Discovery of a strong magnetic field on the O star HD 191612: new clues to the future of θ1 Orionis C

Donati, J.‐F.; Howarth, I. D.; Bouret, J. C.; Petit, P.; Catala, C.; Landstreet, J. D.

doi:10.1111/j.1745-3933.2005.00115.x

Cited by 173 publications

(238 citation statements)

References 23 publications

Supporting

Mentioning

223

Contrasting

Unclassified

Order By: Relevance

“…Summary of LSD line mask properties including the effective temperature, the logarithmic surface gravity and the number of spectral lines used. (Donati et al 2006) located at the 3.6m Canada-France-Hawaii Telescope (CFHT, Hawaii) and in one run with Narval (TBL, France), twin of ESPaDOnS, in 2014. In both instruments, the spectral range covers a large part of the visible domain i.e.…”

Section: The Samplementioning

confidence: 99%

First detection of surface magnetic fields in post-AGB stars: the cases of U Monocerotis and R Scuti

Sabin¹,

Wade²,

Lèbre³

2014

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

While several observational investigations have revealed the presence of magnetic fields in the circumstellar envelopes, jets and outflows of post-Asymptotic Giant Branch stars (PAGBs) and planetary nebulae (PNe), none has clearly demonstrated their presence at the stellar surface. The lack of information on the strength of the surface magnetic fields prevents us from performing any thorough assessment of their dynamic capability (i.e. material mixing, envelope shaping, etc). We present new high resolution spectropolarimetric (Stokes V ) observations of a sample of PAGB stars, realised with the instruments ESPaDOnS and Narval, where we searched for the presence of photospheric magnetic fields. Out of the seven targets investigated the RV Tauri stars U Mon and R Sct display a clear Zeeman signature and return a definite detection after performing a least squares deconvolution (LSD) analysis. The remaining five PAGBs show no significant detection. We derived longitudinal magnetic fields of 10.2 ± 1.7 G for U Mon and 0.6 ± 0.6 G for R Sct. In both cases the Stokes profiles point towards an interaction of the magnetic field with the atmosphere dynamics. This first discovery of weak magnetic fields (i.e. ∼10 gauss level) at the stellar surface of PAGB stars opens the door to a better understanding of magnetism in evolved stars.

show abstract

Section: The Samplementioning

confidence: 99%

First detection of surface magnetic fields in post-AGB stars: the cases of U Monocerotis and R Scuti

Sabin¹,

Wade²,

Lèbre³

2014

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

show abstract

“…The highest detected (surface dipole) magnetic field strengths are B max ∼ 10 3 G in O stars (radius R ∼ 10 R , Donati et al 2002Donati et al , 2006Petit et al 2008), B max ∼ 3 × 10 4 G in chemicallly peculiar A and B stars (Ap/Bp stars, R ∼ 3 R , Mathys et al 1997;Bagnulo et al 1999), B max ∼ 10 9 G in white dwarfs (R ∼ 10 4 km, Schmidt et al 2003), and B max ∼ 10 15 G in "magnetars", a subclass of strongly magnetized neutron stars (R ∼ 10 km, Kouveliotou et al 1998;Woods et al 1999), in all cases yielding very similar total magnetic fluxes, Φ max = πR 2 B max ∼ 10 27.5 G cm 2 . This coincidence has often been interpreted as an argument for flux freezing during stellar evolution (Ruderman 1972;Reisenegger 2001bReisenegger , 2003Ferrario & Wickramasinghe 2005a,b, 2006, although its feasibility has been called into question (Thompson & Duncan 1993;Spruit 2008).…”

Section: Introductionmentioning

confidence: 99%

Stable magnetic equilibria and their evolution in the upper main sequence, white dwarfs, and neutron stars

