Celestia Forums

Posted: **09.02.2007, 18:31**

I'm back from a very interesting conference held in my good'old University of Montreal. It was about ... magnetic stars, dipolar fields as good models to describe some real stars and ... rigid rotation of fields ! Talk about a good coincidence !

According to the lecturer, there's an important system of stars in the Orion nebula which doesn't seems to be in Celestia : Sig Orionis.

If they really aren't included in Celestia, I may try to add them, since two of those stars have a strong magnetic field and are very interesting for astrophysicists. Any clue why they aren't included in the standard database ? Distance accuracy again, I guess ...

Posted: **09.02.2007, 19:27**

You'll have to replace two of Celestia's catalog entries:

Celestia's "SIG Ori" = HIP 26549 = A+B
Celestia's HIP 26551 = SIG Ori D

This info was taken from WebDA, which lists some of the other members of the SIG Ori cluster, also known as the "Garrison 1" cluster.

See http://www.univie.ac.at/webda/cgi-bin/o ... name=gar01
and the Hipparcos catalog notes, which say

Code: Select all

 26549| | | 7| 1|Triple system with two catalogue entries, HIP 26549 and HIP 26551. The          
 26549| | | 7| 2|Hp magnitude given in the main catalogue is derived directly from               
 26549| | | 7| 3|the photon counts recorded with the detector pointing at HIP 26549              
 26549| | | 7| 4|and has not been corrected for the multiplicity effect or for the               
 26549| | | 7| 5|attenuation profile of the detector. The corrected magnitudes of                
 26549| | | 7| 6|the components are given in the Double and Multiple Systems Annex.              
 26549| | | 7| 7|The position in Fields H8-9 is for the photocentre of components A+B.  
         
 26551| | | 6| 1|Triple system with two catalogue entries, HIP 26549 and HIP 26551. The          
 26551| | | 6| 2|Hp magnitude given in the main catalogue is derived directly from               
 26551| | | 6| 3|the photon counts recorded with the detector pointing at HIP 26551              
 26551| | | 6| 4|and has not been corrected for the multiplicity effect or for the               
 26551| | | 6| 5|attenuation profile of the detector. The corrected magnitudes of                
 26551| | | 6| 6|the components are given in the Double and Multiple Systems Annex.

See http://vizier.hia.nrc.ca/viz-bin/ftp-in ... _notes.doc

Posted: **10.02.2007, 01:03**

Here's one paper published by the lecturer, about Sig Orionis E, a strongly magnetized star, with a dominent dipolar field :

http://zuserver2.star.ucl.ac.uk/~rhdt/p ... igorie.pdf

Posted: **10.02.2007, 06:02**

selden wrote:You'll have to replace two of Celestia's catalog entries:

Celestia's "SIG Ori" = HIP 26549 = A+B
Celestia's HIP 26551 = SIG Ori D

This is pretty embarassing. Celestia is showing a double system like a single star : HIP 26549 = A+B. The star database should be updated.

Posted: **10.02.2007, 12:43**

Cham,

Celestia uses the Hipparcos catalog.
That description of SIG Ori is what is in the Hipparcos catalog.

Some multiple stars have been replaced by automated conversion from other published catalogs which contain well defined stellar orbits. In general, it is not appropriate to manually insert parameters for individual star systems from random sources for the standard distribution of Celestia.

If you can provide a reference to a published catalog of stellar orbital parameters which includes the SIG Ori star system, I suspect Fridger might be persuaded to add it to the set of catalogs used to generate the double star catalogs that Celestia uses.

Celestia Forums

Sigma Orionis A, B, C, D and E not in Celestia ?

Sigma Orionis A, B, C, D and E not in Celestia ?