Monitoring and Multi-Messenger Astronomy with IceCube

Round  1

Reviewer 1 Report

The manuscript reports on the detection methods, recent results and monitoring capabilities of the IceCube observatory. The observation of neutrinos is one of the key ingredients for doing multi-messenger astronomy, which makes this review relevant as a future reference for scientists. The main contribution of the review is the description of the techniques used by IceCube to search of sources of astrophysical neutrinos, two of which are relevant for multi-messenger astronomy. The contribution accomplishes the role as a review and just a few comments and suggestions are presented here.

Comments:

Abstract: There’s a mention that TXS 0506+056 is the first multi-messenger of extra-galactic astrophysical sources including neutrinos. However, SN1987A could be considered the first one, since it is in the LMC and was observed in optical and neutrinos were detected. 

Line 28-30: Mentioning that the foreground can also trigger the different detectors will make the statement more explicit. 

Line 37: Cerenkov —> Cherenkov

Line 63: Adding here that atmospheric muons and neutrinos are the main sources of the background for IceCube would be helpful for the next times the word background is mention in the text. 

Line 74: charged-current muon neutrino interaction…

Line 84: the word “muon” seems a bit confusing here, since previously the shape of the event i.e cascade, was mentioned. I would change it to track-like event.

Line 103 and 104: trough-going —> through-going

Line 124: Last month or so an atmospheric neutrino Tau analysis was published by IceCube, I guess it can be included in this section.

Line 142: The title Self-Correlation is used here, while in other parts of the text the word auto-correlation is used. I suggest using the same word, to make it consistent. 

Section 5. Sometimes the units ‘deg’ are used while others the symbol º is used. 

Line 252: First sentence was hard to read/understand, (suggestion: Follow-up observations of 23 observatories…)

Comments for author File: Comments.pdf

Author Response

Point 1: Abstract: There’s a mention that TXS 0506+056 is the first multi-messenger of extra-galactic astrophysical sources including neutrinos. However, SN1987A could be considered the first one, since it is in the LMC and was observed in optical and neutrinos were detected. 

Response: This is a very good comment and thus we mention SN1987A explicitly: "These are the first multi-messenger observations of an extra-galactic astrophysical source including neutrinos since the observation of the supernova SN1987A."

Point 2: Line 28-30: Mentioning that the foreground can also trigger the different detectors will make the statement more explicit. 

Respons: We include that this background also triggers the detector. "In addition there is a huge foreground of atmospheric neutrinos and muons that are produced in air showers resulting from cosmic-ray interactions with molecules in Earth's atmosphere [4] which can trigger the detector as well."

Point 3: Line 37: Cerenkov —> Cherenkov

Respons: implemented

Point 4: Line 63: Adding here that atmospheric muons and neutrinos are the main sources of the background for IceCube would be helpful for the next times the word background is mention in the text. 

Response: We add that these events are a main background in searches for astrophysical neutrinos. "With an energy threshold of about 100 GeV, the IceCube detector measures mainly atmospheric muons and neutrinos produced in cosmic-ray induced air showers which are the main background in searches for astrophysical neutrinos."

Point 5: Line 74: charged-current muon neutrino interaction…

Response: implemented

Point 6: Line 84: the word “muon” seems a bit confusing here, since previously the shape of the event i.e cascade, was mentioned. I would change it to track-like event.

Response: implemented

Point 7: Line 103 and 104: trough-going —> through-going

Response:  implemented

Point 8: Line 124: Last month or so an atmospheric neutrino Tau analysis was published by IceCube, I guess it can be included in this section.

Response: Note that this review only covers the astrophysical neutrino flux and searches for their sources. Therefor we left out all particle physics results based on atmospheric neutrinos. Therefor we propose not to mix in this result at this point.

Point 9: Line 142: The title Self-Correlation is used here, while in other parts of the text the word auto-correlation is used. I suggest using the same word, to make it consistent. 

Response: changed all self-correlation to auto-correlation

Point 10: Section 5. Sometimes the units ‘deg’ are used while others the symbol º is used. 

