Talk:GW170817

Created talk-page

Created talk-page for the GW170817 article - Enjoy! :) Drbogdan (talk) 00:52, 28 August 2017 (UTC)

Too speculative?

This is more speculation than anything else. I don't think this is an article Wikipedia should have at the moment. Pages should be about things with lasting significance. What do you write if the analysis shows there was no event? If an article can lose its significance, then it never had enough significance. --mfb (talk) 12:59, 28 August 2017 (UTC)

@Mfb: Thank you for your comments - yes, you may be right about this - however - there seems to be some responsibly cited basis (and specific informations re detection dates and possible discoverers) for the tentatively named article, as well as a related WP:RS noting that there are “promising gravitational-wave candidates” for confirming the findings - perhaps other editors would like to comment? - in any case - Enjoy! :) Drbogdan (talk) 13:49, 28 August 2017 (UTC)

I'm not even sure about the date. Where do you get that from? Does any news include "GW170818"? Yes, there are rumors, but nothing confirmed. LIGO released a statement about candidates - in the plural. Can you figure out which part of the rumor corresponds to which candidate? I cannot. --mfb (talk) 16:44, 28 August 2017 (UTC)

FWIW - seems the following may be relevant re the detection date (at least, afaik at the moment) => On 18 August [2017], astronomer J. Craig Wheeler of the University of Texas at Austin began the public rumour mill when he tweeted, “New LIGO. Source with optical counterpart. Blow your sox off!” An hour later, astronomer Peter Yoachim of the University of Washington in Seattle tweeted that LIGO had seen a signal with an optical counterpart (that is, something that telescopes could see) from a galaxy called NGC 4993, which is around 40 million parsecs (130 million light years) away in the southern constellation Hydra. “Merging neutron-neutron star is the initial call” - no mention of "GW170818" per se in the news at the moment afaik - the tentative naming of GW170818 may be reasonable based on the quoted passage above - also reasonable afaik => the noted candidates (plural) may all have been near the time/date of the initial detection as noted above - hope this helps in some way - iac - Enjoy! :) Drbogdan (talk) 17:11, 28 August 2017 (UTC)

GW events are not named after the day of tweets. Assuming this is connected to the GRB, it should probably be August 17. But all this is original research, and to make it worse it is based on tweets. --mfb (talk) 00:52, 29 August 2017 (UTC)

This is currently a rumour, not a confirmed event, so I'm not sure if it should have a Wikipedia article just yet. I don't think that it is original research, though, as the rumours are being quite well documented by the media. Perhaps we can serve a role of providing an objective assessment of the current situation, though. As you might guess from the number of caveats here, I haven't made up my mind at the moment. ;-) Thanks. Mike Peel (talk) 01:06, 29 August 2017 (UTC)

Thanks for all the comments - my present thinking at the moment => seems a wait-and-see approach may be the better road - may not be long I would think - if "GW170818" is confirmed and an official name noted, then the article name (and article contents) can easily be adjusted if necessary - if the GW event is not confirmed, then the article can easily be removed (or at least modified to some extent) if necessary - either way is *entirely* ok with me atm - Thanks again for the comments - and - Enjoy! :) Drbogdan (talk) 01:54, 29 August 2017 (UTC)

I support moving this into draft space, but I won't go through all the bureaucracy to enforce that. If you absolutely think this rumor must be part of the Wikipedia now, keep it here. --mfb (talk) 15:04, 29 August 2017 (UTC)

Update: CERN seminar in an hour. Let's see if there are news. --mfb (talk) 16:28, 29 August 2017 (UTC)

References

Can GRB and GW detection times for same event be different?

QUESTION: Could a "Gamma-Ray Burst (GRB)" of an astrophysical event be detected before the "Gravitational Wave (GW)" of the very same event? - or not? - if so, then "GRB 170817A" could be detected some (brief?) time before "GW170817" for the very same astrophysical event - Comments Welcome if possible - in any regards - Enjoy! :) Drbogdan (talk) 02:55, 29 August 2017 (UTC)

I don't see how. The opposite can happen, if light needs some time before it escapes some object like a star, but there is nothing that would delay gravitational waves. --mfb (talk) 15:02, 29 August 2017 (UTC)

Thank you for your reply - and comment - yes - seems reasonable to me atm as well - Thanks again - and - Enjoy! :) Drbogdan (talk) 15:15, 29 August 2017 (UTC)

It has been argued that a GW could be delayed by corrections to geometric optics (with GWs having much larger wavelenghts than light). However the effects would be very small for LIGO-detectable GWs. A more speculative possibility can be realized in exotic theories of gravity, but the time difference would be very large to be observable. — Preceding unsigned comment added by 192.31.105.227 (talk) 01:00, 1 September 2017 (UTC)

The first reference discusses the opposite, GW arriving faster than an EM counterpart. The second predicts O(1) deviations, a time difference of a day would need some weird fine-tuning. --mfb (talk) 11:48, 2 September 2017 (UTC)

@Drbogdan: As User:mfb has already noted, it seems unlikely. GW radiation peaks just as the objects touch, then rapidly fades as they coalesce, while all other signals start as the objects touch. They have to actually interpenetrate to generate the pressures and temperatures leading to gamma-ray emission, and those conditions are buried inside the stars, so the photons take time to get to the surface. The paper on the relative speed of photons and gravitational waves assumes a 0–10 second source delay for photon emission. 104.153.72.218 (talk) 11:14, 18 October 2017 (UTC)

FWIW - seems related => "... a gamma-ray signal arrived nearly at the same exact time as the gravitational waves, with less than a 2-second difference in arrival time. Across a journey of more than 100 million light-years, that one measurement both confirmed that gravitational waves and electromagnetic waves travel at the same speed to within 15 significant digits ..." - in any case - Enjoy! :) Drbogdan (talk) 16:41, 30 July 2019 (UTC)

Yes, that article is discussing this event. The first 2/3 of it are purely about the past, you have to scroll down a lot before you get to the actual news. --mfb (talk) 05:31, 31 July 2019 (UTC)

BRIEF Followup - according to the current lede (8 July 2020) in the Speed of gravity article => In the relativistic sense, the "speed of gravity" refers to the speed of a gravitational wave, which, as predicted by general relativity and confirmed by observation of the GW170817 neutron star merger, is the same speed as the speed of light (c). - hope this helps in some way - iac - Stay Safe and Healthy !! - Drbogdan (talk) 12:50, 8 July 2020 (UTC)

UPDATE: Seems a gravitational wave may arrive before a light wave in some related instances, according to a recent science report. - Drbogdan (talk) 12:55, 26 October 2023 (UTC)

References

Major rumors can be noteworthy

nature.com gave it a short article, summarizing all the major telescope priority interrupts that suddenly found a certain obscure galaxy interesting, one of them naming this GW by number in its public database. Those interruptions are certainly not a rumor, and such a confluence has made it to the science press.

We are not a crystal ball, but there are only a small number of ways this much "exciting" data collection will play out. Either one or both of the GW/GRB will be confirmed, or both will be disconfirmed. So perhaps this article will be renamed GW170818 anomaly or LVT170818 in the end, reporting on what the RS say about the fluke and what it means for LIGO. Either way, it seems clear there will be an article on this topic.

