New variations of Mg II emission lines of Mira AB with HST

This paper presents results from high resolution observations of the Mira AB binary system taken by the HST (Hubble Space Telescope) in the ultraviolet region through the period (1999–2004). By comparing the results using HST data with those obtained from the IUE (International Ultraviolet Explorer) observations through the period (1979–1995). we found new variations in the profiles, widths and fluxes of Mg II (k&h) emission lines. In addition to this it appears that there are another emission components at some phases in the red and blue sides of both Mg II (k&h) emission lines. These emission components may be of Mira A origin. There is a considerable shift of both Mg II (k&h) emission lines in observation taken on 2nd February 2004. The Mg II profiles extends up to more than 600 km/s, and redshifted as with IUE observations.     

New magnetic field measurements of β Cephei stars and slowly pulsating B stars

We present the results of the continuation of our magnetic survey with FORS 1 at the VLT of a sample of B‐type stars consisting of confirmed or candidate β Cephei stars and Slowly Pulsating B (hereafter SPB) stars, along with a small number of normal B‐type stars. A weak mean longitudinal magnetic field of the order of a few hundred Gauss was detected in three β Cephei stars and two stars suspected to be β Cephei stars, in five SPB stars and eight stars suspected to be SPB stars. Additionally, a longitudinal magnetic field at a level larger than 3σ has been diagnosed in two normal B‐type stars, the nitrogen‐rich early B‐type star HD 52089 and in the B5 IV star HD 153716. Roughly one third of β Cephei stars have detected magnetic fields: Out of 13 β Cephei stars studied to date with FORS 1, four stars possess weak magnetic fields, and out of the sample of six suspected β Cephei stars two show a weak magnetic field. The fraction of magnetic SPBs and candidate SPBs is found to be higher: Roughly half of the 34 SPB stars have been found to be magnetic and among the 16 candidate SPBs eight stars possess magnetic fields. In an attempt to understand why only a fraction of pulsating stars exhibit magnetic fields, we studied the position of magnetic and non‐magnetic pulsating stars in the H‐R diagram. We find that their domains in the H‐R diagram largely overlap, and no clear picture emerges as to the possible evolution of the magnetic field across the main sequence. It is possible that stronger fields tend to be found in stars with lower pulsating frequencies and smaller pulsating amplitudes. A somewhat similar trend is found if we consider a correlation between the field strength and the v sin i ‐values, i.e. stronger magnetic fields tend to be found in more slowly rotating stars (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Shock wave effects in solar cosmic ray events

Two low-energy ( 1 MeV) solar proton events which display a gradual intensity increase to a maximum near the time of an SSC, followed by an abrupt, large decrease, are interpreted in terms of a population of cosmic rays which are swept ahead of an interplanetary shock wave. A model which describes the variation with time of intensity and anisotropy at the Earth is developed using a Monte Carlo technique which traces the histories of particles released impulsively at the Sun. A good fit to each of the profiles observed at 0.6 to 0.9 MeV proton energies is obtained with a diffusion coefficient 2 × 10²⁰ cm² s^–) = 13.46 - 2.99 sin²1 and a near perfect shock reflector.Now at University of California, LASL, Los Alamos, New Mexico.     

On the application of Cramér's theorem to axisymmetric,incompressible turbulence

In the theory of homogeneous, stationary, axisymmetric, incompressible velocity turbulence there arise four scalar functions. The incompressibility condition provides two relations between these four functions.We will demonstrate here that application of Cramér's theorem imposes two additional constraints on the four functions. These constraints do not uniquely define the allowed functional form but they do provide very powerful criteria for limiting the class of functions which are permitted. In view of the growing use of velocity turbulence in kinematic dynamo theory and its importance in astrophysical situations (e.g., Earth, Sun, Galaxy) to maintain or regenerate a large scale magnetic field, we believe that the present constraints are of more than academic interest. In particular, application of the constraints to a form of velocity turbulence used by Steenbeck, Krause and Rädler when computing kinematic dynamo action, shows that their assumed turbulence is not physically realizable in nature.     