Response: changed all 'deg' to °

Point 11: Line 252: First sentence was hard to read/understand, (suggestion: Follow-up observations of 23 observatories…)

Response: implemented the suggestion

Reviewer 2 Report

It was a pleasure to read this review article. It is presented nicely, with polished results. I could only find minor wording errors, and some other minor issues that should be easy to clear up.

line 15: sources -> source (or rephrase)

30: makes -> make

42: in-> at

53: "runs global trigger conditions on the whole detector." sounded odd to my ears. Could the author rephrase to say what the triggers are and how this is done? E.g. "Performs searches for pre-defined excess" or something similar.

75: range over several km - the author means the track length can be in a range spanning several km? similar issue in line 76.

82 at TeV energies or at 1 TeV energy.

84: Perhaps: "case for a muon event"?

line 121: How does the author reconcile saying no tau signature was found (earlier) with finding 2 events here. 

line 160: order f magnitude time scale example would be appropriate

90-91: "up-going through-going events" maybe a comma is missing?

108 "and there's no need for a cut-off..."

169: constraints

173:

correction for the trials factor

203 send -> sent

200 positions - position

252 observatories

259 an high -> a high

294 or somewhere close: it should be noted that (as far as I know) there is no evidence of flaring in at GeV energies e.g. during the 2014 December excess. 

301: I think it would be interesting to state in this review if other individual blazars, perhaps similar in their energetics/variability do show similar excess. Are other energetic blazars in general compatible with the expectation of nondetection of neutrinos?

341: I think this may be deleted

Author Response

Point 1: line 15: sources -> source (or rephrase)

Response: implemented

Point 2: 30: makes -> make

Response: implemented

Point 3: 42: in-> at

Response: implemented

Point 4: 53: "runs global trigger conditions on the whole detector." sounded odd to my ears. Could the author rephrase to say what the triggers are and how this is done? E.g. "Performs searches for pre-defined excess" or something similar.

Response: We reformulated the sentence to: " With read-out electronics onboard, the DOMs send their data to the surface where a large computing-farm applies global trigger conditions, requiring e.g. several local coincidences within the full detector."

Point 5: 75: range over several km - the author means the track length can be in a range spanning several km? similar issue in line 76.

Response: reword to "where the produced muon can travel several km in the ice emitting a track-like light signal. All other types of neutrino interactions result in a  cascade-like signature as the produced particle showers span only a few meters."

Point 6: 82 at TeV energies or at 1 TeV energy.

Response: implemented

Point 7: 84: Perhaps: "case for a muon event"?

Response: implemented

Point 8: line 121: How does the author reconcile saying no tau signature was found (earlier) with finding 2 events here. 

Response: The 2 events are not clear signatures but candidate events. In the text we always refer to them as candidate events and mention that these events under further investigation. As the true topology is still uncertain a zero nu-tau flux can not be excluded at high confidence.

Point 9: line 160: order f magnitude time scale example would be appropriate

Response: we give a rough time scale estimate by adding " with a characteristic time scale of less than a second."

Point 10: 90-91: "up-going through-going events" maybe a comma is missing?

Response: implemented

Point 11: 108 "and there's no need for a cut-off..."

Response: implemented

Point 12: 169: constraints

Response: implemented

Point 13: 173: correction for the trials factor

Response: implemented

Point 14: 203 send -> sent

Response: implemented

Point 15: 200 positions - position

Response: implemented

Point 16: 252 observatories

Response: implemented

Point 17: 259 an high -> a high

Response: implemented

Point 18: 294 or somewhere close: it should be noted that (as far as I know) there is no evidence of flaring in at GeV energies e.g. during the 2014 December excess. 

Response: In the following paragraph we explain that observations in other wave-length bands are limited as the neutrino flare was reported years after its occurrence. We add at the end of the paragraph: "In the GeV gamma-ray band no flare can be seen."

Point 19: 301: I think it would be interesting to state in this review if other individual blazars, perhaps similar in their energetics/variability do show similar excess. Are other energetic blazars in general compatible with the expectation of nondetection of neutrinos?

Response: We add: "Studies on other individual blazars are currently on-going."

Point 20: 341: I think this may be deleted

Response: this section is deleted