Context. There is still no consensus about progenitor masses of type IIP supernovae. Aims. We study a normal type IIP SN 1999em in detail and compare it to a peculiar type IIP SN 1987A. Methods. We computed the hydrodynamic and time-dependent atmosphere models interpreting simultaneously both the photometric and spectroscopic observations. Results. The bolometric light curve of SN 1999em and the spectral evolution of its Hα line are consistent with a presupernova radius of 500 ± 200 R , an ejecta mass of 19.0 ± 1.2 M , an explosion energy of (1.3 ± 0.1) × 10 51 erg, and a radioactive 56 Ni mass of 0.036 ± 0.009 M . 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. The hydrodynamic and atmosphere models of SN 1999em are inconsistent with the short distance of 7.85 Mpc to the host galaxy. Conclusions. 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 56 Ni mixing up to ≈660 km s −1 compared to a moderate 56 Ni mixing up to ∼3000 km s −1 in SN 1987A, hydrogen being mixed deeply downward to ∼650 km s −1 .

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 8 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 timedependent 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 8 at a radial velocity of about À10 4 km s À1 . We identify HV absorption in H and He i 10830 8 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 À6 M yr À1 for both supernovae, assuming a wind velocity 10 km s À1 . 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, k60 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.

Context. The progenitor mass of type IIP supernova can be determined from either hydrodynamic modeling of the event or preexplosion 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 imply that a serious revision of the present-day view on the progenitors of type IIP supernovae is required.

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.

Context. The well-observed and well-studied type IIP Supernova 1987A (SN 1987A), produced by the explosion of a blue supergiant in the Large Magellanic Cloud, is a touchstone for the evolution of massive stars, the simulation of neutrino-driven explosions, and the modeling of light curves and spectra. Aims. In the framework of the neutrino-driven explosion mechanism, we study the dependence of explosion properties on the structure of different blue supergiant progenitors and compare the corresponding light curves with observations of SN 1987A. Methods. Three-dimensional (3D) simulations of neutrino-driven explosions are performed with the explicit, finite-volume, Eulerian, multifluid hydrodynamics code Prometheus, using of four available presupernova models as initial data. At a stage of almost homologous expansion, the hydrodynamical and composition variables of the 3D models are mapped to a spherically symmetric configuration, and the simulations are continued with the implicit, Lagrangian radiation-hydrodynamics code Crab to follow the blast-wave evolution into the SN outburst. Results. All of our 3D neutrino-driven explosion models, with explosion energies compatible with SN 1987A, produce 56 Ni in rough agreement with the amount deduced from fitting the radioactively powered light-curve tail. Two of our models (based on the same progenitor) yield maximum velocities of around 3000 km s −1 for the bulk of ejected 56 Ni, consistent with observational data. In all of our models inward mixing of hydrogen during the 3D evolution leads to minimum velocities of hydrogen-rich matter below 100 km s −1 , which is in good agreement with spectral observations. However, the explosion of only one of the considered progenitors reproduces the shape of the broad light curve maximum of SN 1987A fairly well. Conclusions. The considered presupernova models, 3D explosion simulations, and light-curve calculations can explain the basic observational features of SN 1987A, except for those connected to the presupernova structure of the outer stellar layers. All progenitors have presupernova radii that are too large 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 helium core and the He/H composition interface that enables sufficient outward mixing of 56 Ni 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 helium-core mass of 6 M inferred from the absolute luminosity of the presupernova star. The lack of an adequate presupernova model for the well-studied SN 1987A is a real and pressing challenge for the theory of the evolution of massive stars.