1,782 research outputs found
Seyfert galaxies with Swift: giant flares, rapid drops, and other surprises
Swift has initiated a new era of understanding the extremes of active
galactic nuclei (AGN) variability, their drivers and underlying physics. This
is based on its rapid response, high sensitivity, good spatial resolution, and
its ability to collect simultaneously X--ray-to-optical SEDs. Here, we present
results from our recent monitoring campaigns with Swift of highly variable AGN,
including outbursts, deep low states, and unusual long-term trends in several
Seyfert galaxies including Mrk 335, WPVS007, and RXJ2314.9+2243. We also report
detection of a new X-ray and optical outburst of IC 3599 and our Swift
follow-ups. IC 3599 was previously known as one of the AGN with the
highest-amplitude outbursts. We briefly discuss implications of this second
outburst of IC 3599 for emission scenarios including accretion-disk
variability, repeat tidal disruption events, and the presence of a binary
supermassive black hole.Comment: to appear in "Swift: 10 years of discovery", Proceedings of Scienc
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Somatosensory Perception of Running Shoe Mass may be influenced by Extended Wearing Time or Inclusion of a Personal Reference Shoe, Depending on Testing Method
International Journal of Exercise Science 13(6): 342-357, 2020. Consumers may purchase running shoes on the basis of their masses, yet little is known about shoe mass perceptual abilities. In this multi-part experiment, four groups of twenty-five young adult males (total n= 100) were challenged to gauge the relative masses of five unfamiliar running shoes. The four groups differed by the length of time they were given to wear the shoes (up to 1 minute versus 5 minutes) and whether or not they were able to use their own personal running shoes as a reference. After wearing each individual pair of shoes, participants provided perceived comfort and heaviness rankings using visual analogue scales (VAS). After wearing all five pairs of unfamiliar shoes, participants gave a verbal ranking of relative shoe mass. Participants also hefted the shoes with their hands and positioned them in order of relative mass. Extended wearing time improved overall verbal ranking accuracy, but did not improve mass perception accuracy as determined by comparing VAS heaviness rankings to actual shoe masses. Conversely, use of a personal reference shoe improved mass perception accuracy as determined by comparing VAS heaviness rankings to actual shoe masses, but did not improve overall verbal ranking accuracy. Hand perceptual scores were similar across the four groups, likely due to a ceiling effect. VAS comfort scores were unrelated to shoe masses. The results suggest that wearing time and reference shoes may influence mass perception by the lower limb in a context-specific manner
Knee joint neuromuscular activation performance during muscle damage and superimposed fatigue
This study examined the concurrent effects of exercise-induced muscle damage and superimposed acute fatigue on the neuromuscular activation performance of the knee flexors of nine males (age: 26.7 ± 6.1yrs; height 1.81 ± 0.05m; body mass 81.2 ± 11.7kg [mean ± SD]). Measures were obtained during three experimental conditions: (i) FAT-EEVID, involving acute fatiguing exercise performed on each assessment occasion plus a single episode of eccentric exercise performed on the first occasion and after the fatigue trial; (ii) FAT, involving the fatiguing exercise only and; (iii) CON consisting of no exercise. Assessments were performed prior to (pre) and at lh, 24h, 48h, 72h, and 168h relative to the eccentric exercise. Repeated-measures ANOVAs showed that muscle damage within the FAT-EEVID condition elicited reductions of up to 38%, 24%) and 65%> in volitional peak force, electromechanical delay and rate of force development compared to baseline and controls, respectively (F[io, 80] = 2.3 to 4.6; p to 30.7%>) following acute fatigue (Fp; i6] = 4.3 to 9.1; p ; Fp, iq = 3.9; p <0.05). The safeguarding of evoked muscle activation capability despite compromised volitional performance might reveal aspects of capabilities for emergency and protective responses during episodes of fatigue and antecedent muscle damaging exercise
