Ultraviolet spectropolarimetric diagnostics of hot star magnetospheres

ud‐Doula, Asif; Cheung, Mark C. M.; David-Uraz, Alexandre; Erba, C.; Folsom, C. P.; Gayley, K. G.; Nazé, Yaël; Neiner, C.; Petit, Véronique; Prinja, R. K.; Shultz, Matthew; Sudnik, N.; Wade, G. A.

doi:10.1007/s10509-022-04097-8

Cited by 5 publications

(1 citation statement)

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“…The majority of the detected large-scale magnetic fields of the magnetic hot stars are stable over time spans of up to decades (e.g., Oksala et al 2012;Sikora et al 2019), and have a predominantly dipole topological structure inclined to the rotational axis, with magnetic field strengths ranging from tens of Gauss to tens of kilo-Gauss (e.g., Shultz et al 2018;Järvinen et al 2021). Strong magnetic fields have been considered to explain the particular properties of these hot stars, such as photometric variations (e.g., Oksala et al 2015;Shen et al 2023), Hα line variations (e.g., Wisniewski et al 2015;Hubrig et al 2017;Shultz et al 2020), the UV resonance line variations (e.g., Shore & Brown 1990;ud-Doula et al 2022), the X-ray properties (e.g., Wade et al 2012;Petit et al 2015), and the radio emissions (e.g., Leto et al 2017;Shultz et al 2022).…”

Section: Introductionmentioning

confidence: 99%

Variability of Magnetic Hot Stars from the TESS Observations

Shen,

Li,

Abdusamatjan

et al. 2023

ApJ

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Magnetic hot stars refer to stars that have effective temperatures approximately in the range from 7000–50,000 K, and with large-scale globally organized magnetic fields. These magnetic fields exhibit strengths ranging from tens of Gauss to tens of kilo-Gauss. They are key in understanding the effects caused by magnetic fields in the stellar evolution. However, there are only three magnetic hot stars studied via a combination of spectropolarimetric and asteroseismic modeling. Combined with Transiting Exoplanet Survey Satellite sectors 1–56 data sets, we provided a photometric variability and stochastic low-frequency (SLF) variability study of 118 magnetic hot stars. Nine new rotating variable stars are identified. Using the Bayesian Markov Chain Monte Carlo framework, we fitted the morphologies of SLF variability for magnetic hot stars. Our analysis reveals that the magnetic hot stars in our sample have γ < 5.5 with the vast majority having 1 ≤ γ ≤ 3. The ν char is primarily in the ranges of 0 day−1 < ν char < 6.3 day−1. The amplitude of SLF variability, log α 0, shows a dominant distribution ranging from 0.8–3. No significant correlations are observed between the luminosity and fitting parameters, suggesting no clear dependence of SLF variability on stellar mass for our sample of magnetic hot stars with masses between approximately 1.5 M ⊙ < M < 20 M ⊙. We found a significant negative correlation between the B p and ν char. This suppression effect of magnetic fields on ν char may be a result of their inhibition of macroturbulence.

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Section: Introductionmentioning

confidence: 99%

Variability of Magnetic Hot Stars from the TESS Observations

Shen,

Li,

Abdusamatjan

et al. 2023

ApJ

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UV spectropolarimetry with Polstar: massive star binary colliding winds

St-Louis

Gayley

Hillier³

et al. 2022

Astrophys Space Sci

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The winds of massive stars are important for their direct impact on the interstellar medium, and for their influence on the final state of a star prior to it exploding as a supernova. However, the dynamics of these winds is understood primarily via their illumination from a single central source. The Doppler shift seen in resonance lines is a useful tool for inferring these dynamics, but the mapping from that Doppler shift to the radial distance from the source is ambiguous. Binary systems can reduce this ambiguity by providing a second light source at a known radius in the wind, seen from orbitally modulated directions. From the nature of the collision between the winds, a massive companion also provides unique additional information about wind momentum fluxes. Since massive stars are strong ultraviolet (UV) sources, and UV resonance line opacity in the wind is strong, UV instruments with a high resolution spectroscopic capability are essential for extracting this dynamical information. Polarimetric capability also helps to further resolve ambiguities in aspects of the wind geometry that are not axisymmetric about the line of sight, because of its unique access to scattering direction information. We review how the proposed MIDEX-scale mission Polstar can use UV spectropolarimetric observations to critically constrain the physics of colliding winds, and hence radiatively-driven winds in general. We propose a sample of 20 binary targets, capitalizing on this unique combination of illumination by companion starlight, and collision with a companion wind, to probe wind attributes over a range in wind strengths. Of particular interest is the hypothesis that the radial distribution of the wind acceleration is altered significantly, when the radiative transfer within the winds becomes optically thick to resonance scattering in multiple overlapping UV lines.

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