Spectropolarimetry of SN 1993J in NGC 3031

Trammell, Susan R.; Hines, Dean C.; Wheeler, J. C.

doi:10.1086/186986

Cited by 88 publications

(93 citation statements)

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“…The line forming region is still within the hydrogen rich part of the envelope 3 weeks after the explosion, although the continuum may form in deeper layers. Although the residual polarization across Hα is not zero, the interstellar component derived herein is consistent with that deduced by Trammell et al (1993). The power of this technique for investigating the structure of other SN II, as a method for independently deriving the interstellar polarization, and the implications of these results on the use of SN II to determine distances through the Baade-Wesselink method are discussed.…”

supporting

confidence: 78%

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Analysis of the Polarization and Flux Spectra of SN 1993J

Hoêflich

Wheeler²,

Hines

et al. 1996

ApJ

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105

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Synthetic polarization and flux spectra are presented for aspherical, electron scattering-dominated photospheres of Type II supernovae (SN II) in general and the specific case of SN 1993J. Monte Carlo calculations are based on the following assumptions: a) ellipsoidal envelopes with power law density profiles; b) occupation numbers given by local thermodynamical equilibrium (LTE); c) pure electron scattering for continuum opacities; d) lines treated in a Sobolev approximation with an assumed constant thermalization fraction; e) line transitions result in depolarization; and f) the temperature structure is given by a gray extended atmosphere.The observed luminosity of a Type II supernova depends on the unknown inclination angle i. Spectral analysis alone will fail to detect even strong deviations from spherical symmetry. Line scattering depolarizes incident polarized light, but the residual intrinsic polarization does not completely vanish because of electron scattering effects that depend on the electron density distribution. By combining results on the polarization and velocity structure of the emission lines, and the degree of polarization in the continuum, we place strong constraints on the degree of asphericity, the inclination of the system and the electron density distribution. In addition, since the problem is over constrained, we can independently test for the contribution to the polarization caused by aligned interstellar grains between the SN and earth.These modelling techniques have been applied to SN1993J. Both the flux spectra and the percentage of polarization as a function of wavelength can be reproduced by an aspherical model with an axis ratio of 0.6, radial electron densities proportional to r −5 and an effective temperature of 4800 K. In an oblate model, SN 1993J is seen almost equator on. The line forming region is still within the hydrogen rich part of the envelope 3 weeks after the explosion, although the continuum may form in deeper layers. Although the residual polarization across Hα is not zero, the interstellar component derived herein is consistent with that deduced by Trammell et al. (1993). The power of this technique for investigating the structure of other SN II, as a method for independently deriving the interstellar polarization, and the implications of these results on the use of SN II to determine distances through the Baade-Wesselink method are discussed.-2 -

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supporting

confidence: 78%

“…As the polarization is a (pseudo)vector, the size and temporal behavior of the intrinsic component of the polarization depend sensitively on the correction for the interstellar component. An independent check of the value of the ISM polarization derived by Trammell et al (1993) is appropriate.…”

Section: Introductionmentioning

confidence: 99%

Analysis of the Polarization and Flux Spectra of SN 1993J

Hoêflich

Wheeler²,

Hines

et al. 1996

ApJ

Self Cite

105

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“…Tidal distortion of the progenitor star as a result of binary interaction has been discussed as the source of the observed polarisation in numerous Type IIb SNe including SN 1993J and recently in SN 2011dh by Mauerhan et al (2015). Tran et al (1997) and Trammell et al (1993) observed high levels of continuum polarisation in SN 1993J, of p ∼1-2% which exhibited no strong temporal dependence. Höflich (1995) found that this could be produced by an oblate model with an axis ratio of 0.6, while Tran et al and Trammell et al argued that the lack of strong temporal change in the polarisation was an indication that the asymmetry was not intrinsic to the explosion but due to a distorted envelope.…”

Section: Polarimetric Evolution and The Implications For The Progenitmentioning

confidence: 97%

“…This implies that the inner ejecta are more spherical than the outer layers. Conversely, core collapse SNe (CCSNe) such as SNe 1993J, 2002ap, 2005bf and 2008D were observed to be highly polarised across particular lines and show asymmetries in the shape of the photosphere on the order of ∼10% (Trammell et al 1993;Tran et al 1997;Kawabata et al 2002;Wang et al 2003;Maund et al 2007bMaund et al , 2009. In CCSNe, the degree of asymmetry appears to increase as the photosphere recedes into the deeper layers of the ejecta.…”

Section: Introductionmentioning

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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“…The data are consistent with models in which the polarization is produced by an asymmetric He core configuration of material. Trammell, Hines, & Wheeler (1993; see also Höflich 1995, Höflich et al 1996 also found that SN 1993J was polarized and intrinsically asymmetric, although their derived level of interstellar polarization differed from that derived with the more extensive data set of Tran et al (1997).…”

Section: Sne Iibmentioning

confidence: 92%