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Register a new userSupernova PTF12glz: a possible shock breakout driven through an aspherical wind
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We present visible-light and ultraviolet (UV) observations of the supernova PTF12glz. The SN was discovered and monitored in near-UV and R bands as part of a joint GALEX and Palomar Transient Factory campaign. It is among the most energetic Type IIn supernovae observed to date (~10^{51} erg). If the radiated energy mainly came from the thermalization of the shock kinetic energy, we show that PTF12glz was surrounded by ~1 solar mass of circumstellar material (CSM) prior to its explosive death. PTF12glz shows a puzzling peculiarity: at early times, while the freely expanding ejecta are presumably masked by the optically thick CSM, the radius of the blackbody that best fits the observations grows at ~7000 km/s. Such a velocity is characteristic of fast moving ejecta rather than optically thick CSM. This phase of radial expansion takes place before any spectroscopic signature of expanding ejecta appears in the spectrum and while both the spectroscopic data and the bolometric luminosity seem to indicate that the CSM is optically thick. We propose a geometrical solution to this puzzle, involving an aspherical structure of the CSM around PTF12glz. By modelling radiative diffusion through a slab of CSM, we show that an aspherical geometry of the CSM can result in a growing effective radius. This simple model also allows us to recover the decreasing blackbody temperature of PTF12glz. SLAB-Diffusion, the code we wrote to model the radiative diffusion of photons through a slab of CSM and evaluate the observed radius and temperature, is made available on-line.
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High cadence ultraviolet, optical and near-infrared photometric and low-resolution spectroscopic observations of the peculiar Type II supernova (SN) 2018hna are presented. The early phase multiband light curves exhibit the adiabatic cooling envelope emission following the shock breakout up to ~14 days from the explosion. SN~2018hna has a rise time of $sim$,88 days in the V-band, similar to SN 1987A. A $rm^{56}Ni$ mass of ~0.087$pm$0.004 $rm M_{odot}$ is inferred for SN 2018hna from its bolometric light curve. Hydrodynamical modelling of the cooling phase suggests a progenitor with a radius ~50 $rm R_{odot}$, a mass of ~14-20 $rm M_{odot}$ and explosion energy of ~1.7-2.9$rm times$ $rm 10^{51} erg$. The smaller inferred radius of the progenitor than a standard red supergiant is indicative of a blue supergiant progenitor of SN 2018hna. A sub-solar metallicity (~0.3 $rm Z_{odot}$) is inferred for the host galaxy UGC 07534, concurrent with the low-metallicity environments of 1987A-like events.
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The interaction between the ejecta from Supernova 1987A and surrounding material is producing steadily brightening radio and X-ray emission. The new-born supernova remnant has been significantly decelerated by this interaction, while its morphology reflects the axisymmetric nature of the progenitor wind.
We investigate the properties of X-ray emission from shock breakout of a supernova in a stellar wind. We consider a simple model describing aspherical explosions, in which the shock front with an ellipsoidal shape propagates into the dense circumstellar matter. For this model, both X-ray light curves and spectra are simultaneously calculated using a Monte Carlo method. We show that the shock breakout occurs simultaneously in all directions in a steady and spherically symmetric wind. As a result, even for the aspherical explosion, the rise and decay timescales of the light curve do not significantly depend on the viewing angles. This fact suggests that the light curve of the shock breakout may be used as a probe of the wind mass loss rate. We compare our results with the observed spectrum and light curve of XRO 080109/SN 2008D. The observation can be reproduced by an explosion with a shock velocity of 60% of the speed of light and a circumstellar matter with a mass loss rate of 5.e-4 Msun/yr.
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