A Very-High-Energy Gamma-Ray View of the Transient Sky

Round 1

Reviewer 1 Report

 Report on manuscript universe-2877153

“A very-high-energy gamma-ray view of the transient sky”

This review discussed the recent advancements in Imaging Atmospheric Cherenkov Telescopes in revealing extreme astrophysical phenomena in very-high-energy gamma-rays, linking time-domain astronomy to unpredictable transient events. The review spans novae to fast radio bursts, outlining future facility expectations. The study has the potential to be published but after minor revision. I would like the authors to address the following issues:

Main Comments:

-        Please elaborate on the discussion of very high energy gamma-ray production by Novae by the acceleration of particles to extremely high-energies

-        At high energy, transient emission from supernovae has not been confirmed yet. How can we discuss emissions at these high energies then?  

-        L334. Please elaborate on the sentence “Although these Uls ….. a jet-powered model.

-        Figure 5: what are the error bars and the arrow presented in the figure?

-        The conclusion is short and doesn’t reflect many of the discussed points in the manuscript. 

Author Response

We would like to thank the referee for the thorough review of the manuscript.

Main Comments:
-     Please elaborate on the discussion of very high energy gamma-ray production by Novae by the acceleration of particles to extremely high-energies
We believe that the paragraphs between lines 134 and 182 are enough for the scope of the paper. These lines discuss in detail the possible scenarios (hadronic, leptonic, lepto-hadronic) for the production of very high energy gamma-ray emission due to particle acceleration, as well as the possibility of novae having one or several shocks. We hope the referee agrees with this approach.

- At high energy, transient emission from supernovae has not been confirmed yet. How can we discuss emissions at these high energies then?  
We discuss in lines 290-316 possible associations of HE emission with SNe events. Since the manuscript focuses on VHE emission, we do not further explore the theoretical predictions for a HE counterpart from SNe. Regarding the VHE component, there are different theoretical predictions based on (mainly) hadronic scenarios that have been discussed in the manuscript. We believe that it is key to mention this science case since it is important for current IACT as well as for the CTA consortium that is actively working in the perspective of such observations with future IACTs. Thus, although not observed so far, CCSNe are within the “new” science cases for Cherenkov Astronomy.

- L334. Please elaborate on the sentence “Although these Uls ….. a jet-powered model.
We modified it to: “Although these ULs do not help constrain the scenarios of a magnetar as central engine or a shock-acceleration they do discard a jet model powered due to fallback accretion onto a black hole is (model L_{BH} as seen in Fig. 3)”  

- Figure 5: what are the error bars and the arrow presented in the figure?

The y-axis error bars represent the statistical uncertainties in the flux. The downside arrow in the \textit{Fermi}-LAT flaring component is a flux UL. This is the information we obtain from the plot itself, although it is not described in the original figure/paper. We have included this information in the caption.

-     The conclusion is short and doesn’t reflect many of the discussed points in the manuscript.
We have extended the conclusions.

Author Response File: Author Response.pdf

Reviewer 2 Report

Dear authors,

I read your manuscript carefully. I have only some minor comment listed in the attached referee report.

Comments for author File: Comments.pdf

Author Response

We would like to thank the referee for the feedback provided. We have modified the manuscript accordingly. 

Author Response File: Author Response.pdf

Reviewer 3 Report

This paper presents  an overview of the VHE transients field, spanning from  novae to supernovae, neutrino counterparts or fast radio bursts and  Gravitational waves and others in the past decades.   More than 200 citations indicate that this paper gives the development of time-domain and multi-messenger astronomy.  I recommend  accepting this paper.

1.   This manuscript presents the review of the e very-high-energy gamma-ray transient events mainly detected by the Imaging Atmospheric Cherenkov Telescopes in the past decades, including the observations and the associated physics.   It is good for the reader to get to know the new development of time-domain and multi-messenger astronomy.

2.   Although the Imaging Atmospheric Cherenkov Telescopes detects many transient events or emitter at gammay-ray with the energy as E>100 GeV, the discovery of a TeV counterpart of GRBs and other TeV transient emitters is new challenges of the high energy astronomy, and it is need to develop new instrumentation such as the CTA observatory in the future.

3.   In this manuscript, more than 200 papers are cited, and they presents the recent results on both observations and physics in the time-domain and multi-messenger astronomy, especially the novae, supernovae, fast radio bursts and magnetars binary neutron star mergers Gravitational waves.   Although the authors do not give any new observations here, they show their works in this field before, and point the new questions for the researcher in the future.

4.   Based on the findings in the past decades, the manuscript presents that the issue of TeV transient emitters should be studied based on the new telescope.

5.   The conclusion of the manuscript is clear and future development directions are proposed.

6.   The references in the manuscript are appropriate.

7.   No any other comments.

Author Response

We thank the referee for this positive report.

Author Response File: Author Response.pdf