Supernovae, by Chandra and XMM-Newton

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This manuscript is a short review of some X-ray observations of several core-collapse supernovae (CCSNe). The review is valuable in presenting some puzzles that the X-ray and other observations raise and pointing out the need for future X-ray telescopes.  

I recommend publication after the authors have considered my suggestions and comments.

(1) I suggest emphasizing one puzzle that the review discusses related to the explosion mechanism.  

 In section 2.1, the author discusses SN2002ap. Its explosion energy is 4-10 x 10^{51} erg. The neutrino-driven explosion mechanism cannot explain this high explosion energy. Jets are required, like in the jittering jets explosion mechanism. In section 2.3, the author writes: "As explored by Zhu et al. (2023 [46]), all of the simple models invoked to explain SN2017egm's behavior fail to do so (e.g., enhanced 56Ni production, energy from rapidly-rotating magnetic stars, pair instability), . . .". I note that many superluminous CCSNe require powering by jets even when they are modeled by a magnetar (rapidly rotating magnetic NS; e.g., Kumar A., 2025, NewA, 116, 102346). In section 5.2, the author mentions jets in SLSNe and notes they might be choked in the envelope, as the jittering jets explosion mechanism predicts.

My point is that some of the puzzles raised by the author pose problems to the neutrino-driven explosion mechanism and might support jet-driven explosion (like the jittering jets explosion mechanism). This is an interesting point to raise in this review (for a comparison of the two explosion mechanisms, please see a paper in Universe: Soker N., 2024, Univ, 10, 458). Another Universe paper related to the explosion mechanism deals with the morphology of supernova remnants (Soker N., 2024, Univ, 11, 4). In the future, XMM or Chandra may reveal such a point-symmetric morphology in the ejecta of SN 1987A, and the author correctly states that it is now a remnant.  

(2) Section 3.1:The author writes, "Observations in 2010 with the Hubble Space Telescope revealed three circumstellar rings." This is not correct. The three rings were discovered much earlier, e.g., Crotts A.P.S., Kunkel W.E., Heathcote S.R., 1995, ApJ, 438, 724.

(3) Section 3.1: The author cites a quotation from R. Kirshner from a meeting for the idea of a common envelope evolution of SN 1987A. I am asking that the credit be given to the first two papers that suggested this. The first mention of the common envelope is by Chevalier and Soker (1989), who discussed the non-spherical explosion (Chevalier R.~A., Soker N., 1989, ApJ, 341, 867). Then came the idea that the common envelope can form a blue progenitor (Podsiadlowski P., Joss P.C., Rappaport S., 1990, A&A, 227, L9 ).   These two papers were submitted before the 1989 meeting.

Author Response

This manuscript is a short review of some X-ray observations of several core-collapse supernovae (CCSNe). The review is valuable in presenting some puzzles that the X-ray and other observations raise
 and pointing out the need for future X-ray telescopes.

I recommend publication after the authors have considered my suggestions and comments.

(1) I suggest emphasizing one puzzle that the review discusses related to the explosion mechanism.

In section 2.1, the author discusses SN2002ap. Its explosion energy is 4-10 x 10^{51} erg. The neutrino-driven explosion mechanism cannot explain this high explosion energy. Jets are required, like in the
jittering jets explosion mechanism. In section 2.3, the author writes: "As explored by Zhu et al. (2023 [46]), all of the simple models invoked to explain SN2017egm's behavior fail to do so (e.g., enhanced
56Ni production, energy from rapidly-rotating magnetic stars, pair instability), . . .". I note that many superluminous CCSNe require powering by jets even when they are modeled by a magnetar (rapidly
rotating magnetic NS; e.g., Kumar A., 2025, NewA, 116, 102346). In section 5.2, the author mentions jets in SLSNe and notes they might be choked in the envelope, as the jittering jets explosion mechanism
predicts.

My point is that some of the puzzles raised by the author pose problems to the neutrino-driven explosion mechanism and might support jet-driven explosion (like the jittering jets explosion mechanism). This is an interesting point to raise in this review (for a comparison of the two explosion mechanisms, please see a paper in Universe: Soker N., 2024, Univ, 10, 458). Another Universe paper related to the explosion mechanism deals with the morphology of supernova remnants (Soker N., 2024, Univ, 11, 4). In the future, XMM or Chandra may reveal such a point-symmetric morphology in the ejecta of SN 1987A, and the author correctly states that it is now a remnant.

>> A paragraph has been added at the end of the discussion of SN2002ap
>> that I think summarizes the situation within a sentence or three.
>> I thank the referee for pointing out this paper as I had somehow
>> missed it in my daily arXiv review.

