Accurate X-ray position and multiwavelength observations of the isolated neutron star RBS 1774

Abstract

We report on X-ray, optical, infrared and radio observations of the X-ray dim isolated neutron star (XDINS) 1RXS J214303.7+065419 (also known as RBS 1774). The X-ray observation was performed with the High Resolution Camera on board of the Chandra X-ray Observatory, allowing us to derive the most accurate position for this source (alpha = 21h43m3.38s, delta= +6deg54'17".53; 90% uncertainty of 0."6). Furthermore, we confirmed with a higher spatial accuracy the point-like nature of this X-ray source. Optical and infrared observations were taken in B, V, r', i', J, H and Ks filters using the Keck, VLT, Blanco and Magellan telescopes, while radio observations were obtained from the ATNF Parkes single dish at 2.9GHz and 708MHz. No plausible optical and/or infrared counterpart for RBS 1774 was detected within the refined sub-arsecond Chandra X-ray error circle. Present upper limits to the optical and infrared magnitudes are r'>25.7 and J>22.6 (5 sigma confidence level). Radio observations did not show evidence for radio pulsations down to a luminosity at 1.4 GHz of L < 0.02 mJy kpc^2, the deepest limit up to date for any XDINS, and lower than what expected for the majority of radio pulsars. We can hence conclude that, if RBS 1774 is active as radio pulsar, its non detection is more probably due to a geometrical bias rather than to a luminosity bias. Furthermore, no convincing evidence for RRAT-like radio bursts have been found. Our results on RBS 1774 are discussed and compared with the known properties of other thermally emitting neutron stars and of the radio pulsar population.