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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?

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dc.contributorVirginia Techen
dc.contributor.authorLuo, B.en
dc.contributor.authorBrandt, W. N.en
dc.contributor.authorAlexander, D. M.en
dc.contributor.authorHarrison, F. A.en
dc.contributor.authorStern, D.en
dc.contributor.authorBauer, F. E.en
dc.contributor.authorBoggs, S. E.en
dc.contributor.authorChristensen, F. E.en
dc.contributor.authorComastri, A.en
dc.contributor.authorCraig, W. W.en
dc.contributor.authorFabian, A. C.en
dc.contributor.authorFarrah, D.en
dc.contributor.authorFiore, F.en
dc.contributor.authorFuerst, F.en
dc.contributor.authorGrefenstette, B. W.en
dc.contributor.authorHailey, C. J.en
dc.contributor.authorHickox, R.en
dc.contributor.authorMadsen, K. K.en
dc.contributor.authorMatt, G.en
dc.contributor.authorOgle, P.en
dc.contributor.authorRisaliti, G.en
dc.contributor.authorSaez, C.en
dc.contributor.authorTeng, S. H.en
dc.contributor.authorWalton, D. J.en
dc.contributor.authorZhang, W. W.en
dc.contributor.departmentPhysicsen
dc.date.accessed2014-02-05en
dc.date.accessioned2014-02-25T13:57:05Zen
dc.date.available2014-02-25T13:57:05Zen
dc.date.issued2013-08en
dc.description.abstractWe 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 approximate to 400-600 hard X-ray (greater than or similar to 10 keV) photons with NuSTAR, provided that these photons are not significantly absorbed (N-H less than or similar to 10(24) cm(-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-H approximate to 7 x 10(24) cm(-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 K alpha 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%.en
dc.description.sponsorshipCalifornia Institute of Technology (Caltech) NuSTAR 44A-1092750en
dc.description.sponsorshipNASA ADP Grant NNX10AC99Gen
dc.description.sponsorshipLeverhulme trusten
dc.description.sponsorshipScience Technology and Facilities Councilen
dc.description.sponsorshipBasal-CATA PFB-06/2007en
dc.description.sponsorshipCONICYT-Chile FONDECYT 1101024, Anillo ACT1101, FONDECYT 3120198en
dc.description.sponsorshipNASA NNG08FD60Cen
dc.identifier.citationB. Luo et al. 2013. "Weak hard X-ray emission from two broad absorption line quasars observed with NuSTAR: Compton-thick absorption or intrinsic X-ray weakness?," ApJ 772 153 doi:10.1088/0004-637X/772/2/153en
dc.identifier.doihttps://doi.org/10.1088/0004-637x/772/2/153en
dc.identifier.issn0004-637Xen
dc.identifier.urihttp://hdl.handle.net/10919/25553en
dc.identifier.urlhttp://m.iopscience.iop.org/0004-637X/772/2/153/pdf/0004-637X_772_2_153.pdfen
dc.language.isoen_USen
dc.publisherIOP Publishing Ltd.en
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectaccretion, accretion disksen
dc.subjectgalaxies: activeen
dc.subjectgalaxies: nucleien
dc.subjectquasars:en
dc.subjectabsorption linesen
dc.subjectquasars: emission linesen
dc.subjectx-rays: generalen
dc.subjectactive galactic nucleien
dc.subjectdigital sky surveyen
dc.subjectspectralen
dc.subjectenergy-distributionsen
dc.subjectoptically selected quasarsen
dc.subjectxmm-newtonen
dc.subjectspectroscopyen
dc.subjecthubble-space-telescopeen
dc.subjectaccretion disk windsen
dc.subjectradio-louden
dc.subjectquasarsen
dc.subjectseyfert 1 galaxiesen
dc.subject7th data releaseen
dc.titleWeak hard X-ray emission from two broad absorption line quasars observed with NuSTAR: Compton-thick absorption or intrinsic X-ray weakness?en
dc.title.serialAstrophysical Journalen
dc.typeArticle - Refereeden

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