Compare 750 GeV diphoton excess. 129.68.81.144 (talk) 15:31, 29 August 2017 (UTC)

The diphoton excess got an article long after ATLAS and CMS released their analyses, it didn't have an article in the days before the announcement when it was a rumor. The notice could have been due to a statistical fluctuation, a glitch in the data analysis or whatever else. Anyway, there is a CERN seminar in an hour, we'll know more after that. --mfb (talk) 16:27, 29 August 2017 (UTC)

I'm just spitballing here, but I predict we'll not know more after that. Supposedly LIGO/Virgo will go public with their data in almost-real-time after their fourth confirmed announcement. 129.68.81.144 (talk) 16:33, 29 August 2017 (UTC)

I couldn't listen to it and I don't see the slides or the talk recorded. Did someone have a look? --mfb (talk) 23:39, 29 August 2017 (UTC)

Rewrite

I rewrote the body of the article. I also edited Wikidata. Note that we cannot call this the "fourth" signal, nor identify what the "previous" signal was. LSC/Virgo has said they are analyzing seven [possible correction by (Drbogdan (talk) 11:52, 30 August 2017 (UTC)): better "several" instead? - please see => “promising gravitational-wave candidates”] earlier triggers, and I expect their next signal announcement will be for something seen in February or March. The one detail missing is that this might have been seen under triple lock.

I don't think it's worth naming anyone except the fellow who started the rumor game.

I think maybe we can leave out the under construction template, it's just normal editing now. Drbogdan? 129.68.81.144 (talk) 16:29, 29 August 2017 (UTC)

 Done - Thank you for your comments - and rewrite - no problem whatsoever - rm "under construction" template as suggested - Thanks again - and - Enjoy! :) Drbogdan (talk) 17:36, 29 August 2017 (UTC)

References

Where did you get the name?

I had entered the claim that the name GW170818 was seen in a trigger statement, which I had recalled reading earlier in the week, I thought in Nature or Quanta or New Scientist. I was unable to find it, so I deleted the claim.

Now I have to ask: Drbogdan, where did you get the name? Did you mistake the date of Wheeler's tweet for the discovery date? If so, it seems you should just rename the article to one day earlier. The most information seems to be the discussion at [1]. 129.68.81.144 (talk) 20:32, 29 August 2017 (UTC)

Thanks for the comment - and suggestion - yes - the name was based on Wheeler's tweet as noted earlier above - I've also tried to find a mention of "GW170818" in the various "public logs of several major telescopes list priority interrupts" as noted earlier in the article content - I've also not been able to locate the mention, which is why I tagged the earlier article text with "{{cn|date=August 2017}}" - for my part at the moment => until an official name has been posted in a "WP:RS", the present article name (ie, "GW170818") may be as good as any other - however - if someone thinks otherwise - renaming the article (esp if there's some ok rationale to do so), is *entirely* ok with me - hope this helps in some way - iac - Enjoy! :) Drbogdan (talk) 21:18, 29 August 2017 (UTC)

 Done - BRIEF Followup - renamed the article => to "GW170817" - maybe better after all - iac - Enjoy! :) Drbogdan (talk) 21:40, 29 August 2017 (UTC)

Maybe, maybe not. You have to fix all the links.

While I'm OK with an article on the rumors being reported in RS, I'm concerned with us inventing the name. But maybe we're not really inventing the name, we're relaying the information and then giving the most efficient, recognizable name.

Since the GRB seems to have been confirmed and definitively named, it might be best to merge the contents of this article with the GRB, and leave in a redirect. I have no strong opinions. 129.68.81.144 (talk) 22:05, 29 August 2017 (UTC)

 Done - related links have all been updated (and/or automatically redirected) earlier - at least afaik - iac - Enjoy! :) Drbogdan (talk) 22:10, 29 August 2017 (UTC)

Seven triggers

Yes, there are seven triggers in the source. Move down the page to 7/7/17 news. They mention 8 triggers, and then state that one of them has been confirmed.

All year LSC had been announcing updates on exact trigger counts. (Scroll down, you'll see the numbers grew over time.) My guess is they decided to go vague in response to the rumors, refusing to give an exact count, which if more than 8, would provide more fuel for speculation. 129.68.81.173 (talk) 15:43, 31 August 2017 (UTC)

Yes - seems there's a mention of "8 trigers" in the 7/7/17 entry after all - it's *entirely* ok with me to undo my earlier edit if ok - iac - Enjoy! :) Drbogdan (talk) 15:59, 31 August 2017 (UTC)

They had a false trigger rate of 1 per month, and the 7/7 news was made after 7 months of data-taking. We should expect most of these 7 unpublished triggers to be false. --mfb (talk) 00:49, 1 September 2017 (UTC)

What is your point? The question at hand is how to report LSC news, not how to interpret it.

As it is, you statement is inaccurate. Speaking precisely, what we expect is lower significance. The collective information from numerous low significant triggers is generally of scientific interest—this is what is done in HEP all the time. And coincidence with a GRB will elevate the significance beyond raw LIGO/Virgo numbers.

Personally, I don't believe LIGO events follow a Bell curve. O1 saw two 5σ events and only one 2σ event? Extrapolating suggests most of the triggers will be 5σ. (According to Harry Collins, the four-decade-embedded sociology of science researcher, there were no false alarms on O1, i.e., triggers they could ascribe to known noise.) What they are doing with the raw signals is, among other things, crosschecking as many of their seismic detectors and similar instruments as they can to rule out traffic, oversea storms, tumbleweeds, and the like. They are also looking for fake coincidences by time-shifting.

Of course, none of this is suitable for the article, but it may color our opinions on how to weigh the RS information we have. I view the use of "very exciting" in the LSC News headline as grounds for optimistic weighing. 129.68.81.110 (talk) 15:24, 3 September 2017 (UTC)

If you expect 7 triggers from noise or other non-GW sources and see 7 triggers, then you cannot claim that you found anything just based on these numbers. Some of them could be actual GW events, but that needs further investigation. We don't have the result of this investigation yet. --mfb (talk) 16:34, 3 September 2017 (UTC)

You are correct. But since no one has stated otherwise, I do not understand what your point could possibly be. I created this section in regards to an explicit statement from LSC News that one editor had not noticed. Having done so, the editor noticed the explicit statement. What does your evaluation of what 7 triggers might mean have to do with anything? 129.68.81.110 (talk) 20:30, 3 September 2017 (UTC)

Page for collision event as a whole

Before we repeat the same detailed information in lots of places, I think we need a page that deals with the detected collision event as a whole. That is, one that is separate from the specific components, e.g. the gravity wave GW170817 and the GRB 170817A, the many observatories involved, its location NGC 4993 and also separate from the type of event neutron star collision. Does the detected event itself have an official name?

The new page would cover all the aspects mentioned in the 2-hour press release that is on Youtube, whereas the above linked pages do not need to contain all that information. (Not suggesting that they do, but there is that temptation).

