Dust in comet McNaught-Hartley (C/1999 T1) from Jan. 25 to Feb. 04, 2001: IR and optical CCD imaging

Broad-band optical and infrared observations in the R, I, and J, H, Ks bands of comet McNaught-Hartley (C/1999 T1) were performed from Jan. 25 to Feb. 4, 2001, shortly after the comet perihelion on Dec. 14, 2000. For the time the comet was observed, it did not show any peculiar behaviour either in the infrared or in the optical, that is, no non-spherical structures, besides the dust tail, or outburst or daily activity variations were detected. Calibration of the images in the Afρ frame provide us with values of dust production between 1000 and 3000 cm, depending on the date and on the wavelength. The general behaviour of the dust coma of C/1999 T1 is that described by a steady-state production of long-lived grains expanding radially outwards from the nucleus. The dust color does not clearly change with projected cometocentric distance. During a time span of 10 days, the cometary dust grains observed in the K, filter seemed to become slightly redder on Feb. 05 than they were on Jan. 26, 2001.