arXiv subjects

V. P. Utrobin

Publications and source records attributed to V. P. Utrobin.

28 records · Page 2Linked to original sources

arXiv2010

Type IIP Supernova 2009kf: Explosion Driven by Black Hole Accretion?

Unusually bright type IIP supernova (SN) 2009kf is studied employing the hydrodynamic modelling. We derived optimal values of the ejecta mass of 28.1 Msun, explosion energy of 2.2x10^{52} erg, and presupernova radius of 2x10^3 Rsun assuming that Ni-56 mass is equal to the upper limit of 0.4 Msun. We analyzed effects of the uncertainties in the extinction and Ni-56 mass and concluded that both the ejecta mass and explosion energy cannot be significantly reduced compared with the optimal values. The huge explosion energy of SN 2009kf indicates that the explosion is caused by the same mechanism which operates in energetic SNe Ibc (hypernovae), i.e., via a rapid disk accretion onto black hole. The ejecta mass combined with the black hole mass and the mass lost by stellar wind yields the progenitor mass of about 36 Msun. We propose a scenario in which massive binary evolution might result in the SN 2009kf event.

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arXiv2009

High mass of the type IIP supernova 2004et inferred from hydrodynamic modeling

Previous studies of type IIP supernovae have inferred that progenitor masses recovered from hydrodynamic models are higher than 15 Msun. To verify the progenitor mass of this supernova category, we attempt a parameter determination of the well-observed luminous type IIP supernova 2004et. We model the bolometric light curve and the photospheric velocities of SN 2004et by means of hydrodynamic simulations in an extended parameter space. From hydrodynamic simulations and observational data, we infer a presupernova radius of 1500 Rsun, an ejecta mass of 24.5 Msun, an explosion energy of 2.3x10^{51} erg, and a radioactive Ni-56 mass of 0.068 Msun. The estimated progenitor mass on the main sequence is in the range of 25-29 Msun. In addition, we find clear signatures of the explosion asymmetry in the nebular spectra of SN 2004et. The measured progenitor mass of SN 2004et is significantly higher than the progenitor mass suggested by the pre-explosion images. We speculate that the mass inferred from hydrodynamic modeling is overestimated and crucial missing factors are multi-dimensional effects.

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arXiv2008

Progenitor mass of the type IIP supernova 2005cs

The progenitor mass of type IIP supernova can be determined from either hydrodynamic modeling of the event or pre-explosion observations. To compare these approaches, we determine parameters of the sub-luminous supernova 2005cs and estimate its progenitor mass. We compute the hydrodynamic models of the supernova to describe its light curves and expansion velocity data. We estimate a presupernova mass of 17.3 Msun, an explosion energy of 4.1x10^{50} erg, a presupernova radius of 600 Rsun, and a radioactive Ni-56 mass of 0.0082 Msun. The derived progenitor mass of SN 2005cs is 18.2 Msun, which is in-between those of low-luminosity and normal type IIP supernovae. The obtained progenitor mass of SN 2005cs is higher than derived from pre-explosion images. The masses of four type IIP supernovae estimated by means of hydrodynamic modeling are systematically higher than the average progenitor mass for the 9-25 Msun mass range. This result, if confirmed for a larger sample, would imply that a serious revision of the present-day view on the progenitors of type IIP supernovae is required.

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arXiv2008

Circumstellar Na I and Ca II lines in type IIP supernovae and SN 1998S

We study a possibility of detection of circumstellar absorption lines of Na I D$_{1,2}$ and Ca II H,K in spectra of type IIP supernovae at the photospheric epoch. The modelling shows that the circumstellar lines of Na I doublet will not be seen in type IIP supernovae for moderate wind density, e.g., characteristic of SN 1999em, whereas rather pronounced Ca II lines with P Cygni profile should be detectable. A similar model is used to describe Na I and Ca II circumstellar lines seen in SN 1998S, type IIL with a dense wind. We show that line intensities in this supernova are reproduced, if one assumes an ultraviolet excess, which is caused primarily by the comptonization of supernova radiation in the shock wave.

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arXiv2007

Ejecta and progenitor of the low-luminosity Type IIP supernova 2003Z

The origin of low-luminosity Type IIP supernovae is unclear: they have been proposed to originate either from massive (about 25 Msun) or low-mass (about 9 Msun) stars. We wish to determine parameters of the low-luminosity Type IIP supernova 2003Z, to estimate a mass-loss rate of the presupernova, and to recover a progenitor mass. We compute the hydrodynamic models of the supernova to describe the light curves and the observed expansion velocities. The wind density of the presupernova is estimated using a thin shell model for the interaction with circumstellar matter. We estimate an ejecta mass of 14 Msun, an explosion energy of 2.45x10^50 erg, a presupernova radius of 229 Rsun, and a radioactive Ni-56 amount of 0.0063 Msun. The upper limit of the wind density parameter in the presupernova vicinity is 10^13 g/cm, and the mass lost at the red/yellow supergiant stage is less than 0.6 Msun assuming the constant mass-loss rate. The estimated progenitor mass is in the range of 14.4-17.4 Msun. The presupernova of SN 2003Z was probably a yellow supergiant at the time of the explosion. The progenitor mass of SN 2003Z is lower than those of SN 1987A and SN 1999em, normal Type IIP supernovae, but higher than the lower limit of stars undergoing a core collapse. We propose an observational test based on the circumstellar interaction to discriminate between the massive (about 25 Msun) and moderate-mass (about 16 Msun) scenarios.

