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File Plot

HERA Tool: File Plot

Let's plot a lightcurve from the raw data to take a look at what the source is actually doing. On the Hera interface, click on the data set to select it. Click on File Plot, then Run, and a parameter box will appear .

Professional astronomers make multiple plots searching for the parameters that produce the best plot: they keep a log of the parameters they choose to be able to play with the software without repeating settings. You should do this too. Print out this page and write in a table of values that go with each plot, or make a table on a blank piece of paper.

The X axis will be TIME in seconds, and the Y axis will be RATE -- type these into the File Plot parameter box. RATE is the number of photons per second collected by the satellite -- this is an indication of how bright the source is, as the brighter the source, the more photons per second we receive from it.

This data set is too large to look at all at once -- it covers almost seven years or 2480 days. You probably wouldn't want to draw this graph by hand! Even for this software, if you try to plot too many data points at once the plot will be blank or crash your computer! Use the Lists of Rows parameter to select a subsection of the entire data set to plot, for example, type 1200-1300 into the parameter box.

Now you're ready to plot! Click Run at the bottom of the File Plot parameter box. An output box will appear with the specified plot of the raw data. (A second window will appear, but you can ignore it for now.) If the plot is too small to read on the screen you can re-size it by clicking and dragging at the corner. You can also print or save the plot to your local machine by clicking on "File", "Print/Save" and following the directions. Important - In order to make sure that your plot takes up as much of the page as possible, you must expand the POW window on your computer screen to its maximum. Then, when printing, click on the "stretch to page" radio button. If you are using Windows 98 and are having printing problems, click here.

Plotting note: To change the appearance of your plot, look at the Plotting Basics help.

Exercise 4

For a graph using rows 1200-1300, how many days was the telescope collecting data from this binary system?

A. 3


A service of the High Energy Astrophysics Science Archive Research Center (HEASARC), Dr. Alan Smale (Director), within the Astrophysics Science Division (ASD) at NASA/GSFC

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