114 research outputs found
VLBI Monitoring of 3C 84 (NGC 1275) in Early Phase of the 2005 Outburst
Multi-epoch Very Long Baseline Interferometry (VLBI) study of the sub-pc
scale jet of 3C 84 is presented. We carried out 14-epoch VLBI observations
during 2006-2009 with the Japanese VLBI Network (JVN) and the VLBI Exploration
of Radio Astrometry (VERA), immediately following the radio outburst that began
in 2005. We confirmed that the outburst was associated with the central ~1 pc
core, accompanying the emergence of a new component. This is striking evidence
of the recurrence of jet activity. The new component became brighter during
2008, in contrast to the constant gamma-ray emission that was observed with the
Fermi Gamma-ray Space Telescope during the same time. We found that the
projected speed of the new component is 0.23c from 2007/297 (2007 October 24)
to 2009/114 (2009 April 24). The direction of movement of this component
differs from that of the pre-existing component by ~40 degree. This is the
first measurement of kinematics of a sub-pc jet in a gamma-ray active phase.
Possible detection of jet deceleration and the jet kinematics in connection
with the gamma-ray emission is discussed.Comment: 5 pages, 3 figures. Accepted for publication in PAS
Analysis of H2O Masers in Sharpless 269 using VERA Archival data --- Effect of maser structures on astrometric accuracy
Astrometry using H2O maser sources in star forming regions is expected to be
a powerful tool to study the structures and dynamics of our Galaxy. Honma et
al. (2007) (hereafter H2007) claimed that the annual parallax of S269 is
determined within an error of 0.008 milliarcsec (mas), concluding that S269 is
located at 5.3 kpc +- 0.2 kpc from the sun, and R= 13.1 kpc. They claimed that
the rotational velocity of S269 is equal to that of the sun within a 3% error.
This small error, however, is hardly understood when taking into account the
results of other observations and theoretical studies of galactic dynamics. We
here reanalyzed the VERA archival data using the self-calibration method
(hybrid mapping), and found that clusters of maser features of S269 are
distributed in much wider area than that investigated in H2007. We confirmed
that, if we make a narrow region image without considering the presence of
multiple maser spots, and only the phase calibration is applied, we can
reproduce the same maser structures in H2007. The distribution extent of maser
spots in the feature differs 0.2 mas from east to west between our results and
H2007. Moreover, we found that change of relative positions of maser spots in
the cluster reaches 0.1 mas or larger between observational epochs. This
suggests that if one simply assumes the time-dependent, widely distributed
maser sources as a stable single point source, it could cause errors of up to
0.1 mas in the annual parallax of S269. Taking into account the internal
motions of maser spot clusters, the proper motion of S269 cannot be determined
precisely. We estimated that the peculiar motion of S269 with respect to a
Galactic circular rotation is ~20 km/s. These results imply that the observed
kinematics of maser emissions in S269 cannot give a strong constraint on
dynamics of the outer part of the Galaxy, in contrast to the claim by H2007.Comment: 33 pages, 11 figures, to be published in New Astronom
Interleukin-17 Promotes Autoimmunity by Triggering a Positive-Feedback Loop via Interleukin-6 Induction
Tensile deformation and failure behavior at room temperature of the open cell nickel and copper foams with high porosity (96%) fabricated with the slurry foaming process at Mitsubishi Materials Corporation, Japan, was studied. In-situ observation of the deformation and failure behavior was conducted with a digital microscope. Stress-strain curves were measured, in which a non-contact extensometer was employed to detect the strain of the samples accurately. Electric resistance was measured to monitor the damage evolution. Finite element stress analysis was conducted to calculate the morphological change of cells with applied strain and the stress distribution in cells. It was revealed that the deformation and failure progressed through the following four stages; stage I characterized by the elastic deformation, stage II by plastic deformation, stage III by the co-occurrence of plastic deformation and cumulative failure of struts and stage IV by the chain reaction of strut failure nearly in a limited cross-section, respectively. Also it was found that the distribution of failure strain of struts in stage III, measured from the serrations in the stress-strain curve, could be described by the Weibull distribution, with which the transition from stage II to III was identified. Also, the result of the statistical analysis suggested that the average failure strain of the struts in the foam is much higher than the strain at ultimate stress of the foam
Multifrequency VLBI Observations of the Broad Absorption Line Quasar J1020+4320: Recently Restarted Jet Activity?
