Photometric Constraints on Activity of Centaur 174P/Echeclus from 2021 Through 2024

Abstract We present results from an observing campaign focused on monitoring the dust coma of centaur 174P/Echeclus using the 8.1 m Gemini North and South telescopes. Six epochs of imaging data were acquired from 2021 November through 2024 February. No conspicuous dust coma was detected in the imaging data. The images were used for upper-limit dust production rate estimates, nucleus color measurements, and nucleus size estimates. The weighted mean nucleus colors are <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo>(</mml:mo> <mml:msup> <mml:mrow> <mml:mi>g</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>′</mml:mo> </mml:mrow> </mml:msup> <mml:mo>−</mml:mo> <mml:msup> <mml:mrow> <mml:mi>r</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>′</mml:mo> </mml:mrow> </mml:msup> <mml:mo>)</mml:mo> <mml:mo>=</mml:mo> <mml:mn>0.64</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.03</mml:mn> </mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo>(</mml:mo> <mml:msup> <mml:mrow> <mml:mi>r</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>′</mml:mo> </mml:mrow> </mml:msup> <mml:mo>−</mml:mo> <mml:msup> <mml:mrow> <mml:mi>i</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>′</mml:mo> </mml:mrow> </mml:msup> <mml:mo>)</mml:mo> <mml:mo>=</mml:mo> <mml:mn>0.27</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.03</mml:mn> </mml:math> , where the uncertainties provided are the standard deviations of the individual color measurements. The colors are consistent with the gray/neutral centaur population and indicate no appreciable color evolution or rotational variation observed. We estimate the effective nucleus diameter to be 66.8 ± 2.0 km, which is consistent with previous reports, further supporting the assessment of no dust coma being present.