A Search for Cosmic Ray Bursts at 0.1 PeV with a Small Air Shower Array
, Jassimar Singh 1, Piotr Homola 2, Olaf Bar 3, Dmitry Beznosko 4, Apoorva Bhatt 2, Gopal Bhatta 5, Łukasz Bibrzycki 3, Nikolay Budnev 6, David E. Alvarez-Castillo 2,7, Niraj Dhital 8, Alan R. Duffy 9, Michał Frontczak 3, Dariusz Góra 2, Alok C. Gupta 10, Bartosz Łozowski 11, Mikhail V. Medvedev 12,13, Justyna Mędrala 14, Justyna Miszczyk 2, Michał Niedźwiecki 15, Marcin Piekarczyk 3, Krzysztof Rzecki 14, Sławomir Stuglik 2, Oleksandr Sushchov 2, Arman Tursunov 18 and Tadeusz Wibig 19add
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Round 1
Reviewer 1 Report
The paper discuss interesting results concerning the search for time clustering of the cosmic ray events. The paper is well written and the analysis well explained.
My comment/suggestion concerns the burst direction analysis which seems to me could be improved.
In the last year the LHAASO experiment observed about 15 gamma sources emitting photons well above 100 TeV in the northern hemisphere. In particular an emission above the PeV from the Cygnus region. This suggest that in the Inner Galaxxy, visible from the southern
Hemisphere, a large number of UHE gamma sources, probably flaring, could be observed by a suitable experiment. This means that in principle burst events could be associated to still unknown gamma sources. Therefore, a discussion of possible galactic sources associated with detected bursts could be interesting.
Anyway, the paper is worth of publication even in the present form.
Author Response
The suggestion of Reviewer 1 is appreciated and the comments resulted in the addition of a paragraph in the Interpretation section (and two references) concerning recent HAWC and LHAASO results and their relation to this paper. There is a clear need for more southern hemisphere data on gamma-ray sources following from H.E.S.S.
Reviewer 2 Report
Report on the paper titled: A search for cosmic ray bursts at 0.1 PeV with a small air shower array.
This work is relevant and should be published in this journal.
In this paper, the authors explore an astrophysical phenomenon that has not been studied much in recent times with surface detectors such as the Burst in the first knee region of the cosmic ray spectrum.
The article is well organized and clearly shows the analysis that the authors want to develop. The exploration of the detection of burst-type events is relevant in an area of the spectrum usually dominated by the search for gamma-ray sources.
In addition, it overcomes its weaknesses as an array with small dimensions compared to observatories such as Auger or HAWK. Therefore, converting a detector used for teaching activities into one that works for research. The data analysis, especially the filtering, is careful and exhaustive. Distinguishing the signal from the noise is very important in this type of analysis.
On the other hand, I suggest citing and commenting about the area of the spectrum in which the work takes place, specifically around the first knee. Also, it would be worthwhile to describe further the technical aspects of the detectors, e.g., what kind of scintillators and PMTs were used. Also, Figure 2 shows a fit of the data that is neither used in the analysis nor discussion.
However, it is not clear how, with so few detectors, do you reconstruct the direction of the events. Is it an estimation based on the detector field of view or do you reconstruct geometrically the direction of the event? If so, I suggest explaining better how you have achieved it.
Author Response
The helpful comments of Reviewer 2 were appreciated and the manuscript revised though considering them.
The location of the knee of the energy spectrum is now noted in the discussion.
The model numbers of the scintillator and photomultipliers have been added.
It is noted in the text that Figure 2 is fitted with an exponential and that this fit provides a measure of the mean event spacing.
Comments have been added that the event directions are through fitting fast-timing data and the resulting overall zenith angle distribution is mentioned (the mode).
Reviewer 3 Report
In this paper it is shown the capability of a mini array to search for cosmic ray bursts. Even if the experimental results suffers in terms of angular resolution, I consider this paper interesting especially due to the very clear description of the analysis procedure. These detailed descriptions could be very useful for other such mini arrays which aim to seek for cosmic ray bursts.
The paper is clearly written and very well organized. I recommend this paper for publication.
I have only few minor suggestions:
Why don't you represent the Figures 2 and 3 as histograms ? The squares seem to overlap in some places and can mislead the reader.
l 104: "with poor angular uncertainty (below)" -> maybe you missed to insert the angular resolution ?
l 167: "figure 2" -> Figure 2
l 171: It is missing the point at the end of the caption of Fig 2.
l 174: "figure 3" -> Figure 3 (please be consistent with this notation throughout the paper)
All the best,
the reviewer.
Author Response
The comments of Reviewer 3 are appreciated.
The statement on the limitations of the event angular resolution was extended and (I hope) clarified.
The editorial suggestions were addressed. However, figures 2 and 3 were not revised as histograms did not seem to improve the clarity of the figures (sorry).
