Petr V. Baklanov

Supernovae from Red Supergiants with Extensive Mass Loss

We calculate multicolour light curves (LCs) of supernovae (SNe) from red supergiants (RSGs) that have exploded within a dense circumstellar medium (CSM). Multicolour LCs are calculated by using the multigroup radiation hydrodynamics code STELLA. If the CSM is dense enough, the shock breakout signal is delayed and smeared by the CSM and the kinetic energy of SN ejecta is efficiently converted to thermal energy, which is eventually released as radiation. We find that explosions of RSGs are affected by the CSM in the early epochs, when the mass-loss rate just before the explosions is higher than ∼10 ―4 M ⊙ yr ―1 . Their characteristic features are that the LC has a luminous round peak followed by a flat part, that multicolour LCs are simultaneously bright in both ultraviolet and optical at the peak, and that the photo-spheric velocity is very low at these epochs. We calculate LCs for various CSM conditions and explosion properties, i.e. mass-loss rates, radii of the CSM, density slopes of the CSM, explosion energies of SN ejecta and the SN progenitors contained within, to see their influence. We compare our model LCs with those of ultraviolet-bright Type IIP SN 2009kf and show that the mass-loss rate of the progenitor of SN 2009kf just before the explosion is likely to be higher than 10- 4 M ⊙ yr ―1 . Combined with the fact that SN 2009kf is likely to be an energetic explosion and has large 56 Ni production, which implies that the progenitor of SN 2009kf is a massive RSG, our results indicate that there could be some mechanism to induce extensive mass loss in massive RSGs just before their explosions.

RAPIDLY RISING TRANSIENTS FROM THE SUBARU HYPER SUPRIME-CAM TRANSIENT SURVEY*

We present rapidly rising transients discovered by a high-cadence transient survey with the Subaru telescope and Hyper Suprime-Cam. We discovered five transients at z = 0.384–0.821, showing a rate of rise faster than 1 mag per day in the restframe near-ultraviolet wavelengths. The fast rate of rise and brightness are most similar to SN 2010aq and PS1-13arp, for which ultraviolet emission was detected within a few days after the shock breakout. The lower limit of the event rate of rapidly rising transients is ~9% of core-collapse supernova rates, assuming the duration of rapid rise to be 1 day. We show that the light curves of the three faint objects agree with the cooling envelope emission from the explosion of red supergiants. The other two luminous objects, however, are brighter and faster than the cooling envelope emission. We interpret these two objects to be the shock breakout from a dense wind with a mass loss rate of ~10−3 yr−1, as also proposed for PS1-13arp. This mass loss rate is higher than that typically observed for red supergiants. The event rate of these luminous objects is 1% of the core-collapse supernova rate, and thus our study implies that more than ~1% of massive stars can experience intense mass loss a few years before the explosion.

Synthetic light curves of shocked dense circumstellar shells

We numerically investigate light curves (LCs) of shocked circumstellar shells which are suggested to reproduce the observed LC of superluminous SN 2006gy analytically. In the previous analytical model, the effects of the recombination and the bolometric correction on LCs are not taken into account. To see the effects, we perform numerical radiation hydrodynamic calculations of shocked shells by using STELLA, which can numerically treat multigroup radiation transfer with realistic opacities. We show that the effects of the recombination and the bolometric correction are significant and the analytical model should be compare to the bolometric LC instead of a single band LC. We find that shocked circumstellar shells have a rapid LC decline initially because of the adiabatic expansion rather than the luminosity increase and the shocked shells fail to explain the LC properties of SN 2006gy. However, our synthetic LCs are qualitatively similar to those of superluminous SN 2003ma and SN 1988Z and they may be related to shocked circumstellar shells.

Hydrogenless superluminous supernova PTF12dam in the model of an explosion inside an extended envelope

Amodel of a supernova explosion inside a dense extended hydrogenless envelope is proposed to explain the properties of the light curve for one of the superluminous supernovae PTF12dam. It is argued in the literature that the flux of this supernova rises too fast to be explained by the explosion model due to the instability associated with the electron-positron pair production (pair-instability supernova, PISNe), but it is well described by the models with energy input by a magnetar. We show that the PTF12dam-type supernovae can be explained without a magnetar in a model with a radiative shock in a dense circumstellar envelope that does not require an excessively large explosion energy.

