Talk:VV Cephei

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VV Cephei

W Cephei is by far I know the bigest star in the Unerverse there might be bigger stars that havnt been discovred —Preceding unsigned comment added by 81.156.32.168 (talk) 13:47, 22 February 2008 (UTC)[reply]

The size of this monster is completely incomprehensible to me. My head hurts just trying to imagine it. Primal Eighties (talk) 23:42, 4 August 2008 (UTC)[reply]

How big of a tatonka size telescope do you need for this? —Preceding unsigned comment added by Kingkong77 (talk • contribs) 14:30, 7 October 2008 (UTC)[reply]

W Cephei is not VV Cephei. — Preceding unsigned comment added by Red Planet X (Hercolubus) (talk • contribs) 15:48, 3 September 2016 (UTC)[reply]

Location

Doesn't seem to be right that puts me right outside of hercules, not cepheus--Vennificus (talk) 01:24, 15 March 2010 (UTC)[reply]

The location checks out correct according to my printed Norton's Star Atlas: it lies between iota and alhpa Cepheus. I have added this location map. -84user (talk) 19:17, 16 March 2010 (UTC)[reply]

Pronunciation

Is this "Vee Vee" Cephei, or "Five Five", or something else? Or is it something in Greek that hadn't occurred to me? :o) - 94.194.113.136 (talk) 16:25, 16 May 2012 (UTC) (just a passer-by)[reply]

It's vee vee, it's from the Bayer designation, which initially used Latin letters after the 24 Greek ones had expired, but this only survived mainly in designations for variable stars, which always begin with a letter from R to Z. - filelake shoe 20:03, 16 May 2012 (UTC)[reply]

Image submitted for deletion

An image on this page has been submitted for deletion from Commons. See c:Commons:Deletion requests/File:VVCephei1.png Lithopsian (talk) 16:11, 29 November 2016 (UTC)[reply]

How much is "dramatically lower"?

From the "Properties" section (emphasis not in original):

"The traditional model, from the spectroscopically derived orbit, has the masses of both stars around 20 M☉, which is typical for a luminous red supergiant and an early A main sequence star.[7] An alternative model has been proposed based on the unexpected timing of the 1997 eclipse. Assuming that the change is due to mass transfer altering the orbit, dramatically lower mass values are required. In this model, the primary is a 18.2 M☉ AGB star and the secondary is an 18.4 M☉ B star."

Depending on the meaning of "around", 18.2 and 18.4 could be well within the error anticipated. Unless it means "19 to 21", where it would be a near miss, or "20 rounded to the nearest integer", where it would be definitely on the low side. But even if it is, 18.2 and 18.4 would be 9% and 8% low, nothing I'd call "dramatically."

If an 8% discrepancy is unusual, I'd recommend adding a few words why it is (not exactly WEASEL wording, but a similar, less malicious issue). - ¡Ouch! (^{hurt me} / _{more pain}) 15:11, 6 July 2017 (UTC)[reply]

Good catch. They got changed at some point. I've changed them back to what the references says. Lithopsian (talk) 15:22, 6 July 2017 (UTC)[reply]

Cool. Now what to put into the infobox? I'd think we should put a note there, say a [note 1] which reads

"according to high-mass model (see "Properties" section)"

At any rate, good work. I ran into that other infobox earlier today, which I repaired on my own... ;) - ¡Ouch! (^{hurt me} / _{more pain}) 16:26, 6 July 2017 (UTC)[reply]

A Commons file used on this page has been nominated for deletion

The following Wikimedia Commons file used on this page has been nominated for deletion:

Comparison of planets and stars (2017 update).png

Participate in the deletion discussion at the nomination page. Community Tech bot (talk) 07:52, 28 June 2018 (UTC)[reply]

New estimate for VV Cephei A

According to Nussun05, Messineo & Brown 2019 listed VV Cephei A as 388 R_☉ based on the luminosity and temperature though I can't find luminosity and temperature of the listed stars in any tables or pages in the given citation. Should we use it? 2A01:E0A:47A:F100:D025:C6CB:707E:5CDA (talk) 07:44, 23 May 2020 (UTC)[reply]

