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The September 2012 outburst of the type IIn supernova 2009ip was simulated using two independent codes, STELLA and FRONT. The light curves obtained agree well with one another and with observational data. Special attention is given to the dynamics of the emerging dense shell, which determines the luminosity of the object and is used for the direct method of determining the distance to the supernova. Two-dimensional spectral radiation-hydrodynamics computations of the SN 2009ip model were carried out, which confirmed the conclusion about the stability of this shell on the times scales of the method application. [ABSTRACT FROM AUTHOR]

We present the results of BVRI photometry for the type II-P supernova (SN) 2019edo in NGC 4162 obtained from April 29, 2019, to January 26, 2020, with several telescopes, including the 60-cm telescope at the Caucasus Mountain Observatory of the Sternberg Astronomical Institute of the Moscow State University. The shape of the light curves is typical for SN II-P. However, the plateau lasted for about 76 days, which is less than the typical value for SN of this class, while the luminosity rise to the peak was unusually fast. The absolute magnitude at maximum light was 9, which is close to the mean value for SN II-P. The brightness decline rate at the late phase is slightly higher than the expected one for the radiation due to Co decay. As a result of our radiation-hydrodynamics simulations of the SN explosion with the STELLA code, we have managed to consistently reproduce the initial rise and plateau phases in the light curves. The constructed SN model has the following parameters: an ejecta mass , an SN progenitor radius , and a mass of radioactive . The SN progenitor was inside a cocoon, a stellar wind, with a total mass and a radius cm. The energy release during the explosion was erg. [ABSTRACT FROM AUTHOR]

We compare the results of our computations of a simplified one-dimensional model for a type II supernova with a free expansion stage by the STELLA and FRONT codes that are based on different hydrodynamic approaches. We describe the problems that arise in numerical simulations of such supernovae on Eulerian grids using explicit schemes and possible ways of their solution. The profiles of physical quantities and the light curves of a model supernova obtained using these different approaches are shown to agree well with each other. We have also demonstrated that the light curve of such a type II supernova in the band has a characteristic double-peaked structure. The amplitudes of both peaks virtually coincide between themselves, while the duration of the second peak is longer than that of the first one by orders of magnitude. [ABSTRACT FROM AUTHOR]

The results of UBVRIJHK photometry for the type II-P supernova SN 2018aoq in NGC 4151 obtained from April 4, 2018, to January 14, 2019, with several telescopes, including the 2.5-m telescope at the Caucasus Mountain Observatory of the Sternberg Astronomical Institute of the Moscow State University, are presented. The main parameters of its light curves have been determined. The light and color curves of SN 2018aoq and several well-studied SNe II-P are compared. SN 2018aoq is shown to be intermediate in peak luminosity between SNe II-P with normal and reduced luminosities. Radiation-hydrodynamics simulations of the light curves and velocities of the expanding envelope of SN 2018aoq have been performed using the STELLA code. The best agreement with the observations has been achieved for SN progenitor models with an ejecta mass , a mass of radioactive Ni , and an explosion energy erg at metallicity . The SN progenitor radius depends on the adopted distance to NGC 4151 and its values are at Mpc and at Mpc. [ABSTRACT FROM AUTHOR]

The oxygen density in the central zone of the ejecta of nine type IIP supernovae (SNe IIP) at the nebular phase has been determined from the [O I] 6300, 6364 Å doublet lines. In combination with the known estimates for two supernovae, the results of measurements show that the oxygen densities on day 300 are distributed in a narrow range, (2.3 ± 1) × 109 cm. This result does not depend on the distance, extinction, and model assumptions. Analysis of the density distribution found leads to the conclusion that the SN IIP explosion energy increases with stellar mass. [ABSTRACT FROM AUTHOR]

We study disparity between H α and H β in early spectra of the type IIP supernova SN 2008in. The point is that these lines cannot be described simultaneously in a spherically-symmetric model with the smooth density distribution. It is shown that an assumption of a clumpy structure of external layers of the envelope resolves the problem. We obtain estimates of the velocity at the inner border of the inhomogeneous zone (≈6100 km s), the filing factor of inhomogeneities (≤0.5), and the mass of the inhomogeneous layers (∼0.03 M). The amplitude of flux fluctuations in the early spectrum of H α (Δ F/F ∼ 10) imposes a constraint on the size of inhomogeneities (≤200 km s). A detection of fluctuations in the early H α of type IIP supernovae might become an observational test of the inhomogeneous structure of their envelopes. We propose also the indirect test of the clumpy structure of external layers: the study of properties of the initial radiation outburst due to the shock breakout. The inhomogeneous structure of external layers of type IIP supernovae could be an outcome of density perturbations and density inversion in outer convective layers of presupernova red supergiant. [ABSTRACT FROM AUTHOR]

