena affecting the formation of spectral lines and their broadening, which can obliterate the information carried by Vsin i concerning the actual stellar rotation. Methods. We studied the line broadening produced by several differential rotational laws, but adopted Maunder's expression Ω(0) = Ω0(1 + α cos2 0) as an attempt to account for all of these laws with the lowest possible number of free parameters. We studied the effect of the differential rotation parameter a on the measured Vsin i parameter and on the distribution Φ(u) of ratios u = V/Vc. Results. We conclude that the inferred Vsin i is smaller than implied by the actual equatorial linear rotation velocity Veq if the stars rotate with α < 0, but is larger if the stars have a α > 0. For a given |α| the deviations of Vsin i are larger when α < 0. If the studied Be stars have on average α < 0, the number of rotators with Veq 0.9Vc is larger than expected from the observed distribution Φ(u); if these stars have on average α > 0, this number is lower than expected. We discuss seven phenomena that contribute either to narrow or broaden spectral lines, which blur the information on the rotation carried by Vsin i and, in particular, to decide whether the Be phenomenon mostly rely on the critical rotation. We show that two-dimensional radiation transfer calculations are needed in rapid rotators to diagnose the stellar rotation more reliably.
Facultad de Ciencias Astronómicas y Geofísicas
description Aims. We assume that stars may undergo surface differential rotation to study its impact on the interpretation of Vsin i and on the observed distribution Φ(u) of ratios of true rotational velocities u = V/Vc (Vc is the equatorial critical velocity). We discuss some phenomena affecting the formation of spectral lines and their broadening, which can obliterate the information carried by Vsin i concerning the actual stellar rotation. Methods. We studied the line broadening produced by several differential rotational laws, but adopted Maunder's expression Ω(0) = Ω0(1 + α cos2 0) as an attempt to account for all of these laws with the lowest possible number of free parameters. We studied the effect of the differential rotation parameter a on the measured Vsin i parameter and on the distribution Φ(u) of ratios u = V/Vc. Results. We conclude that the inferred Vsin i is smaller than implied by the actual equatorial linear rotation velocity Veq if the stars rotate with α < 0, but is larger if the stars have a α > 0. For a given |α| the deviations of Vsin i are larger when α < 0. If the studied Be stars have on average α < 0, the number of rotators with Veq 0.9Vc is larger than expected from the observed distribution Φ(u); if these stars have on average α > 0, this number is lower than expected. We discuss seven phenomena that contribute either to narrow or broaden spectral lines, which blur the information on the rotation carried by Vsin i and, in particular, to decide whether the Be phenomenon mostly rely on the critical rotation. We show that two-dimensional radiation transfer calculations are needed in rapid rotators to diagnose the stellar rotation more reliably.
publishDate 2017
dc.date.none.fl_str_mv 2017-06
dc.type.none.fl_str_mv info:eu-repo/semantics/article
info:eu-repo/semantics/publishedVersion
Articulo
http://purl.org/coar/resource_type/c_6501
info:ar-repo/semantics/articulo
format article
status_str publishedVersion
dc.identifier.none.fl_str_mv http://sedici.unlp.edu.ar/handle/10915/77716
url http://sedici.unlp.edu.ar/handle/10915/77716
dc.language.none.fl_str_mv eng
language eng
dc.relation.none.fl_str_mv info:eu-repo/semantics/altIdentifier/issn/1432-0746
info:eu-repo/semantics/altIdentifier/doi/10.1051/0004-6361/201628761
dc.rights.none.fl_str_mv info:eu-repo/semantics/openAccess
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/
Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International (CC BY-NC-SA 4.0)
dc.format.none.fl_str_mv application/pdf
dc.source.none.fl_str_mv reponame:SEDICI (UNLP)
instname:Universidad Nacional de La Plata
instacron:UNLP
reponame_str SEDICI (UNLP)
collection SEDICI (UNLP)
instname_str Universidad Nacional de La Plata
instacron_str UNLP
institution UNLP
repository.name.fl_str_mv SEDICI (UNLP) - Universidad Nacional de La Plata
repository.mail.fl_str_mv alira@sedici.unlp.edu.ar
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