A broad-line region origin for the iron Kα line in NGC 7213

Mon, 30 Jun 2008 22:00:00 GMT

A broad-line region origin for the iron Kα line in NGC 7213 Bianchi, Stefano; La Franca, Fabio; Matt, Giorgio; Guainazzi, Matteo; Jimenez Bailon, Elena; Longinotti, Anna Lia; Nicastro, Fabrizio; Pentericci, Laura 2008-07 Monthly Notices of the Royal Astronomical Society: Letters 389 52-56 The X-ray spectrum of NGC 7213 is known to present no evidence for Compton reflection, a unique result among bright Seyfert 1s. The observed neutral iron Kα line, therefore, cannot be associated with a Compton-thick material, like the disc or the torus, but is due to Compton-thin gas, with the broad-line region (BLR) as the most likely candidate. To check this hypothesis, a long Chandra High-Energy Transmission Grating observation, together with a quasi-simultaneous optical spectroscopic observation at the ESO NTT EMMI were performed. We found that the iron line is resolved with a full width at half-maximum (FWHM) = 2400+1100-600kms-1, in perfect agreement with the value measured for the broad component of the Hα, 2640+110-90kms-1. Therefore, NGC 7213 is the only Seyfert 1 galaxy whose iron Kα line is unambiguously produced in the BLR. We also confirmed the presence of two ionized iron lines and studied them in greater detail than before. The resonant line is the dominant component in the Fe XXV triplet, therefore suggesting an origin in collisionally ionized gas. If this is the case, the blueshift of around 1000kms-1 of the two ionized iron lines could be the first measure of the velocity of a starburst wind from its X-ray emission.

How complex is the obscuration in active galactic nuclei? new cluesfrom the suzaku monitoring of the x-ray absorbers in ngc 7582

Tue, 31 Mar 2009 22:00:00 GMT

How complex is the obscuration in active galactic nuclei? new cluesfrom the suzaku monitoring of the x-ray absorbers in ngc 7582 Bianchi, Stefano; Piconcelli, Enrico; Chiaberge, Marco; Jimenez Bailon, Elena; Matt, Giorgio; Fiore, Fabrizio 2009-04 Astrophysical Journal 695 781-787 We present the results of a Suzaku monitoring campaign of the Seyfert 2galaxy, NGC 7582. The source is characterized by very rapid (ontimescales even lower than a day) changes of the column density of aninner absorber, together with the presence of constant componentsarising as reprocessing from a Compton-thick material. The best-fittingscenario implies important modifications to the zeroth-order view ofUnified Models. While the existence of a pc-scale torus is needed inorder to produce a constant Compton reflection component and an ironKa-emission line, in this Seyfert 2 galaxy this is not viewed along theline of sight. On the other hand, the absorption of the primarycontinuum is due to another material, much closer to the black hole,roughly at the distance of the broad-line region, which can produce theobserved rapid spectral variability. On top of that, the constantpresence of a 10(22) cm(-2) column density can be ascribed to thepresence of a dust lane, extended on a galactic scale, as previouslyconfirmed by Chandra. There is now mounting evidence that complexity inthe obscuration of active galactic nuclei (AGNs) may be the rule ratherthan the exception. We therefore propose to modify the UnificationModel, adding to the torus the presence of two furtherabsorbers/emitters. Their combination along the line of sight canreproduce all the observed phenomenology.

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A broad-line region origin for the iron Kα line in NGC 7213

How complex is the obscuration in active galactic nuclei? new cluesfrom the suzaku monitoring of the x-ray absorbers in ngc 7582