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 K alpha 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(-600)(+1100) km s(-1), in perfect agreement with the value measured for the broad component of the H alpha, 2640(-90)(+110) km s(-1). Therefore, NGC 7213 is the only Seyfert 1 galaxy whose iron K alpha 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 1000 km s(-1) of the two ionized iron lines could be the first measure of the velocity of a starburst wind from its X-ray emission.

Bianchi, S., LA FRANCA, F., Matt, G., Guainazzi, M., Bailon, E.j., Longinotti, A.l., et al. (2008). A broad-line region origin for the iron K alpha line in NGC 7213 RID B-4804-2010. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 389(1), L52-L56 [10.1111/j.1745-3933.2008.00521.x].

A broad-line region origin for the iron K alpha line in NGC 7213 RID B-4804-2010

LA FRANCA, Fabio;MATT, Giorgio;
2008-01-01

Abstract

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 K alpha 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(-600)(+1100) km s(-1), in perfect agreement with the value measured for the broad component of the H alpha, 2640(-90)(+110) km s(-1). Therefore, NGC 7213 is the only Seyfert 1 galaxy whose iron K alpha 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 1000 km s(-1) of the two ionized iron lines could be the first measure of the velocity of a starburst wind from its X-ray emission.
Bianchi, S., LA FRANCA, F., Matt, G., Guainazzi, M., Bailon, E.j., Longinotti, A.l., et al. (2008). A broad-line region origin for the iron K alpha line in NGC 7213 RID B-4804-2010. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 389(1), L52-L56 [10.1111/j.1745-3933.2008.00521.x].
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11590/148204
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