November 28, 2012 Prof. John Lattanzio, XII International Symposium on Nuclei in the Cosmos Local Organizing Committee Dear Prof. John Lattanzio, Enclosed please find the manuscript of our proceeding entitled: "Evolution of Very Massive Stars and Type Ic Supernova" by Takashi Yoshida, Shinpei Okita, and Hideyuki Umeda We thank the referee who evaluated our present study favorably and gave many valuable comments. We are sorry that our response was delayed. The modifications were made in the revised manuscript in accordance with the referee's comments. Responses to the referee's comments: The paper presents nice new work and gives a comprehensive overview of possible models for some superluminous supernovae laien 2007bi and therefore generally could deserve publication. I do have, however, some serious questions that the authors need to address before the paper can be published (below). The text does require significant English editing, especially toward the end where the authors seemed to to have run out of time or energy (all was put into the explosions, it seems).  It cannot be published in the present form. 1) In the abstract the authors mention they adopt progenitor WO star of 43 and 61 M_sun.  In this mass range the pulsational pair instability is active.  Usually we should expect the mass is reduced by the pulses, and the outer layers be ejected.  Could the authors please comment on this?   Is this included in the calculations?  How would this affect the model?  And the light curves? Response: We did not include the ejection of outer layers by pulsational pair instability in our calculation. So, it is difficult to discuss details for the effect of the mass loss by pulsational pair instability SN. So, we described some discussions about mass loss effects of pulsational pair instability SNe in Abstract and Sections 2 (the last paragraph of page 4) and 3 (the last paragraph of page 6). In Abstract, we mentioned "Stars with ~ 110 - 150 Msun and Z < 0.001 (which form a CO core with ~ 40 - 60 Msun) may become Type Ic supernovae if the whole H-envelope and He-layer is lost during pulsational pair instability" in lines 8-10. 2) In the abstract, could the authors please also clearly state that the pair instability also are Type Ic SNe, as a clarification to the current formulation. Response: I added the sentence "If mass loss rate is smaller than the currently adopted rate, very massive stars with >~ 170 Msun and Z~0.004 would explode as Type Ic pair-instability supernovae." on lines 11-13. \S 2.1: "In Z = 0:02" ---> "At ..." Response: We changed the word "In" to "At" in page 3, line 2 of section 2.1. "Metal-poorer" --> "More metal-poor .. " Response: We changed the words "Metal-poorer" to "More metal-poor" in page 3, line 3 of section 2.1. "scarcely depends on the metallicity" -->       "shows little dependence on the metallicity" Response: We changed the words "scarcely depends on the metallicity" to "shows little dependence on the metallicity" in page 3, lines 2-3 from the bottom. "Larger metallicity of stars" --> "stars of higher       initial metallicity" Response: We changed the words "Larger metallicity of stars" to "Stars of higher initial metallicity" between the last line of page 3 and the first line of page 4. "because of *the* small mass loss rate" Response: We added "the" between "because of" and "small mass loss rate" in page 4, line 3. 3) You write you simulate masses up to 300 M_sun but one of the figures shows masses up to 500 M_sun.   Is the figure axis wrong? Or where do the data come from? Response: In the case of Z=0.004, we extended the initial mass range to 500 M_sun and calculated with three cases of the mass loss rate for M_MS = 100 - 500 M_sun stars in order to discuss possible explosion mechanisms for SN 2007bi. We added the description "For Z=0.004 stars, we extended the mass range to 500 M_sun and calculated the evolution taking into account three cases of mass loss rate (see section 2.2 for details) among M_MS = 100 - 500 M_sun stars to investigate the influence of the CO-core mass on the mass loss rate [10]" in Page 3, lines 7-10. 4) You write "Since the mass loss effect is negligible after the C-burning, they will explode as Type II or Type Ib SNe."  This, of course, would not be true if the stars become pulsational pair instability supernovae.  