Correlation factors between bands
If the brightness variation is true variability then there should be a correlation between brightness changes recorded in different filter bands. The following table are the R-squared linear correlation factors calculated for the pairs of bands. The number in parentheses next to the R-squared value is the number of elements used to calculate the correlation factor. The number in square brackets next to the band is the range of magnitudes measured.
| V [0.50 mag] | B [0.20 mag] | R [0.88 mag] |
|---|
| B [0.20 mag] | 0.16 (32) | | |
|---|
| R [0.88 mag] | 0.76 (23) | 0.13 (9) | |
|---|
| I [0.70 mag] | 0.62 (21) | 0.17 (8) | 0.91 (9) |
|---|
Magnitude-Magnitude Plots
The plots below are provided to check the values in the table above and also to show any non-linear correlations
I & R Statistics
Welch & Stetson (1993, AJ, 105, 1813) present a method for varible star detection in CCD images from automated surveys. Data from two bands are compared and two statistics are calculated: R and I.
The I-statistic has an expectation value of zero for stars that are NOT variable. A larger non-zero I-value indicates a higher likelihood that the star is variable. The R statistic indicates how the color of the star changes as the variable grows brighter with R = 1.0 being no change in color.
R and I values have only been calculated if there are more than four (4) matched measurements of brightness in each band.
| V
(I|R) | B
(I|R) | R
(I|R) |
|---|
B
(I|R) | 1.56 | 0.45 | | |
|---|
R
(I|R) | 8.01 | 0.89 | 1.43 | 0.08 | |
|---|
I
(I|R) | 4.82 | 1.10 | 0.56 | 0.34 | 6.28 | 1.23 |
|---|
By John C. Martin, University of Illinois Springfield Henry R. Barber Research Observatory
Generated on 2026-01-19 14:34:50 UT-5
