Spectropolarimetry of SN 1987A: observations up to 1987 July 8

Cropper, Mark; Bailey, Jeremy; McCowage, J.; Cannon, R. D.; Couch, Warrick J.; Walsh, John R.; Strade, J. O.; Freeman, F. F.

doi:10.1093/mnras/231.3.695

Cited by 96 publications

(68 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Cropper et al (1988) observed q-u loops across both the H and Ca ii k8600 emission lines of the Type II SN 1987A. More recently, Wang et al (2003b) and Kasen et al (2003) found a similar effect in the Si ii and highly blueshifted Ca ii absorption lines of the Type Ia SN 2001el, while Maund et al (2007aMaund et al ( , 2007b observed q-u loops across the He i k5876 line in the Type Ib/c SN 2005bf and the broad Ca ii near-infrared triplet in the Type IIb SN 2001ig.…”

Section: Polarized Broad Lines and Loops In Q-u Spacementioning

confidence: 99%

“…Despite indications that the continuum and line polarization characteristics of all types of supernovae (SNe) can change dramatically with time (Cropper et al 1988;Wang et al 2003b; Leonard et al 2006), multi-epoch spectropolarimetry of SNe is still rare. We present here flux spectra at 12 epochs and polarization spectra at 3 epochs for the Type IIn (''narrow line'') SN 1997eg; this array of complementary observations makes it possible to construct a detailed picture of a core-collapse supernova and its surrounding CSM over the first 1.5 yr of evolution.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

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

Hoffman

Leonard

Chornock

et al. 2008

Astrophysical Journal

View full text Add to dashboard Cite

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.

show abstract

Section: Polarized Broad Lines and Loops In Q-u Spacementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Hoffman

Leonard

Chornock

et al. 2008

Astrophysical Journal

View full text Add to dashboard Cite

show abstract

“…Based on the optical polarization, several authors (e.g., Barrett 1988 ;Cropper et al 1988 ;Mendez et al 1988 ;Je †ery 1991) concluded that the ejecta were characterized by asymmetries of at least 10%. The radio images of SN 1987A (Gaensler et al 1997) appear relatively round, although asymmetries of up to 10% are not excluded.…”

Section: Constraint On Asymmetry Of the Explosionmentioning

confidence: 99%

SN 1993J VLBI. I. The Center of the Explosion and a Limit on Anisotropic Expansion

Bietenholz

Bartel

Rupen

2001

ApJ

View full text Add to dashboard Cite

Phase-referenced VLBI observations of supernova 1993J at 24 epochs, from 50 days after shock breakout to the present, allowed us to determine the coordinates of the explosion center relative to the quasistationary core of the host galaxy M81 with an accuracy of 45 kas and to determine the nominal proper motion of the geometric center of the radio shell with an accuracy of 9 kas yr~1. The uncertainties correspond to 160 AU for the position and 160 km s~1 for the proper motion at the distance of the source of 3.63 Mpc. After correcting for the expected galactic proper motion of the supernova around the core of M81 using H I rotation curves, we obtain a peculiar proper motion of the radio shell center of only 320^160 km s~1 to the south, which limits any possible one-sided expansion of the shell. We also Ðnd that the shell is highly circular, the outer contours in fact being circular to within 3%. Combining our proper-motion values with the degree of circular symmetry, we Ðnd that the expansion of the shock front from the explosion center is isotropic to within 5.5% in the plane of the sky. This is a more fundamental result on isotropic expansion than can be derived from the circularity of the images alone. The brightness of the radio shell, however, varies along the ridge and systematically changes with time. The degree of isotropy in the expansion of the shock front contrasts with the asymmetries and polarization found in optical spectral lines. Asymmetric density distributions in the ejecta, or more likely in the circumstellar medium, are favored to reconcile the radio and optical results. We see no sign of any disklike density distribution of the circumstellar material, with the average axis ratio of the radio shell of SN 1993J being less than 1.04.

show abstract

“…Arnett et al 1989;McCray 1993). Direct evidence for large scale instabilities came from HST observations, which have resolved the ejecta, and both the morphology and the kinematics have been discussed by Wang et al (2002) where it was claimed that the kinematics and morphology as seen in the optical indicated a bipolar structure, possibly consistent with a jet outflow and possibly connected to the asymmetry observed of the outer ejecta in early spectropolarimetry (Cropper et al 1988;Jeffery 1991;Wang & Wheeler 2008). The asymmetry in the explosion was suggested to have the same preferred overall axis as detected in early speckle interferometric observations (Meikle et al 1987;Nisenson et al 1987) and towards the first emission knot appearing in the equatorial ring (Sonneborn et al 1998;Pun et al 2002).…”

Section: Introductionmentioning

confidence: 99%

The 3-D structure of SN 1987A's inner ejecta

Kjaer¹,

Leibundgut

Fransson

et al. 2010

A&A

View full text Add to dashboard Cite

Context. Observing the inner ejecta of a supernova is possible only in a handful of nearby supernova remnants. The core-collapse explosion mechanism has been extensively explored in recent models and predict large asymmetries. SN 1987A is the first modern stellar explosion that has been continuously observed from its beginning to the supernova remnant phase. Twenty years after the explosion, we are now able to observe the three-dimensional spatially resolved inner ejecta of this supernova. Aims. Detailed mapping of newly synthesised material and its radioactive decay daughter products sheds light on the explosion mechanism. This may reveal the geometry of the explosion and its connection to the equatorial ring and the outer rings around SN 1987A. Methods. We have used integral field spectroscopy to image the supernova ejecta and the equatorial ring in the emission lines of [Si I] + [Fe II] (λ1.64 μm) and He I (λ2.058 μm). The spectral information can be mapped into a radial velocity image revealing the expansion of the ejecta both as projected onto the sky and perpendicular to the sky plane. Results. The inner ejecta are spatially resolved in a North-South direction and are clearly asymmetric. Like the ring emission, the northern parts of the ejecta are blueshifted, while the material projected to the South of the supernova centre is moving away from us. We argue that the bulk of the ejecta is situated in the same plane as defined by the equatorial ring and does not form a bipolar structure as has been suggested. The exact shape of the ejecta is modelled and we find that an elongated triaxial ellipsoid fits the observations best. The velocity measured in the [Si I] + [Fe II] line corresponds to ∼3000 km s −1 and is the same as the width of the IR [Fe II] line profiles during the first years. From our spectral analyses of the ejecta spectrum we find that most of the He I, [Si I] and [Fe I-II] emission originates in the core material which has undergone explosive nucleosynthesis. The He I emission may be the result of α-rich freeze-out if the positron energy is deposited locally. Conclusions. Our observations clearly indicate a non-symmetric explosion mechanism for SN 1987A. The elongation and velocity asymmetries point towards a large-scale spatial non-spherical distribution as predicted in recent explosion models. The orientation of the ejecta in the plane of the equatorial ring argues against a jet-induced explosion through the poles due to stellar rotation.

show abstract

Spectropolarimetry of SN 1987A: observations up to 1987 July 8

Cited by 96 publications

References 0 publications

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

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

SN 1993J VLBI. I. The Center of the Explosion and a Limit on Anisotropic Expansion

The 3-D structure of SN 1987A's inner ejecta

Contact Info

Product

Resources

About