V. P. Utrobin

Progenitor mass of the type IIP supernova 2005cs

Context. The progenitor mass of type IIP supernova can be determined from either hydrodynamic modeling of the event or pre-explosion observations. Aims. To compare these approaches, we determine parameters of the sub-luminous supernova 2005cs and estimate its progenitor mass. Methods. We compute the hydrodynamic models of the supernova to describe its light curves and expansion velocity data. Results. We estimate a presupernova mass of 17.3± 1 M⊙, an explosion energy of (4.1± 0.3)× 10 50 erg, a presupernova radius of 600± 140 R⊙, and a radioactive 56 Ni mass of 0.0082± 0.0016 M⊙. The derived progenitor mass of SN 2005cs is 18.2± 1 M⊙, which is in-between those of low-luminosity and normal type IIP supernovae. Conclusions. 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 M⊙ mass range. This result, if confirmed for a larger sample, would im ply that a serious revision of the present-day view on the pro genitors of type IIP supernovae is required.

Optical Signatures of Circumstellar Interaction in Type IIP Supernovae

We propose new diagnostics for circumstellar interaction in Type IIP supernovae (SNe IIP) by the detection of high-velocity (HV) absorption features in H? and He I 10830 ? lines during the photospheric stage. To demonstrate the method, we compute the ionization and excitation of H and He in supernova ejecta taking into account time-dependent effects and X-ray irradiation. We find that the interaction with a typical red supergiant wind should result in the enhanced excitation of the outer layers of unshocked ejecta and the emergence of corresponding HV absorption, i.e., a depression in the blue absorption wing of H? and a pronounced absorption of He I 10830 ? at a radial velocity of about -104 km s-1. We identify HV absorption in H? and He I 10830 ? lines of SN 1999em and in H? of SN 2004dj as being due to this effect. The derived mass-loss rate is close to 10-6 M? yr-1 for both supernovae, assuming a wind velocity 10 km s-1. We argue that in addition to the HV absorption formed in the unshocked ejecta, spectra of SN 2004dj and SN 1999em show a HV notch feature that is formed in the cool dense shell (CDS) modified by the Rayleigh-Taylor instability. The CDS results from both shock breakout and radiative cooling of gas that has passed through the reverse shock wave. The notch becomes dominant in the HV absorption during the late photospheric phase, 60 days. The wind density deduced from the velocity of the CDS is consistent with the wind density found from the HV absorption produced by unshocked ejecta.

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

Context. Previous studies of type IIP supernovae have inferred that progenitor masses recovered from hydrodynamic models are higher than 15 M� . Aims. To verify the progenitor mass of this supernova category, we attempt a parameter determination of the well-observed luminous type IIP supernova 2004et. Methods. We model the bolometric light curve and the photospheric velocities of SN 2004et by means of hydrodynamic simulations in an extended parameter space. Results. From hydrodynamic simulations and observational data, we infer a presupernova radius of 1500 ± 140 R� , an ejecta mass of 24.5 ± 1 M� , an explosion energy of (2.3 ± 0.3) × 10 51 erg, and a radioactive 56 Ni mass of 0.068 ± 0.009 M� . The estimated progenitor mass on the main sequence is in the range of 25−29 M� . In addition, we find clear signatures of the explosion asymmetry in the nebular spectra of SN 2004et. Conclusions. The measured progenitor mass of SN 2004et is significantly higher than the progenitor mass suggested by the preexplosion images. We speculate that the mass inferred from hydrodynamic modeling is overestimated and crucial missing factors are multi-dimensional effects.

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 56Ni 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 its opacity. Our study shows that moderate 56Ni mixing at velocities ≤2500 km s−1 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 ≈36000 km s−1; this additional acceleration affects the outer layers with a mass of ≈10−6M⊙. Proper calculations of the supernova luminosity require that not only the delay effects, but also the limb-darkening effects be taken into account.

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

Context. The origin of low-luminosity type IIP supernovae is unclear: they have been proposed to originate either from massive (∼25 M� )o r low-mass (∼9 M� )s tars. Aims. 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. Methods. 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. Results. We estimate an ejecta mass of 14.0 ± 1.2 M� , an explosion energy of (2.45 ± 0.18) × 10 50 erg, a presupernova radius of 229 ± 39 R� , and a radioactive 56 Ni amount of 0.0063 ± 0.0006 M� . The upper limit of the wind density parameter in the presupernova

