Open AccessUltrasoft X‐ray components in the high‐temperature extreme
Author(s) -
Puchnarewicz E. M.
Publication year - 1998
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.1998.01827.x
Subject(s) - physics , rosat , astrophysics , redshift , line (geometry) , flux (metallurgy) , rest frame , accretion disc , active galactic nucleus , accretion (finance) , astronomy , galaxy , geometry , mathematics , materials science , metallurgy
A search for high‐redshift ( z > 0.5) ultrasoft X‐ray AGN in pointed ROSAT PSPC observations is made, using the wgacat catalogue. Evidence for a further three such objects is found, adding to three identified previously (E1346+266, EXO 1346.4+2637 and RX J0947.0+4721). The flux of one new object [1WGA J1342.4+2720; L (0.1–2 keV)∼ 2 × 10 45 erg s −1 )] was found to be variable (a factor of 1.7 over 2 d), and this object has relatively narrow permitted line emission. These properties, also seen in E1346+266 and EXO 1346.4+2637, are typical of ultrasoft AGN at all redshifts, in particular the narrow‐line Seyfert 1s (NLS1s). The rarity of high‐ z ultrasoft AGN places limits on the ‘temperature’ of the soft X‐ray component in the rest frame of AGN in general. It also provides an opportunity to investigate models for the soft component in the high‐temperature extreme, e.g., for accretion disc models, testing the physics at the inner edge of the disc, and the effects of Comptonization in a hot, optically thin corona.