(2) Section 3.1:The author writes, "Observations in 2010 with the Hubble Space Telescope revealed three circumstellar rings." This is not correct. The three rings were discovered much earlier, e.g., Crotts A.P.S., Kunkel W.E., Heathcote S.R., 1995, ApJ, 438, 724.

>> This error has been corrected.  I thank the referee for
>> the correction.

(3) Section 3.1: The author cites a quotation from R. Kirshner from a meeting for the idea of a common envelope evolution of SN 1987A. I am asking that the credit be given to the first two papers that suggested this. The first mention of the common envelope is by Chevalier and Soker (1989), who discussed the non-spherical explosion (Chevalier R.~A., Soker N., 1989, ApJ, 341, 867). Then came the idea that the common envelope can form a blue progenitor (Podsiadlowski P., Joss P.C., Rappaport S., 1990, A&A, 227, L9 ).  These two papers were submitted before the 1989 meeting.

>> The recommended papers have now been cited in what I deem is an
>> appropriate manner, but I also retain Kirshner's phrase.

Reviewer 2 Report

Comments and Suggestions for Authors

I have reviewed the manuscript Supernovae, by Chandra and XMM-Newton by E M Schlegel. This review paper provides an overview of notable supernova science cases for which Chandra and XMM observations were collected, while emphasizing the pivotal role of these instruments (and others, such as Swift) and suggesting improvements needed for the future of this research field. I am happy to recommend it for publication in Universe. Below, I have listed some minor comments that the author could consider before submitting the final version of the manuscript.

——

--Abstract
1. The first and the second sentence are not really linked in my opinion.

--2. Advancements from XMM and Chandra

1. Why does the author speak about an “apparent” connection between SNe Ic/hypernovae and GRBs?

2. The author should provide a reference while mentioning the measurements of mass-loss rates for Wolf Rayet stars.

3. The author might also want to recall that some lines of evidences might favor the binary scenario for type-Ic SNe ( e.g. https://ui.adsabs.harvard.edu/abs/2024NatCo..15.7667S/abstract , but see also …. ).

--2.1. XMM: Type Ic SN2002ap in NGC 62

1. The author writes “Two different interpretations of the dataexist.” to introduce a list of scenarios, but it would be better to list them as bullies or to introduce the two new paragraphs with a statement summarizing them.

2. The author is right in pointing out that “At this point, the reader could wonder why the discussion of SN2002ap seems tohave two separate branches: ” , but I do not really understand why the author need to structure the discussion in this way. I suggest to change a bit the structure of the discussion about 2002ap.

--2.3. Chandra: Type Ic SN2017egm

1. The title of this subsection might be confusing. The author probably means that sometimes many hydrogen-poor SLSNe are referred to as SLSNe Ic as they are both hydrogen and helium devoid. In the case of SN 2017egm, this is quite false as it is He-rich (these SNe are sometimes dubbed SLSNe Ib, see e.g. Quimby et al. 2018, ApJ, 855, 1; Yan et al. 2020, ApJ, 902, 1), as also correctly pointed out by the author.

2. The author writes that SN 2017egm was perhaps the only SLSN I found in a metal-rich galaxy. While this claim was reported by Chen et al. (2017, ApjL, 849, 1), subsequent and more detailed studies by Izzo et al. (2018, A&A, 610) suggested reconsidering the previous claim as long as the metallicity of interest is the environmental one (i.e. the metallicity measured *at* the SN location). For the same reason, also the final statement “So, too, that SN2017egm exploded in a massive, metal-rich galaxy” should be reconsidered. In addition: I suspect that some comments have been accidentally left in this subsection.

--2.5. XMM and Chandra: Type IIn SN2010j

1. I guess that the reference [6] is wrong, as it corresponds to:

[6] Chandra, P., Chevalier, R. A., Chugai, N. et al. 2012. “Radio and X-ray Observations of SN2006jd: Another Strongly InteractingType IIn Supernova”. ApJ, 755, 110

while the author probably meant https://ui.adsabs.harvard.edu/abs/2012ApJ...750L...2C/abstract .

--3. Older Supernovae

1. When introducing neutrino detections from SN 1987A, the author cites a review (McCray 2017)  from the Handbook of Supernovae, which is perfectly fine (maybe worth specifying it is a review, e.g. “see also McCray (2017) for a review”), but maybe also the original papers from 1987 should be cited here.

