摘要：Context. 2MASS is the reference survey in the near-infrared (NIR) part of the spectrum due to its whole-sky coverage, large dynamic range, and proven calibration uniformity. However, previous studies disagree on the value of the zero points (ZPs) for its three bandsJHKat the hundredth of a magnitude level. The disagreement should become more noticeable now thatGaiaprovides whole-sky optical photometry calibrated below that level.Aims. We want to establish the value of the 2MASS ZPs based on NICMOS/HST spectrophotometry of the CALSPEC standard stars and test it with the help ofGaiaDR2 parallaxes.Methods. We have computed the syntheticJHKphotometry for a sample of stars using the HST CALSPEC spectroscopic standards and compared it with their 2MASS magnitudes to evaluate the ZPs. We have tested our results by analyzing a sample of FGK dwarfs with excellent 2MASS photometry and accurateGaiaDR2 parallaxes.Results. The Vega ZPs for 2MASSJ,H, andKare found to be −0.025 ± 0.005, 0.004 ± 0.005, and −0.015 ± 0.005 mag, respectively. The analysis of the FGK sample indicates that the new ZPs are more accurate than previous ones.
关键词：ensurveysmethods: data analysistechniques: photometric
