Detection of optical linear polarization in the SN 2006aj/XRF 060218
 non-spherical expansion

Gorosabel, J.; Ларионов, В. М.; Castro-Tirado, A. J.; Guziy, S.; Larionova, L. V.; Olmo, A. del; Martinez, M. A. G.; Cepa, J.; Cedrés, B.; Postigo, A. de Ugarte; Jelínek, M.; Bogdanov, O.; Llorente, A.

doi:10.1051/0004-6361:20066391

Cited by 32 publications

(44 citation statements)

References 27 publications

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“…In the illustrative models of Höflich (1991), the lower limit of p % 3% for choices in this range would imply an axis ratio E P 0:5 for an oblate spheroidal scattering atmosphere viewed edge-on. Explosion dates much earlier than 60 days prediscovery lead to extrapolated intrinsic continuum polarization values significantly larger than any yet observed in a supernova (Wang et al 2001;Gorosabel et al 2006); this suggests that our estimate of t exp based on spectral comparison with SN 1988Z (x 1) is reasonable. Figure 11 also shows that removing our preferred ISP choice, Case A, from the observed data leads immediately to an independent estimate of the explosion date for SN 1997eg as the epoch at which the intrinsic polarization decreases to zero (see Appendix for details).…”

Section: Interstellar Contributions and Limits On Intrinsic Polarizationmentioning

confidence: 57%

The Dual‐Axis Circumstellar Environment of the Type IIn Supernova 1997eg

Hoffman

Leonard

Chornock

et al. 2008

Astrophysical Journal

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We present multi-epoch spectral and spectropolarimetric observations of the Type IIn supernova (SN ) 1997eg that indicate the presence of a flattened disklike concentration of circumstellar material surrounding aspherical ejecta, with which the disk is misaligned. The polarization across the broad H , H , and He i k5876 lines of SN 1997eg forms closed loops when viewed in the Stokes q-u plane. Such loops occur when the geometrical symmetry of one or both of the Stokes parameters across spectral lines is broken, in this case most likely by occultation of the ejecta by the equatorial circumstellar matter concentration. The polarization of the narrow Balmer lines possesses an intrinsic axis that differs by 12 from that of the elongated ejecta and probably indicates the orientation of the disklike circumstellar material. The existence of two different axes of symmetry in SN 1997eg suggests that neither rotation of the progenitor nor the influence of a companion star can be the sole mechanism creating a preferred axis within the supernova system. Our model supports the emerging hypothesis that the progenitors of some Type IIn supernovae are luminous blue variable stars, whose presupernova mass eruptions form the circumstellar shells that physically characterize the SN IIn subclass. These conclusions, which are independent of interstellar polarization effects, would have been unobservable with only a single epoch of spectropolarimetry.

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Section: Interstellar Contributions and Limits On Intrinsic Polarizationmentioning

confidence: 57%

The Dual‐Axis Circumstellar Environment of the Type IIn Supernova 1997eg

Hoffman

Leonard

Chornock

et al. 2008

Astrophysical Journal

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“…SN 2008D/XT 080109 seemed to be surrounded by an external thick He mantle (Mazzali et al 2008;Modjaz et al 2009;Soderberg et al 2008;Tanaka et al 2009b), in contrast to the He-poor XRF 060218/SN 2006aj (Pian et al 2006;Soderberg et al 2006;Sollerman et al 2006). Given that the asphericity of core-collapse supernovae is more pronounced in the inner layers Wang & Wheeler (2008), this could explain to some degree the modest SN 2008D/XT 080109 intrinsic polarization in comparison to XRF 060218/SN 2006aj (Gorosabel et al 2006;Maund et al 2007).…”

Section: Discussionmentioning

confidence: 98%

“…The dominant intrinsic polarization in SNe is thought to originate by Thompson photon scattering through an aspherical photospheric expansion (Höflich 1991). If the SN photosphere projection on the sky plane is an ellipse, in general a non-cancelled linear polarization is expected perpendicular or parallel to the major axis (Kasen et al 2003).…”

Section: Introductionmentioning

confidence: 99%

Simultaneous polarization monitoring of supernovae SN 2008D/XT 080109 and SN 2007uy: isolating geometry from dust

