Eruptive mass loss less than a year before the explosion of superluminous supernovae

We present photometric and spectroscopic observations of SN 2020xga and SN 2022xgc, two hydrogen-poor superluminous supernovae (SLSNe-I) at z = 0.4296 and z = 0.3103, respectively, which show an additional set of broad Mg II absorption lines, blueshifted by a few thousands kilometer second −1 with respect to the host galaxy absorption system. Previous work interpreted this as due to resonance line scattering of the SLSN continuum by rapidly expanding circumstellar material (CSM) expelled shortly before the explosion. The peak rest-frame g -band magnitude of SN 2020xga is −22.30 ± 0.04 mag and of SN 2022xgc is −21.97 ± 0.05 mag, placing them among the brightest SLSNe-I. We used high-quality spectra from ultraviolet to near-infrared wavelengths to model the Mg II line profiles and infer the properties of the CSM shells. We find that the CSM shell of SN 2020xga resides at ∼1.3 × 10 16 cm, moving with a maximum velocity of 4275 km s −1 , and the shell of SN 2022xgc is located at ∼0.8 × 10 16 cm, reaching up to 4400 km s −1 . These shells were expelled ∼11 and ∼5 months before the explosions of SN 2020xga and SN 2022xgc, respectively, possibly as a result of luminous-blue-variable-like eruptions or pulsational pair instability (PPI) mass loss. We also analyzed optical photometric data and modeled the light curves, considering powering from the magnetar spin-down mechanism. The results support very energetic magnetars, approaching the mass-shedding limit, powering these SNe with ejecta masses of ∼7 − 9 M ⊙ . The ejecta masses inferred from the magnetar modeling are not consistent with the PPI scenario pointing toward stars > 50 M ⊙ He-core; hence, alternative scenarios such as fallback accretion and CSM interaction are discussed. Modeling the spectral energy distribution of the host galaxy of SN 2020xga reveals a host mass of 10 7.8 M ⊙ , a star formation rate of 0.96 −0.26 +0.47 M ⊙ yr −1 , and a metallicity of ∼0.2 Z ⊙ .

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Publication Details

Journal
Astronomy and Astrophysics
Published
2025-01-09
DOI
https://doi.org/10.1051/0004-6361/202452357
Citations
5
Primary Topic
Gamma-ray bursts and supernovae
Type
article
Field-Weighted Citation Impact
5.77

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article

Eruptive mass loss less than a year before the explosion of superluminous supernovae

J. P. Anderson, M. Fraser, Ludovic Lacroix, D. Hiramatsu et al.
5 citations
Astronomy and Astrophysics
Gamma-ray bursts and supernovae
5.77
article

Eruptive mass loss less than a year before the explosion of superluminous supernovae

J. P. Anderson, M. Fraser, Ludovic Lacroix, D. Hiramatsu, A. Gangopadhyay, P. J. Pessi, M. Bronikowski, Claes Fransson, M. Gromadzki, A. Sahu, K. Matilainen, R. Konyves-Toth, C. Inserra, J. Sollerman, R. Dekany, S. Geier, C. Fremling, L. Yan, D.A. Perley, A. Gal‐Yam, M. Kopsacheili, T. Moore, S.J. Brennan, F. Poidevin, C. P. Gutiérrez, S. Schulze, Fabio Ragosta, A. Gkini, C. McCully, R. Lunnan, L. Galbany, C. Pellegrino, T. -W. Chen, G. Pignata, Shubham Srivastav, Avinash Singh, T. Petrushevska, Yi Hu, Michael Nicholl
article en
5 citations

Abstract

We present photometric and spectroscopic observations of SN 2020xga and SN 2022xgc, two hydrogen-poor superluminous supernovae (SLSNe-I) at z = 0.4296 and z = 0.3103, respectively, which show an additional set of broad Mg II absorption lines, blueshifted by a few thousands kilometer second −1 with respect to the host galaxy absorption system. Previous work interpreted this as due to resonance line scattering of the SLSN continuum by rapidly expanding circumstellar material (CSM) expelled shortly before the explosion. The peak rest-frame g -band magnitude of SN 2020xga is −22.30 ± 0.04 mag and of SN 2022xgc is −21.97 ± 0.05 mag, placing them among the brightest SLSNe-I. We used high-quality spectra from ultraviolet to near-infrared wavelengths to model the Mg II line profiles and infer the properties of the CSM shells. We find that the CSM shell of SN 2020xga resides at ∼1.3 × 10 16 cm, moving with a maximum velocity of 4275 km s −1 , and the shell of SN 2022xgc is located at ∼0.8 × 10 16 cm, reaching up to 4400 km s −1 . These shells were expelled ∼11 and ∼5 months before the explosions of SN 2020xga and SN 2022xgc, respectively, possibly as a result of luminous-blue-variable-like eruptions or pulsational pair instability (PPI) mass loss. We also analyzed optical photometric data and modeled the light curves, considering powering from the magnetar spin-down mechanism. The results support very energetic magnetars, approaching the mass-shedding limit, powering these SNe with ejecta masses of ∼7 − 9 M ⊙ . The ejecta masses inferred from the magnetar modeling are not consistent with the PPI scenario pointing toward stars > 50 M ⊙ He-core; hence, alternative scenarios such as fallback accretion and CSM interaction are discussed. Modeling the spectral energy distribution of the host galaxy of SN 2020xga reveals a host mass of 10 7.8 M ⊙ , a star formation rate of 0.96 −0.26 +0.47 M ⊙ yr −1 , and a metallicity of ∼0.2 Z ⊙ .

Astronomy and AstrophysicsVol. 694
University College Dublin (IE), California Institute of Technology (US), Queen's University Belfast (GB), Las Cumbres Observatory Global Telescope Network (US), Centre National de la Recherche Scientifique (FR), University of Turku (FI), Universidad de La Laguna (ES), University of Tarapacá (CL), University of Nova Gorica (SI), Université Paris Cité (FR), National Central University (TW), University of Szeged (HU), Konkoly Observatory (HU), Northwest University (CN), University of Warwick (GB), Sorbonne Université (FR), University of Oxford (GB), Institute of Experimental Physics of the Slovak Academy of Sciences (SK), Institut d'Estudis Espacials de Catalunya (ES), Millennium Institute of Astrophysics (CL), Queens University (BD), Laboratoire de Physique Nucléaire et de Hautes Énergies (FR), Institute of Space Sciences (ES), Institute of Astronomy (RU), Center for Astrophysics Harvard & Smithsonian (US), Instituto de Astrofísica de Canarias (ES), AlbaNova (SE), Gran Telescopio Canarias (Spain) (ES), Astronomical Observatory (RS), The NSF AI Institute for Artificial Intelligence and Fundamental Interactions (US), Infrared Processing and Analysis Center (US), University of Warsaw (PL), Weizmann Institute of Science (IL), Optica (US), Liverpool John Moores University (GB), University of Naples Federico II (IT), Cardiff University (GB), KTH Royal Institute of Technology (SE), National Institute for Astrophysics (IT)
Science and Technology Facilities Council
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Gamma-ray bursts and supernovae
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