Direct distance measurements to SN 2009ip

ABSTRACT We demonstrate the applicability of our new method (the Dense Shell Method orDSM)forthedeterminationofastronomicaldistancesbycalculatingthedistancetoSN 2009ip. The distance to this supernova has been accurately determined in thestandardapproachviathecosmicdistanceladderandhasbeenfoundtobe20.4Mpc.Ourdirectmethod,assumingthemostreasonableparametervalues,givesaverycloseresult,namely≈ 20.1±0.8(68%CL)MpctoSN2009ip.Key words: supernovae:cosmography–supernovae:individual(SN2009ip) 1 INTRODUCTIONIn ref. (Blinnikov et al. 2012) we introduced a new methodfor measuring cosmological distances, which we suggest call-ing the Dense Shell Method (DSM). The method relieson observations of an expanding dense shell in SN IInand allows one to determine the linear size of such ashell in absolute units, and hence the distance to it, with-out addressing the cosmological distance ladder. Using thismethod Blinnikov et al. (2012) have calculated the distanceto SN 2006gy. But the result suffers from quite a large er-ror due to uncertainty in the interstellar extinction and inthe color temperature. Moreover, a small number of obser-vations of the rising part of the light curve, when the shellis believed not to fragment, also lead to a larger uncertaintyin the measurements. In this paper, we examine the appli-cability of our method to the case of the SN 2009ip, whichexploded again in 2012. We show that the DSM allows oneto obtain much more accurate results in this case.2 DIRECT DISTANCEDETERMINATION BYTHE DSMSupernovae of type IIn are observed at very large redshifts(Cooke 2008; Cooke et al. 2009; Moriya et al. 2012). Sincethey do not enter the coasting-free expansion phase, neitherexpanding photosphere method (Kirshner & Kwan 1974)nor spectra-fitting expanding atmosphere method (SEAM,

Pulsational Pair-instability Model for Superluminous Supernova PTF12dam:Interaction and Radioactive Decay

Being a superluminous supernova, PTF12dam can be explained by a 56Ni-powered model, a magnetar-powered model, or an interaction model. We propose that PTF12dam is a pulsational pair-instability supernova, where the outer envelope of a progenitor is ejected during the pulsations. Thus, it is powered by a double energy source: radioactive decay of 56Ni and a radiative shock in a dense circumstellar medium. To describe multicolor light curves and spectra, we use radiation-hydrodynamics calculations of the STELLA code. We found that light curves are well described in the model with 40 M⊙ ejecta and 20–40 M⊙ circumstellar medium. The ejected 56Ni mass is about 6 M⊙, which results from explosive nucleosynthesis with large explosion energy (2–3) × 1052 erg. In comparison with alternative scenarios of pair-instability supernova and magnetar-powered supernova, in the interaction model, all the observed main photometric characteristics are well reproduced: multicolor light curves, color temperatures, and photospheric velocities.

Early light curves for Type Ia supernova explosion models

Upcoming high-cadence transient survey programmes will produce a wealth of observational data for Type Ia supernovae. These data sets will contain numerous events detected very early in their evolution, shortly after explosion. Here, we present synthetic light curves, calculated with the radiation hydrodynamical approach Stella for a number of different explosion models, specifically focusing on these first few days after explosion. We show that overall the early light curve evolution is similar for most of the investigated models. Characteristic imprints are induced by radioactive material located close to the surface. However, these are very similar to the signatures expected from ejecta-CSM or ejecta-companion interaction. Apart from the pure deflagration explosion models, none of our synthetic light curves exhibit the commonly assumed power-law rise. We demonstrate that this can lead to substantial errors in the determination of the time of explosion. In summary, we illustrate with our calculations that even with very early data an identification of specific explosion scenarios is challenging, if only photometric observations are available.

Study of Supernovae Important for Cosmology

The dense shell method for the determination of distances to type IIn supernovae has been briefly reviewed. Applying our method to SN 2006gy, SN 2009ip, and SN 2010jl supernovae, we have obtained distances in excellent agreement with the previously known distances to the parent galaxies. The dense shell method is based on the radiation hydrodynamic model of a supernova. The method of the blackbody model, as well as the correctness of its application for simple estimates of distances from observation data, has been justified.The dense shell method for the determination of distances to type-IIn supernovae has been briefly reviewed. Applying our method to SN 2006gy, SN 2009ip, and SN 2010jl supernovae, we have obtained distances in excellent agreement with the previously known distances to the parent galaxies. The dense shell method is based on the radiation hydrodynamic model of a supernova. The method of the blackbody model, as well as the correctness of its application for simple estimates of distances from observation data, has been justified.

Direct determination of the hubble parameter using type IIn supernovae

A novel approach, a Dense Shell Method, is proposed for measuring distances for cosmology. It is based on original Baade idea to relate absolute difference of photospheric radii with photospheric velocity. We demonstrate that this idea works: the new method does not rely on the Cosmic Distance Ladder and gives satisfactory results for the most luminous Type IIn Supernovae. This allows one to make them good primary distance indicators for cosmology. Fixing correction factors for illustration, we obtain with this method the median distance of ≈ 68−15+19(68%CL) Mpc to SN 2006gy and median Hubble parameter 79−17+23(68%CL) km/(s Mpc).