Oxygen and helium in stripped-envelope supernovae

Journal Article · 10 October 2018 · Astronomy and Astrophysics

DOI: https://doi.org/10.1051/0004-6361/201731701 · OSTI ID:1480816

Fremling, C. ^[1]; Sollerman, J. ^[2]; Kasliwal, M. M. ^[3]; Kulkarni, S. R. ^[3]; Barbarino, C. ^[2]; Ergon, M. ^[2]; Karamehmetoglu, E. ^[2]; Taddia, F. ^[2]; Arcavi, I. ^[4]; Cenko, S. B. ^[5]; Clubb, K. ^[6]; De Cia, A. ^[7]; Duggan, G. ^[3]; Filippenko, A. V. ^[6]; Gal-Yam, A. ^[8]; Graham, M. L. ^[9]; Horesh, A. ^[10]; Hosseinzadeh, G. ^[11]; Howell, D. A. ^[11]; Kuesters, D. ^[12] ; Lunnan, R. ^[1]; Matheson, T. ^[13]; Nugent, P. E. ^[14]; Perley, D. A. ^[15]; Quimby, R. M. ^[16]; Saunders, C. ^[17]

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1. Stockholm University (Sweden); California Institute of Technology (CalTech), Pasadena, CA (United States)
2. Stockholm University (Sweden)
3. California Institute of Technology (CalTech), Pasadena, CA (United States)
4. Las Cumbres Observatory, Goleta, CA (United States); University of California, Santa Barbara, CA (United States)
5. NASA Goddard Space Flight Center (GSFC), Greenbelt, MD (United States); University of Maryland, College Park, MD (United States)
6. University of California, Berkeley, CA (United States)
7. European Southern Observatory, Garching bei München (Germany)
8. Weizmann Institute of Science, Rehovot (Israel)
9. University of Washington, Seattle, WA (United States)
10. Hebrew University of Jerusalem (Israel)
11. University of California, Santa Barbara, CA (United States); Las Cumbres Observatory, Goleta, CA (United States)
12. Humboldt University of Berlin (Germany)
13. National Optical Astronomy Observatory, Tucson, AZ (United States)
14. University of California, Berkeley, CA (United States); Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
15. Liverpool John Moores University (United Kingdom)
16. San Diego State University, CA (United States); University of Tokyo (Japan). Kavli Institute for the Physics and Mathematics of the Universe (WPI)
17. Université Pierre et Marie Curie Paris 6, Université Paris Diderot Paris 7 (France)

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 (Vm = $$\sqrt{2E_k/M_{ej}}$$ ≈ 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.

• Research Organization: Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: Knut and Alice Wallenberg Foundation; National Science Foundation (NSF); Swedish Research Council; USDOE Office of Science (SC), High Energy Physics (HEP); W. M. Keck Foundation
• Grant/Contract Number: AC02-05CH11231
• OSTI ID: 1480816
• Journal Information: Astronomy and Astrophysics, Journal Name: Astronomy and Astrophysics Vol. 618; ISSN 0004-6361
• Publisher: EDP SciencesCopyright Statement
• Country of Publication: United States
• Language: English