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Register a new userExtraordinary supernova iPTF14hls: An attempt at interpretation
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N. N. Chugai
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It is shown that the H$alpha$ luminosity and the Thomson optical depth of the iPTF14hls on day 600 after the detection provide us with the estimate of the envelope age which turns to be about 1000 days. I propose a model that suggests an explosion of a massive star with the radius of $sim 2times10^{13}$ cm at 450 days prior to the discovery. For the optimal model the ejected mass is $30,M_{odot}$, and the kinetic energy is $8times10^{51}$ erg. The energy source at the dominant luminosity stage is presumably related to the relativistic bipolar outflow originated from a disk accretion onto the black hole. The [O,I] 6300, 6364 AA doublet in the spectrum on day 600 is shown to be the result of the emission of at least $1-3,M_{odot}$ of oxygen in the ejecta inner zone. The oxygen distribution is non-spherical and can be represented either by two components with blue and red shifts (in the optically thin case), or by one blue shifted component, in the case of optically thick lines for the filling factor of $sim 2times10^{-3}$.
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We study iPTF14hls, a luminous and extraordinary long-lived Type II supernova, which lately has attracted much attention and disparate interpretation. We present new optical photometry that extends the light curves until more than 3 yr past discovery. We also obtained optical spectroscopy over this period, and furthermore present additional space-based observations using Swift and HST. After an almost constant luminosity for hundreds of days, the later light curve of iPTF14hls finally fades and then displays a dramatic drop after about 1000 d, but the supernova is still visible at the latest epochs presented. The spectra have finally turned nebular, and the very last optical spectrum likely displays signatures from the deep and dense interior of the explosion. The high-resolution HST image highlights the complex environment of the explosion in this low-luminosity galaxy. We provide a large number of additional late-time observations of iPTF14hls, which are (and will continue to be) used to assess the many different interpretations for this intriguing object. In particular, the very late (+1000 d) steep decline of the optical light curve, the lack of very strong X-ray emission, and the emergence of intermediate-width emission lines including of [S II] that likely originate from dense, processed material in the core of the supernova ejecta, are all key observational tests for existing and future models.
We present observations of SN 2020faa. This Type II supernova displays a luminous light curve that started to rebrighten from an initial decline. We investigate this in relation to the famous supernova iPTF14hls, which received a lot of attention and multiple interpretations in the literature, however whose nature and source of energy still remains unknown. We demonstrate the great similarity between SN 2020faa and iPTF14hls during the first 6 months, and use this comparison both to forecast the evolution of SN 2020faa and to reflect on the less well observed early evolution of iPTF14hls. We present and analyse our observational data, consisting mainly of optical light curves from the Zwicky Transient Facility in the gri bands as well as a sequence of optical spectra. We construct colour curves, a bolometric light curve, compare ejecta-velocity and Black-body radius evolutions for the two supernovae, as well as for more typical Type II supernovae. The light curves show a great similarity with those of iPTF14hls over the first 6 months, in luminosity, timescale and colours. Also the spectral evolution of SN 2020faa is that of a Type II supernova, although it probes earlier epochs than those available for iPTF14hls. The similar light curve behaviour is suggestive of SN 2020faa being a new iPTF14hls. We present these observations now to advocate follow-up observations, since most of the more striking evolution of supernova iPTF14hls came later, with light curve undulations and a spectacular longevity. On the other hand, for SN 2020faa we have better constraints on the explosion epoch than we had for iPTF14hls, and we have been able to spectroscopically monitor it from earlier phases than was done for the more famous sibling.
The Intermediate Palomar Transient Factory reported the discovery of an unusual type II-P supernova iPTF14hls. Instead of a ~100-day plateau as observed for ordinary type II-P supernovae, the light curve of iPTF14hls has at least five distinct peaks, followed by a steep decline at ~1000 days since discovery. Until 500 days since discovery, the effective temperature of iPTF14hls is roughly constant at 5000-6000K . In this paper we propose that iPTF14hls is likely powered by intermittent fallback accretion. It is found that the light curve of iPTF14hls can be well fit by the usual t^{-5/3} accretion law until ~1000 days post discovery when the light curve transitions to a steep decline. To account for this steep decline, we suggest a power-law density profile for the late accreted material, rather than the constant profile as appropriated for the t^{-5/3} accretion law. Detailed modeling indicates that the total fallback mass is ~0.2M_{sun}, with an ejecta mass M_{ej}~21M_{sun}. We find the third peak of the light curve cannot be well fit by the fallback model, indicating that there could be some extra rapid energy injection. We suggest that this extra energy injection may be a result of a magnetic outburst if the central object is a neutron star. These results indicate that the progenitor of iPTF14hls could be a massive red supergiant.
The remnant of supernova explosion is widely believed to be the acceleration site of high-energy cosmic ray particles. The acceleration timescale is, however, typically very long. Here we report the detection of a variable $gamma$-ray source with the Fermi Large Area Telescope, which is positionally and temporally consistent with a peculiar supernova, iPTF14hls. A quasi-stellar object SDSS J092054.04+504251.5, which is probably a blazar according to the infrared data, is found in the error circle of the $gamma$-ray source. More data about the $gamma$-ray source and SDSS J092054.04+504251.5 are needed to confirm their association. On the other hand, if the association between the $gamma$-ray source and the supernova is confirmed, this would be the first time to detect high-energy $gamma$-ray emission from a supernova, suggesting very fast particle acceleration by supernova explosions.
Logarithmic conformal field theories are based on vertex algebras with non-semisimple representation categories. While examples of such theories have been known for more than 25 years, some crucial aspects of local logarithmic CFTs have been understood only recently, with the help of a description of conformal blocks by modular functors. We present some of these results, both about bulk fields and about boundary fields and boundary states. We also describe some recent progress towards a derived modular functor. This is a summary of work with Terry Gannon, Simon Lentner, Svea Mierach, Gregor Schaumann and Yorck Sommerhauser.
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