We present Very Large Array observations of twelve late M and L dwarfs in the Solar neighborhood. The observed sources were chosen to cover a wide range of physical characteristics — spectral type, rotation, age, binarity, and X-ray and Hα activity — to determine the role of these properties in the production of radio emission, and hence magnetic fields. Three of the twelve sources, TVLM 513-46...

We report on the results of a systematic study of X-ray flares from low-mass young stellar objects, using two deep exposure Chandra observations of the main region of the ρ Ophiuchi star-forming cloud. From 195 X-ray sources, including class I–III sources and some young brown dwarfs, we detected a total of 71 X-ray flares. Most of the flares have the typical profile of solar and stellar flares,...

We conducted wide-field JHKs imaging polarimetry toward NGC 2024, which is a massive star-forming region in the Orion B cloud. We found a prominent and extended polarized nebula over NGC 2024, and constrained the location of illuminating source of the nebula through the analysis of polarization vectors. A massive star, IRS 2b with a spectral type of O8 − B2, is located in the center of the symm...

Faraday rotation (RM) probes of magnetic fields in the universe are sensitive to cosmological and evolutionary effects as z increases beyond ∼1 because of the scalings of electron density and magnetic fields, and the growth in the number of expected intersections with galaxy-scale intervenors, dN/dz. In this new global analysis of an unprecedented large sample of RM’s of high latitude quasars e...

pollution of urban soils dramatically reduces life and environmental quality. the most commonpollutants are heavymetals and organic contaminants like polycyclic aromatic hydrocarbons and polychlorinatedbiphenyl. main source of these pollutants is fossil fuels which are pervasive in urban and/or industrializedareas. identifying type and intensity of the pollution is essential to prepare an effec...

Spectropolarimetry using IR wavelength of 1075 nm has been proved to be a powerful tool for directly mapping solar coronal magnetic fields including transverse component directions and line-of-sight component intensities. Solar tomography, or stereoscopy based on EUV observations, can supply 3-D information for some magnetic field lines in bright EUV loops. In a previous paper (Liu and Lin, 200...

This paper introduces the formalism which connects between rotation measure (RM) measurements for extragalactic sources and the cosmological magnetic field power spectrum. It is shown that the amplitude and shape of the cosmological magnetic field power spectrum can be constrained by using a few hundred radio sources, for which Faraday RMs are available. This constraint is of the form Brms <∼ 1...

One interpretation of the unexplained signature observed in the PVLAS experiment invokes a new axion-like particle (ALP) with a two-photon vertex, allowing for photon-ALP oscillations in the presence of magnetic fields. In the range of masses and couplings suggested by PVLAS, the same effect would lead to a peculiar dimming of high-energy photon sources. For typical parameters of the turbulent ...

In this paper we suggest a new way to identify single bright sources of UHECR on sky on top of background. We look for doublets of events at the highest energies, E > 6 × 10eV, and identify low energy tails, mainly deflected by the regular Galactic Magnetic Field (GMF). With the parameters adopted in this paper, for 68% of reconstructed sources, angular position is less than one degree from rea...

We study the evolution of electromagnetic fields in curved spacetimes and calculate the exact wave equations of the associated electric and magnetic components. Our analysis applies to a general spacetime, is fully covariant and isolates all the sources that affect the propagation of these waves. Among others, we explicitly show how the different parts of the gravitational field act as driving ...