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arXiv2006

An optimal hydrodynamic model for the normal Type IIP supernova 1999em

There is still no consensus about progenitor masses of Type IIP supernovae. We study a normal Type IIP SN 1999em in detail and compare it to a peculiar Type IIP SN 1987A. We computed the hydrodynamic and time-dependent atmosphere models interpreting simultaneously both the photometric and spectroscopic observations. The bolometric light curve of SN 1999em and the spectral evolution of its H-alpha line are consistent with a presupernova radius of 500 Rsun, an ejecta mass of 19.0 Msun, an explosion energy of 1.3x10^51 erg, and a radioactive 56Ni mass of 0.036 Msun. A mutual mixing of hydrogen-rich and helium-rich matter in the inner layers of the ejecta guarantees a good fit of the calculated light curve to that observed. Based on the hydrodynamic models in the vicinity of the optimal model, we derive the approximate relationships between the basic physical and observed parameters. We find that the hydrogen recombination in the atmosphere of a normal Type IIP SN 1999em, as well as most likely other Type IIP supernovae at the photospheric epoch, is essentially a time-dependent phenomenon. It is also shown that in normal Type IIP supernovae the homologous expansion of the ejecta in its atmosphere takes place starting from nearly the third day after the supernova explosion. A comparison of SN 1999em with SN 1987A reveals two very important results for supernova theory. First, the comparability of the helium core masses and the explosion energies implies a unique explosion mechanism for these core collapse supernovae. Second, the optimal model for SN 1999em is characterized by a weaker 56Ni mixing up to 660 km/s compared to a moderate 56Ni mixing up to 3000 km/s in SN 1987A, hydrogen being mixed deeply downward to 650 km/s.

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arXiv2005

Strong effects of time-dependent ionization in early SN 1987A

We study a time-dependent hydrogen ionization in the atmosphere of SN 1987A during the first month after the explosion. The model includes kinetics of hydrogen ionization and excitation, molecular hydrogen kinetics, and a time-dependent energy balance. The primary strong effect of the time-dependent ionization is the enhanced hydrogen ionization compared to the steady-state model. The time-dependent ionization provides a sufficient population of excited hydrogen levels to account for the observed H-alpha without invoking the external Ni-56. We find that the Ba II 6142 A line in SN 1987A can be reproduced for the LMC barium abundance. This resolves the long-standing problem of the unacceptably high barium overabundance in SN 1987A. The key missing factor that should be blamed for the "barium problem" is the time-dependent ionization. The modelling of the H-alpha profile on day 4.64 indicates the ratio of the kinetic energy to the ejected mass about 0.83 10^{50} erg/Msun.

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arXiv2004

The Light Curve of Supernova 1987A: The Structure of the Presupernova and Radioactive Nickel Mixing

We have studied the influence of the presupernova structure and the degree of Ni-56 mixing on the bolometric light curve of SN 1987A in terms of radiation hydrodynamics in the one-group approximation by abandoning LTE and by taking into account nonthermal ionization and the contribution of spectral lines to opacity. Our study shows that moderate Ni-56 mixing at velocities of < 2500 km/s can explain the observed light curve if the density of the outer layers of the presupernova exceeds the value obtained in the evolutionary model of a single nonrotating star severalfold. Abandoning LTE and allowing for nonthermal ionization when solving the equation of state and calculating the mean opacities and the thermal emission coefficient leads to a significant difference between the gas temperature and the radiation temperature in the optically thin layers of the supernova envelope. We demonstrate the fundamental role of the contribution of spectral lines to the opacity in an expanding envelope and of the accurate description of radiative transfer in reproducing the observed shape of the bolometric light curve. We have found that disregarding the contribution of spectral lines to the opacity introduces an error of 20% into the explosion energy, and that a similar error is possible when determining the mass of the ejected matter. The resonant scattering of radiation in numerous lines accelerates the outer layers to velocities of 36 000 km/s; this additional acceleration affects the outer layers with a mass of 10^{-6} Msun. Proper calculations of the supernova luminosity require that not only the delay effects, but also the limb-darkening effects be taken into account.

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arXiv2002

Freeze-out Effects in Hydrogen and Helium Lines of SN 1987A at the Early Photospheric Epoch

We have developed a time-dependent model of ionization, excitation and energy balance of SN 1987A atmosphere at the photospheric epoch to study early behavior of hydrogen and helium lines. The ionization freeze-out effects play a key role in producing both the strong H-alpha during nearly the first month and the He I 5876 A scattering line on day 1.76. Using an extended reaction network between hydrogen molecules and their ions demonstrates that ion-molecular processes are likely responsible for the blue peak in H-alpha profile at the Bochum event epoch.

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arXiv2002

Ionization freeze-out and barium problem in supernova 1987A

We have shown that in the atmosphere of SN 1987A level populations of hydrogen are mostly controlled by an ionization freeze-out and ion-molecular processes up to 40 days. The ionization freeze-out effects are important for normal SNe II-P as well. The time dependent effects and the mutual neutralization between H^- and H^+ may result in a non-monotonic radial dependence of the Sobolev optical depth for H-alpha and then in a blue emission satellite of H-alpha observed in SN 1987A spectra at Bochum event phase. The relative abundance of molecular hydrogen about 0.0001-0.001 is high enough for the photospheric phase of SN 1987A. We emphasize that the poor knowledge of the far UV radiation field in the envelope of SN 1987A still forbids a truly reliable estimate of the Ba abundance but well-constructed and tested models may improve this situation.

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