Thoughts? Tayste (edits) 21:34, 16 October 2017 (UTC)

I think the article here (i.e., GW170817) is currently playing the role of covering all aspects, it's not just about the GW signal by its name. I wouldn't mind keeping it that way because otherwise it would be hard to come up with a title for an umbrella article. Articles like GRB 170817A can have mostly content that relates strictly to those respective observations, plus a short note about how it fits in the GW picture, with a link to here. Gap9551 (talk) 21:53, 16 October 2017 (UTC)

We seem to have a page at Kilonova that looks like it covers this type of event. Some research needs to be done to make sure that's the correct name/place for this, though. Thanks. Mike Peel (talk) 23:15, 16 October 2017 (UTC)

Some are calling it the Golden binary :D Tayste (edits) 03:41, 18 October 2017 (UTC)

According to your edit description, you think this is an informal name being used by LIGO for the event. It is not. It was from a title for the Nature announcement about the neutron star collision, typical journalese, nothing more, with an indefinite article even.

The phrase is in fact used by LIGO, and has been for used for over a decade. It refers to any binary collision with a very strong, unambiguous signal at both high and low frequencies, so the redirect is factually incorrect. GW150914, for example, was a golden binary, the next two signals were not. These golden binaries can be used for testing GR versus alternative theories.

As a reminder, we do not introduce redirects here because we can, but because it helps Wikipedia readers who have likely heard the alternate name. A nickname like "God Particle" has caught on, this one has not. It may in the future. 129.68.81.143 (talk) 14:12, 18 October 2017 (UTC

• • • • I have turned the incorrect redirect Golden binary into a standalone stub, with references. 129.68.81.143 (talk) 16:35, 18 October 2017 (UTC)

---

• There should only be one article for the event, presumably this one. Anything else is annoying and/or confusing, as there is very little that would be specific to just one such article, and anyone trying to follow the whole story is forced to waste his time. Ridiculous. For example, we almost never have separate articles for a person and pseudonym (say Lewis Carroll and Charles Dodgson).

For the record, there are at least a half-dozen official and unofficial names already:

1. GW170817
2. GRB 170817A (with a space)
3. Swope Supernova Survey 2017a aka SSS17a
4. AT 2017gfo (IAU Astronomical Transient)
5. DLT17ck (Distance Less Than 40 Mpc survey)
6. MASTER OT J130948.10-232253.3 (MASTER-OAFA robotic telescope)
7. LIGO/Virgo G297595 (Gamma-ray Coordination Network [GCN] Circular name for the trigger)

Any logic that says two are OK would say that the three we have already are OK and heck, we should have articles for all of them. The multiple names exist for technical reasons that professional astronomers keep to for their own professional reasons, but that has nothing to do with Wikipedia.

Compare with SS433, which has one article and dozens of designations. 129.68.81.143 (talk) 14:12, 18 October 2017 (UTC)

I agree, after thinking more about it. GRB 170817A has almost no content, certainly nothing in addition to the article here. SSS17a also has virtually no additional content beyond this article. Expanding them would create a lot of redundancy. Both should be redirected to this article, which isn't too long to fit a description of the gamma-ray and optical events. Comparing this event to GRB 970228, the first GRB with observed optical afterglow, there is no separate article about the afterglow there. Gap9551 (talk) 15:19, 18 October 2017 (UTC)

In addition, we follow, as much as possible, secondary sources. Popular science articles (NYT,SciAm,PopSci) don't seem to be giving any name. More technical secondary sources (Nature,arXiv blog) seem to be only using the GW name. 129.68.81.143 (talk) 16:35, 18 October 2017 (UTC)

References

For non-experts

I thought I read somewhere (in the Wiki-guidelines?) that all articles are supposed to be aimed at "an intelligent college student". This article, as is sits right now, is more of a graduate textbook section in multi-messenger astronomy. If you don't supply context in the article itself, the vast number of readers (intelligent college students) will be turned off and won't follow the wiki-links.

I'm not saying that any of the material you have already should be eliminated. I am saying that what you have should be explained down to an undergraduate level. For example, the phrase in the lead paragraph "the first gravitational wave detection of the merger of two neutron stars, and was associated with a soft short gamma-ray burst GRB 170817A, and an optical transient that was found in the galaxy NGC 4993" should explain (a) what a "gamma-ray burst" and an "optical transient" are and (b) which of the two events (merger of two neutron stars or the association of a gamma-ray burst and an optical transient) was the first. I'm right, aren't I, that whatever is first makes the event worthy of inclusion as a separate article?

I could start to make the additions myself but, as you can see, I don't really have the depth of knowledge to judge the precedence of what I'm adding. And when you get into "scalar–tensor theory and Hořava–Lifshitz gravity", I am totally lost. --RoyGoldsmith (talk) 05:33, 18 October 2017 (UTC)

Thanks, these are constructive comments. When time permits, I'll try to put some non-technical explanation around the technical facts. I suppose a good place to start would be "what questions would an undergraduate ask for clarification on when reading this?"... Tayste (edits) 05:39, 18 October 2017 (UTC)

Mentioning 1.7 s in the lead

@Earthandmoon: I'm not sure I like this second-try edit, but it's not wrong so I'll discuss it here rather than reverting for a second time.

The details are already there, in GW170817 § Electromagnetic observations. Your edit consists of copying them into the lead, and I think it's cluttering more than helping. Could you explain why you think that helps? 104.153.72.218 (talk)

Hallo, I only tried to explain the question of @RoyGoldsmith: above talk [For non-experts].Earthandmoon (talk) 12:35, 18 October 2017 (UTC)

@Earthandmoon, Anthrcer, and Gap9551: I took a crack at a more extensive rewrite of the lead, organizing it with a bulleted list to keep things clear for the reader. What do you think? I'm not really happy with the "strong evidence that they come from the same astronomical source" part; there's both evidence for and a lack of reason to doubt, but I can't think of a concise way to say that. 104.153.72.218 (talk) 15:34, 18 October 2017 (UTC)

Bulleted lists are quite uncommon in leads, but as far as I can see not explicitly discouraged by the Manual of Style. The list does a good job of clarifying the multiple separate observations. Gap9551 (talk) 19:02, 18 October 2017 (UTC)

Isn't the main reason for the three articles on GW170817, GRB 170817A and AT 2017gfo that together they indicate the first observed merger of two neutron stars? As a matter of fact (and check me if I'm wrong), the only reason these three articles have notability is because of the merger.

Perhaps we should transfer the second, bulleted paragraph (or most of it) to the "Observed merger" section in the Neutron star merger article? Or, if we really want to be bold, perhaps we should start transferring everything after the "Gravitational wave detection" section to the merger article? All the three feeder articles could wind up as stubs with just the lead section. The main analysis could go to the Neutron star merger article. Just an idea. --RoyGoldsmith (talk) 00:51, 20 October 2017 (UTC)

@RoyGoldsmith: "the only reason these three articles have notability is because of the merger" That seems disingenuous. The signals were produced by the merger and wouldn't exist without it, so discussing them without the merger is impossible. Would the Trinity test be notable if it weren't at atomic bomb? That's so speculative there's nothing to discuss.

