Spectral dataset of stripped-envelope supernovae from the Tsinghua supernova group

¹ Beijing Planetarium, Beijing Academy of Sciences and Technology, Beijing, 100044, China
² Department of Physics, Tsinghua University, Haidian District, Beijing, 100084, China
³ Yunnan Observatories, Chinese Academy of Sciences, Kunming, 650216, China
⁴ International Centre of Supernovae, Yunnan Key Laboratory, Kunming, 650216, China
⁵ Key Laboratory for the Structure and Evolution of Celestial Objects, Chinese Academy of Sciences, Kunming, 650011, China
⁶ School of Physics and Information Engineering, Jiangsu Second Normal University, Nanjing, Jiangsu, 211200, China
⁷ Institute for Frontiers in Astronomy and Astrophysics, Beijing Normal University, Beijing, 102206, China
⁸ Key Laboratory of Space Astronomy and Technology, National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Beijing, 100101, China
⁹ School of Astronomy and Space Science, University of Chinese Academy of Sciences, Beijing, 100049, China
¹⁰ National Astronomical Observatories, Chinese Academy of Sciences, Beijing, 100101, China
¹¹ School of Science, Tianjin University of Technology, Tianjin, 300384, China
¹² Department of Astronomy, Shanghai Jiao Tong University, Shanghai, 200240, China
¹³ Department of Astronomy, University of Science and Technology, Hefei, 230026, China
¹⁴ School of Physics and Astronomy, Beijing Normal University, Beijing, 100875, China
¹⁵ Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing, 100101, China
¹⁶ Schools of Electronics and Information Engineering, Wuzhou University, Wuzhou, 543002, China
¹⁷ Institute for Frontiers in Astronomy and Astrophysics, Beijing Normal University, Beijing, 102206, China
¹⁸ Department of Astronomy, School of Physics and Astronomy, Yunnan University, Kunming, 650091, China
¹⁹ Department of Astronomy, School of Physics, Peking University, Beijing, 100871, China
²⁰ College of Physics, Guizhou University, Guiyang, 550025, China

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Received: 28 November 2025
Accepted: 9 March 2026

Abstract

Context. The extent of envelope stripping in progenitor stars is directly reflected in the diversity of spectral features that are observed in stripped-envelope supernovae (SESNe).

Aims. Through extensive spectral observation and analysis, we aim to clarify the statistical differences between the subclasses of SESNe.

Methods. The Tsinghua supernova group obtained 249 optical spectra of 62 SESNe from 2010 to 2020, covering phases from –16 to over 190 days relative to maximum light. Most spectra were obtained during the photospheric phases after the supernova explosion. For each spectrum, the pseudo-equivalent widths and blueshift velocities of the principal lines were measured. We further investigated the common spectral features by analyzing their velocity and strength correlations across all subtypes.

Results. We identified the feature near 6200 Å in SNe Ib as Hα through a comparison with SNe IIb and Ic. This resolves inconsistent interpretations in the literature. Our finding reveals prevalent residual hydrogen in SNe Ib, further supporting a continuous stripping sequence from SNe IIb to Ib. The velocity among different subtypes of stripped-envelope SNe increases, with SNe IIb exhibiting the lowest line velocities, followed by Ib, Ic, and Ic-BL. Typically, the O I lines in SNe Ic/Ic-BL are stronger than those seen in SNe IIb/Ib. In nebular phases, the [Ca II] emission dominates [O I] in SNe IIb/Ib, while [O I] is stronger in SNe Ic, including in the He-rich SN 2016coi. This spectral dichotomy implies that progenitors of SNe Ic (BL) have more massive CO cores and hence higher initial masses.