Searching for Debris Disks around Seven Radio Pulsars

We report on our searches for debris disks around seven relatively nearby radio pulsars, which are isolated sources and were carefully selected as the targets on the basis of our deep $K_s$-band imaging survey. The $K_s$ images obtained with the 6.5\,m Baade Magellan Telescope at Las Campanas Observatory are analyzed together with the \textit{Spitzer}/IRAC images at 4.5 and 8.0~$\mu$m and the \textit{WISE} images at 3.4, 4.6, 12 and 22~$\mu$m. No infrared (IR) counterparts of these pulsars are found, with flux upper limits of $\sim \mu$Jy at near-infrared ($\lambda<10\ \mu$m) and $\sim$10--1000\,$\mu$Jy at mid-infrared wavelengths ($\lambda>10\ \mu$m). The results of this search are discussed in terms of the efficiency of converting the pulsar spin-down energy to thermal energy and X-ray heating of debris disks, with comparison made to the two magnetars 4U~0142+61 and 1E~2259+586 which are suggested to harbor a debris disk.