We compared the J, H, Ks magnitudes for the R1 Saturated sources
derived from the second
OPS test with 2MASS magnitudes estimated using Version 3.0 of the Cohen
and Walker Atlas of Calibrated Spectra (CW). The 2MASS magnitudes of the CW
stars were determined by integrating the spectra over the 2MASS relative
response functions, converting to flux density and magnitude using
isophotal bandwidths and zero magnitude fluxes
provided by Martin Cohen.
Thirty-eight of the
2017 OPS test sources have CW counterparts.
Results
Most of the R1 magnitudes are within 1 sigma of the CW magnitudes.
The error estimates are the root sum square of the OPS error estimates and the
integrated CW errors (which are much smaller than the OPS errors).
The distribution of residuals (2MASS - CW) is tight with a spread of 0.1
magnitudes in Ks and slightly larger in J and H.
There is a bias between 2MASS and CW of 0.06-0.09 magnitudes with 2MASS
fainter than the CW estimates. Independent calibration of CW stars shows that
the CW values are too low by 1%. Therefore, the bias is in an opposite sense
to the known CW bias.
Mean and Standard Deviation of 2MASS-CW magnitudes
