S617 and a question on how to proceed

Forums Spectroscopy S617 and a question on how to proceed S617 and a question on how to proceed

Robin Leadbeater

Hi Matt and welcome to the BAA !  

Sorry I did not get back to you on the stargazer’s lounge thread about your latest spectrum of S617b.  This one is much less noisy and as you say now seems to match much better with what would be expected for a G0v star.  I am not sure why it looked so much bluer than its companion in your image though. (It is hotter (compared with the late G/early K companion) but not as much as the image colour difference might suggest)  Overlaying your latest spectrum of the b component over the spectrum of the a component or A comparison of B-V for the two stars should clarify the colour difference.

Precise spectral classification is a bit limited with the Star Analyser as the resolution is not really high enough (you really need around 10A resolution or higher to do this) It is not so bad at showing the difference between hot eg A stars and cool M stars but in the middle temperature range say mid F to mid K, you get hundreds of metal lines which merge at Star Analyser resolution. You can get an idea from the shape of the spectrum continuum but interstellar extinction can distort this so you have to be careful. Spectral classification is all about what lines appear and how strong they are so matching the details in the spectrum with the Pickles library can help decide what type as star is. I suggest overlaying the Pickles spectra on your spectra looking for matches in the features and general shape.