Thermal histories of IVA iron meteorites from transmission electron microscopy of the cloudy zone microstructure

Abstract— We have measured the size of the high‐Ni particles in the cloudy zone and the width of the outer taenite rim in eight low shocked and eight moderately to heavily shocked IVA irons using a transmission electron microscope (TEM). Thin sections for TEM analysis were produced by a focused ion beam instrument. Use of the TEM allowed us to avoid potential artifacts which may be introduced during specimen preparation for SEM analysis of high Ni particles <30 nm in size and to identify microchemical and microstructural changes due to the effects of shock induced reheating. No cloudy zone was observed in five of the eight moderately to highly shocked (>13 GPa) IVA irons that were examined in the TEM. Shock induced reheating has allowed for diffusion from 20 nm to 400 nm across kamacite/taenite boundaries, recrystallization of kamacite, and the formation, in Jamestown, of taenite grain boundaries. In the eleven IVA irons with cloudy zone microstructures, the size of the high‐Ni particles in the cloudy zone increases directly with increasing bulk Ni content. Our data and the inverse correlation between cooling rate and high‐Ni particle size for irons and stony‐irons show that IVA cooling rates at 350‐200 °C are inversely correlated with bulk Ni concentration and vary by a factor of about 15. This cooling rate variation is incompatible with cooling in a metallic core that was insulated with a silicate mantle, but is compatible with cooling in a metallic body of radius 150 ± 50 km. The widths of the tetrataenite regions next to the cloudy zone correlate directly with high‐Ni particle size providing another method to measure low temperature cooling rates.     

Doppler and modulation tomography of XTE J1118+480 in quiescence

We present Doppler and modulation tomography of the X-ray nova XTE J1118+480 with data obtained during quiescence using the 10-m Keck II telescope. The hotspot where the gas stream hits the accretion disc is seen in Hα, Hβ, He  i λ5876 and Ca  ii λ8662, thus verifying the presence of continued mass transfer within the system. The disc is clearly seen in Hα and Ca  ii λ8662. We image the mass-donor star in narrow absorption lines of Na  i  λλ5890, 5896, 8183, 8195  and Ca  ii λ8662, implying an origin from the secondary itself rather than the interstellar medium. We also detect deviations in the centroid of the double peak of Hα akin to those found by Zurita et al. suggesting disc eccentricity.     

An optimal method for determining the time of the minimum of the 23rd solar cycle,July 2008

The time of the minimum of the solar cycle is usually determined by the minimum of the average monthly sunspot number smoothed over 13 months, i.e., with a large time delay, not earlier than eight months after the event. A new optimal method which allows one to establish the time of the minimum of the cycle as early as four months after the event is proposed. In the new method, the indicator of the time of a cycle minimum is the time of reaching the minimum level of average monthly values of the solar constant after which four succeeding values of this constant are larger than the pre-ceding minimum level. It is shown that the minimum of the past 23rd solar cycle took place in July, and the new 24th cycle started in August 2008.     

Radiation conditions of a mission to Jupiter and Europa

Radiation conditions in Jupiter’s environment and the plasma environment in interplanetary space during a Jupiter-Europa mission are estimated. The numerical modeling results can be used when planning the mission.     

A search of a connection between the polarization of decam-type III bursts and magnetic fields in different heights of the solar atmosphere

Polarization measurements of type III bursts at 23.5 and 29.5 MHz have been compared for several years with indicators of magnetic fields in different height levels such as sunspot data, S-component characteristics, and noise storm data. By applying the Mount-Wilson and Brunner types of the related spot groups there results a positive relationship between the average degree of type III burst polarization and the magnitude or complexity of photospheric magnetic fields. For other parameters (leading spot area, peak intensity of the S-component at 9.1 cm wavelength) such a clear monotonic relation has not been found. Possibly the degree of polarization is influenced by height variations of the emitting level of the type III bursts at a fixed frequency due to variable electron densities. No connection has been detected between the type III burst polarization and noise storm fluxes which may be due to the local distance of the origin of both emissions.