X-ray emission from the enigmatic Rotating RAdio Transients ( RRATs ) offers a vital clue to understanding these objects and how they relate to the greater neutron star population .
An X-ray counterpart to RRAT J1819 - 1458 is known , and its properties are similar to those of other middle-aged ( 0.1 Myr ) neutron stars .
We have searched for X-ray emission with Chandra /ACIS at the positions of two RRATs with arcsecond ( or better ) localisation , J0847 - 4316 and J1846 - 0257 .
Despite deep searches ( especially for RRAT J1846 - 0257 ) we did not detect any emission with 0.3–8 keV count-rate limits of 1 { counts ks } ^ { -1 } and 0.068 { counts ks } ^ { -1 } , respectively , at 3 \sigma confidence .
Assuming thermal emission similar to that seen from RRAT J1819 - 1458 ( a blackbody with radius \approx 20 km ) , we derive effective temperature limits of 77 eV and 91 eV for the nominal values of the distances and column densities to both sources , although both of those quantities are highly uncertain and correlated .
If we instead fix the temperature of the emission ( a blackbody with kT = 0.14 keV ) , we derive unabsorbed luminosity limits in the 0.3–8 keV range of 1 \times 10 ^ { 32 } { erg s } ^ { -1 } and 3 \times 10 ^ { 32 } { erg s } ^ { -1 } .
These limits are considerably below the luminosity of RRAT J1819 - 1458 ( 4 \times 10 ^ { 33 } { erg s } ^ { -1 } ) , suggesting that RRATs J0847 - 4316 and J1846 - 0257 have cooled beyond the point of visibility ( plausible given the differences in characteristic age ) .
However , as we have not detected X-ray emission , it may also be that the emission from RRATs J0847 - 4316 and J1846 - 0257 has a different character from that of RRAT J1819 - 1458 .
The two non-detections may prove a counterpoint to RRAT J1819 - 1458 , but more detections are certainly needed before we can begin to derive general X-ray emission properties for the RRAT populations .