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Weak hard x-ray emission from two broad absorption line quasars observed with nustar: compton-thick absorption or intrinsic x-ray weakness?
| Content Provider | NASA Technical Reports Server (NTRS) |
|---|---|
| Author | Comastri, A. Saez, C. Brandt, W. N. Farrah, D. Risaliti, G. Fabian, A. C. Ogle, P. Matt, G. Madsen, K. K. Boggs, S. E. Craig, W. W. Hickox, R. Hailey, C. J. Stern, D. Harrison, F. A. Fiore, F. Alexander, D. M. Christensen, F. E. Bauer, F. E. Walton, D. J. Grefenstette, B. W. Teng, S. H. Fuerst, F. Luo, B. Zhang, W. W. |
| Copyright Year | 2013 |
| Description | We present Nuclear Spectroscopic Telescope Array (NuSTAR) hard X-ray observations of two X-ray weak broad absorption line (BAL) quasars, PG 1004+130 (radio loud) and PG 1700+518 (radio quiet). Many BAL quasars appear X-ray weak, probably due to absorption by the shielding gas between the nucleus and the accretion-disk wind. The two targets are among the optically brightest BAL quasars, yet they are known to be significantly X-ray weak at rest-frame 2-10 keV (16-120 times fainter than typical quasars). We would expect to obtain approx. or equal to 400-600 hard X-ray (is greater than or equal to 10 keV) photons with NuSTAR, provided that these photons are not significantly absorbed N(sub H) is less than or equal to 10(exp24) cm(exp-2). However, both BAL quasars are only detected in the softer NuSTAR bands (e.g., 4-20 keV) but not in its harder bands (e.g., 20-30 keV), suggesting that either the shielding gas is highly Compton-thick or the two targets are intrinsically X-ray weak. We constrain the column densities for both to be N(sub H) 7 à 10(exp 24) cm(exp-2) if the weak hard X-ray emission is caused by obscuration from the shielding gas. We discuss a few possibilities for how PG 1004+130 could have Compton-thick shielding gas without strong Fe Kα line emission; dilution from jet-linked X-ray emission is one likely explanation. We also discuss the intrinsic X-ray weakness scenario based on a coronal-quenching model relevant to the shielding gas and disk wind of BAL quasars. Motivated by our NuSTAR results, we perform a Chandra stacking analysis with the Large Bright Quasar Survey BAL quasar sample and place statistical constraints upon the fraction of intrinsically X-ray weak BAL quasars; this fraction is likely 17%-40%. |
| File Size | 679486 |
| Page Count | 17 |
| File Format | |
| Alternate Webpage(s) | http://archive.org/details/NASA_NTRS_Archive_20140017785 |
| Archival Resource Key | ark:/13960/t5jb15654 |
| Language | English |
| Publisher Date | 2013-07-17 |
| Access Restriction | Open |
| Subject Keyword | Nuclei Absorption Lines Accretion Quasars Coronas X Rays Emission Spectra Spectroscopic Telescopes Targets Shielding Absorption Spectra Line Spectra Accretion Disks X Ray Absorption Ntrs Nasa Technical Reports Server (ntrs) Nasa Technical Reports Server Aerodynamics Aircraft Aerospace Engineering Aerospace Aeronautic Space Science |
| Content Type | Text |
| Resource Type | Article |
