1. Select the Spectra tab from the main menu.

2. Select in the left-hand top subpanel two stars. The left-hand radio button sets the spectrum of the star shown in the top part of the central subpanel. The right-hand radio button sets the spectrum of the star shown in the bottom part of the central subpanel. Note the same star can also be selected for simultaneously viewing different wavelength portions of the spectrum.

3. Select the wavelength region of the spectrum of 30 Å wide in the bottom left-hand subpanel. This wavelength region loads for both stars selected in the top left-hand panel.

4. Press the Load Region #1 button in the top menu of the central subpanel. It displays the spectral regions selected for both stars. Wait a few seconds until the spinner timer vanishes signaling the spectra are fully loaded in the BRASS Spectra Data Interface.

5. The red and blue line labels marked on the wavelength axis can be lifted onto the stellar spectrum by checking the Up radio button and pressing the Shift top labels button next to it.

6. The selected wavelength region can be enlarged. Press the left-hand mouse button for marking the starting wavelength region on the spectrum display. Hold down while sliding along the spectrum wavelength scale and release at the endpoint of the region for enlargement. The mouse zooming function can also be applied along the vertical direction of the spectrum for enlarging the Normalized flux region.

7. The loaded spectral regions can be used for measuring the equivalent line width values of lines selected by the user. The spectral region displayed in the top central subpanel can be sent to the Gauss Line fit tab by pressing the send to top Gauss pane button in the top right-hand corner. The spectral region displayed in the bottom central subpanel can also be sent this tab by pressing the send to bottom Gauss pane button in the bottom right-hand corner. The Gauss fitting page can be displayed by clicking on the Gauss Line fit tab.

8. For measuring line equivalent widths zoom in on one spectral line with the mouse, for example in the observed spectrum shown in the top central subpanel. The interactive sliders shown below the spectrum can be moved for enlarging the wavelength region around the selected line. By clicking the blue label the line identification information will populate the green colored my list in the right-hand top (or bottom) subpanels. The line information in this table can be saved to the user’s disc (see point 12. below).

9. By pressing the run top Gauss fit button in the top left-hand corner the Gaussian best fit to the observed line fluxes is calculated and over-plotted with the solid red line. The line equivalent width values (Eqv. width) are listed in red color to the right-hand side of the central subpanel. Other fit parameters are listed in this table as well.

10. By moving the interactive sliders below the spectrum the wavelength region for the line equivalent width calculation can be modified.

11. Next press once more the run top Gauss fit button to re-calculate the best fit shown with the red over-plotted line. It also updates the best-fit line values listed in the red right-hand table for the wavelength region set by the user. The final best fit line values can be added to the green colored table in the right-hand subpanel by pressing the Add top fit to my list button.

12. The green table with the line identification, equivalent line width, and more information in the right-hand subpanel can be exported to the user’s disc by pressing the Save my list to file: button at the top side of the top or bottom right-hand subpanels. Additional lines can be added to the list green lists for user saving by selecting and Gauss fitting more lines in point 7.