English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

X-ray observations performed with ROSAT led to the discovery of a group(seven to date) of X-ray dim and radio-silent middle-aged isolated neutronstars (a.k.a. XDINSs), which are characterised by pure blackbody spectra(kT~40-100 eV), long X-ray pulsations (P=3-12 s), and appear to be endowed withrelatively high magnetic fields, (B~10d13-14 G). RBS 1774 is one of the fewXDINSs with a candidate optical counterpart, which we discovered with the VLT.We performed deep observations of RBS 1774 in the R band with the VLT todisentangle a non-thermal power-law spectrum from a Rayleigh-Jeans, whosecontributions are expected to be very much different in the red part of thespectrum. We did not detect the RBS 1774 candidate counterpart down to a 3sigma limiting magnitude of R~27. The constraint on its colour, (B-R)<0.6,rules out that it is a background object, positionally coincident with theX-ray source. Our R-band upper limit is consistent with the extrapolation ofthe B-band flux (assuming a 3 sigma uncertainty) for a set of power-laws F_nu~nu^alpha with spectral indeces alpha<0.07. If the optical spectrum of RBS 1774were non-thermal, its power-law slope would be very much unlike those of allisolated neutron stars with non-thermal optical emission, suggesting that it ismost likely thermal. For instance, a Rayleigh-Jeans with temperature T_O = 11eV, for an optically emitting radius r_O=15 km and a source distance d=150 pc,would be consistent with the optical measurements. The implied low distance iscompatible with the 0.04 X-ray pulsed fraction if either the star spin axis isnearly aligned with the magnetic axis or with the line of sight, or it isslightly misaligned with respect to both the magnetic axis and the line ofsight by 5-10 degrees

VLT/FORS2 observations of the optical counterpart of the isolated neutron star RBS 1774