Further evidence for a cosmic ray selection mechanism

A comparison has been made between the overabundance of heavy elements in the primordial cosmic radiation and the cross-section for ionization by charged particle impacts. It is found that there is evidence that this type of ionization is important for the selection of cosmic ray particles.     

A search for neutrons of solar origin using balloon borne detectors 1967–69

A series of telescopes having approximately a 30° half opening angle and responding to neutrons in the energy range 50 MeV to 350 MeV has been flown to the top of the atmosphere on balloons released from an equatorial launching site at Kampala, Uganda, between 1967 and 1969. The aim of the experiment was to attempt to detect solar neutrons during periods of enhanced solar activity. No neutrons of solar origin were detected, but an upper limit of the order of 30 neutrons m^–2 s^–1 at the Earth has been placed on the continuous solar neutron flux in the above energy range, and a limit of four photons m^–2 s^–1 has also been placed on the corresponding -ray flux above 80 MeV. Limits have likewise been placed on the total emission from various flares. For a 1B flare the values were 23 × 10⁴ neutrons m^–2 and 6 × 10⁴ photons m^–2.     

A galactic formation model based on post-big bang fragmentation

A new model of galactic formation is presented. A primeval distribution of angular momentum is derived, which rests on the postulated presence of mass flows at the early stage of the post-big bang universal expansion, when fragmentation occurs. The shape of any particular fragment and its orientation with respect to the mass flow predestine the morphology of the galaxy that will be produced in the subsequent collapse.A fragment-to-disk mapping transform allows examination of the galactic disk mass distributions that result from the postulates of the model. One class of distribution adequately describes the observed luminosity profiles of elliptical galaxies. Another class indicates the allocation of a large mass fraction to an extended disk, and the intrinsic two-sided symmetry of the model further indicates that the disk formation process will begin with the establishment of two major spiral arms.     

Observation of cosmic soft X-rays

Cosmic X-rays in the energy range between 0.210 keV were observed with polypropylene window proportional counters on board a sounding rocket. The field of view crossed the galactic plane in the Sgr region and reached galactic latitudes of 50° and –90°. A new soft X-ray source was found in the Aries-Taurus region. The soft X-ray flux from the direction of NGC 1275 was conspicuous, whereas that of Sgr region source were very weak. The distribution of the intensity of diffuse soft X-rays over the scanned region indicates the galactic emission of soft X-rays.     

Upper limit concentrations of trapped xenon in individual interplanetary dust particles from the stratosphere

Abstract— The Xe contents in 25 individual stratospheric interplanetary dust particles were measured in two different laboratories using focused laser micro‐gas extraction and (1) a conventional low‐blank magnetic sector mass spectrometer (Washington University), and (2) a resonance ionization time of flight mass spectrometer (RELAX‐University of Manchester). Data from both laboratories yielded a remarkably similar upper‐limit ¹³²Xe concentration in the IDPs (>2.7, 6.8 and 2.2 × 10^?8ccSTP/g for Washington University Run 1, Washington University Run 2 and University of Manchester analyses, respectively), which is up to a factor of five smaller than previous estimates. The upper‐limit ¹³²Xe/³⁶Ar ratio in the IDPs (¹³²Xe/³⁶Ar > ?8 × 10^?4for Run 1 and ¹³²Xe/³⁶Ar > ?19 × 10^?4for Run 2), computed using ³⁶Ar concentration data reported elsewhere is consistent with a mixture between implanted solar wind, primordial, and atmospheric noble gases. Most significantly, there is no evidence that IDPs are particularly enriched in primordial noble gases compared to chondritic meteorites, as implied by previous work.     

