ArcBuilders add-on

[Tegmine]

I hope I'm not stepping on JDollan's toes with this one (or anyone else's for that matter.) On the older ArcBuilders site it lists Xi Scorpii D and E as having planets of note. I started making such a system, but started with the full 5-star complex of Xi Scorpii. I have, however, encountered a couple of issues...

Celestia has Xi Scorp as being 58.547 ly away, online sources say it is 95+ ly. How would I go about fixing this?

Another problem is orbital information...I can't seem to find anything on C, D or E outside of mass, lum, mag and distance from one another. I know nothing about eccentricity of said stars, orbital periods, etc.

Finally (amazingly, only three issues so far) I run into an artifact (presumably) when travelling to Xi Scorp. It appears to be two stars very close to one another and when I click on them, get no info on them.

Code: Select all

#The complex multiple star system Xi Scorpii


Barycenter "Xi Sco: HIP 78727"
{
RA       241.092458
Dec      -11.372944
Distance  58.547
}

"Xi Sco C"
{

   OrbitBarycenter "Xi Sco"
   SpectralType "G8V"
   AppMag 7.3
   Radius 625500
   EllipticalOrbit {
      Period 1100
      SemiMajorAxis 210
      Eccentricity .13
      Inclination 21
      AscendingNode 0
      ArgOfPericenter 0
      MeanAnomaly 0
   }
}


Barycenter "Xi Sco DE"
{
OrbitBarycenter "Xi Sco"
   EllipticalOrbit{
   Period 10000
   SemiMajorAxis 8000
   Inclination 65
   ArgOfPericenter 180
   MeanAnomaly 0
   }
}

"Xi Sco D"
{
OrbitBarycenter "Xi Sco DE"
SpectralType "G8V"
Radius 597700
AppMag  7.4
   EllipticalOrbit{
   Period   200
   SemiMajorAxis 160
   Inclination 15
   AscendingNode 0
   ArgOfPericenter 0
   MeanAnomaly 0
   }
}

"XI Sco E"
{
OrbitBarycenter "Xi Sco DE"
SpectralType "K2V"
Radius 562950
AppMag 8.0
   EllipticalOrbit{
   Period   200
   SemiMajorAxis 160
   Inclination 15
   AscendingNode 0
   ArgOfPericenter 180
   MeanAnomaly 0
   }
}




Here's what I've got. Feel free to tell me where I goofed. I'm sure I have. I just don't know where. Be honest, but please be polite!

Thanks
-M-

[Tegmine]

I'm also doing one for Gliese 511.1 I don't know why...I just like it!

-M-

[ajtribick]

You should write the letter as XI rather than Xi to get it to be recognised as a Greek letter. It will also allow you to replace the existing definitions of these stars.

As far as I can tell, the Hipparcos designations are as follows:

ABC = HIP 78727 (implemented as a barycentre in Celestia)
D = HIP 78738
E = HIP 78739

In the original version of the Hipparcos catalogue, no parallax was assigned for HIP 78727 and there is no record at all in the new reduction. The final version of the system is implemented in visualbins.stc, derived from S?derhjelm (1999). This reference lists a parallax of 37.0±1.2 mas, corresponding to a distance of 88.2±2.9 light years.

However the erroneous distance is from the revised.stc file, which gives the comment "Xi Sco: missing parallax taken from companion star Hip 78738". The distance value given there turns out not to correspond to HIP 78738, I'm not sure where it is from. Fixing the value here will then require regenerating the binaries files (but there are other changes that need to be made to the binaries generation scripts as well).

So regarding D (HIP 78738) and E (HIP 78739)...

Original version of Hipparcos catalogue has parallaxes of 35.25±2.56 mas and 30.89±6.86 mas respectively, corresponding to distances of 92.5±6.7 and 106±23 light years.

New version of the Hipparcos catalogue (which is the basis for the Celestia star database) has parallaxes of 39.59±3.49 and 44.25±4.80 mas respectively, corresponding to distances of 82.4±7.3 and 73.7±8.0 light years.

Weighted mean of new Hipparcos parallaxes for D and E, and the S?derhjelm (1999) parallax for ABC is 37.64±1.10 mas, giving a distance of 86.6±2.5 light years.

[Tegmine]

So if I am understanding you correctly, if I enter in the new values for stellar distances, that should fix it? And the two pairs appear to not be so gravitationally bound, then? Sorry for the questions, and I appreciate the answers.

-M-

[ajtribick]

Well the parallaxes are sufficiently similar given the quoted uncertainties to make the idea that they are gravitationally-bound plausible. As far as I am aware, the system is regarded as bound.

You'd have to modify the barycentre of the ABC system to change the distance.

Stars D and E should be represented using their HIP numbers as well, e.g.

Code: Select all

Barycenter 78727
{
RA       241.092458
Dec      -11.372944
Distance  86.6
}

78738 "XI Sco D"
{
...
}

78739 "XI Sco E"
{
...
}

Given the orbital elements seem to be unknown except for the AB orbit (the outer orbits are on very long timescales), I'd personally represent C, D and E as fixed stars. Your call as to whether you want to go about implementing all the barycentres.

[Tegmine]

I'm almost sorry I asked.

-M-

[ajtribick]

Well if you do want to go implementing complex multi-star systems like this one then you must be prepared for things to be less than straightforward...

[Tegmine]

Don't misunderstand me...I'm a sucker for complexity. Thank you for your help.

-M-