Catalog construction for the secondary stars

Having found provisional positions for the primary stars, I then moved on to the secondary stars. While the primary-to-primary separations were measured many times, the primary-to-secondary measures were limited to just one secondary to each of two primary stars, with each separation measured twice; a total of four measurements for each secondary star. This was done to limit the size of the dataset.

With ~100 primary stars and 600+ secondary stars, the total number of possible separation measurements is huge. I put this limitation in place in order to make the task achievable in a year. Four measurements of 600+ secondary stars plus ~6 measurements of each of more than 350 primary star pairs put the total number of measurements near 6000, just for separations (actual 6335). Multiple meridian altitudes for each of the 700+ stars adds several thousand (actual 3178) more measures. With the many thousands of solar limb measurements also needed (actual ~5400), I had to set boundaries for the project.

To work on the secondary stars, I needed to use grep again on the prime dataset:

isolate just the secondaries:

grep '^[^~]*~[^~]*$' TYOUT_2022-02-06.TXT > secondaries_all_2022-02-06.txt

isolate just the secondaries, with the primary star in the second position:

grep -E '.{15}.{10}~' secondaries_all_2022-02-06.txt > secondaries_2nd~706.txt (706 lines)

isolate just the secondaries, with the primary star in the first position:

grep -E '^.{2}.{0,10}~' secondaries_all_2022-02-06.txt > secondaries_1st~703.txt (703 lines)

This dissection of the data is necessary to permit the measured delta ra values to be used in two directions. In the master file, secondaries_all_2022-02-06.txt, the variables are not ordered well for catalog construction so, in the extracted files, I have reordered some columns.

The input file "secondaries_1st~703.txt" file now looked like this:

The first 5 columns held the data specific to the first star in the pair; the Ycat_ra , dec, and magnitude, and the measured average meridian altitude. The second 5 columns held the similar data specific to the second star in the pair. The entries in the rest of a line referred to properties defined by the pair. Those quantities were the measured delta ra (mdra) and the error when compared to modern catalogs (draerr), all in degrees.

The next input file was "secondaries_2nd~706.txt":

This file, above, was similar to the previous one except that the primary stars were in the second position. I wanted them to be in the first position, so I swapped cols 0-4 with cols 5-9 to get the same logical order as the first file, but without disturbing the common pair data. This second file was then concatenated with the first file to form a longer file with all the pairs in a common format, primary stars in the first position, secondary stars in the second position:

Then, with the first position being the primary stars, two things were done; changed the signs of the mdras so that they indicate the direction of the separation, and added the provisional ras from an earlier step. Here was where the catalog began to take shape. Below, each line now had the key data for a given pair of stars; the meridian altitudes (malt1, malt2), the signed delta right ascension (mdra), and the provisional right ascension of the primary star. Note that each secondary star appeared only twice because its separations were only measured to two primary stars.

The delta ras (mdra) could now be added to the primary's provisional ra (prov_ra1) to get the provisional ra of the secondary star. In addition, the altitudes were converted to declinations. Because there were separations to two primary stars, there are two provisional ra values (a,b) calculated and then averaged to form the final provisional ra of the secondary star.

Now that the provisional ra has been found, the first five columns, those related to the primary star, can be deleted, leaving the secondary and its position to stand alone (below). To get a preview of the quality of the catalog, we find the estimated ra2_err by adding in the known offset of alphaAri (32.08 deg) to the provisional ras and then subtracting the Ycat_ra2 value. This ra2_err will change slightly when the tie is made between the solar ra and a stellar ra. See the "right ascension zero point" page.

This provisional catalog of the secondary stars and can be found here.

Next to be done was to integrate the two provisional catalogs (primary star and secondary stars).

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