Yes, it's three perspectives on one event (the merger), nobody seriously doubts the common origin of the three signals, and a common page would make sense. It shouldn't be merged with Neutron star merger, however. That's neutron star mergers in general, and while it might be merged with kilonova, it's not an appropriate home for details of this particular one. 104.153.72.218 (talk) 17:58, 20 October 2017 (UTC)

Please see further comments under "First observed merger — NOT" section below. --RoyGoldsmith (talk) 14:41, 21 October 2017 (UTC)

Timeline at speed of light

I'm familiar with basic physics, but I'm missing information to understand the topic at first reading. I understand first indication was the gravity wave detection (by LIGO/Virgo), and then ~all available telescopes were directed to measure other radiation from that point. That came 11 hrs later, enough time to redirect a telescope OK. But hey, when everything is happening at speed of light, how these 11 hrs of extra time? IMO, this could be explained in article body, and should be mentioned in the lede. -DePiep (talk) 20:20, 19 October 2017 (UTC)

It took time to find the galaxy where the event happened. --mfb (talk) 20:37, 19 October 2017 (UTC)

And many ground-based telescopes had to wait for nightfall. Gap9551 (talk) 20:58, 19 October 2017 (UTC)

? The waves and radiation were not waiting for this. There physically was a delay of 11 hrs. I don't understand. (Unless, of course, astronomical event HG2G42 is involved, with a busstop). -DePiep (talk) 21:09, 19 October 2017 (UTC)

They didn't know where the source was, only that it was in a large 31 square degree region (the initial estimate). And during the day the sky is normally too bright to see astronomical sources. Gap9551 (talk) 21:14, 19 October 2017 (UTC)

Yes I understand that: Earthly issues. But my question is: why was there an 11 hr delay in the arrivals in the first place? What kept up the waves so long? This is all speed of light stuff. -DePiep (talk) 22:00, 19 October 2017 (UTC)

It doesn't say anything about a delay in arrival. The optical source was seen 11 hours later, but may have appeared at the same time as the GRB. Gap9551 (talk) 22:13, 19 October 2017 (UTC)

All correct, and none an answer. Please answer this one question: why did certain waves arrive at Earth 11 hrs later that other waves? -DePiep (talk) 22:18, 19 October 2017 (UTC)

The source of the waves (hot gas) continued to exist and emit radiation for weeks. The waves arrived right after the merger signal, and continued to arrive for seconds (GRB) to over a week (optical). So 11 hours after the merger, optical waves were still arriving, just like they were (likely) 1 hour after the merger, and 1 week after the merger. Only the GRB was a brief burst of radiation, the optical was arriving over a much longer time. In other words, the optical light did not only arrive 11 hours after the merger. Gap9551 (talk) 22:41, 19 October 2017 (UTC)

Thanks. Hope we can agree that this deserves a place in the article(-lede). -DePiep (talk) 22:44, 19 October 2017 (UTC)

Other reason for optical waves delay 11 hours because at the time of event, NGC 4993 sit very near the Sun, many optical observatories are in day light, and Swope telescope can start observing sources and finally find out NGC 4993 after sunset.Earthandmoon (talk) 01:05, 20 October 2017 (UTC)

As long as we're on the subject, what event do we think we observed? (Let's say of the gravitational wave signal since it appears first.) Let's say it was the merging of two neutron starts to create a black hole. What was the first event we could observe? Was it the forming of the event horizon surrounding the first particle (quanta) of the neutron stars? Or something before the event horizon, when the stars are dancing around each other at a speed approaching that of light? What about the relativity effects? The GWS lasted about 100 seconds. Could that be the total time it took to transform the two stars into one singularity? What if the merging only created a more massive neutron star? --RoyGoldsmith (talk)

When you say "see", what sort of observation are you talking about? Gravitational, gamma-ray, or conventional electromagnetic (meaning radiation from X-ray to radio which we can focus, and thus image)?

The GW signal was from their orbits decaying before they touched. During that time, it's just two hot glowing balls spinning around each other. Close to the end, things get a bit exciting as they are deformed by tidal forces and thereby heated. (This also accelerates the decay as the energy comes from the orbital kinetic energy.) When they touch, the fireworks start.

The merger causes a tidal disruption, throwing clouds of neutron star material outward and forming jets due to the magnetic fields. That's what's actually seen optically. The gamma rays are produced during the stars' interpenetration when temperatures rise to insane levels. The ejected material produces the lower-energy photons.

One thing that's nice about this kilonova compared to others is that we're not looking directly down the jet. While that makes it appear dimmer and thus harder to find, it means we can see the site of the collision without the jet in the way. While we don't have anything close to the angular resolution required to separate the two in a telescope, at least the jet isn't blocking the light from the core. It arrives mixed-up with the light from the key, but at least it arrives, and can be separated spectroscopically by Doppler shift.

Note that we can not see an event horizon forming. A black hole is black and invisible, from the moment of its formation. (In fact, from slightly before. Emitted light is dimmed to imperceptibility before the emitter crosses the event horizon.) What we see is the glow emitted by surrounding material being compressed as it's pulled in.

There are basically three scenarios for what happens in the middle:

1. A larger neutron star forms. Since it's spinning quite fast, it might be observable after the surrounding debris cloud cools and fades. The physics of neutronium involves a lot of guesswork, so the maximum possible size of a neutron star (the Tolman–Oppenheimer–Volkoff limit) is only approximately known.
2. A black hole. Astronomers think this will lead to a dimmer event, since the hole eats a lot of material whose glow we would see otherwise.
3. An unstable neutron star which then decays into a black hole after a delay. (When its spin slows, or some ejected material falls back.) This is hard to distinguish from case 1.

104.153.72.218 (talk) 09:09, 20 October 2017 (UTC)

First observed merger — NOT

@RoyGoldsmith: I undid your edit for several reasons, actually, and I'd like to figure out what you're trying to do in order to better achieve it. The boilerplace in undos doesn't leave a lot of room for a good edit comment, so let me expand here:

1. This is not the first observation of what is thought to be a neutron star merger. As mentioned in kilonova, GRB 130603B was the first observed optically. (Although maybe GRB 050709 deserves the crown instead?)
2. It's the first observed gravitationally, of course, but that's the entire point of the second sentence. Isn't that good enough?
3. You downgraded the definite verb "was" to the mushier "thought to be". While technically true of everything in science, the evidence is convincing enough that there's no need to use such WP:WEASEL words. Every SGRB detection is an observation of what's thought to be a neutron star merger. This one is interesting because the data is so rich and unambiguous.

Although I used point 1 as justification for the undo, it's actually point 3 that got my attention first; I quite dislike that phrasing. I'm having a hard time inferring what the problem is that you were trying to fix. Could we discuss it to find a fix that we both like? 104.153.72.218 (talk) 08:31, 20 October 2017 (UTC)

I agree with all your points. See below for more discussion. --RoyGoldsmith (talk) 15:42, 21 October 2017 (UTC)

@Eric Kvaalen: Likewise. This is not repeat not the first observation of merging neutron stars; it's just by far the best observation. Perhaps I need to put words in the article to that effect?

• It is the first gravitational detection of colliding neutron stars. The second sentence of the lead says that.
• If the theory that all short GRBs are neutron star mergers is correct, then all observed short GRBs have been observations of mergers. (We just didn't know that at the time, and the "observation" is very uninformative.)
• If the theory that all short GRBs are neutron star mergers is correct, then the first time merging neutron stars were observed optically (not just in gamma rays) was GRB 050709, whose optical afterglow was seen by the High Energy Transient Explorer-2 satellite.
• The first confirmation of the theory, observation of a short GRB source which astronomers are sure was a neutron star merger (a "kilonova"), was GRB 130603B (popular article describing it). However, optical follow-up was ten days later, so a lot of information was lost.
• This is by far the best observed, and the GW data makes the neutron star source incontrovertible.
• Excitingly, there were two significant delays in observations of this GRB: the GW position was delayed several hours by an unlucky glitch in one detector, and the sky position was close to the sun, which required waiting a few hours for an observing opportunity. Once those delays ended, it took about an hour to find it. It's likely that the next NS inspiral detected will be imaged far faster.

