Oxygen and helium in stripped-envelope supernovae
Abstract
We present an analysis of 507 spectra of 173 stripped-envelope (SE) supernovae (SNe) discovered by the untargeted Palomar Transient Factory (PTF) and intermediate PTF (iPTF) surveys. Our sample contains 55 Type IIb SNe (SNe IIb), 45 Type Ib SNe (SNe Ib), 56 Type Ic SNe (SNe Ic), and 17 Type Ib/c SNe (SNe Ib/c). We have compared the SE SN subtypes via measurements of the pseudo-equivalent widths (pEWs) and velocities of the He I λλ5876, 7065 and O I λ7774 absorption lines. Consistent with previous work, we find that SNe Ic show higher pEWs and velocities in O I λ7774 compared to SNe IIb and Ib. The pEWs of the He I λλ5876, 7065 lines are similar in SNe Ib and IIb after maximum light. The He I λλ5876, 7065 velocities at maximum light are higher in SNe Ib compared to SNe IIb. We identify an anticorrelation between the He I λ7065 pEW and O I λ7774 velocity among SNe IIb and Ib. This can be interpreted as a continuum in the amount of He present at the time of explosion. It has been suggested that SNe Ib and Ic have similar amounts of He, and that lower mixing could be responsible for hiding He in SNe Ic. However, our data contradict this mixing hypothesis. The observed difference in the expansion rate of the ejecta around maximum light of SNe Ic (V_m = √2E_k/M_(ej) ≈ 15 000 km s^(−1)) and SNe Ib (V_m ≈ 9000 km s^(−1)) would imply an average He mass difference of ∼1.4 M⊙, if the other explosion parameters are assumed to be unchanged between the SE SN subtypes. We conclude that SNe Ic do not hide He but lose He due to envelope stripping.
Additional Information
© 2018 ESO. Article published by EDP Sciences. Received 3 August 2017; Accepted 3 July 2018; Published online 11 October 2018. We gratefully acknowledge support from the Knut and Alice Wallenberg Foundation. The Oskar Klein Centre is funded by the Swedish Research Council. We acknowledge the contributions from the full PTF and iPTF collaborations that made it possible to discover and monitor the SE SNe analyzed in this work. This work was supported by the GROWTH project funded by the National Science Foundation (NSF) under grant AST-1545949. D.A.H. and G.H. are supported by NSF grant AST-1313484. A.V.F. is grateful for financial assistance from NSF grant AST-1211916, the TABASGO Foundation, the Christopher R. Redlich Fund, and the Miller Institute for Basic Research in Science (UC Berkeley). His work was conducted in part at the Aspen Center for Physics, which is supported by NSF grant PHY-1607611; he thanks the Center for its hospitality during the neutron stars workshop in June and July 2017. Research at Lick Observatory is partially supported by a generous gift from Google. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA; the observatory was made possible by the generous financial support of the W. M. Keck Foundation. This work is based in part on observations from the LCO network. The William Herschel Telescope is operated on the island of La Palma by the Isaac Newton Group of Telescopes in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias, which is also the site of the Nordic Optical Telescope (NOT) and the Gran Telescopio Canarias (GTC). This work is partly based on observations made with DOLoResatTNG. Our results made use of the Discovery Channel Telescope (DCT) at Lowell Observatory. Lowell is a private, nonprofit institution dedicated to astrophysical research and public appreciation of astronomy, and it operates the DCT in partnership with Boston University, the University of Maryland, the University of Toledo, Northern Arizona University, and Yale University. The upgrade of the DeVeny optical spectrograph has been funded by a generous grant from John and Ginger Giovale. Initial classification of some SNe was done with the SuperNova Integral Field Spectrograph (SNIFS) on the University of Hawaii 2.2 m telescope as part of the Nearby Supernova Factory II project. We acknowledge the large number of observers and reducers that helped aquire this spectroscopic database over the years, including R. Ellis and M. Sullivan for contributing spectral data obtained under their respective observing programs. A.V.F. thanks the following members of his group for assistance with the observations and reductions: J. Choi, R. J. Foley, O. D. Fox, M. Kandrashoff, P. J. Kelly, I. Kleiser, J. Kong, A. Miller, A. Morton, D. Poznanski, and I. Shivvers. We thank the staffs at the observatories where data were obtained.Attached Files
Published - aa31701-17.pdf
Accepted Version - 1807.00100.pdf
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Additional details
- Eprint ID
- 90424
- Resolver ID
- CaltechAUTHORS:20181026-084422016
- Knut and Alice Wallenberg Foundation
- Swedish Research Council
- AST-1545949
- NSF
- AST-1313484
- NSF
- AST-1211916
- NSF
- TABASGO Foundation
- Christopher R. Redlich Fund
- Miller Institute for Basic Research in Science
- PHY-1607611
- NSF
- W. M. Keck Foundation
- Created
-
2018-10-26Created from EPrint's datestamp field
- Updated
-
2021-11-16Created from EPrint's last_modified field
- Caltech groups
- Astronomy Department, Division of Geological and Planetary Sciences