Analysis of 14 Years of X-Ray Emission from SN 2011DH

Ejecta from core-collapse supernovae interact with the circumstellar medium shed by the progenitor star, producing X-ray emission. Previous studies analyzed the X-ray spectrum of the Type IIb supernova SN 2011dh up to ∼500 days after explosion. Long-term monitoring of X-ray emission provides valuable constraints on supernova evolution and progenitor systems, yet such studies remain rare for Type IIb events due to limited data. Here we present the most comprehensive X-ray light curve of SN 2011dh to date, combining all available Chandra and XMM-Newton data with previously published and newly released Swift observations, extending coverage to ∼5100 days. We measure a luminosity decline consistent with $L_X\propto t^{-0.74\pm 0.04}$ and infer a mass-loss rate of $(1.0$–$2.2)\times {10}^{-6}{M}_{\odot }{\mathrm{yr}}^{-1}$ for $v_w=10\mathrm{km}{\mathrm{s}}^{-1}$, or $(2.0$–$4.4)\times {10}^{-6}{M}_{\odot }{\mathrm{yr}}^{-1}$ for $v_w=20\mathrm{km}{\mathrm{s}}^{-1}$. These estimates agree with earlier results, supporting the interpretation that the X-ray emission has been dominated by an adiabatic reverse shock. The consistency of our late-time results with previous studies demonstrates that SN 2011dh has evolved steadily for nearly 14 years.