Abstract
We present X-ray and radio observations of the recently discovered bow-shock pulsar wind nebula (PWN) associated with PSR J0002+6216, characterizing the PWN morphology, which was unresolved ...in previous studies. The multifrequency, multiepoch Very Large Array (VLA) radio observations reveal a cometary tail trailing the pulsar and extending up to 5.′3, with multiple kinks along the emission. The presented radio continuum images from multiconfiguration broadband VLA observations are one of the first results from the application of multiterm multifrequency synthesis deconvolution in combination with the AWProject gridder implemented in the Common Astronomy Software Applications (CASA) package. The X-ray emission observed with Chandra extends to only 21″, fades quickly, and has some hot spots present along the extended radio emission. These kinks could indicate the presence of density variations in the local interstellar medium or turbulence. The bow-shock standoff distance estimates a small bow-shock region with a size of 0.003–0.009 pc, consistent with the pulsar spin-down power of
E
̇
= 1.51 × 10
35
erg s
−1
estimated from timing. The high-resolution radio image reveals the presence of an asymmetry in the bow-shock region, which is also present in the X-ray image. The broadband radio image shows an unusually steep spectrum along with a flat-spectrum sheath, which could indicate varying opacity or energy injection into the region. Spatially resolved X-ray spectra provide marginal evidence of synchrotron cooling along the extended tail. Our analysis of the X-ray data also shows that this pulsar has a low spin-down power and one of the lowest X-ray efficiencies observed in these objects.
We present multifrequency Very Long Baseline Array (VLBA) follow-up observations of VLBA Imaging and Polarimetry Survey sources identified as likely compact symmetric objects (CSOs) or supermassive ...binary black holes (SBBHs). We also present new spectroscopic redshifts for 11 sources observed with the Hobby–Eberly Telescope. While no new SBBHs can be confirmed from these observations, we have identified 24 CSOs in the sample, 15 of which are newly designated, and refuted 52 candidates leaving 33 unconfirmed candidates. This is the first large uniform sample of CSOs which can be used to elicit some of the general properties of these sources, including morphological evolution and environmental interaction. We have detected polarized emission from two of these CSOs the properties of which are consistent with active galactic nuclei unification schemes.
PSR B1508+55 is known to have a single component profile above 300 MHz. However, when we study it at frequencies below 100 MHz using the first station of the Long Wavelength Array, it shows multiple ...components. These include the main pulse, a precursor, a postcursor, and a trailing component. The separation of the trailing component from the main peak evolves over the course of a three year study. This evolution is likely an effect of the pulse signal getting refracted off an ionized gas cloud (acting as a lens) leading to what appears to be a trailing component in the profile as the pulsar signal traverses the interstellar medium. Using this interpretation, we identify the location and electron density of the lens affecting the pulse profile.
Randomized trial data support the superiority of coronary artery bypass grafting (CABG) surgery over percutaneous coronary intervention (PCI) in diabetic patients with multivessel coronary artery ...disease (MV-CAD). However, whether this benefit is seen in a real-world population among subjects with stable ischemic heart disease (SIHD) and acute coronary syndromes (ACS) is unknown.
The main objective of this study was to assess the generalizability of the FREEDOM (Future REvascularization Evaluation in Patients with Diabetes Mellitus: Optimal Management of Multi-vessel Disease) trial in real-world practice among patients with diabetes mellitus and MV-CAD in residents of British Columbia, Canada. Additionally, the study evaluated the impact of mode of revascularization (CABG vs. PCI with drug-eluting stents) in diabetic patients with ACS and MV-CAD.
In a large population-based database from British Columbia, this study evaluated major cardiovascular outcomes in all diabetic patients who underwent coronary revascularization between 2007 and 2014 (n = 4,661, 2,947 patients with ACS). The primary endpoint (major adverse cardiac or cerebrovascular events MACCE) was a composite of all-cause death, nonfatal myocardial infarction, and nonfatal stroke. The risk of MACCE with CABG or PCI was compared using multivariable adjustment and a propensity score model.
At 30-days post-revascularization, for ACS patients the odds ratio for MACCE favored CABG 0.49 (95% confidence interval CI: 0.34 to 0.71), whereas among SIHD patients MACCE was not affected by revascularization strategy (odds ratio: 1.46; 95% CI: 0.71 to 3.01; pinteraction <0.01). With a median follow-up of 3.3 years, the late (31-day to 5-year) benefit of CABG over PCI no longer varied by acuity of presentation, with a hazard ratio for MACCE in ACS patients of 0.67 (95% CI: 0.55 to 0.81) and the hazard ratio for SIHD patients of 0.55 (95% CI: 0.40 to 0.74; pinteraction = 0.28).
In diabetic patients with MV-CAD, CABG was associated with a lower rate of long-term MACCE relative to PCI for both ACS and SIHD. A well-powered randomized trial of CABG versus PCI in the ACS population is warranted because these patients have been largely excluded from prior trials.
