scholarly journals The MiMeS survey of magnetism in massive stars: magnetic properties of the O-type star population

2019 ◽  
Vol 489 (4) ◽  
pp. 5669-5687 ◽  
Author(s):  
V Petit ◽  
G A Wade ◽  
F R N Schneider ◽  
L Fossati ◽  
K Kamp ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Massive Stars ◽  
Field Function ◽  
Apparent Lack ◽  
Upper Limits ◽  
Noise Statistics ◽  
Polarization Spectra ◽  
Stars Survey ◽  
Rule Out

ABSTRACT In this paper, we describe an analysis of the MiMeS (Magnetism in Massive Stars) survey of O-type stars to explore the range of dipolar field strengths permitted by the polarization spectra that do not yield a magnetic detection. We directly model the Stokes V profiles with a dipolar topology model using Bayesian inference. The noise statistics of the Stokes V profiles are in excellent agreement with those of the null profiles. Using a Monte Carlo approach, we conclude that a model in which all the stars in our sample were to host 100 G, dipolar magnetic field can be ruled out by the MiMeS data. Furthermore, if all the stars with no detection were to host a magnetic field just below their detection limit, the inferred distribution in strength of these undetected fields would be distinct from the known distribution in strength of the known magnetic O-type stars. This indicates that the 'initial magnetic field function' (IBF) is likely bimodal – young O-type stars are expected to have either weak/absent magnetic fields or strong magnetic fields. We also find that better upper limits, by at least a factor of 10, would have been necessary to rule out a detection bias as an explanation for the apparent lack of evolved main-sequence magnetic O-type stars reported in the literature, and we conclude that the MiMeS survey cannot confirm or refute a magnetic flux decay in O-type stars.

scholarly journals On the stability of a general magnetic field topology in stellar radiative zones

2019 ◽  
Vol 82 ◽  
pp. 365-371
Author(s):  
K. Augustson ◽  
S. Mathis ◽  
A. Strugarek
Keyword(s):  
Magnetic Field ◽  
Global Change ◽  
Magnetic Fields ◽  
Potential Energy ◽  
Massive Stars ◽  
Spherical Geometry ◽  
Stable Region ◽  
Magnetic Field Topology ◽  
The Stability ◽  
The Magnetic Field

This paper provides a brief overview of the formation of stellar fossil magnetic fields and what potential instabilities may occur given certain configurations of the magnetic field. One such instability is the purely magnetic Tayler instability, which can occur for poloidal, toroidal, and mixed poloidal-toroidal axisymmetric magnetic field configurations. However, most of the magnetic field configurations observed at the surface of massive stars are non-axisymmetric. Thus, extending earlier studies in spherical geometry, we introduce a formulation for the global change in the potential energy contained in a convectively-stable region for both axisymmetric and non-axisymmetric magnetic fields.

scholarly journals Magnetic fields of massive stars

2010 ◽  
Vol 6 (S272) ◽  
pp. 196-197
Author(s):  
Swetlana Hubrig ◽  
Michel Curé ◽  
Ilya Ilyin ◽  
Markus Schöller
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Massive Stars ◽  
Low Resolution ◽  
Echelle Spectrograph ◽  
Optical Telescope

AbstractWe recently carried out a spectropolarimetric study of a sample of massive O-type stars and pulsating β Cephei stars using the SOFIN echelle spectrograph at the 2.56 m Nordic Optical Telescope and the low-resolution FORS 2 spectrograph at the VLT in spectropolarimetric mode. The sample consists of massive stars already detected as magnetic in the course of our previous low-resolution polarimetric observations with FORS 1 and a few O-type stars with magnetic field detections reported in the literature.

scholarly journals A search for strong magnetic fields in massive and very massive stars in the Magellanic Clouds

2020 ◽  
Vol 635 ◽  
pp. A163
Author(s):  
S. Bagnulo ◽  
G. A. Wade ◽  
Y. Nazé ◽  
J. H. Grunhut ◽  
M. E. Shultz ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Longitudinal Magnetic Field ◽  
Massive Stars ◽  
Magellanic Clouds ◽  
Dipolar Field ◽  
Strong Magnetic Fields ◽  
Ob Stars ◽  
Stellar Magnetic Fields ◽  
The Universe

