SN 2018hti: a nearby superluminous supernova discovered in a metal-poor galaxy. Issue 1 (6th July 2020)

• Record Type: Journal Article
• Authors: 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; Chen, Z H
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 497:Issue 1(2020)
• Page Start: 318
• Page End: 335
• Publication Date: 2020-07-06
• Subjects: supernovae: general -- supernovae: individual (SN 2018hti); Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/staa1918
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: SN 2018hti is a Type I superluminous supernova (SLSN I) with an absolute g -band magnitude of −22.2 at maximum brightness, discovered by the Asteroid Terrestrial-impact Last Alert System 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 ∼−35 d to more than +340 d from the r -band maximum. Combining our BVgri -band photometry with Swift UVOT optical/ultraviolet photometry, we calculated the peak luminosity as ∼3.5 × 10 44 erg s −1 . Modelling the observed light curve reveals that the luminosity evolution of SN 2018hti can be produced by an ejecta mass of 5.8 M⊙ and a magnetar with a magnetic field of B = 1.8 × 10 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 ( Mg = −17.75 mag) and of low metallicity ( Z = 0.3 Z⊙ ), with a star formation rate of 0.3 M⊙ 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⊙, or from a less massive rotating star with M ZAMS ≈ 16–25 M⊙ . For the case of a binary system, its progenitor could also be a star with $M_\mathrm{ZAMS} \gtrsim 25\, \mathrm{ M}_\odot$ .