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We report on the study of an intriguing active galaxy that was selected as a potential multiple supermassive black hole merger in the early-type host SDSS J151709.20+335324.7 (z = 0.135) from a ...complete search for double-peaked O III lines from the SDSS spectroscopic quasi-stellar object (QSO) database. Ground-based SDSS imaging reveals two blue structures on either side of the photometric center of the host galaxy, separated from each other by about 5.7 kpc. From a combination of SDSS fiber and Keck/HIRES long-slit spectroscopy, it is demonstrated that, in addition to these two features, a third distinct structure surrounds the nucleus of the host galaxy. All three structures exhibit highly ionized line emission with line ratios characteristic of Seyfert II active galactic nuclei. The analysis of spatially resolved emission-line profiles from the HIRES spectrum reveal three distinct kinematic subcomponents, one at rest and the other two moving at -350 km s{sup -1} and 500 km s{sup -1} with respect to the systemic velocity of the host galaxy. A comparison of imaging and spectral data confirm a strong association between the kinematic components and the spatial knots, which implies a highly disturbed and complex active region in this object. A comparative analysis of the broadband positions, colors, kinematics, and spectral properties of the knots in this system lead to two plausible explanations: (1) a multiple active galactic nucleus (AGN) produced due to a massive dry merger, or (2) a very powerful radio jet-driven outflow. Subsequent VLA radio imaging reveals a clear jet aligned with the emission-line gas, confirming the latter explanation. We use the broadband radio measurements to examine the impact of the jet on the interstellar medium of the host galaxy, and find that the energy in the radio lobes can heat a significant fraction of the gas to the virial temperature. Finally, we discuss tests that may help future surveys distinguish between jet-driven kinematics and true black-hole binaries. J1517+3353 is a remarkable laboratory for AGN feedback and warrants deeper follow-up study. In the Appendix, we present high-resolution radio imaging of a second AGN with double-peaked O III lines, SDSS J112939.78+605742.6, which shows a sub-arcsecond radio jet. If the double-peaked nature of the narrow lines in radio-loud AGNs are generally due to radio jet interactions, we suggest that extended radio structure should be expected in most of such systems.
Abstract
We report the results of careful astrometric measurements of the cannonball pulsar J0002+6216 carried out over 3 yr using the High Sensitivity Array. We significantly refine the proper ...motion to
μ
= 35.3 ± 0.6 mas yr
−1
and place new constraints on the distance, with the overall effect of lowering the velocity and increasing the inferred age to 47.60 ± 0.80 kyr. Although the pulsar is brought more in line with the standard natal kick distribution, this new velocity has implications for the morphology of the pulsar wind nebula that surrounds it, the density of the interstellar medium through which it travels, and the age of the supernova remnant (CTB 1) from which it originates.
Abstract
We use a sample of 54 compact symmetric objects (CSOs) to confirm that there are two unrelated CSO classes: an edge-dimmed, low-luminosity class (CSO 1), and an edge-brightened, ...high-luminosity class (CSO 2). Using blind tests, we show that CSO 2s consist of three subclasses: CSO 2.0, having prominent hot spots at the leading edges of narrow jets and/or narrow lobes; CSO 2.2, without prominent hot spots and with broad jets and/or lobes; and CSO 2.1, which exhibit mixed properties. Most CSO 2s do not evolve into larger jetted active galactic nuclei (AGN), but spend their whole life cycle as CSOs of size ≲500 pc and age ≲5000 yr. The minimum energies needed to produce the radio luminosity and structure in CSO 2s range from ∼10
−4
M
⊙
c
2
to ∼7
M
⊙
c
2
. We show that the transient nature of most CSO 2s, and their birth rate, can be explained through ignition in the tidal disruption events of stars. We also consider possibilities of tapping the spin energy of the supermassive black hole, and tapping the energy of the accretion disk. Our results demonstrate that CSOs constitute a large family of AGN in which we have thus far studied only the brightest. More comprehensive CSO studies, with higher sensitivity, resolution, and dynamic range, will revolutionize our understanding of AGN and the central engines that power them.
Narrow-band HST imaging has resolved the detailed internal structure of the 10 kpc diameter H α+N ii emission line nebulosity in NGC4696, the central galaxy in the nearby Centaurus cluster, showing ...that the dusty, molecular, filaments have a width of about 60 pc. Optical morphology and velocity measurements indicate that the filaments are dragged out by the bubbling action of the radio source as part of the active galactic nucleus feedback cycle. Using the drag force we find that the magnetic field in the filaments is in approximate pressure equipartition with the hot gas. The filamentary nature of the cold gas continues inwards, swirling around and within the Bondi accretion radius of the central black hole, revealing the magnetic nature of the gas flows in massive elliptical galaxies. HST imaging resolves the magnetic, dusty, molecular filaments at the centre of the Centaurus cluster to a swirl around and within the Bondi radius.
Abstract
For the duration of the Fermi Gamma-Ray Space Telescope's mission, approximately one-third of the point sources detected have been noted as “unassociated,” meaning that they seem to have no ...known counterpart at any other wavelength/frequency. This mysterious part of the gamma-ray sky is perhaps one of the largest unknowns in current astronomical pursuits and as such has been probed extensively by various techniques at various frequencies. Radio frequencies have been perhaps one of the most fruitful, producing a large fraction of the identified and associated active galactic nuclei and pulsars noted in each update of the point-source catalogs. Here we present a catalog of 7432 radio counterpart candidates for unassociated gamma-ray fields in the Second Data Release of the Fourth Fermi Point Source Catalog (4FGL-DR2). A description of the catalog and source types is provided followed by a discussion that demonstrates how the results of this work will aid new associations and identifications. As part of this work, we also present a first catalog derived from “quicklook” images of the Very Large Array Sky Survey.
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