Despite their rarity, massive stars dominate the ecology of galaxies via their strong, radiatively-driven winds throughout their lives and as supernovae in their deaths. However, their evolution and subsequent impact on their environment can be significantly affected by the presence of a magnetic field. While recent studies indicate that about 7% of OB stars in the Milky Way host strong, stable, organised (fossil) magnetic fields at their surfaces, little is known about the fields of very massive stars, nor the magnetic properties of stars outside our Galaxy. We aim to continue searching for strong magnetic fields in a diverse set of massive and very massive stars (VMS) in the Large and Small Magellanic Clouds (LMC/SMC), and we evaluate the overall capability of FORS2 to usefully search for and detect stellar magnetic fields in extra-galactic environments. We have obtained FORS2 spectropolarimetry of a sample of 41 stars, which principally consist of spectral types B, O, Of/WN, WNh, and classical WR stars in the LMC and SMC. Four of our targets are Of?p stars; one of them was just recently discovered. Each spectrum was analysed to infer the longitudinal magnetic field. No magnetic fields were formally detected in our study, although Bayesian statistical considerations suggest that the Of?p star SMC 159-2 is magnetic with a dipolar field of the order of 2.4–4.4 kG. In addition, our first constraints of magnetic fields in VMS provide interesting insights into the formation of the most massive stars in the Universe.

scholarly journals New observations of NGC 1624-2 reveal a complex magnetospheric structure and underlying surface magnetic geometry*

2020 ◽  
Author(s):  
A David-Uraz ◽  
V Petit ◽  
M E Shultz ◽  
A W Fullerton ◽  
C Erba ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Time Series ◽  
Magnetic Fields ◽  
Hubble Space Telescope ◽  
Massive Stars ◽  
Complex Structure ◽  
Type Star ◽  
Origin And Evolution ◽  
Field Geometry

Abstract NGC 1624-2 is the most strongly magnetized O-type star known. Previous spectroscopic observations of this object in the ultraviolet provided evidence that it hosts a large and dense circumstellar magnetosphere. Follow-up observations obtained with the Hubble Space Telescope not only confirm that previous inference, but also suggest that NGC 1624-2’s magnetosphere has a complex structure. Furthermore, an expanded spectropolarimetric time series shows a potential departure from a dipolar magnetic field geometry, which could mean that the strongest field detected at the surface of an O-type star is also topologically complex. This result raises important questions regarding the origin and evolution of magnetic fields in massive stars.

scholarly journals SGRs and AXPs: Evidence for Delayed Amplification of Magnetic Field after Neutron Star Formation?

2009 ◽  
Vol 2009 ◽  
pp. 1-8 ◽  
Author(s):  
Denis Leahy ◽  
Rachid Ouyed
Keyword(s):  
Magnetic Field ◽  
Neutron Star ◽  
Magnetic Fields ◽  
Neutron Stars ◽  
Birth Rate ◽  
Massive Stars ◽  
Robust Estimator ◽  
High Magnetic Fields ◽  
Field Amplification ◽  
Kolmogorov Smirnov

We present new analysis of the birth rate of AXPs and SGRS and their associated SNRs. Using Kolmogorov-Smirnov statistics together with parametric fits based on a robust estimator, we find a birth rate of ∼1/(1000 years) for AXPs/SGRs and their associated SNRs. These high rates suggest that all massive stars (greater than ∼(23–32)M⊙) give rise to remnants with magnetar-like fields. Observations indicate a limited fraction of high magnetic fields in these progenitors; thus our study is suggestive of magnetic field amplification. Dynamo mechanisms during the birth of the neutron stars require spin rates much faster than either observations or theory indicate. We propose that massive stars produce neutron stars with normal (∼1012 G) magnetic fields, which are then amplified to1014-1015 G after a delay of hundreds of years. The amplification is speculated to be a consequence of color ferromagnetism and to occur with a delay after the neutron star core reaches quark deconfinement density (i.e., the quark-nova scenario). The delayed amplification allows one to interpret simultaneously the high birth rate and high magnetic fields of AXPs/SGRs and their link to massive stars.

scholarly journals Magnetic Field - Stellar Winds Interaction

2014 ◽  
Vol 9 (S307) ◽  
pp. 321-329
Author(s):  
Asif ud-Doula
Keyword(s):  
Magnetic Field ◽  
Numerical Modeling ◽  
Magnetic Fields ◽  
Massive Star ◽  
Massive Stars ◽  
Complex Interaction ◽  
Stellar Winds ◽  
X Ray ◽  
Mhd Simulations ◽  
Non Linear

AbstractAs per the recent study by the MiMeS collaboration, only about 10% of massive stars possess organized global magnetic fields, typically dipolar in nature. The competition between such magnetic fields and highly non-linear radiative forces that drive the stellar winds leads to a highly complex interaction. Such an interplay can lead to a number of observable phenomena, e.g. X-ray, wind confinement, rapid stellar spindown. However, due to its complexity, such an interaction cannot usually be modeled analytically, instead numerical modeling becomes a necessary tool. In this talk, I will discuss how numerical magnetohydrodynamic (MHD) simulations are employed to understand the nature of such magnetized massive star winds.

