Intrinsic 2MASS J-H and H-Ks Colors of Field M Dwarfs

Eric Mamajek (UR)

Last updated: 19 June 2009

Summary

Here I calculate median near-IR colors for M dwarfs on the 2MASS photometric system.

Data

The DwarfArchives website maintained by Chris Gelino, Davy Kirkpatrick, and Adam Burgasser provides 2MASS photometry and spectral types for 536 M stars. Spectral types are provided on the spectral sequence defined by Kirkpatrick, Henry, & McCarthy 1991. From this list, I rejected all giants and subdwarfs, any stars with ":" (uncertain) spectral types, and any objects with "nulls" for uncertainties in any of the 2MASS photometric bands, leaving 458 K7-M9.5 stars. From this list, I calculated the median, standard error of the median, and 68% range (effectively the r.m.s., but more immune to the effects of outliers) of the J-H and H-Ks colors from the 2MASS photometry (Cutri et al. 2003). The median(mean) J-H uncertainty is 0.034(0.044) mag, and 0.035(0.049) for H-Ks. These mean uncertainties should be kept in mind when interpreting the 68% color range.
Spec.
Type		 < J-H > s.e.m.
< J-H > 		68% CL
< J-H > 		< H-Ks > s.e.m.
< H-Ks > 		68% CL
< H-Ks > 		N*s < J-Ks >
K7V 0.613 0.017 0.029 0.175 0.017 0.127 17 0.788
M0V 0.643 0.036 0.089 0.184 0.018 0.042 17 0.827
M0.5V 0.627 0.023 0.043 0.180 0.030 0.047 8 0.807
M1V 0.609 0.032 0.072 0.227 0.005 0.027 12 0.836
M1.5V 0.618 0.022 0.098 0.230 0.014 0.083 15 0.848
M2V 0.594 0.023 0.042 0.235 0.012 0.038 18 0.829
M2.5V 0.588 0.013 0.060 0.253 0.005 0.027 21 0.841
M3V 0.579 0.006 0.042 0.265 0.005 0.037 48 0.844
M3.5V 0.576 0.013 0.056 0.263 0.010 0.043 41 0.839
M4V 0.559 0.007 0.059 0.281 0.005 0.038 49 0.840
M4.5V 0.568 0.008 0.062 0.304 0.007 0.037 56 0.872
M5V 0.582 0.011 0.047 0.311 0.013 0.058 24 0.892
M5.5V 0.606 0.010 0.068 0.329 0.006 0.054 43 0.935
M6V 0.584 0.017 0.072 0.364 0.010 0.029 29 0.948
M6.5V 0.620 0.017 0.076 0.376 0.010 0.055 20 0.996
M7V 0.599 0.024 0.038 0.385 0.007 0.023 5 0.984
M7.5V 0.660 0.013 0.043 0.381 0.017 0.065 8 1.041
M8V 0.683 0.009 0.023 0.438 0.021 0.046 12 1.121
M8.5V 0.686 0.002 0.034 0.437 0.020 0.049 8 1.123
M9V 0.749 0.015 0.026 0.481 0.016 0.024 5 1.230
M9.5V 0.908 NA NA 0.545 NA NA 1 1.453