52,616 research outputs found
On the graphical extraction of multipole mixing ratios of nuclear transitions
We propose a novel graphical method for determining the mixing ratios
{\delta} and their associated uncertainties for mixed nuclear transitions. It
incorporates the uncertainties both on both the measured and the theoretical
conversion coefficients. The accuracy of the method has been studied by
deriving the corresponding probability density function. The domains of
applicability of the method are carefully defined
NuSTAR Observations of G11.2–0.3
We present in this paper the hard X-ray view of the pulsar wind nebula in G11.2−0.3 and its central pulsar powered pulsar J1811−1925 as seen by NuSTAR. We complement the data with Chandra for a more complete picture and confirm the existence of a hard, power-law component in the shell with photon index Γ = 2.1 ± 0.1, which we attribute to synchrotron emission. Our imaging observations of the shell show a slightly smaller radius at higher energies, consistent with Chandra results, and we find shrinkage as a function of increased energy along the jet direction, indicating that the electron outflow in the PWN may be simpler than that seen in other young PWNe. Combining NuSTAR with INTEGRAL, we find that the pulsar spectrum can be fit by a power law with Γ = 1.32 ± 0.07 up to 300 keV without evidence of curvature
Propagating Waves Transverse to the Magnetic Field in a Solar Prominence
We report an unusual set of observations of waves in a large prominence
pillar which consist of pulses propagating perpendicular to the prominence
magnetic field. We observe a huge quiescent prominence with the Solar Dynamics
Observatory (SDO) Atmospheric Imaging Assembly (AIA) in EUV on 2012 October 10
and only a part of it, the pillar, which is a foot or barb of the prominence,
with the Hinode Solar Optical Telescope (SOT) (in Ca II and H\alpha lines), Sac
Peak (in H\alpha, H\beta\ and Na-D lines), THEMIS ("T\'elescope
H\'eliographique pour l' Etude du Magn\'etisme et des Instabilit\'es Solaires")
with the MTR (MulTi-Raies) spectropolarimeter (in He D_3 line). The THEMIS/MTR
data indicates that the magnetic field in the pillar is essentially horizontal
and the observations in the optical domain show a large number of horizontally
aligned features on a much smaller scale than the pillar as a whole. The data
is consistent with a model of cool prominence plasma trapped in the dips of
horizontal field lines. The SOT and Sac Peak data over the 4 hour observing
period show vertical oscillations appearing as wave pulses. These pulses, which
include a Doppler signature, move vertically, perpendicular to the field
direction, along thin quasi-vertical columns in the much broader pillar. The
pulses have a velocity of propagation of about 10 km/s, a period about 300 sec,
and a wavelength around 2000 km. We interpret these waves in terms of fast
magneto-sonic waves and discuss possible wave drivers.Comment: Accepted for publication in The Astrophysical Journa
Evidence of Particle Acceleration in the Superbubble 30 Doradus C with NuSTAR
We present evidence of diffuse, non-thermal X-ray emission from the
superbubble 30 Doradus C (30 Dor C) using hard X-ray images and spectra from
NuSTAR observations. For this analysis, we utilize data from a 200 ks targeted
observation of 30 Dor C as well as 2.8 Ms of serendipitous off-axis
observations from the monitoring of nearby SN 1987A. The complete shell of 30
Dor C is detected up to 20 keV, and the young supernova remnant MCSNR
J0536-6913 in the southeast of 30 Dor C is not detected above 8 keV.
Additionally, six point sources identified in previous Chandra and XMM-Newton
investigations have hard X-ray emission coincident with their locations. Joint
spectral fits to the NuSTAR and XMM-Newton spectra across the 30 Dor C shell
confirm the non-thermal nature of the diffuse emission. Given the best-fit
rolloff frequencies of the X-ray spectra, we find maximum electron energies of
70-110 TeV (assuming a B-field strength of 4G), suggesting 30 Dor C is
accelerating particles. Particles are either accelerated via diffusive shock
acceleration at locations where the shocks have not stalled behind the
H shell, or cosmic-rays are accelerated through repeated acceleration
of low-energy particles via turbulence and magnetohydrodynamic waves in the
bubble's interior.Comment: 14 pages, 8 figures, ApJ, in pres
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