Academic Journal
Rotation, spectral variability, magnetic geometry and magnetosphere of the Of?p star CPD -28° 2561
| العنوان: | Rotation, spectral variability, magnetic geometry and magnetosphere of the Of?p star CPD -28° 2561 |
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| المؤلفون: | Wade, G. A., Barbá, R. H., Grunhut, J., Martins, F., Petit, V., Sundqvist, J. O., Townsend, R. H. D., Walborn, N. R., Alecian, E., Alfaro, E. J., sMaíz Apellániz, J., Arias, J. I., Gamen, R., Morrell, N., Nazé, Yaël, Sota, A., ud-Doula, A., MiMeS Collaboration |
| المساهمون: | LiSRI - Liège Space Research Institute - ULiège |
| المصدر: | Monthly Notices of the Royal Astronomical Society, 447, 2551-2567 (2015-03-01) |
| بيانات النشر: | Oxford University Press, 2015. |
| سنة النشر: | 2015 |
| مصطلحات موضوعية: | stars: individual: CPD -28° 2561, stars: magnetic field, stars: massive, stars: rotation, Physical, chemical, mathematical & earth Sciences, Space science, astronomy & astrophysics, Physique, chimie, mathématiques & sciences de la terre, Aérospatiale, astronomie & astrophysique |
| الوصف: | We report magnetic and spectroscopic observations and modelling of the Of?p star CPD -28° 2561. Using more than 75 new spectra, we have measured the equivalent width variations and examined the dynamic spectra of photospheric and wind-sensitive spectral lines. A period search results in an unambiguous 73.41 d variability period. High-resolution spectropolarimetric data analysed using least-squares deconvolution yield a Zeeman signature detected in the mean Stokes V profile corresponding to phase 0.5 of the spectral ephemeris. Interpreting the 73.41 d period as the stellar rotational period, we have phased the equivalent widths and inferred longitudinal field measurements. The phased magnetic data exhibit a weak sinusoidal variation, with maximum of about 565 G at phase 0.5, and a minimum of about -335 G at phase 0.0, with extrema approximately in phase with the (double-wave) Hα equivalent width variation. Modelling of the Hα equivalent width variation assuming a quasi-3D magnetospheric model produces a unique solution for the ambiguous couplet of inclination and magnetic obliquity angles: (i, β) or (β, i) = (35°, 90°). Adopting either geometry, the longitudinal field variation yields a dipole polar intensity B[SUB]d[/SUB] = 2.6 ± 0.9 kG, consistent with that obtained from direct modelling of the Stokes V profiles. We derive a wind magnetic confinement parameter η[SUB]*[/SUB] ≃ 100, leading to an Alfvén radius R[SUB]A[/SUB] ≃ 3-5R[SUB]*[/SUB], and a Kepler radius R[SUB]K[/SUB] ≃ 20R[SUB]*[/SUB]. This supports a physical scenario in which the Hα emission and other line variability have their origin in an oblique, corotating `dynamical magnetosphere' structure resulting from a magnetically channelled wind. Nevertheless, the details of the formation of spectral lines and their variability within this framework remain generally poorly understood. |
| نوع الوثيقة: | journal article http://purl.org/coar/resource_type/c_6501 article peer reviewed |
| اللغة: | English |
| Relation: | http://cdsads.u-strasbg.fr/abs/2015MNRAS.447.2551W; urn:issn:0035-8711; urn:issn:1365-2966 |
| DOI: | 10.1093/mnras/stu2548 |
| URL الوصول: | https://orbi.uliege.be/handle/2268/177649 |
| Rights: | open access http://purl.org/coar/access_right/c_abf2 info:eu-repo/semantics/openAccess |
| رقم الانضمام: | edsorb.177649 |
| قاعدة البيانات: | ORBi |
| DOI: | 10.1093/mnras/stu2548 |
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