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3C 273 with NuSTAR: Unveiling the AGN | | Kristin K. Madsen
; Felix Fürst
; Dominic J. Walton
; Fiona A. Harrison
; David R. Ballantyne
; Steve E. Boggs
; Laura W. Brenneman
; Finn E. Christensen
; William W. Craig
; Andrew C. Fabian
; Karl Forster
; Brian W. Grefenstette
; Matteo Guainazzi
; Charles J. Hailey
; Greg M. Madejski
; Giorgio Matt
; Daniel Stern
; William W. Zhang
; | | Date: |
20 Jun 2015 | | Abstract: | We present results from a 244 ks $NuSTAR$ observation of 3C 273, obtained
during a cross-calibration campaign with the $Chandra$, $INTEGRAL$, $Suzaku$,
$Swift$, and $XMM-Newton$ observatories. We show that the spectrum, when fit
with a power-law model using data from all observatories except $INTEGRAL$ over
the 1-78 keV band, leaves significant residuals in the $NuSTAR$ data between
30-78 keV. The $NuSTAR$ 3-78 keV spectrum is well-described by an exponentially
cutoff power-law ($Gamma = 1.646 pm 0.006$, E$_mathrm{cutoff} =
202_{-34}^{+51}$ keV) with a weak reflection component from cold, dense
material. There is also evidence for a weak ($EW = 23 pm 11$ eV) neutral iron
line. We interpret these features as arising from coronal emission plus
reflection off an accretion disk or distant material. Beyond 80 keV $INTEGRAL$
data show clear excess flux relative to an extrapolation of the AGN model fit
to $NuSTAR$. This high-energy power-law is consistent with the presence of a
beamed jet, which begins to dominate over emission from the inner accretion
flow at 30-40 keV. Modeling the jet as a power-law, we find the coronal
component is fit by $Gamma_mathrm{AGN} = 1.638 pm 0.045$,
$E_mathrm{cutfoff} = 47 pm 15$ keV, and jet photon index by
$Gamma_mathrm{jet} = 1.05 pm 0.4$. We applied comptonizing coronal electron
plasma models to place constraints on the plasma temperature and optical depth.
Finally, we investigate the variability and find an inverse correlation between
flux and $Gamma$. We interpret this hardening of the spectrum with increasing
flux to be due to the jet. | | Source: | arXiv, 1506.6182 | | Services: | Forum | Review | PDF | Favorites | |
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