This paper reports very-long-baseline interferometry observations of the
radio-loud broad absorption line (BAL) quasar J1020+4320 at 1.7, 2.3, 6.7, and
8.4 GHz using the Japanese VLBI network (JVN) and European VLBI network (EVN).
The radio morphology is compact with a size of ~10 pc. The convex radio
spectrum is stable over the last decade; an observed peak frequency of 3.2 GHz
is equivalent to 9.5 GHz in the rest frame, suggesting an age of the order of
~100 years as a radio source, according to an observed correlation between
linear size and peak frequency of compact steep spectrum (CSS) and giga-hertz
peaked spectrum (GPS) radio sources. A low-frequency radio excess suggests
relic of past jet activity. J1020+4320 may be one of the quasars with recurrent
and short-lived jet activity during a BAL-outflowing phase.Comment: 7 pages, 2 figures, 2 tables, accepted for publication in PAS
Parabolic Jets from the Spinning Black Hole in M87
The M87 jet is extensively examined by utilizing general relativistic
magnetohydrodynamic (GRMHD) simulations as well as the steady axisymmetric
force-free electrodynamic (FFE) solution. Quasi-steady funnel jets are obtained
in GRMHD simulations up to the scale of gravitational radius
() for various black hole (BH) spins. As is known, the funnel edge
is approximately determined by the following equipartitions; i) the magnetic
and rest-mass energy densities and ii) the gas and magnetic pressures. Our
numerical results give an additional factor that they follow the outermost
parabolic streamline of the FFE solution, which is anchored to the event
horizon on the equatorial plane. We also identify the matter dominated,
non-relativistic corona/wind play a dynamical role in shaping the funnel jet
into the parabolic geometry. We confirm a quantitative overlap between the
outermost parabolic streamline of the FFE jet and the edge of jet sheath in
VLBI observations at -, suggesting that the
M87 jet is likely powered by the spinning BH. Our GRMHD simulations also
indicate a lateral stratification of the bulk acceleration (i.e., the
spine-sheath structure) as well as an emergence of knotty superluminal
features. The spin characterizes the location of the jet stagnation surface
inside the funnel. We suggest that the limb-brightened feature could be
associated with the nature of the BH-driven jet, if the Doppler beaming is a
dominant factor. Our findings can be examined with (sub-)mm VLBI observations,
giving a clue for the origin of the M87 jet.Comment: 29 pages, 23 figures, accepted for publication in Ap
Parabolic Jets from the Spinning Black Hole in M87
The M87 jet is extensively examined by utilizing general relativistic magnetohydrodynamic (GRMHD) simulations, as well as the steady axisymmetric force-free electrodynamic (FFE) solution. Quasi-steady funnel jets are obtained in GRMHD simulations up to the scale of ~100 gravitational radii (r(sub g)) for various black hole (BH) spins. As is known, the funnel edge is approximately determined by the following equipartitions: (i) the magnetic and rest-mass energy densities and (ii) the gas and magnetic pressures. Our numerical results give an additional factor that they follow the outermost parabolic streamline of the FFE solution, which is anchored to the event horizon on the equatorial plane. We also show that the matter-dominated, nonrelativistic corona/wind plays a dynamical role in shaping the funnel jet into the parabolic geometry. We confirm a quantitative overlap between the outermost parabolic streamline of the FFE jet and the edge of the jet sheath in very long baseline interferometry (VLBI) observations at ~(10(exp 1)10(exp 5))r(sub g), suggesting that the M87 jet is likely powered by the spinning BH. Our GRMHD simulations also indicate a lateral stratification of the bulk acceleration (i.e., the spine-sheath structure), as well as an emergence of knotty superluminal features. The spin characterizes the location of the jet stagnation surface inside the funnel. We suggest that the limb-brightened feature could be associated with the nature of the BH-driven jet, if the Doppler beaming is a dominant factor. Our findings can be examined with (sub)millimeter VLBI observations, giving a clue for the origin of the M87 jet
Detection of intrinsic source structure at ~3 Schwarzschild radii with Millimeter-VLBI observations of SAGITTARIUS A*
We report results from very long baseline interferometric (VLBI) observations
of the supermassive black hole in the Galactic center, Sgr A*, at 1.3 mm (230
GHz). The observations were performed in 2013 March using six VLBI stations in
Hawaii, California, Arizona, and Chile. Compared to earlier observations, the
addition of the APEX telescope in Chile almost doubles the longest baseline
length in the array, provides additional {\it uv} coverage in the N-S
direction, and leads to a spatial resolution of 30 as (3
Schwarzschild radii) for Sgr A*. The source is detected even at the longest
baselines with visibility amplitudes of 4-13% of the total flux density.
We argue that such flux densities cannot result from interstellar refractive
scattering alone, but indicate the presence of compact intrinsic source
structure on scales of 3 Schwarzschild radii. The measured nonzero
closure phases rule out point-symmetric emission. We discuss our results in the
context of simple geometric models that capture the basic characteristics and
brightness distributions of disk- and jet-dominated models and show that both
can reproduce the observed data. Common to these models are the brightness
asymmetry, the orientation, and characteristic sizes, which are comparable to
the expected size of the black hole shadow. Future 1.3 mm VLBI observations
with an expanded array and better sensitivity will allow a more detailed
imaging of the horizon-scale structure and bear the potential for a deep
insight into the physical processes at the black hole boundary.Comment: 11 pages, 5 figures, accepted to Ap
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