Any ideas how to boil all that down to a short message that can fit into the article? Any any ideas where to put it? 104.153.72.218 (talk) 12:15, 20 October 2017 (UTC)

P.S. I added a paragraph to § Scientific importance since this appears to be a common misunderstanding. Feel free to revise/improve/move, of course. 104.153.72.218 (talk) 12:40, 20 October 2017 (UTC)

So you believe this article is notable, according to WP:N, because it is the first gravitational detection of colliding neutron stars and this is by far the best observed, regardless of how the GW was created. I assume by "this" (in the second reason) that you mean the gravitational wave event GW170817. Are the GRB 170817A and AT 2017gfo observations "the best observed" and so make each of them notable? If not, what makes each of the two articles notable?

So far as a common page for all three events, we don't know if the object produced by the merger is a light black hole or a heavy neutron star. Do you think that astrophysicists will determine that in fairly short order; say, in less than a month? If so, they'll probably give it a name and we can use that name for the title of the common article. The suggestion that all the common elements for the three articles be consolidated into Neutron star merger or (better) Kilonova was just temporary until they invent the name. (By the way, shouldn't the articles Neutron star merger and Kilonova be merged?) --RoyGoldsmith (talk) 15:42, 21 October 2017 (UTC)

Well, it certainly "received significant coverage in reliable sources that are independent of the subject" (as WP:N puts it), so why would anyone suggest it isn't notable? Aside from just policy reasons, it is noted as the "first multi-messenger" detection, as confirmation that (to within a tiny uncertainty) GWs travel at the speed of light, as an independent confirmation of the Hubble constant and hence the age of the universe, and as a long-awaited observational confirmation of the theoretical model for neutron star mergers. What more could one ask? LeadSongDog come howl! 17:17, 23 October 2017 (UTC)

@RoyGoldsmith and LeadSongDog: As LeadSongDog says, the fact that it's got a shit-ton of press is the single most significant factor in Wikipedia's standards for WP:Notability. See also the first paragraph in § Scientific importance. Science and Nature are the most prestigious scientific journals in the word. One article in either is notable. Fourteen spanning both? Yeah, that's notable.

The underlying reason for that notability is that it's the first time a GW observation has been confirmed by non-gravitational means. Although they were very careful, LIGO's first detection was a bit oracular. "The gods have spoken words that only we can hear." Then Virgo confirmed a detection. Now, a GW detection has been confirmed by seventy different astronomical teams. That retires a lot of doubt.

The ultimate test of good science is whether it can make accurate predictions. LIGO/Virgo sent out a prediction that "if you look here in the sky, you'll see a neutron star merger", and a few hours later the prediction came true.

Scientifically, while this is not the first neutron star collision observed, it's by far the most certain. In particular, the inference chain from observation to the conclusion that they're neutron stars is much shorter: the GW signal gives the mass of the objects, and the frequency when it ends tells you their sizes. 104.153.72.218 (talk) 12:26, 24 October 2017 (UTC)

@104.153.72.218, LeadSongDog, Rkinch, and Anyone else: I made two edits:

1. Added GRB so we'd list all three multi-messenger astronomy events.

2. Inserted my third try at notability at the end of paragraph 2, based on underlined sentence above by 104. I agreed that it's only one reason but at least it gives some reason. (Do you want to add more?) I don't think it interferes with non-scientific readers.

Please address them separately and don't delete both without reasons for both. --RoyGoldsmith (talk) 04:32, 27 October 2017 (UTC)

The murky term "conventional telescopes" is supposed to include all the electromagnetic instruments across the spectrum (radio, infrared, visible, UV, gamma), although calling these "conventional" is not informative because a cold reader might assume this means somebody looking through an eyepiece on a Celestron. So it's not logical to be adding "satellites" (etc) after "conventional", although the logic is not well expressed by the word "conventional". The point of notability, as we editors are aware, is that this was the first independent observation in both GW and EM modes of one and the same event. The independence is not just GW vs EM, and numerous instances of each, but also interferometry vs telescopy. The article is still flawed with "event" ambiguously meaning the astrophysical event versus the GW/EM emissions versus the instrument detections versus the social announcement. The label "conventional" is supposed to equate to EM instruments, that is, the GW interferometers are not telescopes and not "conventional" EM detectors. "Optical" is the appropriate word, not "conventional", although "optical" is typically misunderstood as a "visible light" instrument instead of anything EM. So it's just a tangle of confusion, and no economical introduction can get this elaborately explained. We also have the common WP difficulty of detailed textbook ideas being prerequisite to introducing what is newsworthy and notable to an intelligent non-expert. The full story has so many notable angles, it's a tough task to get the logic and specifics across to an intelligent reader who isn't already aware of how instruments are classified and designated as GW vs optical. But that's essential to the story's notable nuggets. The article is self-conflicting in places, being journalistic vs scientific in tone, because this article attempts to be the place to meet both these aspects of the story. We have to be careful to not say too much and make these terms ambiguous, while still getting the logic of the story across. "Triangulation" is a prime case of an informative and appropriate word for directional analysis that has ambiguous meanings. We can't get hung up that it can mean something else, whether a surveyor's term, a love triangle, kinematic rigidity, or what Bill Clinton did in 1990s US politics. I'm hopeful we can explain the basic story in a few introductory sentences: "something went bang way out there" and "a new kind of ear heard it before all the old eyes saw the same thing", without being pendantic and precious. Richard J Kinch (talk) 05:22, 27 October 2017 (UTC)

Black holes are black

@Mike Peel: 'so' implies causality that isn't definite. Er, what? The causality absolutely is definite. Black holes cannot be seen, full stop. They can be detected optically only by to their gravitational effects on other visible, matter: gravitational lensing, perturbation of the orbits of visible matter, or heating of infalling matter. However, a closely spaced binary pair has long since eaten or ejected all nearby normal matter, so there's nothing else to glow, either. If an optical counterpart were seen, that would be very unexpected indeed.

To quote this LIGO press release:

LIGO and VIRGO’s partner electromagnetic facilities around the world didn’t identify a counterpart for GW170814, which was similar to the three prior LIGO observations of black hole mergers. Black holes produce gravitational waves but not light.