Supernova 1987A : The envelope mass and the explosion energy

Our study of the photometric and spectroscopic observations of SN 1987A based on the hydrodynamic modeling of its bolometric light curve and nonstationary hydrogen kinetics and energy balance when modeling the hydrogen spectral lines at the photospheric stage has shown that good agreement with the observations can be achieved only at a ratio of the explosion energy to the ejected-envelope mass of ≈0.83 × 1050 erg M⊙−1. In this case, the radius of the presupernova is 35.0 ± 5R⊙, and the surface chemical composition is typical of the LMC with the mass fractions of hydrogen X = 0.743, helium Y = 0.251, and heavy elements Z = 0.006. The analyzed dependence of the bolometric light curve on the mass of the ejected envelope at the above ratio of the explosion energy to the envelope mass suggests that the optimal mass is 18.0M⊙ with an admissible spread of ±1.5M⊙, and, accordingly, the explosion energy of SN 1987A is (1.50 ± 0.12) × 1051 erg. If a neutron star with a mass of ≈1.6M⊙ was formed through the gravitational collapse of an iron stellar core, then the mass of the presupernova immediately before the explosion of SN 1987A was 19.6 ± 1.5M⊙.

TYPE IIP SUPERNOVA 2009kf: EXPLOSION DRIVEN BY BLACK HOLE ACCRETION?

The unusually bright type IIP supernova (SN) 2009kf is studied employing hydrodynamic modeling. We derived optimal values of the ejecta mass of 28.1 M ☉, explosion energy of 2.2 × 1052 erg, and presupernova radius of 2 × 103 R ☉ assuming that 56Ni mass is equal to the upper limit of 0.4 M ☉. We analyzed effects of the uncertainties in the extinction and 56Ni 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 M ☉. We propose a scenario in which massive binary evolution might result in the SN 2009kf event.

Supernova 1987A: neutrino-driven explosions in three dimensions and light curves

The well-studied type IIP SN 1987A, produced by the explosion of a blue supergiant (BSG) star, is a touchstone for massive-star evolution, simulations of neutrino-driven explosions, and modeling of light curves and spectra. In the framework of the neutrino-driven mechanism, we study the dependence of explosion properties on the structure of four different BSGs and compare the corresponding light curves with observations of SN 1987A. We perform 3D simulations with the PROMETHEUS code until about one day and map the results to the 1D code CRAB for the light curve calculations. All of our 3D models with explosion energies compatible with SN 1987A produce 56Ni in rough agreement with the amount deduced from fitting the radioactively powered light-curve tail. One of the progenitors yields maximum velocities of ~3000 km/s for the bulk of ejected 56Ni, consistent with observations. In all of our models inward mixing of hydrogen during the 3D evolution leads to minimum H-velocities below 100 km/s, in good agreement with spectral observations. The considered BSG models, 3D explosion simulations, and light-curve calculations can thus explain basic observational features of SN 1987A. However, all progenitors have too large pre-SN radii to reproduce the narrow initial luminosity peak, and the structure of their outer layers is not suitable to match the observed light curve during the first 30-40 days. Only one stellar model has a structure of the He core and the He/H composition interface that enables sufficient outward mixing of 56Ni and inward mixing of hydrogen to produce a good match of the dome-like shape of the observed light-curve maximum. But this model falls short of the He-core mass of 6 Msun inferred from the absolute luminosity of the pre-SN star. The lack of an adequate pre-SN model for SN 1987A is a pressing challenge for the theory of massive-star evolution. (Abridged)

The spectacular evolution of Supernova 1996al over 15 yr: a low-energy explosion of a stripped massive star in a highly structured environment

Spectrophotometry of SN 1996al carried out throughout 15 years is presented. The early photometry suggests that SN 1996al is a Linear type-II supernova, with an absolute peak of MV 18:2 mag. Early spectra present broad, asymmetric Balmer emissions, with super-imposed narrow lines with P-Cygni prole, and He I features with asymmetric, broad emission components. The analysis of the line proles shows that the H and He broad components form in the same region of the ejecta. By day +142, the H prole dramatically changes: the narrow P-Cygni prole disappears,

Type IIP supernova 2008in: the explosion of a normal red supergiant

Context. The explosion energy and the ejecta mass of a type IIP supernova make up the basis for the theory of explosion mechanism. So far, these parameters have only been determined for seven events. Aims. Type IIP supernova 2008in is another well-observed event for which a detailed hydrodynamic modeling can be used to derive the supernova parameters. Methods. Hydrodynamic modeling was employed to describe the bolometric light curve and the expansion velocities at the photosphere level. A time-dependent model for hydrogen ionization and excitation was applied to model the H and H line profiles. Results. We found an ejecta mass of 13:6 1:9 M , an explosion energy of (5:05 3:4) 10 50 erg, a presupernova radius of 570 100 R , and a radioactive 56 Ni mass of 0:015 0:005 M . The estimated progenitor mass is 15:5 2:2 M . We uncovered a problem of the H and H description at the early phase, which cannot be resolved within a spherically symmetric model. Conclusions. The presupernova of SN 2008in was a normal red supergiant with the minimum mass of the progenitor among eight type IIP supernovae explored by means of the hydrodynamic modeling. The problem of the absence of type IIP supernovae with the progenitor masses <15 M in this sample remains open.