Talk:HR 6819

Is this the black hole system?
In "other designations" it lists HR 6819, which is the one given in the recent news, e.g. "New closest-known black hole lies in a visible star system". Is it the same? If so, this page is incorrect in the structure given, as HR 6819 was known to be at least a binary before. If not, then the designations needs fixing instead... Fig (talk) 13:00, 6 May 2020 (UTC)


 * Yes, see this account on ESO's site: ESO, with photo and IAU chart. Our article is now quite out of date. -- Elphion (talk) 13:17, 6 May 2020 (UTC)
 * I have uploaded the image here. Diki Ananta  ●  Talk  16:26, 7 May 2020 (UTC)
 * We're getting closer, though the info box still reports older conclusions. (Not likely to change until more standard references get up to speed.) -- Elphion (talk) 18:07, 6 May 2020 (UTC)


 * How about replacing older valuations with "TBD"? A similar issue exists with LB-1.  There was a bit of disbelief regarding the report of 70 solar masses for its black hole.  Rivinius et al treat LB-1 as a triple system and thereby bring that black hole's mass down by a factor of about 10. 73.81.117.132 (talk) 14:06, 8 May 2020 (UTC)

Name
I was sorry to see the name change from QV Telescopii to HR-whatever. Names with 4 digit numbers in them are about as memorable as telephone numbers. Rwflammang (talk) 22:50, 9 May 2020 (UTC)


 * According to Google, “HR 6819” has about 434 times as many search results as “QV Telescopii”. See WP:COMMONNAME. sam1370 (talk / contribs) 09:21, 10 May 2020 (UTC)
 * The star is referred to as HR 6819 in the recent popular coverage. Whatever the situation before, it is now and for some time to come going to be known as HR 6819 to the vast majority of people looking for this article.  Lithopsian (talk) 10:46, 10 May 2020 (UTC)
 * Yeah I much prefer variable star designations over HD- and HR- names due to their easier memorability, however wikipedia reflects not dictates usage and (annoyingly) the HR designation seems to be most widespread....Cas Liber (talk · contribs) 13:36, 10 May 2020 (UTC)


 * Question, what is HR 6819's HIP (from a telescope) name? --StaleGuy22 (talk) 05:48, 12 May 2020 (UTC)
 * From a telescope? It has a Hipparcos designation of HIP 89605.  See the starbox.  Lithopsian (talk) 13:48, 12 May 2020 (UTC)

Each radius of orbit, just roughly please
Whilst a period of about 40 days for the inner pair (of objects) is helpful; as the pair would have to be hurtling at an unprecedented pace if not it is quite obvious they are from this distance so close as to be hard to observe the orbit without a powerful telescope, surely less than 10 AU? Any stats? also...

Someone please describe the outer orbit in size. And add that this is a close-triple star system. Or non-visual, i.e. highly telescopic one. The outer orbit, largely undescribed, might encourage far more people to believe they might be able to tell the the objects apart (as a non-telescopic multiple star). Regardless the artist's depiction of about 8-times the inner orbit (being the outer orbit), coupled with what is just stated about 40-day orbits having to be close, must put paid to that idea. Plus no separate catalogue designation I can find for the outer star. Apologies for any minor mistakes in any technical nomenclature. IT is quite clear we should aim for people to be under no illusion - only under high resolution can this star system be made out to be more than one star, from this sub-arm corner within the galaxy.- Adam37 Talk  16:58, 14 May 2020 (UTC)


 * The outer orbit is almost completely unknown. The existence of the star is inferred from the spectrum, but no radial velocity variations have been measured so the orbit could be almost any size.  An upper limit to the separation is that they haven't been split visually, and a lower limit is that the radial velocity of the outer star is undetected but that could also be due to orientation.
 * The semi-major axis of the inner orbit can be calculated easily from the total mass of the components and the period. The orbit is circular so we can call this a radius.  Unfortunately we don't know the total mass, but it is of the order of .  This gives a radius around half an astronomical unit.  The total mass could be considerably higher and then the orbit would be larger, but the radius scales as the cube root of the total mass so half an AU is a good guess.  Someone else might want to run the numbers and see if they get the same answer.  Lithopsian (talk) 17:32, 14 May 2020 (UTC)

New studies find HR 6819 is a binary and doesn't contain a black hole
At least two papers now claim HR 6819 is a binary containing two luminous stars. It may be necessary to significantly revise this article, or at least note the system is controversial. https://arxiv.org/abs/2006.11974 https://arxiv.org/abs/2006.10770
 * Not yet accepted for publication, so no panic yet. You might consider how the article should be structured assuming the new research is published.  Ideas on the back of an envelope by Monday.  Or better yet, here.  Lithopsian (talk) 19:27, 26 June 2020 (UTC)
 * Just to update that this paper here is accepted: https://arxiv.org/pdf/2006.10770.pdf . There are currently three independent studies (https://ui.adsabs.harvard.edu/abs/2020arXiv200705797G/abstract on top of the ones above) claiming the same model for HR 6819 (Be + stripped star), which is the same model suggested for LB-1. In contrast, Rivinius et al. have not published the analysis on which their claims are based (there is no analysis in their work showing that the Be star is static).  — Preceding unsigned comment added by 2A02:8109:B6C0:32A0:545D:6FC:BDF8:1B39 (talk) 18:05, 17 July 2020 (UTC)

Component identification
Validated Academic papers :

Read https://www.aanda.org/articles/aa/full_html/2022/03/aa43004-21/aa43004-21.html and

https://www.eso.org/public/france/news/eso2204/?lang

From what I read, the A-B components 'd be inverted : The system includes a ~6 Ms Be (B3IIIpe) star cataloged as a variable star and surrounded with a decretion disk, and a companion B3 III type of about 0.5 Ms. --luxorion


 * The nature of the system is disputed, with two possibilities. This latest paper opts for a system with two stars and no black hole.  The nomenclature of the system components depends on their masses and how many objects there are.  It might be best to word the article in such a way that it refers to the components in an unambiguous way that does not depend on the nature of the system, whatever that may ultimately turn out to be.  Lithopsian (talk) 13:43, 6 March 2022 (UTC)

There was also a theoretical paper in 2022
On top of the observations on HR 6819 there was also this paper that estimated the probability, according to their evolutionary models, of a black hole to form under that configuration in HR 6819. Also from their side the black hole was estimated to be unlikely to exist

https://ui.adsabs.harvard.edu/abs/2022A%26A...667A..55R/abstract 134.171.69.87 (talk) 07:45, 11 October 2023 (UTC)