Hubble Space Telescope observations of the old pulsar PSR J0108-1431

Understand

We present results of optical-UV observations of the 200 Myr old rotation-powered radio pulsar J0108$-$1431 with the Hubble Space Telescope.

• We found a putative candidate for the far-UV (FUV) pulsar counterpart, with the flux density $f_\nu = 9.0\pm 3.2$ nJy at $\lambda = 1528$ \AA.
• The pulsar was not detected, however, at longer wavelengths, with $3\sigma$ upper limits of 52, 37, and 87 nJy at $\lambda =$ 4326, 3355, and 2366 \AA, respectively.
• Assuming that the pulsar counterpart was indeed detected in FUV, and the previously reported marginal $U$ and $B$ detections with the Very Large Telescope were real, the optical-UV spectrum of the pulsar can be described by a power-law model with a nearly flat $f_\nu$ spectrum.