A sample of Type II-L supernovae

• Published in: Monthly notices of the Royal Astronomical Society Vol. 445; no. 1; pp. 554 - 569
• Main Authors: Faran, T., Poznanski, D., Filippenko, A. V., Chornock, R., Foley, R. J., Ganeshalingam, M., Leonard, D. C., Li, W., Modjaz, M., Serduke, F. J. D., Silverman, J. M.
• Format: Journal Article
• Language: English
• Published: London Oxford University Press 21.11.2014
• Subjects: Brightness; Helium; Hydrogen; Hydrogen storage; Light curve; Luminosity; Photometry; Shells; Supernovae; Symbols; supernovae: general
• DOI: 10.1093/mnras/stu1760
• ISSN: 0035-8711

What are Type II-Linear supernovae (SNe II-L)? This class, which has been ill defined for decades, now receives significant attention – both theoretically, in order to understand what happens to stars in the ∼15–25 M⊙ range, and observationally, with two independent studies suggesting that they cannot be cleanly separated photometrically from the regular hydrogen-rich SNe II-P characterized by a marked plateau in their light curve. Here, we analyse the multiband light curves and extensive spectroscopic coverage of a sample of 35 SNe II and find that 11 of them could be SNe II-L. The spectra of these SNe are hydrogen deficient, typically have shallow Hα absorption, may show indirect signs of helium via strong O i λ7774 absorption, and have faster line velocities consistent with a thin hydrogen shell. The light curves can be mostly differentiated from those of the regular, hydrogen-rich SNe II-P by their steeper decline rates and higher luminosity, and we propose to define them based on their decline in the V band: SNe II-L decline by more than 0.5 mag from peak brightness by day 50 after explosion. Using our sample we provide template light curves for SNe II-L and II-P in four photometric bands.