Which occurs after central C depletion. Response: As referee's claim, if stars become pulsational pair-instability supernovae, eruptive mass loss will occur. In this case, the prediction for the resultant supernova type is very difficult. Some stars may become Type Ic supernovae. So we changed the last sentence of the 1st paragraph of section 2.1 (page 3) to "If eruptive mass loss does not occur in luminous blue variable-like events or by pulsational pair-instability (abbreviated as PPI) after the C-burning, the mass loss effect is not negligible. We will discuss mass loss effect by PPI later." We also added the discussion about mass loss effects during PPI from line 19 in page 4 to line 4 in page 5; "The stars in the region enclosed by the red line in Fig. 1(a) has a CO core of M_CO ~ 40 - 60 Msun, thus, they will become PPI SNe and lose their outer envelope [18,19]. Their SN types are quite uncertain because the lost mass during PPI has not been evaluated in details yet. Stars with M_MS ~ 110 - 150 Msun and Z <~ 0.001 have an H-envelope and become PPI SNe. If the whole H-envelope and He-layer is lost by PPI, these stars will become Type Ic SNe. The radiation induced by the collision of the ejected outer envelope with the earlier ejecta during PPI is also a candidate for super-luminous SNe [18,19]." 5) could you add a figure caption with all the symbols and colors next to Figure 2 - there is plenty of space. Response: We worry that the referee could not read the figure caption of Figure 2 by some technical reasons. We have written the figure caption in the previous version. Could you please check if the figure caption can be read? If the referee could not read the figure caption again, please ask editorial staff. It may depend on OS. 6) Could you please introduce all abbreviations used?   E.g., "MS", "SN", etc.  This is a question of convention and style. Response: We introduced all abbreviations used in the text as follows: - Page 2, line 1: supernova (hereafter abbreviated as SN), - Page 2, lines 3-4 in the last paragraph of section 1: main-sequence mass range (main-sequence is abbreviated as MS), - Page 3, line 7 in section 2.1: pulsational pair-instability (hereafter abbreviated as PPI), 7) In section 3: "we expect that stars with" - you "expect" this (on what physics grounds?) or assume it - for what kind of stars, why, what is the physics that causes the explosion, provides the energy?  Is this assumption based on any known physics and/or demonstrated model? Please elaborate, this point is key to the conclusions of your paper. Response: We showed in section 2.2 that the mass range of the MS mass producing 56Ni of more than 3 M_sun from core-collapse explosion is ~ 110 - 270 M_sun in case A. This result was evaluated based on the result in Umeda and Nomoto [16]. So, we expect that they will explode as core-collapse SNe and eject more than 3 M_sun of 56Ni. We replaced the first sentence of section 3 in page 5 to "In the previous section, we showed that stars with M_MS = 110 - 270 M_sun will explode as core-collapse SNe and eject more than 3 M_sun of 56Ni in the standard mass loss." 8) in \S 3 you briefly mention the pulsational pair SN.   What is the effect?  (see also comments above) Response: We added the sentences in lines 9-12 in section 3, page 5; "The 250 Msun star experienced PPI during the Si-burning stage. In this study, we do not take into account eruptive mass loss during PPI. Recent study on the mass ejection from metal-poor rotating very massive stars showed that an outer layer of a few solar-masses is lost from a CO core during PPI [19]." We also discuss the mass loss effect in the last paragraph of page 6 (to line 6 of page 7). 9) the number of particles in the simulation does not seem appropriate to the resolution for state of the art calculations of SNe.  Fryer et al. has done 3D SN 10 yr ago with a million particles or more.  