Can you explain why you think it's not definite? Astronomers looked, just in case, but didn't expect to find anything. Anything that would produce such an effect is a WP:FRINGE theory that doesn't deserve undue weight. 104.153.72.218 (talk) 14:31, 20 October 2017 (UTC)

If you want to make a strong claim along the lines of 'this means that', you must reference it (and with a better source than a press release that implies but doesn't state this). I changed "so produced no corresponding" to "had no detectable", which is a weaker statement (it's an observational constraint rather than a statement of fundamental physics). I work in observational astronomy rather than theory, and my naive expectation was that there could be some matter around that could radiate as a result of the merger, but I'm happy to be shown wrong by a good reference. Also: thank you for your work in general to make the article more accurate! Thanks. Mike Peel (talk) 14:55, 20 October 2017 (UTC)

(edit conflict) There have been a bunch of papers studying scenarios for EM counterparts to binary BH mergers; all consider large amounts of gas left behind by the BH progenitors. For example [2][3][4][5]. Gap9551 (talk) 15:51, 20 October 2017 (UTC)

@Mike Peel: (edit conflict) You're right that it's not utterly impossible, but I think without diving down rabbit holes of implausibility, "is not expected" is true enough for a passing mention in an article about something else. Yes, there are conditions under which something visible could happen. For example, a nearby orbiting star (which somehow survived the inspiral) would be shaken by the gravitational radiation and might flare. As I mentioned earlier, you can't have normal matter very nearby, because it would have been absorbed or ejected by three-body interactions. I guess my problem is that if we're only saying empirically "nothing was observed", there's no reason to mention the black holes at all. The whole reason for mentioning them is to point out that we don't expect to see any light from such an event. (The much larger distances also play a factor. It would take quite something to stand out from 440 Mpc.)

I quite agree that astronomers aren't crazy for looking. We know so little it's a possibility worth exploring, and the potential payoff is huge. For example, could a binary pair have a shared accretion disc? (That would tend to align the individual spins with the orbit, but I can see how that process would be far from complete in a 20 Msun BH.)

Here's some discussion: Siegel, Ethan (2017-06-08). "Newest LIGO signal raises a huge question: do merging black holes emit light?". Starts With a Bang. Medium.com. {{cite news}}: Cite has empty unknown parameter: |1= (help)

Can we find something mutually acceptable which is a bit more cautious that still implies some connection? "so are not expected to produce a significant optical signal"? "which lack an obvious mechanism that would produce an optical signal"? "which require the presence of additional matter in the system to produce an optical signal"?

It's easy to find implicit acknowledgement of the long-shot nature of optical viewing of black hole events, e.g. Arcavi, Iair; et al. (20 October 2017). "Optical Follow-up of Gravitational-wave Events with Las Cumbres Observatory". The Astrophysical Journal Letters. 848 (L33): 6. doi:10.3847/2041-8213/aa910f. Despite the lack of an NS component and the large distance, we triggered our follow-up program given the relatively small localization region.{{cite journal}}: CS1 maint: unflagged free DOI (link)</ref>

But I'm still looking for an explicit statement. 104.153.72.218 (talk) 16:02, 20 October 2017 (UTC)

@Gap9551: Thank you! That first paper says right up front in the abstract "Mergers of stellar-mass black holes (BHs) [...] are not expected to have electromagnetic counterparts." And then it goes on to imagine how it could happen anyway. The third paper is also (but less explicitly) saying that we won't get light except in the following weird situation, and here's how to see if that applies. 104.153.72.218 (talk) 16:12, 20 October 2017 (UTC)

I'm happy with "is not expected to produce", which is a statement of human understanding. That's different from "so produced no corresponding", which is a statement of physics. Thanks. Mike Peel (talk) 16:22, 20 October 2017 (UTC)

I agree something like that should be communicated in the first paragraph. Another option, softening the above suggestions: ... of merging black holes and were generally not expected to have detectable electromagnetic counterparts. Gap9551 (talk) 16:31, 20 October 2017 (UTC)

@Mike Peel and Gap9551: Implemented; how does it look? That's basically the wording I ended up (independently) writing, minus the word "generally". I added the details in an {{efn}} explanatory footnote, which you should both feel free to edit fiercely; I'm not sure I like it myself. 104.153.72.218 (talk) 17:01, 20 October 2017 (UTC)

Thanks, I made some minor edits. Gap9551 (talk) 18:33, 20 October 2017 (UTC)

@Gap9551 and anon, it would be good if some of the refs you've mentioned here could be included in the footnote, or a wikilink to a page where this is discussed more. Thanks. Mike Peel (talk) 00:20, 21 October 2017 (UTC)

 Done Gap9551 (talk) 02:43, 21 October 2017 (UTC)

From LIGO's twitter stream: "We don't know if remnant of merger is a #NeutronStar or a #BlackHole. X-rays suggest black hole." [6] We expect a black hole, the evidence is consistent with a black hole, but if a remnant neutron star had formed we wouldn't necessarily be able to tell. At that distance you need either a certain abundance of infalling matter or a favorable pulsar orientation to see a neutron star, so we can't completely rule out the possibility that a neutron star remnant remains but with characteristics that make it too difficult to see. Most likely though, it is a black hole. Dragons flight (talk) 15:47, 20 October 2017 (UTC)

@Dragons flight: Yes, thank you, but we're talking about the earlier GW events, where the merging objects were already black holes. The lead contrasts the current event, where a prominent nova is expected, with those earlier ones, where a mechanism is quite speculative. 104.153.72.218 (talk) 16:02, 20 October 2017 (UTC)

Eh, sorry. I only read the prior posts here and misunderstood the context. Dragons flight (talk) 16:38, 20 October 2017 (UTC)

Gallery

Perhaps the image in the gallery could be integrated into the prose somehow? For one, I don't think galleries are encouraged, and two, it looks super awkward with just one image. ---Another Believer _(Talk) 02:15, 22 October 2017 (UTC)

 Done - Thank you for your comments - and suggestion - relocated video-image to a better location in the main-article - seems ok - let me know if otherwise of course - in any case - Thanks again - and - Enjoy! :) Drbogdan (talk) 13:00, 24 October 2017 (UTC)

@Drbogdan and Another Believer: Good work! I was thinking of putting it in § Astrophysical origin and products, but there's already a backlog of right-margin illustrations from the section above, so it doesn't fit well. Your location is better, thanks! I think the caption could use some simplification; I'll go do that 104.153.72.218 (talk) 15:52, 24 October 2017 (UTC)

Triangulation

@Rkinch, Mike Peel, and Gap9551: I'm sorry that an edit message doesn't leave a lot of room for an explanation. I try, but especially if half of the space is taken up with an undo message, what remains has to be quite terse. In full detail, the reason that the GW source location computation should not be described as triangulation:

