Talk:RR Lyrae

Light-curve

The diagram needs to be replaced with a better one. The time-scale of the light-curve is too long which obscures the nature of the light variations.--TristramBrelstaff (talk) 07:50, 14 December 2010 (UTC)

Absolute Magnitude

I replaced the obviously incorrect absolute magnitude of 7.29 by the value -0.7 which James Kaler quotes as the mean absolute magnitude for RR Lyrae type stars.--94.30.104.188

I just noticed a value 0.61 by Benedict et al is given in the article text, so I have used this instead.--TristramBrelstaff (talk) 08:17, 14 December 2010 (UTC)

Merge?

It appears that the article RR Lyrae variable should be merged into this article.

Mark75382 (talk) 19:57, 17 March 2012 (UTC)

Although they share a name, they are not about the same topic. Regards, RJH (talk) 23:20, 17 March 2012 (UTC)

month not needed

I do wish people on this project would stop cluttering up the references with surplus information. We do not need to know the month of publication in any regular scientific journal, and still less do we need to know which month a book was published in. By working with a set of semi-collapsed templates one can make the work of adding references easier. Macdonald-ross (talk) 12:41, 25 March 2013 (UTC)

Text reorganization

The text seems to me complete in the amount of information, but not it organization. Some facts are more important than others, and some need to be placed first. I think the use of RR Lyrae variables as standard candles is the most important fact about this star. It is the "type specimen" for its class. That it produced a standard candle should be stated in the first paragraph. Readers should not need to read through paragraphs to get that information. The person who discovered it should be mentioned, but if they were never mentioned the article would still be fine. However, if the article failed to mention that RR Lyrae is the progenitor of a standard candle, then the article would be defective. That is the test of what should go in the first paragraph. So I reorganized the text to place the most important information in the first paragraph. Nick Beeson (talk) 13:44, 3 September 2014 (UTC)

Buggy ly <-> pc conversion?

The text correctly indicates that the distance measured by the HST is about 854 ly, or roughly 262 pc. Indeed, the reference indicates an absolute parallax of 3.82 milliarcseconds (Benedict et al., Section 5.3), which translates to 262 pc, or 3.26*262 ~ 854 ly.

However, the text also indicates that, "combined with measurements from (Hipparcos) and other sources, the result is a distance estimate of 860 ly" which is automatically, and incorrectly, converted to 260 pc (one can immediately see that the conversion is wrong, since 260 < 262 but 860 > 854). Why this exaggerated rounding error happens is puzzling: it is being carried out automatically (i.e. the pc values are not hard-coded, but rather computed from the ly values), so apparently there is a bug in the automatic conversion software.

In reality, the same reference (Benedict et al., Section 5.3) gives the weighted average of all sources as being 3.87 milliarcseconds, which translates to 258 pc, or about 841 ly rather than the spurious 860 figure. Automatic conversion works fairly well in this case, yielding a value of 840 ly from the 258 pc estimate.

Now one might wonder why not follow the original reference, which gives the distance estimate in milliarcseconds and hence in pc, instead of writing down a manually converted ly value? The problem is, if we do this, a similarly bad conversion ensues: the more faithful HST estimate of 262 pc is automatically converted to 850 ly rather than the expected 854 ly.

In summary: the ky <-> pc conversion rounding error is so coarse as to yield blatant errors and prevent actual information from being directly quoted in Wikipedia articles. While this is not fixed, conversions should be checked manually for rounding error acceptability. Pbarreto.crypto (talk) 04:11, 14 October 2017 (UTC)

Not buggy at all. It's called rounding. If you don't want a rounded number, don't convert it (and probably round it as well yourself) to a different value and then expect the convert template to give you your exact number back again without some care. The rounding precision can be specified if the default is inappropriate. The default for moderately large numbers is -1 (meaning round to the nearest 10), although it may round even more when there are trailing zeroes. The automatic distance-from-parallax numbers in the starbox are a bit more complex than just rounding, involving judgements about how much to round, whether to call them approximate, and whether to just not give a distance at all. In cases like this, I'd suggest giving the distance explicitly because the number derived from the parallax is very likely to be a bit different. Lithopsian (talk) 19:06, 13 October 2017 (UTC)

Kindly read the text before replying, especially if you plan to be patronizing in your reply. The problem is clearly described as an exaggerated rounding error, so rounding was already explicitly acknowledged, and it is excessive to the effect that the improved distance estimate, which decreases (from 262 to 260) when expressed in pc, appeared to increase (from 854 to 860) when expressed in ly. This not only violates the linear scaling between plain pc and ly metrics, it is also misleading when the reader tries to infer if the refined parallax estimate increased or decreased (as presented in the original source) from the stated distance in the Wikipedia article. This being said, we are in agreement that a better rounding precision is needed, but I had tried setting round=0 and somehow got an error that this option is invalid, despite being described in Help:Convert#Parameter_list. I have since remedied this by omitting the option name. Pbarreto.crypto (talk) 04:11, 14 October 2017 (UTC)

RR Lyrae not the brightest RR Lyrae star?

I saw the page mention that RR Lyr is the brightest RR Lyrae star, but I checked simbad, and a star named V764 Mon is slightly brighter at Vmag 7.08 while RR Lyrae has a Vmag of 7.195 Nussun05 (talk) 18:47, 10 November 2020 (UTC)

V764 Mon is probably a δ Sct star. Light curves look similar to a computer (V764 Mon was discovered from Hipparcos photometry), but amplitudes are lower and they're young stars on or near the main sequence, not old post-red giants. There are several even brighter stars that are classified as possible or probable RR Lyr stars, but they're all probably δ Sct types. Lithopsian (talk) 19:44, 10 November 2020 (UTC)