Kornpob Bhirombhakdi
Department of Physics and Astronomy, Ohio University
Athens, Ohio, 45701, USA
SN2006gy is SLSN IIn powered by CSM interaction. At early time, PISN and LBV with great eruption scenarios were candidates (Smith and al. (2007)). However, X-ray emission did not match with the expected mass loss rate, the LBV scenario is less preferrable than PISN one. At mid time, light echo was observed, and the light decay rate did not match with radioactive decay, hence PISN scenario was ruled out, and left over with the idea of strong CSM interaction (Miller and al. (2011)).
SN2006gy was in NGC1260, about \(73Mpc\) away. Its radiated energy \(>{10}^{51}erg\) which makes it be the first superluminous supernova (SNSL) type. Its early time spectra showed strong \(H\alpha\) emission with broad and narrow components. The broad component had about \(4000km/s\), representing the ejecta speed, with blue-wing attenuation, representing front shock interaction. And, the narrow component had about \(130km/s\) with P Cygni profile representing the interaction with dense CSM. Hence, it was classfied as Type IIn. Additionally, soft and unabsorbed X-ray emission was detected at early time; this supported dense CSM interaction.
It took 70 days to reach the peak at \(M_R\approx-22\), and sustained for about 50 days to decrease its brightness down to \(\sim21\). This was considered as slow rising and declining supernova which made first belief to be pair instability supernova (PISN) candidate, rather than regular core-collapse supernova (CCSN). Additional mid-time data rejected the PISN proposal.
The early-time analysis supported the progenitor being very massive. The course of death was constrained as three possible scenarios: PISN, LBV, and thermal radiation.
First, and the most preferrable at the early time, the progenitor contained high amount of \(^{56}{Ni}\), and went through PISN; so, instead of keeping some mass to form a blackhole, the death star exploded and ejected all of the core mass. This scenario is possible to produce such the high energy budget as observed, and expects to see energy decay rate matching with radioactive decay one. However, mid-time analysis rejected the scenario because the rates were not matched.
Second, the progenitor was LBV with great eruption (similar to $Carinae) prior to the explosion. Hence, there existed massively dense CSM before the explosion to efficiently convert the shock kinetic energy into photons. However, the X-ray emission implied significantly lower mass loss rate of the progenitor than it should be for matching with the energy budget.
Last, thermal radiation is a basic scenario where the SN shock heats up gas to excited states, then the gas de-excites and emits photons. Since this basic mechanism has low energy conversion (from shock to photons) efficiency, incredibly massive progenitor was required for the energy budget.
At mid time, …
Miller, A. A., and et al. 2011. “New Observations of the Very Luminous Supernova 2006GY: Evidence for Echoes.” ArXiv:0906.2201.
Smith, Nathan, and et al. 2007. “SN 2006GY: Discovery of the Most Luminous Supernova Ever Recorded Powered by the Death of an Extremely Massive Star Like Eta Carinae.” ArXiv:astro-Ph0612617.