Unmasking the Active Galactic Nucleus in PKS J2310-437

PKS J2310-437 is an AGN with bright X-ray emission relative to its weak radio emission and optical continuum. It is believed that its jet lies far enough from the line of sight that it is not highly relativistically beamed. It thus provides an extreme test of AGN models. We present new observations aimed at refining the measurement of the source's properties. In optical photometry with the NTT we measure a central excess with relatively steep spectrum lying above the bright elliptical galaxy emission, and we associate the excess wholly or in part with the AGN. A new full-track radio observation with the ATCA finds that the core 8.64GHz emission has varied by about 20 per cent over 38 months, and improves the mapping of the weak jet. With Chandra we measure a well-constrained power-law spectral index for the X-ray core, uncontaminated by extended emission from the cluster environment, with a negligible level of intrinsic absorption. Weak X-ray emission from the resolved radio jet is also measured. Our analysis suggests that the optical continuum in this radio galaxy has varied by at least a factor of four over a timescale of about two years, something that should be testable with further observations. We conclude that the most likely explanation for the bright central X-ray emission is synchrotron radiation from high-energy electrons.Comment: 7 pages, 12 figure

The X-ray spectrum of 3C 273

An X-ray spectral measurement of the quasar 3C 273 with the HEAO-A2 experiment in June/July 1978 is reported. The best power law fit to the photon flux over the range 2-60 keV gives a slope of 1.41 + or - 0.02. However, structure is observed, indicating a slope of 1.52 between 2 keV and 9 keV and a slight flattening between 9 keV and 30 keV. Observations with the same experiment in December 1977 and OSO-8 in June 1976 allows confirmation of 40% intensity variability on the time scale of months, although within limits provided by the poorer statistical quality of the additional data no spectral change is discerned. Absorption from the source is found to be low, with the 1978 data yielding a 90% confidence upper limit to the hydrogen column density of 4.5 x 10 to the 21st power atoms/sq cm

The magnetic field and geometry of the oblique shock in the jet of 3C 346

We investigate the brightest regions of the kpc-scale jet in the powerful radio galaxy 3C 346, using new optical HST ACS/F606W polarimetry together with Chandra X-ray data and 14.9 GHz and 22.5 GHz VLA radio polarimetry. The jet shows a close correspondence in optical and radio morphology, while the X-ray emission shows an 0.80 +/- 0.17 kpc offset from the optical and radio peak positions. Optical and radio polarimetry show the same apparent magnetic field position angle and fractional polarization at the brightest knot, where the jet undergoes a large kink of almost 70 degrees in the optical and radio images. The apparent field direction here is well-aligned with the new jet direction, as predicted by earlier work that suggested the kink was the result of an oblique shock. We have explored models of the polarization from oblique shocks to understand the geometry of the 3C 346 jet, and find that the upstream flow is likely to be highly relativistic (0.91 +0.05 / -0.07 c), where the plane of the shock front is inclined at an angle of 51 (+/- 11) degrees to the upstream flow which is at an angle 14 (+8 / -7) degrees to our line of sight. The actual deflection angle of the jet in this case is only 22 degrees.Comment: 11 pages, 5 figures. Accepted by MNRA

Variable X-ray spectra of BL Lac objects: HEAO-1 observations of PKS 0548-322 and 2A 1219+305

X-ray spectra for the BL Lac objects PKS 0548-322 and 2A 1219+305 measured with the HEAO-1 A2 detectors during pointing maneuvers on September 30, 1978 and May 31, 1978 respectively are presented. Both fit single power law components with low energy absorption. For 2A 1219+305, a thermal bremsstrahlung form gives an unacceptable fit. From a comparison with other statistically poorer observations taken at 6 month intervals while the satellite was in its normal scanning mode, it is found that the sources exhibit spectral variability. A summary of measurements of the 5 BL Lac objects detected with the A2 experiment is presented and it is concluded that X-ray spectral changes in this class of source are common. Their general X-ray spectral characteristics distinguish BL Lac objects from other classes of X-ray emitting active galactic nuclei. Analysis of their total spectra indicates that most of the energy is emitted in the 5 to 100 eV band

