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Published September 1, 2014 | Submitted + Published
Journal Article Open

Transparent Helium in Stripped Envelope Supernovae

Abstract

Using simple arguments based on photometric light curves and velocity evolution, we propose that some stripped envelope supernovae (SNe) show signs that a significant fraction of their helium is effectively transparent. The main pieces of evidence are the relatively low velocities with little velocity evolution, as are expected deep inside an exploding star, along with temperatures that are too low to ionize helium. This means that the helium should not contribute to the shaping of the main SN light curve, and thus the total helium mass may be difficult to measure from simple light curve modeling. Conversely, such modeling may be more useful for constraining the mass of the carbon/oxygen core of the SN progenitor. Other stripped envelope SNe show higher velocities and larger velocity gradients, which require an additional opacity source (perhaps the mixing of heavier elements or radioactive nickel) to prevent the helium from being transparent. We discuss ways in which similar analysis can provide insights into the differences and similarities between SNe Ib and Ic, which will lead to a better understanding of their respective formation mechanisms.

Additional Information

© 2014 American Astronomical Society. Received 2014 July 22; accepted 2014 August 2; published 2014 August 14. We thank Drew Clausen for generating the 15M_⊙ model used for Figure 1, Mattias Ergon for helpful discussions, and Dan Kasen and Christian Ott for feedback on previous drafts. We also thank the Carnegie Supernova Project, and in particular Mark Phillips, for generously hosting ALP at the CSP II Team Meeting at St. George Island, Florida where this work was inspired. This work was supported through NSF grants AST-1205732, PHY-1068881, PHY-1151197, PHY-1404569, and the Sherman Fairchild Foundation.

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Published - 2041-8205_792_1_L11.pdf

Submitted - 1407.5992v1.pdf

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