2002PASP..114.1333L -
Publ. Astron. Soc. Pac., 114, 1333-1348 (2002/December-0)
Photospheric-phase spectropolarimetry and nebular-phase spectroscopy of the peculiar type Ic Supernova 2002ap.
LEONARD D.C., FILIPPENKO A.V., CHORNOCK R. and FOLEY R.J.
Abstract (from CDS):
The early-time optical spectrum of the Type Ic supernova (SN) 2002ap was characterized by unusually broad features, leading some authors to designate it a ``hypernova.'' We present optical spectropolarimetry of this object 16 and 37 days after the estimated date of explosion. After correcting for interstellar polarization, we find evidence for a high level of intrinsic continuum polarization at both epochs: p≳1.3% on day 16 and p≳1.0% on day 37. Prominent line polarization is also seen, especially in the trough of the Ca II near-infrared triplet during the second epoch. When interpreted in terms of the oblate, electron-scattering model atmospheres of Höflich, our results imply an asymmetry of at least 20% (day 16) and 17% (day 37). The data suggest a fair degree of axisymmetry, although the polarization angle of the dominant polarization axes are different by about 55° between the two epochs, implying a complex morphology for the thinning ejecta. In particular, there exists some spectropolarimetric evidence for a different distribution of Ca relative to iron-group elements. We also present flux spectra of SN 2002ap taken 131 and 140 days after the explosion. The spectra are characterized by a very weak continuum and broad emission lines, indicating that SN 2002ap has entered the nebular phase. The spectral features are substantially similar to those of ``normal'' SNe Ic in the nebular phase, and the emission lines are not significantly broader. However, some of the broad lines are very sharply peaked and may possess a narrow component (probably unresolved by our spectra, FWHM≲400 km/s) that is redshifted by ∼580 km/s with respect to the systemic velocity of the host galaxy.
Abstract Copyright:
∼
Journal keyword(s):
Polarization - supernovae: individual (SN 2002ap) - Techniques: Polarimetric
Simbad objects:
24
Full paper
View the references in ADS
To bookmark this query, right click on this link: simbad:2002PASP..114.1333L and select 'bookmark this link' or equivalent in the popup menu