19 research outputs found
A single fast radio burst localized to a massive galaxy at cosmological distance
Fast radio bursts (FRBs) are brief radio emissions from distant astronomical sources. Some are known to repeat, but most are single bursts. Nonrepeating FRB observations have had insufficient positional accuracy to localize them to an individual host galaxy. We report the interferometric localization of the single-pulse FRB 180924 to a position 4 kiloparsecs from the center of a luminous galaxy at redshift 0.3214. The burst has not been observed to repeat. The properties of the burst and its host are markedly different from those of the only other accurately localized FRB source. The integrated electron column density along the line of sight closely matches models of the intergalactic medium, indicating that some FRBs are clean probes of the baryonic component of the cosmic web
Hydrostatic pressure, impurity position and electric and magnetic field effects on the binding energy and photo-ionization cross section of a hydrogenic donor impurity in an InAs Pöschl-Teller quantum ring
Using the variational method and the effective mass and parabolic band approximations,
the behaviour of the binding energy and photo-ionization cross section of a
hydrogenic-like donor impurity in an InAs quantum ring, with Pöschl-Teller confinement
potential along the axial direction, has been studied. In the investigation, the combined
effects of hydrostatic pressure and electric and magnetic fields applied in the direction
of growth have been taken into account. Parallel polarization of the incident radiation
and several values of the applied electric and magnetic fields, hydrostatic pressure, and
parameters of the Pöschl-Teller confinement potential were considered. The results
obtained can be summarised as follows: (1) the influence of the applied electric and
magnetic fields and the asymmetry degree of the Pöschl-Teller confinement potential on the
donor binding energy is strongly dependent on the impurity position along the growth and
radial directions of the quantum ring, (2) the binding energy is an increasing function of
hydrostatic pressure and (3) the decrease (increase) in the binding energy with the
electric and magnetic fields and parameters of the confinement potential (hydrostatic
pressure) leads to a red shift (blue shift) of the maximum of the photo-ionization cross
section spectrum of the on-centre impurity
Optical and magneto-optical properties of Fe 4âx Co x (x=1â3)
We report a systematic study of the electronic, optical, and magneto-optical
properties of the Fe4-xCox (x = 1â3) compounds using the
full-potential linearized augmented plane waves (FPLAPW) method within the
local spin density approximation (LSDA). Pure Fe (x = 0) and Co (x = 4) have
also been studied, the latter in hcp as well as bcc structure, to offer a
better comparison. A good agreement is obtained between calculated optical
conductivity spectra and experimental data. We note that the magneto-optical
properties of these compounds are found to be more akin to those of
bcc Co (which has MOKE very similar to that of bcc Fe) than to those of hcp
Co. This shows strong impact of the environment on the MOKE of these
compounds. With respect to the elemental values, the magnetic moments at Fe
sites are found to be larger in general, while those at Co sites are almost
the same. However, interestingly, despite their larger magnetic moment, the
Kerr rotation remains comparable to that of bcc Fe for most of the energy
range. The origin of Kerr spectra has been explained in terms of optical
transitions