scholarly journals The Sun's gravitational quadrupole moment inferred from the fine structure of the acoustic and gravity normal mode spectra of the Sun

1986 ◽  
Vol 114 ◽  
pp. 345-354
Author(s):  
H. A. Hill ◽  
G. R. Rabaey ◽  
R. D. Rosenwald
Keyword(s):  
Magnetic Field ◽  
Fine Structure ◽  
Angular Velocity ◽  
Magnetic Fields ◽  
Velocity Distribution ◽  
Quadrupole Moment ◽  
The Sun ◽  
Upper Limits ◽  
Gravity Mode ◽  
Theories Of Gravitation

The fine structure of the acoustic and gravity mode multiplets of the Sun have been analyzed to infer the internal rotation of the Sun and upper limits of the internal magnetic field. Observed fine structure for 137 multiplets has been obtained (Hill 1984b, 1985a, 1985b) and the fine structure has been examined for dependence on the angular order, m, of the modes. The inferred angular velocity distribution, together with the estimated upper limits on the internal magnetic fields, yields a gravitational quadrupole moment, J2, of ≈7.7 × 10−6. This result is consistent with the result obtained by Hill, Bos and Goode (1982) and has important implications for planetary tests of theories of gravitation.

Magnetic massive stars in star forming regions

2018 ◽  
Vol 14 (A30) ◽  
pp. 132-132
Author(s):  
Swetlana Hubrig ◽  
Markus Schöller ◽  
Silva P. Järvinen
Keyword(s):  
Magnetic Field ◽  
Star Formation ◽  
Magnetic Fields ◽  
Active Sites ◽  
Massive Stars ◽  
High Mass ◽  
Mass Star ◽  
Star Forming ◽  
Star Forming Regions ◽  
Gas Cloud

AbstractOne idea for the origin of magnetic fields in massive stars suggests that the magnetic field is the fossil remnant of the Galactic ISM magnetic field, amplified during the collapse of the magnetised gas cloud. A search for the presence of magnetic fields in massive stars located in active sites of star formation led to the detection of rather strong magnetic fields in a few young stars. Future spectropolarimetric observations are urgently needed to obtain insights into the mechanisms that drive the generation of kG magnetic fields during high-mass star formation.

scholarly journals The magnetic field of ζ Ori A

2014 ◽  
Vol 9 (S307) ◽  
pp. 367-368 ◽  
Author(s):  
A. Blazère ◽  
C. Neiner ◽  
J-C. Bouret ◽  
A. Tkachenko ◽  
Keyword(s):  
Magnetic Field ◽  
Magnetic Properties ◽  
Magnetic Fields ◽  
Significant Role ◽  
Massive Stars ◽  
The Magnetic Field

AbstractMagnetic fields play a significant role in the evolution of massive stars. About 7% of massive stars are found to be magnetic at a level detectable with current instrumentation (Wade et al. 2013) and only a few magnetic O stars are known. Detecting magnetic field in O stars is particularly challenging because they only have few, often broad, lines to measure the field, which leads to a deficit in the knowledge of the basic magnetic properties of O stars. We present new spectropolarimetric Narval observations of ζ Ori A. We also provide a new analysis of both the new and older data taking binarity into account. The aim of this study was to confirm the presence of a magnetic field in ζ Ori A. We identify that it belongs to ζ Ori Aa and characterize it.

scholarly journals Searching for weak or complex magnetic fields in polarized spectra of Rigel

2010 ◽  
Vol 6 (S272) ◽  
pp. 212-213 ◽  
Author(s):  
Matthew Shultz ◽  
Gregg A. Wade ◽  
Coralie Neiner ◽  
Nadine Manset ◽  
Véronique Petit ◽  
...  
Keyword(s):  
Magnetic Field ◽  
High Resolution ◽  
Magnetic Fields ◽  
Massive Stars ◽  
Photospheric Magnetic Field ◽  
Core Collapse ◽  
Core Collapse Supernova ◽  
Large Program

AbstractSeventy-eight high-resolution Stokes V, Q and U spectra of the B8Iae supergiant Rigel were obtained with the ESPaDOnS spectropolarimeter at CFHT and its clone NARVAL at TBL in the context of the Magnetism in Massive Stars (MiMeS) Large Program, in order to scrutinize this core-collapse supernova progenitor for evidence of weak and/or complex magnetic fields. In this paper we describe the reduction and analysis of the data, the constraints obtained on any photospheric magnetic field, and the variability of photospheric and wind lines.

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