Talk:26 Draconis

Separation between AB and C

I think the following is incorrect: The third component, GJ 685, is a red dwarf spectral classification of M1V. As of 1970, this star is separated by 12.2 arc seconds with the AB pair

12.2 arc seconds is not the separation between 26 Dra AB & GL 685. Looking up HIP 86036 and HIP 86087 in the main Hipparcos catalog, I find 86036 (26 Dra AB) at 17h 34' 59.485" +61˚ 52' 29.84" while 86087 (C, GL 685) is at 17h 35' 34.506" +61˚ 40' 53.69". That's about 12.3 arc minutes apart.

The quote in the cited paper (page 18) is:

..the primary being a G0V star and the distant companion a M1V dwarf. The primary is in fact a triple system where A component has a 76 yr orbiting B companion and a wide low-mass C companion at 12.2" (Tokovinin et al. 2006).

I believe that's a typo in the published source. To give my WP:OR, the following Mathematica code:

u = StarData[Entity["Star", "HIP86087"], "HelioCoordinates"]
{-2.31753ly,-3.79284ly,45.7007ly}
v = StarData[Entity["Star", "26Draconis"], "HelioCoordinates"]
{-2.35668ly,-3.63247ly,45.6924ly}
ArcCos[u.v/(Norm[u] Norm[v])] UnitConvert["radian", "arcminute"]
12.2938'

Can someone sanity check this for me, or have a better source? If nothing else, I'll change the "arc seconds" to "arc minutes" and add a footnote indicating the cited source probably has a typo. Tarl N. (discuss) 23:07, 24 March 2018 (UTC)

I'll further comment that the above paper cites Tokovinin, A., et al. 2006, A&A, 450, 681 as its source for the 12.2" mentioned by Makarov, and on tracking that paper down to Astronomy & Astrophyics Vol 450 Page 681, I found it here, and it doesn't mention the two stars in question at all. It uses Hipparcos catalog numbers, and there is no mention of either 86036 or 86087 in that paper. Tarl N. (discuss) 23:22, 24 March 2018 (UTC)

Per WP:BRD fixed the units, added footnote. Any issues, please revert and discuss, thanks. Tarl N. (discuss) 00:51, 3 April 2018 (UTC)

MSC agrees with you. That is essentially Andrei Tokovinin's website, so pretty conclusive. I'll look for a good source so that we can ditch the footnote. Lithopsian (talk) 18:29, 3 April 2018 (UTC)

Ah, thanks - nice to know about that website, never run into it before. Tarl N. (discuss) 23:15, 3 April 2018 (UTC)