Abstract:
We present late-time optical follow-up observations of GRB 171010A/SN 2017htp (𝑧 = 0.33) and low luminosity GRB 171205A/SN 2017iuk (𝑧 = 0.037) acquired using the 4K×4K CCD Imager mounted at the
3.6 m Devasthal Optical Telescope (3.6 m DOT) along with the prompt emission data analysis of these
two interesting bursts. The prompt characteristics (other than brightness) such as spectral hardness, 𝑇90, and
minimum variability time-scale are comparable for both the bursts. The isotropic 𝑋-ray and kinetic energies
of the plateau phase of GRB 171205A are found to be less than the maximum energy budget of magnetars,
supporting magnetar as a central engine powering source. The new optical data of SN 2017htp and SN 2017iuk
presented here, along with published ones, indicate that SN 2017htp is one of the brightest and SN 21017iuk
is among the faintest GRB associated SNe (GRB–SNe). Semi-analytical light-curve modelling of SN 2017htp,
SN 2017iuk and only known GRB associated superluminous supernova (SLSN 2011kl) are performed using the
MINIM code. The model with a spin-down millisecond magnetar as a central engine powering source nicely
reproduced the bolometric light curves of all three GRB–SNe mentioned above. The magnetar central engines
for SN 2017htp, SN 2017iuk, and SLSN 2011kl exhibit values of initial spin periods higher and magnetic
fields closer to those observed for long GRBs and H-deficient SLSNe. Detection of these rare events at such
late epochs also demonstrates the capabilities of the 3.6 m DOT for deep imaging considering longitudinal
advantage in the era of time-domain astronomy.
