Deep optical observations of the gamma-ray pulsar J2055+2539 with the GTC

Abstract

The report gives a broad outline of deep, down to a 28 magnitude limit, optical observations of the γ-ray pulsar J2055+2539 (total exposure time ≈ 7.9 ks), which were obtained with the Gran Telescopio Canarias in the g′-band. To derive the most precise pulsar position we utilized recent Chandra observations, where the pulsar X-ray counterpart is detected with high significance. Using two reference stars detected both in the optical and X-rays we improved the absolute astrometry accuracy for the Chandra image of the PSR J2055+2539 field. The resulting Chandra pulsar position error circle of about 0″.2 is compatible with the 1σ Fermi position of the pulsar (0″.5), obtained from timing analysis.No optical counterpart was detected within the refined pulsar error circle. However, we managed to correct a shallow upper limit on the optical flux of the pulsar, which had been derived from preliminary observations. The new value g′ = 26.6. It is brighter than the limit stated above due to the presence of a nearby star, 0″.8 from the pulsar, with g′ = 20.3. The inspection of the pulsar multiwavelength spectrum suggests a break between the optical and X-rays.