1. SN 2018hti: a nearby superluminous supernova discovered in a metal-poor galaxy
- Author
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Lin, W. L., Wang, X. F., Li, W. X., Zhang, J. J., Mo, J., Sai, H. N., Zhang, X. H., Filippenko, A. V., Zheng, W. K., Brink, T. G., Baron, E., DerKacy, J. M., Ehgamberdiev, S. A., Mirzaqulov, D., Li, X., Zhang, J. C., Yan, S. Y., Xi, G. B., Hsiao, Y., Zhang, T. M., Wang, L. J., Liu, L. D., Xiang, D. F., Wu, C. Y., Rui, L. M., and Chen, Z. H.
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Astrophysics - High Energy Astrophysical Phenomena - Abstract
SN 2018hti is a Type I superluminous supernova (SLSN~I) with an absolute $g$-band magnitude of $-22.2$ at maximum brightness, discovered in a metal-poor galaxy at a redshift of 0.0612. We present extensive photometric and spectroscopic observations of this supernova, covering the phases from $\sim -35$ days to more than +340 days from the $r$-band maximum. Combining our $BVgri$-band photometry with {\it Swift} UVOT optical/ultraviolet photometry, we calculated the peak luminosity as $\sim 3.5\times10^{44}$ erg s$^{-1}$. Modeling the observed light curve reveals that the luminosity evolution of SN 2018hti can be produced by an ejecta mass of 5.8 $M_\odot$ and a magnetar with a magnetic field of $B=1.8\times10^{13}$~G having an initial spin period of $P_0=1.8$ ms. Based on such a magnetar-powered scenario and a larger sample, a correlation between the spin of the magnetar and the kinetic energy of the ejecta can be inferred for most SLSNe~I, suggesting a self-consistent scenario. Like for other SLSNe~I, the host galaxy of SN 2018hti is found to be relatively faint ($M_{g} = -17.75$ mag) and of low metallicity ($Z=0.3~Z_\odot$), with a star-formation rate of 0.3 $M_\odot$ yr$^{-1}$. According to simulation results of single-star evolution, SN 2018hti could originate from a massive, metal-poor star with a zero-age main sequence (ZAMS) mass of 25--40 $M_\odot$, or from a less massive rotating star with $M_\mathrm{ZAMS} \approx 16$--25 $M_\odot$. For the case of a binary system, its progenitor could also be a star with $M_\mathrm{ZAMS} \gtrsim 25$ $M_\odot$., Comment: 26 pages, 12 figures, 7 tables, published in MNRAS
- Published
- 2020
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