2MASS: Catching the Drift

Martin D. Weinberg - Sergei Nikolaev
Department of Physics and Astronomy
University of Massachusetts, Amherst, MA 01003-4525
nikolaev@redtail.phast.umass.edu

Abstract:

This report describes the application of the global calibration procedure to detect internal photometric variation in time and space. As an example, we derive the unconstrained global calibration solution for the K-band Northern calibration fields taken from 05.21.97 to 07.15.98. The residuals of the fiducial Persson NICMOS standards show sinusoidal variations with amplitude $B = 0.015\pm0.002$ mag and the period $T = 400.57\pm39.37$ days. We argue that this variation is due to seasonal changes in the atmospheric K-band extinction.