Can such a small grid properly reproduce the hydrodynamics, shock temperature, mixing? Can you show resolution studies. Response: We calculated hydrodynamics of aspherical SN explosion with 2D axi-symmetrical Roe-scheme, which is Eulerian-mesh scheme and is not SPH. We set 2880 meshes for radial direction and 64 meshes for azimuthal direction. We also assumed the equatorial-plane symmetry. Furthermore, the explosion feature is jet-like, so that it is much simpler than complex convective motion in neutrino cooling and heating regions of normal core-collapse supernova explosions. Fryer et al. (2002; ApJL 574, L65) used 1 million particles or more for 3D hydrodynamical simulations, corresponding to about 100 particles per 1 dimension. Our simulation is 2D and equatorial-plane symmetry. So, although we cannot compere the resolution between mesh scheme and particle scheme, we consider that the resolution of our simulations is higher than that in Fryer et al. Concerning to the number of tracer particles used in the post-processing nucleosynthesis, we consider that 5200 particles give resolution enough to evaluate the ejected amounts of major elements such as 56Ni, Si, and O. Fujimoto et al. [22] confirmed that the obtained abundance profiles are very similar between the models of 6000 particles and that of 3000 particles, when they calculated the nucleosynthesis of 2D simulations (without equatorial-plane symmetry) of a supernova explosion induced by SASI. We added the reference [22] on the resolution in page 6, line2. "Figure 3 shows the special distribution..." --> "Figure 3 shows the spatial distribution" Response: We changed "the special distribution" to "the spatial distribution" in page 6, line3. "... and the material goes off." ??? Response: We changed "material goes off" to "materials are blown off" in page 6, line 5 "and about 12 M  of the central remnant is formed." -->     "and a central remnant of 12 M_sun is formed" Response: We changed to "a central remnant of 12M_sun is formed" in page 6, line 9. "total ejected amount" --> "total amount of ejecta" Response: We changed to "total amount of ejecta" in page 6, line 10. "asphericity of *the* explosion. Response: We changed to "asphericity of the explosion" in page 6, line10. "relating to" --> "as a function of" Response: We changed "relating to" to "as a function of" in page 6, line11. "about a half" --> "about half" Response: We deleted this sentence in this revision. (I give up from here on - please see a native speaker to check the paper before submitting the revised version) "which is slightly smaller angle than that in which the 56Ni amount increases." ??? "is caused by the difference in the effect of accretion." ??? "The dependence of the ... " this entire paragraph and onward is not English and cannot be published. Response: We totally revised section 3 of this manuscript and asked Hamid Hamidani, a member of our group, to check English. He kindly checked English of this manuscript. Although he is not a native English speaker (his native language is French), he speaks English very well. 10) "Some Si has been produced during pulsational pair-instability." You state pulsational pair SN is during Si _burning_ ... how does Si burning _produce_ Si? Response: Of course, Fe-peak elements are produced in the central region during PPI. At the same time, shell oxygen burning occurs in outer O/Ne-rich layer and Si is produced there. We changed the sentence "Some Si has been produced during the pulsation pair-instability." to "Some Si was produced through shell O-burning during and after PPI" in page 6, lines 19-20. "More than 46 M  of the total ejecta is ejected ..." ? Response: We changed to "Ejecta of 46 Msun were obtained, ..." in page 6, line 22. 11) Maybe I overlooked this: You mention the 2 models, CC and pair-SN make different amounts of total mass and in particular Si - what are the constraints for observations on Si for Sn 2007bi? Response: The English is incorrect, as the referee claimed... We changed the sentence "Thus, the observational constraints on the total ejected amount and the Si amount would constrain the explosion mechanism of SN 2007bi." to "If these amounts are more precisely determined from observations, they will help making stronger constraints on the explosion mechanism of SN 2007bi." in page 7, lines 14-15. I do like the figures. Response: Thank you very much. We believe that we addressed referee's comments appropriately and hope that the revised manuscript will soon be reviewed by the referee and accepted for the publication in the proceedings of XII International Symposium on Nuclei in the Cosmos. Best regards, Takashi Yoshida Takashi Yoshida Department of Astronomy, Graduate School of Science University of Tokyo 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan Phone: +81-3-5841-4265 Fax: +81-3-5841-7644 E-mail: tyoshida@astron.s.u-tokyo.ac.jp