33,757 research outputs found
The HI absorption distance of HESS J1943+213 favours its extragalactic nature
The H.E.S.S. collaboration (Abramowski et al. 2011) dicovered a new TeV
point-like source HESS J1943+213 in the Galactic plane and suggested three
possible low-energy-band counterparts: a -ray binary, a pulsar wind
nebula (PWN), or a BL Lacertae object. We measure the distance to the radio
counterpart G57.76-1.29 of HESS J1943+213. We analyze Very Large Array
observations to obtain a reliable HI absorption spectrum.The resulting distance
limit is 16 kpc. This distance strongly supports that HESS J1943+213 is
an extragalactic source, consistent with the preferred counterpart of the HESS
collaboration.Comment: 3 figures, 2 pages, A&A accepte
Hydrogen Lyman emission through the solar cycle
We present observations and results of radiance and irradiance studies
completed by SoHO-SUMER during the past solar cycle. We find that the cycle
variation in Ly-alpha irradiance as observed by e.g. UARS-SOLSTICE can not be
explained by quiet sun radiance data, and conclude that the explanation must be
related to differences in the Ly-alpha radiance of various solar features and
changes in their fractional distribution over the solar cycle. Consequently, we
studied the emission of the hydrogen Ly-alpha line in various solar features -
for the first time observed by SUMER on disk in full resolution - to
investigate the imprint of the magnetic field on line profile and radiance
distribution. We also compare quasi-simultaneous Ly-alpha and Ly-beta line
profiles. Such high-resolution observations - not hampered by geocoronal
absorption - have never been completed before.Comment: 6 pages, 4 figures, to appear in "Understanding a peculiar Solar
Minimum", eds. S Cranmer, T.Hoeksema, J. Kohl, ASPC 201
Pulsars identified from the NRAO VLA Sky Survey
We identified 97 strong pulsars from the NRAO VLA Sky Survey (NVSS) at 1.4
GHz north of Dec(J2000) >-40\degr. The total flux density, linear
polarization intensity and polarization angle (PA) of all pulsars are extracted
from the NVSS catalog. The well-calibrated PA measurement of 5 pulsars can be
used for absolute PA calibrations in other observations. Comparing the source
positions with those in the pulsar catalog, we got the first measurement of the
proper motion upper limit of PSR B0031-07, which is and .Comment: 7 pages; 3 figures; one big table; To appear in A&A Supplement
A new model for the double well potential
A new model for the double well potential is presented in the paper. In the
new potential, the exchanging rate could be easily calculated by the
perturbation method in supersymmetric quantum mechanics. It gives good results
whether the barrier is high or sallow. The new model have many merits and may
be used in the double well problem.Comment: 3pages, 3figure
Can an observer really catch up with light
Given a null geodesic with a point in
conjugate to along , there will be a variation of
which will give a time-like curve from to . This is
a well-known theory proved in the famous book\cite{2}. In the paper we prove
that the time-like curves coming from the above-mentioned variation have a
proper acceleration which approaches infinity as the time-like curve approaches
the null geodesic. This means no observer can be infinitesimally near the light
and begin at the same point with the light and finally catch the light. Only
separated from the light path finitely, does the observer can begin at the same
point with the light and finally catch the light.Comment: 6 pages, no figures, submited to Physical Review
The radio SNR G65.1+0.6 and its associated pulsar J1957+2831
New images of the radio Supernova Remnant (SNR) G65.1+0.6 are presented,
based on the 408 MHz and 1420 MHz continuum emission and the HI-line emission
data of the Canadian Galactic Plane Survey (CGPS). A large shell-like structure
seen in the 2695 MHz Effelsberg map appears to have nonthermal spectral index.
HI observations show structures associated with the SNR G65.1+0.6 in the radial
velocity range of -20 to -26 kms and suggest a distance of 9.2 kpc for the
SNR. The estimated Sedov age for G65.1+0.6 is 4 - 14 x10E4 yr. The pulsar (PSR)
J1957+2831 is possibly associated with G65.1+0.6, with consistent distance and
kinematic age estimate, but different characteristic age than the SNR. The
EGRET source 3EG J1958+2909 and gamma-ray source 2CG 065+00 are also near the
eastern edge of the SNR but do not agree in position with the pulsar and are
likely not associated with the SNR. The SNR's flux densities at 408 MHz
(8.6+-0.8 Jy), 1420 MHz (4.9+-0.5 Jy) and 2695 MHz (3.3+-0.5 Jy) have been
corrected for flux densities from compact sources within the SNR. The
integrated flux density based spectral index between 1420 MHz and 408 MHz is
0.45+-0.11 and agrees with the T-T plot spectral index of 0.34+-0.20. The
nearby SNR DA495 has a T-T plot spectral index of 0.50+-0.01.Comment: 7pages, 5 pictures and tables, will appear in A&
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