Continuing a Chandra Survey of Quasar Radio Jets

We are conducting an X-ray survey of flat spectrum radio quasars (FSRQs) with extended radio structures. We summarize our results from the first stage of our survey, then we present findings from its continuation. We have discovered jet X-ray emission from 12 of our first 20 Chandra targets, establishing that strong 0.5-7.0 keV emission is a common feature of FSRQ jets. The X-ray morphology is varied, but in general closely matches the radio structure until the first sharp radio bend. In the sources with optical data as well as X-ray detections we rule out simple synchrotron models for X-ray emission, suggesting these systems may instead be dominated by inverse Compton (IC) scattering. Fitting models of IC scattering of cosmic microwave background photons suggests that these jets are aligned within a few degrees of our line of sight, with bulk Lorentz factors of a few to ten and magnetic fields a bit stronger than $10^{-5}$ G. In the weeks prior to this meeting, we have discovered two new X-ray jets at $z > 1$. One (PKS B1055+201) has a dramatic, $20''$-long jet. The other (PKS B1421-490) appears unremarkable at radio frequencies, but at higher frequencies the jet is uniquely powerful: its optically-dominated, with jet/core flux ratios of 3.7 at 1 keV and 380 at 480 nm.Comment: 4 pages, 8 figures. To appear in `X-Ray and Radio Connections', ed. L.O. Sjouwerman and K.K. Dyer (published electronicly at http://www.aoc.nrao.edu/events/xraydio/). Additional material and higher resolution figures may be found at http://space.mit.edu/home/jonathan/jets

Forage and silage performance of wheat and triticale varieties in central Texas

Last updated: 10/19/201

The significance of seniority for women managers’ interpretations of organizational restructuring

This paper examines the impact of restructuring within the transport and logistics sector on women managers working at senior and less senior (middle/junior management) levels of the organization. The majority of women experienced increased performance pressures and heavier workloads as well as an increase in working hours. At the same time, there were pressures to work at home (i.e. week-ends and evenings) and reduced opportunities to work from home (i.e. during normal office hours). Management level emerged as an important factor in how these changes were interpreted. Senior managers perceived more positive outcomes in terms of increased motivation and loyalty. Despite a longer working week, they were less likely to report low morale as an outcome from long hours. In fact, irrespective of management level, women working shorter hours were more likely to report low morale as an outcome. Results are discussed in relation to literature on restructuring and careers, in terms of perceptual framing and in relation to different levels of investment in the organization

Simultaneous X-ray and Radio Monitoring of the Unusual Binary LSI+61 303: Measurements of the Lightcurve and High-Energy Spectrum

The binary system, LSI+61 303, is unusual both because of the dramatic, periodic, radio outbursts, and because of its possible association with the 100 MeV gamma-ray source, 2CG135+01. We have performed simultaneous radio and Rossi X-ray Timing Explorer X-ray observations at eleven intervals over the 26.5 day orbit, and in addition searched for variability on timescales ranging from milliseconds to hours. We confirm the modulation of the X-ray emission on orbital timescales originally reported by Taylor et al. (1996), and in addition we find a significant offset between the peak of the X-ray and radio flux. We argue that based on these results, the most likely X-ray emission mechanism is inverse Compton scattering of stellar photons off of electrons accelerated at the shock boundary between the relativistic wind of a young pulsar and the Be star wind. In these observations we also detected 2 -- 150 keV flux from the nearby low-redshift quasar QSO~0241+622. Comparing these measurements to previous hard X-ray and gamma-ray observations of the region containing both LSI+61 303 and QSO~0241+622, it is clear that emission from the QSO dominates.Comment: 23 pages, 6 figures, Accepted for publication in the Astrophysical Journa

A Chandra Survey of Quasar Jets: First Results

We present results from Chandra X-ray imaging and spectroscopy of a flux-limited sample of flat spectrum radio-emitting quasars with jet-like extended structure. Twelve of twenty quasar jets are detected in 5 ks ACIS-S exposures. The quasars without X-ray jets are not significantly different from those in the sample with detected jets except that the extended radio emission is generally fainter. New radio maps are combined with the X-ray images in order to elucidate the relation between radio and X-ray emission in spatially resolved structures. We find a variety of morphologies, including long straight jets and bends up to 90 degrees. All X-ray jets are one-sided although the radio images used for source selection often show lobes opposite the X-ray jets. The FR II X-ray jets can all be interpreted as inverse Compton scattering of cosmic microwave background photons by electrons in large-scale relativistic jets although deeper observations are required to test this interpretation in detail. Applying this interpretation to the jets as a population, we find that the jets would be aligned to within 30 degrees of the line of sight generally, assuming that the bulk Lorentz factor of the jets is 10.Comment: 25 pages with 5 pages of color figures; accepted for publication in the Astrophysical Journal Supplements; higher resolution jpeg images are available at http://space.mit.edu/home/jonathan/jets

X-ray emission in powerful radio galaxies and quasars

ROSAT is the first mission to have detected X‐ray emission in radio galaxies which are both powerful (l_(178 MHz)>10^(27) W Hz^(−1) sr^(−1)) and distant (z>0.4), enabling test of ‘‘unified schemes’’ through a comparison of the X‐ray and radio properties of powerful quasars and radio galaxies. These radio galaxies are faint in X‐rays, but, nevertheless, ROSAT is capable of resolving any associated X‐ray‐emitting gas of cluster dimension. We present ROSAT PSPC observations of two such radio galaxies and suggest that there is a component of unresolved X‐ray emission in powerful, high‐redshift radio galaxies which may be related to the radio core; this will be tested by ROSAT observations of other powerful radio galaxies