Near-infrared observations of rotating radio transients

We report on the first near-infrared observations obtained for rotating radio transients (RRATs). Using adaptive optics devices mounted on the ESO Very Large Telescope (VLT), we observed two objects of this class: RRAT J1819−1458 and RRAT J1317−5759. These observations have been performed in 2006 and 2008, in the J, H and Ks bands. We found no candidate infrared counterpart to RRAT J1317−5759 down to a limiting magnitude of Ks ∼ 21. On the other hand, we found a possible candidate counterpart for RRAT J1819−1458 having a magnitude of Ks = 20.96 ± 0.10. In particular, this is the only source within a 1σ error circle around the source’s accurate X-ray position, although given the crowded field we cannot exclude that this is due to a chance coincidence. The infrared flux of the putative counterpart to the highly magnetic RRAT J1819−1458 is higher than expected from a normal radio pulsar, but consistent with that seen from magnetars. We also searched for the near-infrared counterpart to the X-ray diffuse emission recently discovered around RRAT J1819−1458, but we did not detect this component in the near-infrared band. We discuss the luminosity of the putative counterpart to RRAT J1819−1458 in comparison with the near-infrared emission of all isolated neutron stars detected to date in this band (five pulsars and seven magnetars).