The data is online at VizieR. It assumes the Gaia DR2 distance of 599 pc, which is barely a third of the consensus value of 1,500 pc. Hence a much lower luminosity of 24,000 L_☉ and the smaller radius. The radius value should be treated with caution since it is based on treating the whole system as a single star. Although the parallax has quite a large formal error, as well as no corrections for being a binary, it is consistent with the Hipparcos parallax which has been ignored or dismissed by most authors until now. Surely at least worth a mention in the text even if it isn't yet the accepted value. Lithopsian (talk) 13:09, 23 May 2020 (UTC)[reply]

Contradiction

Recent research contradicts the beginning of this article, where it states that mass transfer occurs via Roche lobe overflow. Whmbkx (talk) 01:44, 21 November 2020 (UTC)[reply]

Could you please provide a link to said research? Primefac (talk) 12:43, 21 November 2020 (UTC)[reply]

How reliable is Stassun, K. G.; et al. (2019)?

Should this value really be used in the starbox? It is based on Gaia Data Release 2 data, and has a massive significance of astrometric excess noise. Pollman, E.; et al. (2018) is a study solely based on VV Cephei itself. It should be used over 516 R_☉. Faren29 (talk) 22:54, 25 December 2020 (UTC)[reply]

Parallaxes from Hipparcos, DR2, and EDR3, are all similar, around a milli-arcsecond. High astrometric noise indicates a possible issue, not that the value is wrong. High astrometric noise is expected for a binary, non-stellar object such as VV Cep, and the parallax may still have some merit. The "classical" distance from other methods is around 1.5 kpc, but also highly uncertain. Pollman et al. adds nothing to the equation, it is just repeating earlier results (eg. Bauer et al., 2008) and not deriving new ones. "~1,000" should probably be dropped from the starbox and replaced with something specific such as 1,050 R_☉ from Bauer et al. Lithopsian (talk) 16:05, 27 December 2020 (UTC)[reply]

1,050 R_☉ from Hagen Bauer, Wendy; et al. (2008) seems trustworthy, but Hopkins, Jeffrey L.; et al. (2015) also references many radii for VV Cephei A. This includes: 1,000 R_☉, which is most likely the same case you described for Pollman, Ernst; et al (2019), 1,015 R_☉, from Bennett, Philip D. (2007), 1,600 R_☉, from Wright, K. O. (1977) and Hack, M.; et al. (1992), and 1,800 R_☉, from Hutchings, J. B. and Wright, K. O. (1971). Aside from the trusted value of 1,050 R_☉, are there any values that could potentially be used in the starbox in Hopkins, Jeffrey L.; et al. (2015)? Faren29 (talk) 19:10, 27 December 2020 (UTC)[reply]

There is a short section about the distance. You could expand that and mention the various estimates and the inconsistencies between the parallaxes (600-1000 pc) and distances from methods like the orbit and eclipses (1,500+ pc). I wouldn't put anything from last century in the starbox. Then decide which of the radius values comes out as most reliable for the starbox. Lithopsian (talk) 14:36, 28 December 2020 (UTC)[reply]

Inconsistency in starbox parallax and distance

The values for parallax and distance in the starbox are mutually exclusive. The given parallax of 1.33±0.20 mas corresponds to between 654 and 885 pc, approximately half the stated 1500 pc.

The reference for the parallax (Van Leeuwen, 2007) is a paper which applies new methodology for processing the Hipparcos to improve its overall accuracy. It deals with the data set as a whole; the only places where it refers to the parallax of specific stars (for purpose of illustration) are in Table 1 on page 7 (stars HIP 70 and HIP 71) and Table 2 on page 10 (ten stars, 5 with names). None of the mentioned stars appear to be VV Cephei.

This edit request has been answered. Set the |answered= or |ans= parameter to no to reactivate your request.

Please change

{{Starbox astrometry | parallax=1.33 | p_error=0.20 | parallax_footnote=<ref name=hipparcos/>

to

{{Starbox astrometry | parallax=1.33 | p_error=0.20 | parallax_footnote=<ref name=hipparcos/>{{Failed verification|date=June 2021}}

98.110.77.253 (talk) 02:14, 26 June 2021 (UTC)[reply]

Done, and thank you for the good catch! We won't change the figures just yet; however, we will continue to dig. P.I. Ellsworth ed. ^put'r there 15:31, 30 June 2021 (UTC)[reply]

