Eruptive mass-loss less than a year before the explosion of superluminous supernovae: I. The cases of SN 2020xga and SN 2022xgc
| Autor: | Gkini, A., Fransson, C., Lunnan, R., Schulze, S., Poidevin, F., Sarin, N., Könyves-Tóth, R., Sollerman, J., Omand, C. M. B., Brennan, S. J., Hinds, K. R., Anderson, J. P., Bronikowski, M., Chen, T. -W., Dekany, R., Fraser, M., Fremling, C., Galbany, L., Gal-Yam, A., Gangopadhyay, A., Geier, S., Gonzalez, E. P., Gromadzki, M., Groom, S. L., Gutiérrez, C. P., Hiramatsu, D., Howell, D. A., Hu, Y., Inserra, C., Kopsacheili, M., Lacroix, L., Masci, F. J., Matilainen, K., McCully, C., Moore, T., Müller-Bravo, T. E., Nicholl, M., Pellegrino, C., Pérez-Fournon, I., Perley, D. A., Pessi, P. J., Petrushevska, T., Pignata, G., Ragosta, F., Sahu, A., Singh, A., Srivastav, S., Wise, J. L., Yan, L., Young, D. R. |
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| Rok vydání: | 2024 |
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| Druh dokumentu: | Working Paper |
| Popis: | We present photometric and spectroscopic observations of SN2020xga and SN2022xgc, two hydrogen-poor superluminous supernovae (SLSNe-I) at $z = 0.4296$ and $z = 0.3103$ respectively, that show an additional set of broad Mg II absorption lines, blueshifted by a few thousand km s$^{-1}$ 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 CSM expelled shortly before the explosion. The peak rest-frame $g$-band magnitude of SN2020xga is $-22.30 \pm 0.04$ mag and of SN2022xgc is $-21.97 \pm 0.05$ mag, placing them among the brightest SLSNe-I. We use 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 SN2020xga resides at $\sim 1.3 \times 10^{16} \rm cm$ moving with a maximum velocity of $4275~\rm km~s^{-1}$, and the shell of SN2022xgc is located at $\sim 0.8 \times 10^{16} \rm cm$ reaching up to $4400~\rm km~s^{-1}$. These shells were expelled $\sim 11$ and $\sim 5$ months before explosion for SN2020xga and SN2022xgc respectively, possibly as a result of Luminous Blue Variable-like eruptions or pulsational pair instability (PPI) mass loss. We also analyze optical photometric data and model 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 $\sim 7-9 \rm~M_\odot$. The ejecta masses inferred from the magnetar modeling are not consistent with the PPI scenario pointing towards stars $> 50~\rm M_\odot$ He-core, hence alternative scenarios such as fallback accretion are discussed. Comment: 25 pages text, 8 pages appendix, 21 figures. Submitted to A&A |
| Databáze: | arXiv |
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