• Even if it were, that doesn't deserve mention in the lead. The lead is already longer than ideal, and anything, including this methodological detail, which can be moved to § Gravitational wave detection should be.
• The LIGO mention is a public relations figure caption, not a formal work of WP:SCHOLARSHIP. Observe that the formal paper which that web page is describing doesn't use "triangulation" or any similar term.
• It's not triangulation, because the detectors are not measuring the angle of incidence. Start with reading the WP article: "triangulation per se involves only angle measurements, rather than measuring distances to the point directly as in trilateration". Although looser use is common, Wikipedia should try to be consistent within itself: either amend that article to include a broader definition, or avoid using the term in this article. (Certainly linking to an article that directly contradicts the link source is pretty questionable.)
  • I'm not citing the fact that GW detectors can only sense arrival time difference and have almost no directional sensitivity, except for their polarization sensitivity. I can if necessary, but I hope we don't have any dispute over that.
• Some formal reliable sources supporting this definition of triangulation, both general and specialized:
  • Encyclopedia Britannica Triangulation "is based on the laws of plane trigonometry, which state that, if one side and two angles of a triangle are known, the other two sides and angle can be readily calculated. One side of the selected triangle is measured; this is the baseline. The two adjacent angles are measured by means of a surveying device known as a theodolite, and the entire triangle is established."
  • dictionary.com "Triangulation":
    • Random House Dictionary: "1. a technique for establishing the distance between any two points, or the relative position of two or more points, by using such points as vertices of a triangle or series of triangles, such that each triangle has a side of known or measurable length (base or base line) that permits the size of the angles of the triangle and the length of its other two sides to be established by observations taken either upon or from the two ends of the base line. 2. the triangles thus formed and measured"
    • Collins English Dictionary: "1. a method of surveying in which an area is divided into triangles, one side (the base line) and all angles of which are measured and the lengths of the other lines calculated trigonometrically 2. the network of triangles so formed 3. the fixing of an unknown point, as in navigation, by making it one vertex of a triangle, the other two being known"
    • American Heritage Science Dictionary: "A method of determining the relative positions of points in space by measuring the distances, and sometimes angles, between those points and other reference points whose positions are known. Triangulation often involves the use of trigonometry. It is commonly used in the navigation of aircraft and boats, and is the method used in the Global Positioning System , in which the reference points are satellites." (this is the broader sense)
  • Mirriam-Webster Dictionary, Triangulation: "the measurement of the elements necessary to determine the network of triangles into which any part of the earth's surface is divided in surveying; broadly: any similar trigonometric operation for finding a position or location by means of bearings from two fixed points a known distance apart."
  • U.S. Army Field Manual FM 6-2: Tactics, Techniques, and Procedures for FIELD ARTILLERY SURVEY Chapter 6 Triangulation: "In FA surveys, the term triangulation is restricted to operations that involve the measurement of all angles within a triangle. (See Figure 6-1.) Other methods of survey, however, use the triangular figure, but the procedures used in the fieldwork and in the computations differ somewhat from the methods used in triangulation."
  • Higher Surveying (textbook) Chapter 1: Triangulation and Trilateration "A triangulation system consists of a series of joined or overlapping triangles in which an occasional side is measured and remaining sides are calculated from angles measured at the vertices of the triangles."
  • U.S. Bureau of Land Management Glossary of mapping terms Letter T: "TRIANGULATION – A method of surveying in which the stations are points on the ground at the vertices of a chain or network of triangles. The angles of the triangles are measured instrumentally and the sides are derived by computation from selected sides or bases, whose lengths are obtained by direct measurement on the ground or by computation from other triangles."
  • Australian and New Zealand Spatial Information Council. Fundamentals of Mapping Surveying for Mapping — Section 2, Surveying Methods "Triangulation is a surveying method that measures the angles in a triangle formed by three survey control points. Using trigonometry and the measured length of just one side, the other distances in the triangle are calculated. The shape of the triangles is important as there is a lot of inaccuracy in a long skinny triangle, but one with base angles of about 45 degrees is ideal."
• "Triangulation" is also used in a broader sense to mean any method which involves measuring part of a triangle to compute the whole. Technically, measuring the sides is trilateration, and measuring the difference in side lengths (which is how GPS works) is multilateration a.k.a. hyperbolic navigation, but those are much less familiar words and many people (e.g. Trimble) use the more familiar "triangulation" to describe those operations as well. However, even this broader sense is still used to produce triangles: a position which includes a distance. The distance to GW170817 is so far that the triangle is degenerate: two sides are parallel, and the vertex is at infinity. This is the point I tried to make in the edit comment: there's no triangle.

Triangulation is used by astronomers; it's the basis of the method of parallax. A star whose parallax is one arc second when measured at opposite ends of the Earth's orbit has a distance of one parsec. One tenth of an arc second is ten parsecs, etc. This is limited to nearby stars; as distances get farther, the angles get smaller and harder to measure. The most accurate astrometric angle measuring instrument today is Gaia (spacecraft), which is capable of measuring angles to 20 microarcseconds, or 50,000 parsec. Even if the baseline were 1 au (as we don't have six months to wait, it's not; it's the much smaller distance between GW detectors) 40,000,000 parsec would produce a parallax angle indistinguishable from zero.

The GW detectors are receiving a plane wave, and even with three receivers only the direction of the source can be computed. (The distance is computed by different means; see Cosmic distance ladder § Standard siren.)

I don't know why LIGO published that figure caption. I presume it's someone tasked with public relations who is being sloppy with language. That doesn't mean that Wikipedia should copy it. 104.153.72.218 (talk) 12:33, 25 October 2017 (UTC)

I agree - this is direction finding, not triangulation. Thanks. Mike Peel (talk) 13:07, 25 October 2017 (UTC)

"Frantic excitement"

@31.18.248.183: Re: this deletion of "and spurred frantic excitement and further analysis." A few days ago, I had a non-technical friend read the article (which led to several edits on my part), and the word "frantic" was specifically called out to me as a good thing which added flavour to an otherwise dry article. AFAICT, it's an accurate description. Your deletion had no edit comment. Can you elaborate on why that needed to die? 104.153.72.218 (talk) 09:44, 27 October 2017 (UTC)

Thanks for correcting my error

@TychosElk: Re: this correction. Thank you; my bad. The press conference included a speaker from the Las Campanas Observatory describing the follow-up search, so I assumed that was the acronym. The source, of course, says Las Cumbres Observatory. Thank you for fixing it. 104.153.72.218 (talk) 10:20, 27 October 2017 (UTC)

Changes undone

My changes were undone. I fixed a major misunderstanding in the AT2017gfo section, added (some) relevant references and removed references that were either not relevant or misplaced. Why? [added => 18:52, 29 October 2017‎ Aldebarahan (talk | contribs)‎]

Thank you for your comments - seems there may have been substantial changes that may benefit from a closer view by other editors before adding the changes to the main article - Comments Welcome from other editors about the suggested changes - in any case - Thanks again for the comments - and - Enjoy! :) Drbogdan (talk) 01:05, 30 October 2017 (UTC)

@Aldebarahan and Drbogdan: Because the changes broke the article (you deleted footnotes referenced multiple times, breaking the additional references) and introduced unjustified statements. Given the lack of edit comments that would help pick out portions worth saving, I agree with reverting them en masse. The diff is confusing because Wikipedia's difference renderer gets confused by newline additions/removals, so I may have missed something,

Going through the revert diff in detail:

• Line 10 et seq.: Why did you reformat the Connaughton reference? I agree that the |volume=826 and |issue=1 parameters were incorrect. And why'd you delete the de Mink reference? That references was needed to support the claim in the explanatory footnote.
• Line 18/46 et seq.: Breaking X-ray and radio observations into a separate detection is unupported and unjustified. The GW and GRB locations are uncertain because of their detectors' inability to focus. All of the other EM telescopes can focus and have a very tight location, which is AT 2017gfo. That specifically includes the Chandra X-ray telescope. It is not a separate detection, just another observation of a known event.
• Line 32/71 et seq.: Why delete the Overbye reference (NYT-20171016)? This left a big red cite error in the article and thus clearly needed to be reverted.
• Line 57/96 et seq.: The first announcement saud the GRB lasted "about two seconds"[7], not "less than two seconds". https://arxiv.org/pdf/1710.05834.pdf page 11 says "The triggering pulse, that lasts about half a second and falls within the usual observer distributions for GBM SGRBs, is shorter and spectrally harder than the subsequent softer, weaker emission that lasts a few seconds (Goldstein et al. 2017)." What's your source for the "less than two seconds" claim? There's no need to capitalize "Gamma-Ray Telescope" when it's used as a descriptive term.
• Line 75/114 et seq.: More deletion of references supporting statements, and information like the X-rays were not detected earlier. No explanation in edit comments. The SSS detection was "with an i-band filter"[8], which is near-infrared. Changing that to "optical" is making the article worse.
• Line 122/161 et seq.: Lots more removed references, not replaced with anything better. The deleted ApJL reference, in particular, is very clearly relevant to the issue of scientific importance.

