NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Radio and X-ray observations of the gamma-ray bright quasar PKS 0528+134We present a study of the z = 2.07 quasar PKS 0528+134, which has been detected as an extraordinarily luminous gamma-ray source. Its radio properties are highly variable in both total and polarized flux density. Milliarcsecond-scale maps from global very long base interferometry (VLBI) experiments, an X-ray spectrum from ROSAT Position Sensitive Proportional Counter (PSPC) observations, and light curves in total flux density and polarization are used to investigate the geometry, radiation mechanism, and physical environment of the emission region in the source. The VLBI images reveal a bent jet extending toward the northeast on parsec scales, with less intense knots of emission appearing on the opposite side of the brightest spot. The position of the core usually found in such sources is unclear. The polarization angle is stable despite strong variability in polarized flux density and indicates that the magnetic field is aligned with the jet axis as defined by our 8.4 GHz image. The ROSAT X-ray flux density of PKS 0528+134 in 1991 March is measured to be 1.6 micro Jy at 1 keV, with a very steep spectral (`energy') index sigma(sub x) approximately equal to 2.2. The X-ray observations reveal the presence of cold gas along the line of sight significantly in excess of that present in the Galaxy. A strong radio flare began within two months of the first observation of a high flux of gamma-rays from PKS 0528+134 by Hunter et al. Using the geometry and spectral chacateristics determined by our VLBI observations, a synchrotron self-Compton calculation indicates that relativistic bulk motion is required in PKS 0528+134, with an estimated Doppler beaming factor delta approximately greater than 4.3, similar to the value delta approximately greater than 7 required to explain the low optical depth of the gamma-rays to photon-photon pair production. We suggest that the core activity of PKS 0528+134 is sporadic in nature, with the nonthermal outburst starting in 1991 representing a violent period involving ejection of relativistic plasma along a compact jet pointed almost directly toward us.
Document ID
19950040760
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Zhang, Yun Fei
(Boston Univ. Boston, MA, United States)
Marscher, Alan P.
(Boston Univ. Boston, MA, United States)
Aller, Hugh D.
(Michigan Univ. Ann Arbor, MI, United States)
Aller, Margo F.
(Michigan Univ. Ann Arbor, MI, United States)
Terasranta, Harri
(Metsahovi Radio Research Station Kylmala, Finland)
Valtaoja, Esko
(Metsahovi Radio Research Station Kylmala, Finland)
Date Acquired
August 16, 2013
Publication Date
September 1, 1994
Publication Information
Publication: Astrophysical Journal, Part 1
Volume: 432
Issue: 1
ISSN: 0004-637X
Subject Category
Astronomy
Accession Number
95A72359
Funding Number(s)
CONTRACT_GRANT: NAG5-1637
CONTRACT_GRANT: NSF AST-88-15848
CONTRACT_GRANT: NSF AST-91-16525
CONTRACT_GRANT: NSF AST-91-20224
Distribution Limits
Public
Copyright
Other

Available Downloads

There are no available downloads for this record.
No Preview Available