Reisenegger

2009

A&A

111

141

View full text Add to dashboard Cite

Context. Long-lived, large-scale magnetic field configurations exist in upper main sequence, white dwarf, and neutron stars. Externally, these fields have a strong dipolar component, while their internal structure and evolution are uncertain but highly relevant to several problems in stellar and high-energy astrophysics. Aims. We discuss the main properties expected for the stable magnetic configurations in these stars from physical arguments and the ways these properties may determine the modes of decay of these configurations. Methods. We explain and emphasize the likely importance of the non-barotropic, stable stratification of matter in all these stars (due to entropy gradients in main-sequence envelopes and white dwarfs, due to composition gradients in neutron stars). We first illustrate it in a toy model involving a single, azimuthal magnetic flux tube. We then discuss the effect of stable stratification or its absence on more general configurations, such as axisymmetric equilibria involving poloidal and toroidal field components. We argue that the main mode of decay for these configurations are processes that lift the constraints set by stable stratification, such as heat diffusion in main-sequence envelopes and white dwarfs, and beta decays or particle diffusion in neutron stars. We estimate the time scales for these processes, as well as their interplay with the cooling processes in the case of neutron stars. Results. Stable magneto-hydrostatic equilibria appear to exist in stars whenever the matter in their interior is stably stratified (not barotropic). These equilibria are not force-free and not required to satisfy the Grad-Shafranov equation, but they do involve both toroidal and poloidal field components. In main sequence stars with radiative envelopes and in white dwarfs, heat diffusion is not fast enough to make these equilibria evolve over the stellar lifetime. In neutron stars, a strong enough field might decay by overcoming the compositional stratification through beta decays (at the highest field strengths) or through ambipolar diffusion (for somewhat weaker fields). These processes convert magnetic energy to thermal energy, and they occur at significant rates only once the latter is less than the former; therefore, they substantially delay the cooling of the neutron star, while slowly decreasing its magnetic energy.

show abstract

“…Donati et al 2006;Martins et al 2010;Wade et al 2012b). Even before these direct detections, an oblique dipole field E-mail: VPetit@fit.edu † FRS-FNRS research associate was suspected in the prototype magnetic O star, θ 1 Ori C, notably due to its luminous, rotationally modulated X-ray emission (Stahl et al 1996;Gagné et al 1997).…”

Section: Introductionmentioning

confidence: 99%

X-ray emission from the giant magnetosphere of the magnetic O-type star NGC 1624-2

Petit

Cohen

Wade

et al. 2015

Mon. Not. R. Astron. Soc.

View full text Add to dashboard Cite

We observed NGC 1624-2, the O-type star with the largest known magnetic field (B p ∼ 20 kG), in X-rays with the ACIS-S camera onboard the Chandra X-ray Observatory. Our two observations were obtained at the minimum and maximum of the periodic Hα emission cycle, corresponding to the rotational phases where the magnetic field is the closest to equator-on and pole-on, respectively. With these observations, we aim to characterise the star's magnetosphere via the X-ray emission produced by magnetically confined wind shocks. Our main findings are: (i) The observed spectrum of NGC 1624-2 is hard, similar to the magnetic O-type star θ 1 Ori C, with only a few photons detected below 0.8 keV. The emergent X-ray flux is 30% lower at the Hα minimum phase. (ii) Our modelling indicated that this seemingly hard spectrum is in fact a consequence of relatively soft intrinsic emission, similar to other magnetic Of?p stars, combined with a large amount of local absorption (∼1-3×10 22 cm −2 ). This combination is necessary to reproduce both the prominent Mg and Si spectral features, and the lack of flux at low energies. NGC 1624-2 is intrinsically luminous in X-rays (log L em X ∼33.4) but 70-95% of the X-ray emission produced by magnetically confined wind shocks is absorbed before it escapes the magnetosphere (log L ISMcor X ∼32.5). (iii) The high X-ray luminosity, its variation with stellar rotation, and its large attenuation are all consistent with a large dynamical magnetosphere with magnetically confined wind shocks.

show abstract

Discovery of a strong magnetic field on the O star HD 191612: new clues to the future of θ1 Orionis C

Cited by 173 publications

References 23 publications

First detection of surface magnetic fields in post-AGB stars: the cases of U Monocerotis and R Scuti

First detection of surface magnetic fields in post-AGB stars: the cases of U Monocerotis and R Scuti

Stable magnetic equilibria and their evolution in the upper main sequence, white dwarfs, and neutron stars

X-ray emission from the giant magnetosphere of the magnetic O-type star NGC 1624-2

Contact Info

Product

Resources

About