We present photometric and spectroscopic observations of the type Ibn supernova (SN) 2019uo, the second ever SN Ibn with flash ionization (He II, C III, N III) features in its early spectra. SN 2019uo displays a rapid post-peak luminosity decline of 0.1 mag d −1 similar to most of the SNe Ibn, but is fainter (M V max = −18.30 ± 0.24 mag) than a typical SN Ibn and shows a color evolution that places it between SNe Ib and the most extreme SNe Ibn. SN 2019uo shows P-cygni He I features in the early spectra which gradually evolves and becomes emission dominated post peak. It also shows faster evolution in line velocities as compared to most other members of the type Ibn subclass. The bolometric light curve is fairly described by a 56 Ni + circumstellar interaction model.

We present spectro-polarimetric analysis of GRB 171010A using data from AstroSat, Fermi, and Swift, to provide insights into the physical mechanisms of the prompt radiation and the jet geometry.Prompt emission from GRB 171010A was very bright (fluence > 10 −4 ergs cm −2 ) and had a complex structure composed of the superimposition of several pulses. The energy spectra deviate from the typical Band function to show a low energy peak ∼ 15 keV -which we interpret as a power-law with two breaks, with a synchrotron origin. Alternately, the prompt spectra can also be interpreted as Comptonized emission, or a blackbody combined with a Band function. Time-resolved analysis confirms the presence of the low energy component, while the peak energy is found to be confined in the range of 100-200 keV.Afterglow emission detected by Fermi-LAT is typical of an external shock model, and we constrain the initial Lorentz factor using the peak time of the emission. Swift-XRT measurements of the afterglow show an indication for a jet break, allowing us to constrain the jet opening angle to > 6 • .Detection of a large number of Compton scattered events by AstroSat-CZTI provides an opportunity to study hard X-ray polarization of the prompt emission. We find that the burst has high, time-variable polarization, with the emission have higher polarization at energies above the peak energy.We discuss all observations in the context of GRB models and polarization arising due to due to physical or geometric effects: synchrotron emission from multiple shocks with ordered or random magnetic fields, Poynting flux dominated jet undergoing abrupt magnetic dissipation, sub-photospheric dissipation, a jet consisting of fragmented fireballs, and the Comptonization model.

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 ($M_{\mathrm{ g,peak}}\, \sim$ –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 (Lmax) of ∼ (3.9 ± 0.7) × 1044 erg s−1 and appears to be symmetric around the peak with $L^{\mathrm{ rise}}_{\mathrm{ max}}$/e ${\approx}L^{\mathrm{ fall}}_{\mathrm{ max}}$/e ≈ 15 d. The semi-analytical light-curve modelling using the minim code suggests a spin-down millisecond magnetar with $P_i\, \sim$ 2.2 ± 0.5 ms and $B\, \sim$ (2.9 ± 0.1) $\times \, 10^{14}$ 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 × 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.