Tuesday, August 16, 2011
Today I got an email from Joel explaining that according to the Pre-MS catalog he found, T Cha and RX J1158.5-7913 (its possible companion) do not have similar proper motions. This was confusing because when I used Topcat to find the possible companions stars, I limited the results so that only stars with a proper motion of within 15 mas/yr of T Cha would be present. At first, I thought I had made a mistake using Topcat and this whole process of investigating RX J1158.5-7913 was a waste of time. But after doing a little investigating, I realized the problem is that some of the proper motions listed in the PPMXL, UCAC3, and Pre-MS catalogs as well as in Simbad are different! So now, we don't really know what source to trust. Instead, I am taking the mean of the PM's found for each star, regardless if it is emitting x-rays or not, and plotting them as vectors on the x-ray images using ds9. This way, we can visually compare the magnitude and angle of the proper motion vectors and decide which could be companion stars. Unfortunately, RX J1158.5-7913's mean PM is about half that of T-Cha's, which probably means that it is in the chamaeleon cloud . . .around 80 parsecs (one parsec= 3.26 light-years) behind T-Cha, and therefore is not a companion star. However, our 'unnamed' star is still in the running to be a companion, so the next step is to calculate the bolometric luminosity and compare that to the x-ray luminosity!