I used Richard Walker’s Spectral Atlas to identify some of the lines in the spectrum. Is this a good approach to take?
I would like to identify and understand all the small absorptions lines. Also to know what is noise. The stacked exposure is 314 seconds.
Next time I’ll try to capture one of the stars mentioned in the atlas.
The image is gam Uma.
Thanks
Steve Hoffman - HSTG
One place to start with identifying spectral lines across the MK system is Richard Gray’s atlas here:
https://ned.ipac.caltech.edu/level5/Gray/frames.html
These cover only the traditional violet-blue part of the spectrum from 3800A to about 5000A (some variation in what’s shown). The lines identified are those most useful for classification.
\Brian
Excellent, thank you!
Steve, I developed a spectral line identification tool in Excel that is available on our section web page. Follow the link to Spectroscopy Tools under the Education and Training section. I’m still working to validate this tool, but it would help me if someone else took a look at it.
The key difference between this and other line identification tools that I’m aware of is that my tool takes into account both temperature and element abundance in determining the relative strengths of spectral lines. So for example, the strength of the H alpha line will be shown as weaker for a star at 5000 K and stronger for a star at 10,000 K as you would normally expect. Same is true with the other elements.
There is an Overview tab which I recomment you read as well as the Instructions tab. Let me know if you run into any problems in either downloading or using this tool. I have seen problems where some of the functions are not supported in older versions of Excel.
What you would typically do is to use the “ID By Wavelength” function first. Input your star’s temperature, the measured wavelength of the line you wish to identify, and a search radius - typically on the order of the FWHM of the line. In some cases the element responsible for the line is obvious, while in other cases it may be a blend of two or more lines, and in yet others it may not be clear what element is causing the line.
So, if you are so inclined, try out my tool, see how well it works for you, and let me know.
I will try it today or tomorrow.
Thanks
Steve
On my laptop with “Open Office” a free sustitue for MS Office it did not work. It did work when I went to the desktop machine that has MS Excel. This is great.
I am not crystal clear about the “Search Radius” & “Wavelength Calibration Delta” perameters. I substituted “164.50nm” & “1.00nm” respectively. (see attachment)
Now I will purchase another copy of MS Office 2021 (for $17.18). Done.
Thanks!!
Steve
LOL nevermind I get those two parameters. When I purchased another Excel license and opened the XLS (without inputing anything) it became crystal clear.
Thanks again Scott!
Steve
Search radius is just the range of wavelengths over which to look. I use the FWHM of the spectral line as the value for this, but if you don’t know this then 1-1.5 nm should be fine. As for the wavelength calibration delta, this parameter shifts the center wavelength to account for any calibration error you may notice. Then the Delta Wavelength column will show you how far a spectral line is from the center wavelength you entered. Set the Delta Wavelength to zero for now. So for this star with temperature 5800 K, set the center wavelength to the wavelength of the feature you are attempting to verify, the Search Radius to 1 nm, and the Wavelength Calibration Delta to 0.
Nothing very strong here, but the S II line at 534.57 is the strongest with the adjacent P I line at 534.59 nm contributing, so I would call this a weak blend of the two. The Fe III line at 536.36 nm is 1.86 nm from the center (measured) wavelength, so I would not include this with the other two.
You can see that in this case, the P I line at 534.59 is about 1/2 the strength of the S II line at 534.57 even though it is much closer to its peak temperature of 7,500K than S II (18,500). The reason is that S is about 50 times more abundant than P, so its greater abundance of S relative to P results in a stronger line at this temperature.
Hello Scott, just to let you know that I am using your excel tool for line identification and I think it’s a fantastic tool! This is really useful! Thanks for making this available!
JL
