A spectropolarimetric survey of northern hemisphere Wolf–Rayet stars

Harries, Tim J.; Hillier, D. J.; Howarth, Ian D.

doi:10.1046/j.1365-8711.1998.01508.x

Cited by 111 publications

(147 citation statements)

References 27 publications

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“…stars (Schulte-Ladbeck et al 1991;Harries et al 1998). In our simulation, this reduced polarisation across the line is a signature of the distinct formation of the continuum and the line.…”

Section: Polarisation Calculationsmentioning

confidence: 99%

Numerical simulations of superluminous supernovae of type IIn

Dessart¹,

Audit²,

Hillier³

2015

Monthly Notices of the Royal Astronomical Society

123

172

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We present numerical simulations that include 1-D Eulerian multi-group radiationhydrodynamics, 1-D non-Local-Thermodynamic-Equilibrium (non-LTE) radiative transfer, and 2-D polarised radiative transfer for super-luminous interacting supernovae (SNe). Our reference model is a ∼10 M ⊙ inner shell with 10 51 erg ramming into a ∼3 M ⊙ cold outer shell (the circumstellar-medium, or CSM) that extends from 10 15 to 2×10 16 cm and moves at 100 km s −1 . We discuss the light curve evolution, which cannot be captured adequately with a grey approach. In these interactions, the shock-crossing time through the optically-thick CSM is much longer than the photon diffusion time. Radiation is thus continuously leaking from the shock through the CSM, in disagreement with the shell-shocked model that is often invoked. Our spectra redden with time, with a peak distribution in the near-UV during the first month gradually shifting to the optical range over the following year. Initially Balmer lines exhibit a narrow line core and the broad line wings that are characteristic of electron scattering in the SNe IIn atmospheres (CSM). At later times they also exhibit a broad blue shifted component which arises from the cold dense shell. Our model results are broadly consistent with the bolometric light curve and spectral evolution observed for SN 2010jl. Invoking a prolate pole-to-equator density ratio in the CSM, we can also reproduce the ∼2% continuum polarisation, and line depolarisation, observed in SN 2010jl. By varying the inner shell kinetic energy and the mass and extent of the outer shell, a large range of peak luminosities and durations, broadly compatible with super-luminous SNe IIn like 2010jl or 2006gy, can be produced.

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“…stars (Schulte-Ladbeck et al 1991;Harries et al 1998). In our simulation, this reduced polarisation across the line is a signature of the distinct formation of the continuum and the line.…”

Section: Polarisation Calculationsmentioning

confidence: 99%

Numerical simulations of superluminous supernovae of type IIn

Dessart¹,

Audit²,

Hillier³

2015

Monthly Notices of the Royal Astronomical Society

123

172

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“…The observations of iPTF 13bvn are also roughly consistent with this model. Spectropolarimetric surveys of galactic and Large Magellenic Cloud (LMC) Wolf-Rayet stars show that the majority (∼80%) are slow rotating spherically symmetric stars (Harries et al 1998;Vink 2007;St-Louis 2011). Based on geometry alone, the progenitor of iPTF 13bvn is unlikely to have been a slowly rotating WR star.…”

Section: Polarimetric Evolution and The Implications For The Progenitmentioning

confidence: 99%

Spectropolarimetry of the Type Ib Supernova iPTF 13bvn: revealing the complex explosion geometry of a stripped-envelope core-collapse supernova

Reilly

Maund

Baade

et al. 2016

Mon. Not. R. Astron. Soc.

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We present six epochs of spectropolarimetric observations and one epoch of spectroscopy of the Type Ib SN iPTF 13bvn. The epochs of these observations correspond to −10 to +61 days with respect to the r-band light curve maximum. The continuum is intrinsically polarised to the 0.2-0.4% level throughout the observations, implying asphericities of ∼10% in the shape of the photosphere. We observe significant line polarisation associated with the spectral features of Ca II IR3, He I/Na I D, He I λλ6678, 7065, Fe II λ4924 and O I λ7774. We propose that an absorption feature at ∼ 6200Å, usually identified as Si II λ6355, is most likely to be high velocity Hα at −16, 400km s −1 . Two distinctly polarised components, separated in velocity, are detected for both He I/Na I D and Ca II IR3 , indicating the presence of two discrete line forming regions in the ejecta in both radial velocity space and in the plane of the sky. We use the polarisation of He I λ5876 as a tracer of sources of non-thermal excitation in the ejecta; finding that the bulk of the radioactive nickel was constrained to lie interior to ∼ 50 − 65% of the ejecta radius. The observed polarisation is also discussed in the context of the possible progenitor system of iPTF 13bvn, with our observations favouring the explosion of a star with an extended, distorted envelope rather than a compact Wolf-Rayet star.

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“…If layers in which electron scattering occurs become axisymmetric, the departure from spherical symmetry may be detected with linear polarimetry via the socalled line effect (e.g. Harries et al 1998), i.e. an enhanced polarization of the continuum radiation relative to that of emission lines.…”

Section: Introductionmentioning

confidence: 99%

The impact of rotation on the line profiles of Wolf-Rayet stars

Shenar

Hamann

Todt

2014

A&A

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Context. Massive Wolf-Rayet stars are recognized today to be in a very common, but short, evolutionary phase of massive stars. While our understanding of Wolf-Rayet stars has increased dramatically over the past decades, it remains unclear whether rapid rotators are among them. There are various indications that rapidly rotating Wolf-Rayet stars should exist. Unfortunately, due to their expanding atmospheres, rotational velocities of Wolf-Rayet stars are very difficult to measure. However, recently observed spectra of several Wolf-Rayet stars reveal peculiarly broad and round emission lines. Could these spectra imply rapid rotation? Aims. In this work, we model the effects of rotation on the atmospheres of Wolf-Rayet stars. We further investigate whether the peculiar spectra of five Wolf-Rayet stars may be explained with the help of stellar rotation, infer appropriate rotation parameters, and discuss the implications of our results. Methods. We make use of the Potsdam Wolf-Rayet (PoWR) non-LTE model atmosphere code. Since the observed spectra of WolfRayet stars are mainly formed in their expanding atmospheres, rotation must be accounted for with a 3D integration scheme of the formal integral. For this purpose, we assume a rotational velocity field consisting of an inner co-rotating domain and an outer domain, where the angular momentum is conserved. Results. We find that rotation can reproduce the unique spectra analyzed here. However, the inferred rotational velocities at the stellar surface are large (∼200 km s −1 ), and the inferred co-rotation radii (∼10R * ) suggest the existence of very strong photospheric magnetic fields (∼20 kG).

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A spectropolarimetric survey of northern hemisphere Wolf–Rayet stars

Cited by 111 publications

References 27 publications

Numerical simulations of superluminous supernovae of type IIn

Numerical simulations of superluminous supernovae of type IIn

Spectropolarimetry of the Type Ib Supernova iPTF 13bvn: revealing the complex explosion geometry of a stripped-envelope core-collapse supernova

The impact of rotation on the line profiles of Wolf-Rayet stars

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