I'm tired and going to stop there. The edits appear to be ill-conceived and unjustified. If there are nuggets of value, they're hard to find among the undesired changes.

Despite this critical tone, the reason I'm going to the effort of responding in detail is in hopes of encouraging you to do better. You appear to be editing in good faith. 104.153.72.218 (talk) 09:18, 30 October 2017 (UTC)

Multi-messenger

@CA2MI: Re: "GW170817 is a transient multi-messenger event observed on 17 August 2017 by the LIGO and Virgo detectors, which recorded a gravitational wave (GW) signal produced by two neutron stars"

There's a grammar problem here. If you're talking about the source, or even the observation, that was; its over and done with. The recorded signal (which is what the previous/reverted text refers to) still exists, so it is.

Also, the article goes to some trouble to distinguish the GW/GRB/AT signals, and this change to the definition of what GW170817 is (from GW signal to astronomical source) a bit too much confusion. When we're conflating things, we use the more generic "event". (I don't have a problem with this conflation in most contexts, as that's how astronomers speak normally. It's akin to how the "event" of a coronation is the ceremony proper and the invited guests and the parade and the parade spectators and the protestors and so on.)

But more than that, "multi-messenger" describes the observation more than the source. Not only are all astronomical sources technically multi-messenger, even potentially detectable ones are apparently not all that rare. What's new is that this is the first time everything has been in place to actually observe one.

The end of the first paragraph and entirety of the second is already all about the multi-messenger aspect. Do we really need to move it up more? 104.153.72.218 (talk) 15:47, 4 November 2017 (UTC)

@CA2MI: Re: "GW170817 was a multi-messenger observation of a transient astronomical event" No, it wasn't that, either. It was a single-messenger observation. GRB 170817A was also a single-messenger observation. The combination of the two was a multi-messenger observation. Does the article not make that clear enough?

I'm assuming you missed what I wrote above about multi-messenger already being quite prominent, so please read that now. 104.153.72.218 (talk) 21:16, 4 November 2017 (UTC)

To continue, while astronomers speaking casually use the names GW170817, GRB 170817A and AT 2017gfo interchangeably to refer to the same astronomical event, more formally they're distinct observations. That's the entire point of the bullet list in the lead. The qualitatively different observations is what makes this multi-messenger astronomy. (The fact that multi-messenger astronomy is very new is why there aren't well-established conventions for resolving the name conflict.) If you think the article should be rewritten to eliminate the distinction, do it (or preferably discuss such a major change here first), but please don't half do it, resulting in an article that contradicts itself.

Just as a minor point, MOS:DUPLINK prefers to wikilink the first occurrence of a phrase in an article, and not subsequent ones. If you add a wikilink to multi-messenger astronomy to the beginning of the lead paragraph, please unlink those words from the end of it. (Or you could leave "multi-messenger" unlinked in preference to an unpiped link of the exact words slightly later.) 104.153.72.218 (talk) 21:35, 4 November 2017 (UTC)

The Astronomer's Telegram

@Drbogdan: Regarding your latest edits:

On 9 December 2017, astronomers reported a brightening of X-ray emissions from GW170817, GRB 170817A and SSS17a, suggesting a common origin.

Is that telegram really speaking about observing separate X-ray emissions from GW170817, GRB170817A and SSS17a? It seems to me that it's just naming the already known connected events, while settling on mostly using the name GRB170817A (which I otherwise thought referred to the 2 second GRB) for the new X-ray observations. --Ørjan (talk) 23:11, 9 December 2017 (UTC)

@Oerjan: Yes - my initial understanding is that the X-ray emissions are separate - however - my closer look at the ATels may suggest otherwise - perhaps someone more knowledgeable in the field can help? - to be more clear about this - and to update the article text if needed. Drbogdan (talk) 23:27, 9 December 2017 (UTC)

BRIEF F0llowup: changed article text to the following:

On 9 December 2017, astronomers reported a brightening of X-ray emissions from GW170817/GRB 170817A/SSS17a.

Hope this helps in some way - at least until the text can be further discussed. Drbogdan (talk) 02:05, 10 December 2017 (UTC)

@Drbogdan: Looking at those ATels, there's only one X-ray source that's claimed to be associated with the event (specifically, the GRB/optical event). They mention other X-ray sources, but as unrelated emission (from the host galaxy and two other X-ray sources without claimed associations). Thanks. Mike Peel (talk) 10:56, 10 December 2017 (UTC)

@Mike Peel and Oerjan: (and others) - Thanks for commenting - it's appreciated - no problem whatsoever - maybe the current text (see copy above) is ok? - if not, suggestions welcome about how best to present the text in the article - iac - Enjoy! :) Drbogdan (talk)

References

Superluminal jets

Apparently GW170817 is putting out a superluminal jet. (This is a well-known relativistic optical illusion; it's not really travelling faster than light.) I don't have time to edit the article, so I'm dumping some references here in case someone else wants to pick up the editorial pen.

• Mooley, Kunal P.; Deller, Adam T.; Gottlieb, Ore; Nakar, Ehud; Hallinan, Gregg; Bourke, S.; Frail, D.A.; Horesh, A.; Corsi, A.; Hotokezaka, K. "Superluminal motion of a relativistic jet in the neutron-star merger GW170817". Nature. arXiv:1806.09693. doi:10.1038/s41586-018-0486-3.
• Williams, Matt (12 September 2018). "Superfast Jet of Material Blasted Out From Last Year's Neutron Star Merger". Universe Today.
• "Radio Observations Confirm Superfast Jet of Material From Neutron Star Merger" (Press release). NRAO. 5 September 2018.
• A bot will complete this citation soon. Click here to jump the queue arXiv:1806.10596.

209.209.238.149 (talk) 20:56, 24 November 2018 (UTC)

Worthy reference?

FWIW - worthy recent reference (in some way?) for this (or related) article? - seems clear - and well written - Comments Welcome - in any case - Enjoy! :) Drbogdan (talk) 14:58, 30 July 2019 (UTC)

Unless there's more news elsewhere, this looks to me like a case of Betteridge's law – it might be neutrino + GW, but a "trifecta" is just hopeful speculation that seems unlikely given no other binary black hole merger has given a definite EM signal. I'd expect the first true trifecta to involve at least one neutron star. --Ørjan (talk) 01:23, 1 August 2019 (UTC)

The event that might have a neutrino is independent of this event. --mfb (talk) 10:18, 1 August 2019 (UTC)

Oh right, I didn't really notice which specific talk page I was on, so I just assumed the interest was in the part of the reference that was news. --Ørjan (talk) 02:11, 2 August 2019 (UTC)

References