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Register a new userThe explosion energy of the type IIP supernova SN 2013fs with a confined dense circumstellar shell
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N. N. Chugai
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The recent study of SN 2013fs flash spectrum suggests enormous for SN IIP explosion energy, far beyond possibilities of the neutrino mechanism. The issue of the explosion energy of SN 2013fs is revisited making use of effects of the early supernova interaction with the dense circumstellar shell. The velocity of the cold dense shell between reverse and forward shocks is inferred from the analysis of the broad heii,4686,AA on day 2.4. This velocity alongside with other observables provide us with an alternative energy estimate of $sim1.8times10^{51}$,erg for the preferred mass of $sim10$msun. The inferred value is within the range of the neutrino driven explosion.
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With the advent of new wide-field, high-cadence optical transient surveys, our understanding of the diversity of core-collapse supernovae has grown tremendously in the last decade. However, the pre-supernova evolution of massive stars, that sets the physical backdrop to these violent events, is theoretically not well understood and difficult to probe observationally. Here we report the discovery of the supernova iPTF13dqy = SN 2013fs, a mere ~3 hr after explosion. Our rapid follow-up observations, which include multiwavelength photometry and extremely early (beginning at ~6 hr post-explosion) spectra, map the distribution of material in the immediate environment (<~ 10^15 cm) of the exploding star and establish that it was surrounded by circumstellar material (CSM) that was ejected during the final ~1 yr prior to explosion at a high rate, around 10^-3 solar masses per year. The complete disappearance of flash-ionised emission lines within the first several days requires that the dense CSM be confined to within <~ 10^15 cm, consistent with radio non-detections at 70--100 days. The observations indicate that iPTF13dqy was a regular Type II SN; thus, the finding that the probable red supergiant (RSG) progenitor of this common explosion ejected material at a highly elevated rate just prior to its demise suggests that pre-supernova instabilities may be common among exploding massive stars.
We present observations and analysis of SN 2020cxd, a Low luminous (LL), long-lived Type IIP SN. This object was a clear outlier in the magnitude-limited SN sample recently presented by the ZTF Bright Transient Survey. We demonstrate that SN 2020cxd is an additional member of the group of LL SNe, and discuss the rarity of LL SNe in the context of the ZTF survey, and how further studies of these faintest members of the CC SN family might help understand the underlying initial mass function for stars that explode.
Type IIP supernovae (SNe IIP), which represent the most common class of core-collapse (CC) SNe, show a rapid increase in continuum polarization just after entering the tail phase. This feature can be explained by a highly asymmetric helium core, which is exposed when the hydrogen envelope becomes transparent. Here we report the case of a SN IIP (SN~2017gmr) that shows an unusually early rise of the polarization, $gtrsim 30$ days before the start of the tail phase. This implies that SN~2017gmr is an SN IIP that has very extended asphericity. The asymmetries are not confined to the helium core, but reach out to a significant part of the outer hydrogen envelope, hence clearly indicating a marked intrinsic diversity in the aspherical structure of CC explosions. These observations provide new constraints on the explosion mechanism, where viable models must be able to produce such extended deviations from spherical symmetry, and account for the observed geometrical diversity.
The unusual Type IIP SN 2017gmr is revisited in order to pinpoint the origin of its anomalous features, including the peculiar light curve after about 100 days. The hydrodynamic modelling suggests the enormous explosion energy of about 10^52 erg. We find that the light curve with the prolonged plateau/tail transition can be reproduced either in the model with a high hydrogen abundance in the inner ejecta and a large amount of radioactive Ni-56, or in the model with an additional central energy source associated with the fallback/magnetar interaction in the propeller regime. The asymmetry of the late H-alpha emission and the reported linear polarization are reproduced by the model of the bipolar Ni-56 ejecta. The similar bipolar structure of the oxygen distribution is responsible for the two-horn structure of the [O I] 6360, 6364 A emission. The bipolar Ni-56 structure along with the high explosion energy are indicative of the magneto-rotational explosion. We identify narrow high-velocity absorption features in H-alpha and He I 10830 A lines with their origin in the fragmented cold dense shell formed due to the outer ejecta deceleration in a confined circumstellar shell.
We present the results the photometric observations of the Type IIP supernova SN 2012aw obtained for the time interval from 7 till 371 days after the explosion. Using the previously published values of the photospheric velocities weve computed the hydrodynamic model which simultaneously reproduced the photometry observations and velocity measurements. The model was calculated with the multi-energy group radiation hydrodynamics code STELLA. We found the parameters of the pre-supernova: radius $R = 500 R_odot$, nickel mass $M(^{56}$Ni$)$ $sim 0.06 M_odot$, pre-supernova mass $25 M_odot$, mass of ejected envelope $23.6 M_odot$, explosion energy $E sim 2 times 10^{51}$ erg. The model progenitor mass $M=25 M_odot$ significantly exceeds the upper limit mass $M=17 M_odot$, obtained from analysis the pre-SNe observations. This result confirms once more that the Red Supergiant Problem must be resolved by stellar evolution and supernova explosion theories in interaction with observations.
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