Organic matter from comet 81P/Wild 2, IDPs,and carbonaceous meteorites; similarities and differences

Abstract— During preliminary examination of 81P/Wild 2 particles collected by the NASA Stardust spacecraft, we analyzed seven, sulfur embedded and ultramicrotomed particles extracted from five different tracks. Sections were analyzed using a scanning transmission X‐ray microscope (SXTM) and carbon X‐ray absorption near edge structure (XANES) spectra were collected. We compared the carbon XANES spectra of these Wild 2 samples with a database of spectra on thirty‐four interplanetary dust particles (IDPs) and with several meteorites. Two of the particles analyzed are iron sulfides and there is evidence that an aliphatic compound associated with these particles can survive high temperatures. An iron sulfide from an IDP demonstrates the same phenomenon. Another, mostly carbon free containing particle radiation damaged, something we have not observed in any IDPs we have analyzed or any indigenous organic matter from the carbonaceous meteorites, Tagish Lake, Orgueil, Bells and Murchison. The carbonaceous material associated with this particle showed no mass loss during the initial analysis but chemically changed over a period of two months. The carbon XANES spectra of the other four particles varied more than spectra from IDPs and indigenous organic matter from meteorites. Comparison of the carbon XANES spectra from these particles with 1. the carbon XANES spectra from thirty‐four IDPs (<15 micron in size) and 2. the carbon XANES spectra from carbonaceous material from the Tagish Lake, Orgueil, Bells, and Murchison meteorites show that 81P/Wild 2 carbon XANES spectra are more similar to IDP carbon XANES spectra then to the carbon XANES spectra of meteorites.     

Hotspots and a clumpy disc: variability of brown dwarfs and stars in the young σ Ori cluster

The properties of accretion discs around stars and brown dwarfs in the σ Ori cluster (age 3 Myr) are studied based on near-infrared (IR) time series photometry supported by mid-IR spectral energy distributions (SEDs). We monitor ∼30 young low-mass sources over eight nights in the J and K band using the duPont telescope at Las Campanas. We find three objects showing variability with J -band amplitudes  ≥0.5 mag  ; five additional objects exhibit low-level variations. All three highly variable sources have been previously identified as highly variable; thus, we establish the long-term nature of their flux changes. The light curves contain periodic components with time-scales of  ∼0.5–8 d  , but have additional irregular variations superimposed – the characteristic behaviour for classical T Tauri stars. Based on the colour variability, we conclude that hotspots are the dominant cause of variations in two objects (#19 and #33), including one likely brown dwarf, with spot temperatures in the range of 6000–7000 K. For the third one (#2), a brown dwarf or very low-mass star, inhomogeneities at the inner edge of the disc are the likely origin of variability. Based on mid-IR data from Spitzer , we confirm that the three highly variable sources are surrounded by circum-(sub)-stellar discs. They show typical SEDs for T Tauri-like objects. Using SED models, we infer an enhanced scaleheight in the disc for the object #2, which favours the detection of disc inhomogeneities in light curves and is thus consistent with the information from variability. In the σ Ori cluster, about every fifth accreting low-mass object shows persistent high-level photometric variability. We demonstrate that estimates for fundamental parameters in such objects can be significantly improved by determining the extent and origin of the variations.     

Wavelet domain Bayesian denoising of string signal in the cosmic microwave background

An algorithm is proposed for denoising the signal induced by cosmic strings in the cosmic microwave background. A Bayesian approach is taken, based on modelling the string signal in the wavelet domain with generalized Gaussian distributions. Good performance of the algorithm is demonstrated by simulated experiments at arcminute resolution under noise conditions including primary and secondary cosmic microwave background anisotropies, as well as instrumental noise.     

High-Energy Emission from a Solar Flare in Hard X-rays and Microwaves

We investigate accelerated electron energy spectra for different sources in a large flare using simultaneous observations obtained with two instruments, the Nobeyama Radio Heliograph (NoRH) at 17 and 34 GHz, and the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) at hard X-rays. This flare is one of the few in which emission up to energies exceeding 200 keV can be imaged in hard X-rays. Furthermore, we can investigate the spectra of individual sources up to this energy. We discuss and compare the HXR and microwave spectra and morphology. Although the event overall appears to correspond to the standard scenario with magnetic reconnection under an eruptive filament, several of its features do not seem to be consistent with popular flare models. In particular we find that (1) microwave emissions might be optically thick at high frequencies despite a low peak frequency in the total flux radio spectrum, presumably due to the inhomogeneity of the emitting source; (2) magnetic fields in high-frequency radio sources might be stronger than sometimes assumed; (3) sources spread over a very large volume can show matching evolution in their hard X-ray spectra that may provide a challenge to acceleration models. Our results emphasize the importance of studies of sunspot-associated flares and total flux measurements of radio bursts in the millimeter range.