Author Response

I have reviewed the manuscript Supernovae, by Chandra and XMM-Newton by E M Schlegel. This review paper provides an overview of notable supernova science cases for which Chandra and XMM observations were collected, while emphasizing the pivotal role of these instruments (and others, such as Swift) and suggesting improvements needed for the future of this research field. I am happy to recommend it for publication in Universe. Below, I have listed some minor comments that the author could consider before submitting the final version of the manuscript.

--Abstract

1. The first and the second sentence are not really linked in my opinion.

>> The abstract has been revised, hopefully to link the sentences
>> more concretely.

--2. Advancements from XMM and Chandra

1. Why does the author speak about an “apparent” connection between SNe Ic/hypernovae and GRBs?

>> I use 'apparent' because my reading of the literature leads me
>> to think that there is another factor present.  I have altered
>> the text to make that somewhat more explicit.  I also cite
>> a recent review by Della Valle (2022).

2. The author should provide a reference while mentioning the measurements of mass-loss rates for Wolf Rayet stars.

>> Fixed!  The citation is to Nugis & Lamers (2000) that appears to be
>> one of the more recent and widely-cited papers on mass-loss rates
>> of W-R stars.

3. The author might also want to recall that some lines of evidences might favor the binary scenario for type-Ic SNe (e.g. https://ui.adsabs.harvard.edu/abs/2024NatCo..15.7667S/abstract ,
but see also …. ).

>> Near the start of the discussion of SN2002ap, I include the
>> above-mentioned reference.  Ironically, this paper was sitting
>> in my 'post-pandemic-I-have-yet-to-read' pile of preprints.

--2.1. XMM: Type Ic SN2002ap in NGC 62

1. The author writes “Two different interpretations of the data exist.” to introduce a list of scenarios, but it would be better to list them as bullies or to introduce the two new paragraphs with a statement
summarizing them.

>> A short description has been added to the paragraph to provide
>> links to the paragraphs that follow.

2. The author is right in pointing out that “At this point, the reader could wonder why the discussion of SN2002ap seems to have two separate branches: ” , but I do not really understand why the author need to
structure the discussion in this way. I suggest to change a bit the structure of the discussion about 2002ap.

>> The text has been slightly revised to emphasize that there remains
>> a fraction of supernovae/GRBs not showing a connection to the other.
>> On that basis, I leave the overall organization of the 2002ap
>> description as originally developed, so to lead the reader through
>> the development as well as the remaining puzzle(s).

--2.3. Chandra: Type Ic SN2017egm

1. The title of this subsection might be confusing. The author probably means that sometimes many hydrogen-poor SLSNe are referred to as SLSNe Ic as they are both hydrogen and helium devoid. In the case of SN 2017egm, this is quite false as it is He-rich (these SNe are sometimes dubbed SLSNe Ib, see e.g. Quimby et al. 2018, ApJ, 855, 1; Yan et al. 2020, ApJ, 902, 1), as also correctly pointed out by the
author.

>> The 'Type Ic' label has been changed to 'Type SLSN I'.

2. The author writes that SN 2017egm was perhaps the only SLSN I found in a metal-rich galaxy. While this claim was reported by Chen et al. (2017, ApjL, 849, 1), subsequent and more detailed studies by Izzo
et al. (2018, A&A, 610) suggested reconsidering the previous claim as long as the metallicity of interest is the environmental one (i.e. the metallicity measured *at* the SN location). For the same reason, also
the final statement “So, too, that SN2017egm exploded in a massive, metal-rich galaxy” should be reconsidered. In addition: I suspect that some comments have been accidentally left in this subsection.

>> The 'metal-rich' last sentence has been deleted.  The 'comments'
>> have been expanded slightly to emphasize the interesting attributes
>> of SN2017egm.

--2.5. XMM and Chandra: Type IIn SN2010j

1. I guess that the reference [6] is wrong, as it corresponds to:

[6] Chandra, P., Chevalier, R. A., Chugai, N. et al. 2012. “Radio and X-ray Observations of SN2006jd: Another Strongly InteractingType IIn Supernova”. ApJ, 755, 110

while the author probably meant
https://ui.adsabs.harvard.edu/abs/2012ApJ...750L...2C/abstract .

>> Yes, I accidentally entered the incorrect paper.  That citation
>> has now been fixed.

--3. Older Supernovae

1. When introducing neutrino detections from SN 1987A, the author cites a review (McCray 2017) from the Handbook of Supernovae, which is perfectly fine (maybe worth specifying it is a review, e.g. “see also
McCray (2017) for a review”), but maybe also the original papers from 1987 should be cited here.

>> The original papers have been cited.