Luminosity

Where can I find a luminosity for VV Cephei? The current luminosity is probably unreliable because it uses a noisy distance from Gaia. No other values were found, and this is already making me very angry. InTheAstronomy32 (talk) 16:06, 19 May 2024 (UTC)[reply]

Luminosity here. InTheAstronomy32 (talk) 16:44, 19 May 2024 (UTC)[reply]

WP:SYNTHESIS

See User_talk:SpaceImplorerExplorerImplorer#List_of_largest_known_stars_2 for the start of a discussion concerning the calculation of stellar radii from an angular diameter and distance in two unrelated sources. Lithopsian (talk) 17:34, 20 May 2024 (UTC)[reply]

Although I think the calculation of radii as described violates WP:SYNTHESIS and so shouldn't generally be used in the starbox, I feel we can stretch things slightly in some cases. One case might be where there is no sensible published radius that could be used in the starbox. A calculated radius, suitably caveated, might be better than nothing. Also, in the body of the article, if such a calculated radius provides useful context to a discussion of the properties, then it could be mentioned and described. Maybe, if the powers-that-be don't pile in and say it is just never acceptable. Lithopsian (talk) 17:37, 20 May 2024 (UTC)[reply]

I believe that we should use common sense here. Calculating a radius by two sources violates only the letter, not the spirit, of the WP:No original research policy, it was further explained in the User talk:SpaceImplorerExplorerImplorer. I think that the radius of 790 R_☉ could be used here, despite being calculated angular diameter and distance of different sources. Both the angular diameter and distance are recent and reliable, then the radius should be reliable too. It can be calculated using the {{Solar radius calculator}} template or the equation R=AD×D.^[1] The another radius of 950 R_☉ uses an effective temperature of 3,463 K which is a bit smaller than the typical temperature of a M2-type red supergiant (3660 K)[1], and both are from big catalogs. InTheAstronomy32 (talk) 22:47, 20 May 2024 (UTC)[reply]

I added back the 779 R_☉ value because it is reliable, so it will be not necessary to insert the other radius. InTheAstronomy32 (talk) 19:08, 21 May 2024 (UTC)[reply]

References

^ (R = Radius in AU, AD = radius in milliarcseconds, D = distance in parsecs.) Later only divide by 107.5 to find radius in R_☉.

Radius

It appears that there is uncertainty about the radius of VV Cephei. The infobox only lists the 1,050 R_☉ from Bauer (2008), but there are other radii, such as 779 R_☉ from Baines (2021). I tried to add it, but my edits were reverted based on the fact that it "results in a temperature inconsistent with the spectral type", but that radius was calculated from the angular diameter and distance (not the luminosity and temperature). If we use the luminosity of 116,000 L_☉, we calculate (using the Stefan-Boltzmann law) a more reasonable temperature of 3,800 K. Anyway, the new radius is reliable and can be added back to the infobox. 21 Andromedae (talk) 13:42, 12 June 2024 (UTC)[reply]

Distance

So far estimates on the distance were uncertain, and there is still no consensus on which distances should be in the infobox. However, with well-known masses and orbital parameters, a dynamical parallax can be computed, using the following equation explained by Takeda 2023:
M_A + M_B = a³ $π$ ⁻³P⁻²
, where a is the semi-major axis in arcseconds; $π$ is the parallax, also in arcseconds; and P is the orbital period in years. We have the following:

a	P	M₁	M₂
0.0162"	20.36 y	2.5 or 18.2	8 or 18.6

With two mass estimates, two parallaxes are found, hence
2.5 + 8 = 0.0162³ • $π$ ⁻³ • 20.36⁻²
18.2 + 18.6 = 0.0162³ • $π$ ⁻³ • 20.36⁻²

$π$ = ((2.5 + 8) / (0.0162³ • 20.36²))^−1/3
$π$ = ((18.2 + 18.6) / (0.0162³ • 20.36²))^−1/3

This give parallaxes of 0.0009922" and 0.000653", or distances of 1,008 and 1,531 parsecs respectively, so both distances might be accurate, and we can put it in the infobox as 1,018–1,500 parsec using recent estimates. 21 Andromedae (talk) 00:21, 22 September 2024 (UTC)[reply]

[1] (R = Radius in AU, AD = radius in milliarcseconds, D = distance in parsecs.) Later only divide by 107.5 to find radius in R_☉.

[1]