2021MNRAS.502.1678K

We investigate the observational properties of a hydrogen-deficient superluminous supernova (SLSN) SN 2020ank (at z = 0.2485), with the help of early phase observations carried out between -21 and +52 d since g-band maximum. Photometrically, SN 2020ank is one of the brightest SLSN (M_ g,peak_ ∼-21.84 ± 0.10 mag), having fast pre-peak rising and post-peak decaying rates. The bolometric light curve of SN 2020ank exhibits a higher peak luminosity (L_max) of ∼ (3.9 ± 0.7) x 10⁴⁴ erg s^–1 and appears to be symmetric around the peak with L^rise_max/e \approxL^fall_max/e ≃ 15 d. The semi-analytical light-curve modelling using the minim code suggests a spin-down millisecond magnetar with P_i∼2.2 ± 0.5 ms and B ∼(2.9 ± 0.1) ×10¹⁴ G as a possible powering source for SN 2020ank. The possible magnetar origin and excess ultraviolet flux at early epochs indicate a central-engine based powering source for SN 2020ank. Near-peak spectra of SN 2020ank are enriched with the W-shaped O II features but with the weaker signatures of C II and Fe III. Using the estimated rise time of ∼ 27.9 d and the photospheric velocity of ∼ 12 050 km s^–1, we constrain the ejecta mass to ∼ 7.2 M_☉ and the kinetic energy of ∼6.3 x 10⁵¹ erg. The near-peak spectrum of SN 2020ank exhibits a close spectral resemblance with that of fast-evolving SN 2010gx. The absorption features of SN 2020ank are blueshifted compared to Gaia16apd, suggesting a higher expansion velocity. The spectral similarity with SN 2010gx and comparatively faster spectral evolution than PTF12dam (a slow-evolving SLSN) indicate the fast-evolving behaviour of SN 2020ank.