Showing papers by "Takashi J. Moriya published in 2011"

Supernovae from red supergiants with extensive mass loss

Abstract: 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.

Diversity of Luminous Supernovae from Non-Steady Mass Loss

Abstract: We show that the diversity in the density slope of the dense wind due to non-steady mass loss can be one way to explain the spectral diversity of Type II luminous supernovae (LSNe). The interaction of SN ejecta and wind surrounding it is considered to be a power source to illuminate LSNe because many LSNe show the wind signature in their spectra (Type IIn LSNe). However, there also exist LSNe without the spectral features caused by the wind (Type IIL LSNe). We show that, even if LSNe are illuminated by the interaction, it is possible that they do not show the narrow spectra from the wind if we take into account of non-steady mass loss of their progenitors. When the shock breakout takes place in the dense wind with the density structure \rho\propto r^{-w}, the ratio of the diffusion timescale in the optically thick region of the wind (td) and the shock propagation timescale of the entire wind after the shock breakout (ts) strongly depends on w. For the case w<~1, both timescales are comparable (td/ts \simeq 1) and td/ts gets smaller as w gets larger. For the case td/ts\simeq 1, the shock goes through the entire wind just after the light curve (LC) peak and narrow spectral lines from the wind cannot be observed after the LC peak (Type IIL LSNe). If td/ts is much smaller, the shock wave continues to propagate in the wind after the LC peak and unshocked wind remains (Type IIn LSNe). This difference can be obtained only through a careful treatment of the shock breakout condition in a dense wind. The lack of narrow Lorentzian line profiles in Type IIL LSNe before the LC peak can also be explained by the difference in the density slope. Furthermore, we apply our model to Type IIn LSN 2006gy and Type IIL LSN 2008es and find that our model is consistent with the observations.

Detection of cytochrome P450 substrates by using a small-molecule droplet array on an NADH-immobilized solid surface

Abstract: Seeing below the surface: A small-molecule droplet array platform on an NADH-immobilized solid surface and a biotinylated acetophenone derivative were developed to identify the substrate candidates for soluble P450 enzymes of interest. This methodology is thought to be easily applicable to other class I P450 systems, including those that use NADPH as cofactor.

Ultraviolet-Bright Type IIP Supernovae from Massive Red Supergiants

Abstract: Red supergiants (RSGs) are progenitors of Type IIP supernovae (SNe). It is suggested that RSGs can experience a mass loss with a very high mass-loss rate (even as high as 0.01 M⊙ yr−1) due to, e.g., dynamical instabilities of their envelopes (e.g., Yoon & Cantiello (2010)). Because of the extensive mass loss, RSGs can have very dense circumstellar medium (CSM) around them. If a SN explosion occurs soon after the extensive mass loss of a RSG, the SN ejecta will collide with the dense CSM. Due to the collision, the kinetic energy of the ejecta is converted to radiation energy and such SNe with collision can be brighter than usual Type IIP SNe. By performing one-dimensional multi-group radiation hydrodynamical calculations, we investigate the effects of the collision on Type IIP SN LCs. We show that if RSGs explode within a dense CSM, the SN will be very bright, especially in ultraviolet, at early epochs. We also compare our models with the ultraviolet-bright Type IIP SN 2009kf and show that the progenitor of SN 2009kf can be a massive RSG which experienced extensive mass loss just before its explosion. We conclude that this is evidence that massive RSGs experience extensive mass loss and the existence of such mass loss can actually be the cause of the contradiction between theoretical and observational mass ranges of Type IIP SN progenitors.