Characterization of AGN from the XMM–Newton Slew Survey
We present optical spectroscopy of candidate active galactic nuclei (AGN) pinpointed by a Swift follow-up campaign on unidentified transients in the XMM-Newton Slew Survey, increasing the completeness of the identifications of AGN in the Survey. Our Swift follow-up campaign identified 17 X-ray Telescope-detected candidate AGN, of which 9 were selected for optical follow-up and a further two were confirmed as AGN elsewhere. Using data obtained at the William Herschel Telescope, Very Large Telescope and New Technology Telescope, we find AGN features in seven of the candidates. We classify six as Seyfert types 1.0-1.5, with broad-line region velocities spanning 2000-12000 km s-1, and identify one as a possible type II AGN, consistent with the lack of a soft band X-ray detection in the Slew Survey. The virial black hole mass estimates for the sample lie between 1 × 108 and 3 × 109 M☉, with one source likely emitting close to its Eddington rate, LBol/LEdd ~ 0.9. We find a wide redshift range 0.08 < z < 0.9 for the nine now confirmed AGN drawn from the unidentified Slew Survey sample. One source remaining unclassified shows outbursts rarely seen before in AGN. We conclude that AGN discovered in this way are consistent with the largely non-varying, Slew-selected, known AGN population. We also find parallels with XMM-Newton Bright Serendipitous Survey AGN selected from pointed observations, and postulate that shallow X-ray surveys select AGN drawn from the same populations that have been characterized in deeper X-ray-selected samples
Swift follow-up of unidentified X-ray sources in the XMM-Newton Slew Survey
We present deep Swift follow-up observations of a sample of 94 unidentified
X-ray sources from the XMM-Newton Slew Survey. The X-ray Telescope on-board
Swift detected 29% of the sample sources; the flux limits for undetected
sources suggests the bulk of the Slew Survey sources are drawn from one or more
transient populations. We report revised X-ray positions for the XRT-detected
sources, with typical uncertainties of 2.9", reducing the number of catalogued
optical matches to just a single source in most cases. We characterise the
sources detected by Swift through their X-ray spectra and variability and via
UVOT photometry and catalogued nIR, optical and radio observations. Six sources
can be associated with known objects and 8 may be associated with unidentified
ROSAT sources within the 3-sigma error radii of our revised X-ray positions. We
find 10 of the 30 XRT-detected sources are clearly stellar in nature, including
one periodic variable star and 2 high proper motion stars. For 11 sources we
propose an AGN classification, among which 4 are detected with BAT and 3 have
redshifts spanning z = 0.2 - 0.9 obtained from the literature or from optical
spectroscopy presented here. The 67 Slew Survey sources we do not detect with
Swift are studied via their characteristics in the Slew Survey and by
comparison with the XRT and BAT detected population. We suggest that these are
mostly if not all extragalactic, though unlikely to be highly absorbed sources
in the X-rays such as Compton thick AGN. A large number of these are highly
variable soft X-ray sources. A small fraction of mainly hard-band detections
may be spurious. This follow-up programme brings us a step further to
completing the identifications of a substantial sample of XMM-Newton Slew
Survey sources, important for understanding the nature of the transient sky and
allowing flux-limited samples to be constructed.Comment: 19 pages, 7 figures. Accepted for publication in MNRA
Sub-arcsecond radio and optical observations of the likely counterpart to the gamma-ray source 2FGL J2056.7+4939
We have searched and reviewed all multi- wavelength data available for the
region towards the gamma-ray source 2FGL J2056.7+4939 in order to con- strain
its possible counterpart at lower energies. As a result, only a point-like
optical/infrared source with flat-spectrum radio emission is found to be
consistent with all X-ray and gamma-ray error circles. Its struc- ture is
marginally resolved at radio wavelengths at the sub-arcsecond level. An
extragalactic scenario appears to be the most likely interpretation for this
object.Comment: 5 pages, 3 figures, 1 tabl
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