We investigate the possibility of detecting the circumstellar Na I D1,2 and Ca II H, K absorption lines in the spectra of type IIP supernovae at the photospheric phase. Our modeling shows that the Na I doublet lines will not be seen in the spectra of type IIP supernovae at moderate stellar wind densities, for example, characteristic of SN 1999em, while the rather intense Ca II lines with P Cyg profiles should be detectable. The same model is used to describe the circumstellar Na I and Ca II lines in the spectrum of SN 1998S, a type IIL supernova with a dense wind. We show that the circumstellar line intensities in this supernova are reproduced only if there is an ultraviolet excess that is mainly attributable to the Comptonization of supernova radiation in the shock wave. [ABSTRACT FROM AUTHOR]

We hypothesize the formation of neon associated with isotopically anomalous xenon (Xe-HL) in meteoritic nanodiamonds and designated as Ne-X through the mixing of the Ne-HL and Ne-S subcomponents. The Ne-HL subcomponent is neon from the helium (He/C) zone of a type II supernova or a mixture of neon from this zone and its hydrogen zone, while the Ne-S subcomponent is spallation neon formed during a supernova explosion in nuclear spallation reactions induced by high-energy protons. Based on this hypothesis and the presumed abundances of neon isotopes in the zones of a high-mass (25 M ⊙) supernova after its explosion, we have calculated the abundances of neon components in nanodiamond separates and its grain-size fractions. Our calculations have shown the following. (1) The main source of Ne-HL is neon from the helium zone of the supernova; as a result, the 20Ne/22Ne and 21Ne/22Ne ratios for Ne-X are 0.26 ± 0.03 and 0.19 ± 0.04, respectively. The isotopic composition of Ne-X is identical to that for Ne-A2 if Ne-HL is produced by the mixing of neon from the helium and hydrogen zones in proportion 1: 1.06. (2) In meteoritic nanodiamonds, the main neon abundance is determined by neon of the P3 component (Ne-P3). Ne-P3 is retained during thermal metamorphism, because it is sited in traps of the crystal lattice of diamond with a high energy of its activation. (3) The Ne-X/Ne-P3 ratio increases with nanodiamond grain size; as a result, there is no need to invoke an additional neon component (Ne-P6) to interpret the data on neon in meteoritic nanodiamonds. [ABSTRACT FROM AUTHOR]

I study the question of whether the asymmetry of 56Ni ejecta that results in the asymmetry of the H α emission line at the nebular epoch of the type-IIP supernova SN 2004dj can account for the recently detected polarization of the supernova radiation. I have developed a model of the H α profile and luminosity with nonthermal ionization and excitation in a spherically symmetric envelope for an asymmetric bipolar 56Ni distribution. I have calculated the polarized radiation transfer against the background of the recovered electron density distribution. The observed polarization is shown to be reproduced at the nebular epoch around day 140 for the same parameters of the envelope, and the 56Ni distribution for which the evolution of the H α luminosity and profile is explained. Yet the model polarization decreases with time more slowly than is observed. The origin of the additional component responsible for the early polarization on day 107 is discussed. [ABSTRACT FROM AUTHOR]

Photometric and spectroscopic observations of the nearby type-IIP supernova 2004dj are presented. The 56Ni mass in the envelope of SN 2004dj was estimated from the light curve to be ≈0.02M⊙. This estimate is confirmed by modeling the Hα luminosity. The Hα emission line exhibits a strong asymmetry characterized by the presence of a blue component in the line with a shift of –1600 km s–1 at the early nebular phase. A similar asymmetry was found in the Hβ, [O I], and [Ca II] lines. The line asymmetry is interpreted as being the result of asymmetric 56Ni ejecta. The Hα profile and its evolution are reproduced in the model of an asymmetric bipolar 56Ni structure for a spherical hydrogen distribution. The mass of the front 56Ni jet is comparable to that of the central component and twice that of the rear 56Ni jet. We point out that the asymmetric bipolar structure of 56Ni ejecta is also present in SN 1999em, a normal type-IIP supernova.© 2005 Pleiades Publishing, Inc. [ABSTRACT FROM AUTHOR]

We model the interaction of the supernova SN 1995G with a dense circumstellar (CS) gas in a thin-shell approximation. A model fit to the observed bolometric light curve combined with data on the supernova expansion velocity gives estimates for the density, mass (≈1 M[sub ⊙]), and age (≈8 yr) of the CS envelope. The determined CS-envelope density is shown to be virtually independent of the assumed mass of the supernova envelope because of the high CS-gas density at which the forward shock wave is essentially radiative. The derived CS-envelope density is consistent with the Hα luminosity and with the presence of distinct Thomson scattering in the red wing of this line. The mass of the CS envelope together with its expansion velocity and age indicate that the CS envelope was ejected by the presupernova eight years before the supernova explosion through violent energy release (∼6 × 10[sup 48] erg).© 2003 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]