Gorosabel

Postigo

Castro-Tirado

et al. 2010

A&A

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Context. The possible existence of a continuum encompassing the diversity of explosive stellar deaths, ranging from ordinary supernovae (SNe; lacking any sign of a relativistic outflow) to relativistic hypernovae associated with energetic long duration gamma-ray bursts (GRBs), is under intense debate. In this context, the supernova SN 2008D associated with the X-ray transient (XT) 080109 could represent a paradigmatic case, since it might exemplify a potential borderline transition event. Optical polarimetric studies could contribute to shed light on the different interpretations given in the literature for this supernova (hereafter, SN 2008D/XT 080109). Aims. The main aim is to infer geometric information of SN 2008D/XT 080109 through the study of the evolution of its linear optical polarization. We also report the polarization evolution of SN 2007uy, and discuss the properties of the host galaxy interstellar medium (ISM) towards the XT. The final goal is to compare the polarization properties, and therefore the geometries, of both SNe. Methods. We present a V-band linear polarization monitoring campaign carried out for SN 2008D/XT 080109 and SN 2007uy, which shone for weeks contemporaneously in NGC 2770. This fortunate coincidence brought us the opportunity to observe both objects simultaneously, and most importantly, with identical instrumental setups. The observations span 74.9 days, starting 3.6 days after the XT and are distributed in 11 visits. In addition we performed observations in the millimetre (mm) range in order to identify the dominant origin of the observed polarization. Results. We report positive linear polarization detections at several epochs for SN 2008D/XT 080109 at a level of ∼1%. For SN 2007uy the measured polarization is around ∼1.5%. In both cases the observed linear polarization seems dominated by the host galaxy interstellar polarization (HGIP), especially for the case of SN 2007uy. SN 2007uy shows Stokes parametres consistent with no time evolution, which could be described by the HGIP plus a constant eccentricity expansion on the sky plane. Over the course of our observations of SN 2007uy, we find that its total polarization signal does not change by more than 0.29% with a 90% confidence interval. Despite the dominant HGIP, a statistical analysis of the distribution of the SN 2008D/XT 080109 Stokes parametres suggests that it could show a possible intrinsic variable polarization component. Moreover, assuming the polarization signal from SN 2007uy is constant, we find that the temporal evolution of the intrinsic SN 2008D/XT 080109 polarization could be explained by an aspherical axisymmetric expansion with variable eccentricity, although other more complex geometric scenarios are also compatible with the data. We come to the same result even if we make no assumption on the SN 2007uy Stokes parametres, although at a lower significance level. Conclusions. We conclude that the data seem to suggest a potential symmetry axis for SN 2008D/XT 080109, which is reinforced when SN 2007...

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“…Gorosabel et al 2006) as they will be extremely useful to better understand the physics and geometry of the emission and to discriminate between energy models when explaining the fluctuations seen in the light curves. Optical photometric calibration is based on the observation of several standard fields (Landolt 1992) using the 1.54 m Danish at La Silla (Chile) and the 1.5 m telescope at Sierra Nevada Observatory (Spain).…”

Section: Discussionmentioning

confidence: 99%

Extensive multiband study of the X-ray rich GRB 050408

Postigo¹,

Фатхуллин

Jóhannesson

et al. 2006

A&A

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Aims. Understand the shape and implications of the multiband ligth curve of GRB 050408, an X-ray rich (XRR) burst. Methods. We present a multiband optical light curve, covering the time from the onset of the γ-ray event to several months after, when we only detect the host galaxy. Together with X-ray, millimetre and radio observations we compile what, to our knowledge, is the most complete multiband coverage of an XRR burst afterglow to date. Results. The optical and X-ray light curve is characterised by an early flattening and an intense bump peaking around 6 days after the burst onset. We explain the former by an off-axis viewed jet, in agreement with the predictions made for XRR by some models, and the latter with an energy injection equivalent in intensity to the initial shock. The analysis of the spectral flux distribution reveals an extinction compatible with a low chemical enrichment surrounding the burst. Together with the detection of an underlying starburst host galaxy we can strengthen the link between XRR and classical long-duration bursts.

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Detection of optical linear polarization in the SN 2006aj/XRF 060218 non-spherical expansion

Cited by 32 publications

References 27 publications

The Dual‐Axis Circumstellar Environment of the Type IIn Supernova 1997eg

The Dual‐Axis Circumstellar Environment of the Type IIn Supernova 1997eg

Simultaneous polarization monitoring of supernovae SN 2008D/XT 080109 and SN 2007uy: isolating geometry from dust

Extensive multiband study of the X-ray rich GRB 050408

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