We use UKIRT and ASCA observations to determine the nature of a high redshift ( z = 2.35 ) narrow-line AGN , previously discovered by Almaini et al .
( 1995 ) .
The UKIRT observations show a broad H _ { \alpha } line while no H _ { \beta } line is detected .
This together with the red colour ( B - K = 5.4 ) suggest that our object is a moderately obscured QSO ( A _ { V } > 3 ) , in optical wavelengths .
The ASCA data suggest a hard spectrum , probably due to a large obscuring column , with \Gamma = 1.93 ^ { +0.62 } _ { -0.46 } ,N _ { H } \sim 10 ^ { 23 } cm ^ { -2 } .
The combined ASCA and ROSAT data again suggest a heavily obscured spectrum ( N _ { H } \sim 10 ^ { 23 } cm ^ { -2 } or A _ { V } \sim 100 ) .
In this picture , the ROSAT soft X-ray emission may arise from electron scattering , in a similar fashion to local Seyfert 1.9 .
Then , there is a large discrepancy between the moderate reddening witnessed by the IR and the large X-ray absorbing column .
This could be possibly explained on the basis of e.g .
high gas metallicities or assuming that the X-ray absorbing column is inside the dust sublimation radius .
An alternative explanation can be obtained when we allow for variability between the ROSAT and ASCA observations .
Then the best fit spectrum is still flat , \Gamma = 1.35 ^ { +0.16 } _ { -0.14 } , but with low intrinsic absorption in better agreement with the IR data , while the ROSAT normalization is a factor of two below the ASCA normalization .
This object may be one of the bright examples of a type-II QSO population at high redshift , previously undetected in optical surveys .
The hard X-ray spectrum of this object suggests that such a population could make a substantial contribution to the X-ray background .