Astronomy and Astrophysics – Astrophysics
Scientific paper
2002-06-21
Astrophys.J. 592 (2003) 457-466
Astronomy and Astrophysics
Astrophysics
AASTeX, 29 pages, 4 postscript figures, submitted to Apj, June 19, 2002
Scientific paper
10.1086/375576
High-quality spectropolarimetric data of SN 2002ap were obtained with the ESO Very Large Telescope Melipal (+ FORS1) at 3 epochs that correspond to -6, -2, and +1 days for a V maximum of 9 Feb 2002. The polarization spectra show three distinct broad features at 400, 550, and 750 nm that evolve in shape, amplitude and orientation in the Q-U plane. The continuum polarization grows from nearly zero to ~0.2 percent. The 750 nm feature is polarized at a level > 1 %. We identify the 550 and 750 nm features as Na I D and OI 777.4 nm moving at about 20,000 km/s. The blue feature may be Fe II. We interpret the polarization evolution in terms of the impact of a bipolar flow from the core that is stopped within the outer envelope of a carbon/oxygen core. Although the symmetry axis remains fixed, as the photosphere retreats by different amounts in different directions due to the asymmetric velocity flow and density distribution, geometrical blocking effects in deeper, Ca-rich layers can lead to a different dominant axis in the Q-U plane. We conclude that the features that characterize SN 2002ap, specifically its high velocity, can be accounted for in an asymmetric model with a larger ejecta mass than SN 1994I such that the photosphere remains longer in higher velocity material. The characteristics of "hypernovae" may be the result of orientation effects in a mildly inhomogeneous set of progenitors, rather than requiring an excessive total energy or luminosity. In the analysis of asymmetric events with spherically symmetric models, it is probably advisable to refer to "isotropic equivalent" energy, luminosity, ejected mass, and nickel mass.
Baade Dietrich
Fransson Claes
Hoeflich Peter
Lundqvist Peter
Wang Lifan
No associations
LandOfFree
Spectropolarimetry of the Type Ic SN 2002ap in M74: More Evidence for Asymmetric Core Collapse does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Spectropolarimetry of the Type Ic SN 2002ap in M74: More Evidence for Asymmetric Core Collapse, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Spectropolarimetry of the Type Ic SN 2002ap in M74: More Evidence for Asymmetric Core Collapse will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-256259