TY - JOUR
T1 - PMN J0525-3343
T2 - Soft X-ray spectral flattening in a blazar at z = 4.4
AU - Fabian, A. C.
AU - Celotti, A.
AU - Iwasawa, K.
AU - McMahon, R. G.
AU - Carilli, C. L.
AU - Brandt, W. N.
AU - Ghisellini, G.
AU - Hook, I. M.
PY - 2001/5/11
Y1 - 2001/5/11
N2 - We report optical, radio and X-ray observations of a new distant blazar, PMN J0525-3343, at a redshift of 4.4. The X-ray spectrum measured from ASCA and BeppoSAX flattens below a few keV, in a manner similar to the spectra of two other z > 4 blazars, GB 1428+4217 (z = 4.72) reported by Boller et al. and RXJ1028.6-0844 (z = 4.28) reported by Yuan et al. The spectrum is well fitted by a power-law continuum which either is absorbed or breaks at a few keV. An intrinsic column density corresponding to 2 × 1023 H-atoms cm-2 at solar abundance is required by the absorption model. This is however a million times greater than the neutral hydrogen, or dust, column density implied by the optical spectrum, which covers the rest-frame ultraviolet emission of the blazar nucleus. We discuss the problems raised and suggest that, unless there is intrinsic flattening in the spectral distribution of the particles/ seed photons producing X-rays via inverse Compton scattering, the most plausible solution is a warm absorber close to the active nucleus.
AB - We report optical, radio and X-ray observations of a new distant blazar, PMN J0525-3343, at a redshift of 4.4. The X-ray spectrum measured from ASCA and BeppoSAX flattens below a few keV, in a manner similar to the spectra of two other z > 4 blazars, GB 1428+4217 (z = 4.72) reported by Boller et al. and RXJ1028.6-0844 (z = 4.28) reported by Yuan et al. The spectrum is well fitted by a power-law continuum which either is absorbed or breaks at a few keV. An intrinsic column density corresponding to 2 × 1023 H-atoms cm-2 at solar abundance is required by the absorption model. This is however a million times greater than the neutral hydrogen, or dust, column density implied by the optical spectrum, which covers the rest-frame ultraviolet emission of the blazar nucleus. We discuss the problems raised and suggest that, unless there is intrinsic flattening in the spectral distribution of the particles/ seed photons producing X-rays via inverse Compton scattering, the most plausible solution is a warm absorber close to the active nucleus.
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U2 - 10.1046/j.1365-8711.2001.04181.x
DO - 10.1046/j.1365-8711.2001.04181.x
M3 - Article
AN - SCOPUS:0000597899
SN - 0035-8711
VL - 323
SP - 373
EP - 379
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 2
ER -