Origin of the giant magnetic moments of Fe impurities on and in Cs films

To explore the origin of the observed giant magnetic moments ($\sim 7 \mu_B$) of Fe impurities on the surface and in the bulk of Cs films, we have performed the relativistic LSDA + U calculations using the linearized muffin-tin orbital (LMTO) band method. We have found that Fe impurities in Cs behave differently from those in noble metals or in Pd. Whereas the induced spin polarization of Cs atoms is negligible, the Fe ion itself is found to be the source of the giant magnetic moment. The 3d electrons of Fe in Cs are localized as the 4f electrons in rare-earth ions so that the orbital magnetic moment becomes as large as the spin magnetic moment. The calculated total magnetic moment of $M = 6.43 \mu_B$, which comes mainly from Fe ion, is close to the experimentally observed value.Comment: 4 pages including 3 figures and 1 table. Submitted to PR

Search for Interstellar Water in the Translucent Molecular Cloud toward HD 154368

We report an upper limit of 9 x 10^{12} cm-2 on the column density of water in the translucent cloud along the line of sight toward HD 154368. This result is based upon a search for the C-X band of water near 1240 \AA carried out using the Goddard High Resolution Spectrograph of the Hubble Space Telescope. Our observational limit on the water abundance together with detailed chemical models of translucent clouds and previous measurements of OH along the line of sight constrain the branching ratio in the dissociative recombination of H_3O+ to form water. We find at the $3\sigma$ level that no more than 30% of dissociative recombinations of H_3O+ can lead to H_2O. The observed spectrum also yielded high-resolution observations of the Mg II doublet at 1239.9 \AA and 1240.4 \AA, allowing the velocity structure of the dominant ionization state of magnesium to be studied along the line of sight. The Mg II spectrum is consistent with GHRS observations at lower spectral resolution that were obtained previously but allow an additional velocity component to be identified.Comment: Accepted by ApJ, uses aasp

First Experimental Characterization of Microwave Emission from Cosmic Ray Air Showers

We report the first direct measurement of the overall characteristics of microwave radio emission from extensive air showers. Using a trigger provided by the KASCADE-Grande air shower array, the signals of the microwave antennas of the CROME (Cosmic-Ray Observation via Microwave Emission) experiment have been read out and searched for signatures of radio emission by high-energy air showers in the GHz frequency range. Microwave signals have been detected for more than 30 showers with energies above 3*10^16 eV. The observations presented in this Letter are consistent with a mainly forward-directed and polarised emission process in the GHz frequency range. The measurements show that microwave radiation offers a new means of studying air showers at energies above 10^17 eV.Comment: Accepted for publication in PR

HI Narrow Line Absorption in Dark Clouds

We have used the Arecibo telescope to carry out an survey of 31 dark clouds in the Taurus/Perseus region for narrow absorption features in HI ($\lambda$ 21cm) and OH (1667 and 1665 MHz) emission. We detected HI narrow self--absorption (HINSA) in 77% of the clouds that we observed. HINSA and OH emission, observed simultaneously are remarkably well correlated. Spectrally, they have the same nonthermal line width and the same line centroid velocity. Spatially, they both peak at the optically--selected central position of each cloud, and both fall off toward the cloud edges. Sources with clear HINSA feature have also been observed in transitions of CO, \13co, \c18o, and CI. HINSA exhibits better correlation with molecular tracers than with CI. The line width of the absorption feature, together with analyses of the relevant radiative transfer provide upper limits to the kinetic temperature of the gas producing the HINSA. Some sources must have a temperature close to or lower than 10 K. The correlation of column densities and line widths of HINSA with those characteristics of molecular tracers suggest that a significant fraction of the atomic hydrogen is located in the cold, well--shielded portions of molecular clouds, and is mixed with the molecular gas. The average number density ratio [HI]/[\h2] is $1.5\times10^{-3}$. The inferred HI density appears consistent with but is slightly higher than the value expected in steady state equilibrium between formation of HI via cosmic ray destruction of H$_2$ and destruction via formation of H$_2$ on grain surfaces. The distribution and abundance of atomic hydrogen in molecular clouds is a critical test of dark cloud chemistry and structure, including the issues of grain surface reaction rates, PDRs, circulation, and turbulent diffusion.Comment: 40 pages, 10 figures, accepted by Ap

Feeling older and wanting to be younger

Two samples of middle-aged women were compared using a questionnaire adapted from Rossi (1980). One sample ( N = 20) consisted of women who felt older than and desired to be younger than their own age. The second sample ( N = 19) was comprised of women who felt and desired to be their own age. Statistically significant differences between the groups were that women who felt older reported more physical changes of aging, less satisfaction with their life context, and more worries than the women who felt their chronological age. Results of this study suggest that current life stress contributes to middle-aged women's perceptions of feeling older and desiring to be younger than their own age.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42987/1/10823_2004_Article_BF00116678.pd

Systematic search for VHE gamma-ray emission from X-ray bright high-frequency BL Lac objects

All but three (M87, BL Lac and 3C 279) extragalactic sources detected so far at very high energy (VHE) gamma-rays belong to the class of high-frequency peaked BL Lac (HBL) objects. This suggested to us a systematic scan of candidate sources with the MAGIC telescope, based on the compilation of X-ray blazars by Donato et al. (2001). The observations took place from December 2004 to March 2006 and cover sources on the northern sky visible under small zenith distances zd < 30 degrees at culmination. The sensitivity of the search was planned for detecting X-ray bright F(1 keV) > 2 uJy) sources emitting at least the same energy flux at 200 GeV as at 1 keV. In order to avoid strong gamma-ray attenuation close to the energy threshold, the redshift of the sources was constrained to values z<0.3. Of the fourteen sources observed, 1ES 1218+304 and 1ES 2344+514 have been detected in addition to the known bright TeV blazars Mrk 421 and Mrk 501. A marginal excess of 3.5 sigma from the position of 1ES 1011+496 was observed and has been confirmed as a source of VHE gamma-rays by a second MAGIC observation triggered by a high optical state (Albert et al. 2007). For the remaining sources, we present here the 99% confidence level upper limits on the integral flux above ~200 GeV. We characterize the sample of HBLs (including all HBLs detected at VHE so far) by looking for correlations between their multi-frequency spectral indices determined from simultaneous optical, archival X-ray, and radio luminosities, finding that the VHE emitting HBLs do not seem to constitute a unique subclass. The absorption corrected gamma-ray luminosities at 200 GeV of the HBLs are generally not higher than their X-ray luminosities at 1 keV.Comment: 15 pages, 7 figures, 5 tables, submitted to ApJ (revised version

Simultaneous multi-frequency observation of the unknown redshift blazar PG 1553+113 in March-April 2008

The blazar PG 1553+113 is a well known TeV gamma-ray emitter. In this paper, we determine its spectral energy distribution using simultaneous multi-frequency data in order to study its emission processes. An extensive campaign was carried out between March and April 2008, where optical, X-ray, high-energy (HE) gamma-ray, and very-high-energy (VHE) gamma-ray data were obtained with the KVA, Abastumani, REM, RossiXTE/ASM, AGILE and MAGIC telescopes, respectively. This is the first simultaneous broad-band (i.e., HE+VHE) gamma-ray observation, though AGILE did not detect the source. We combine data to derive source's spectral energy distribution and interpret its double peaked shape within the framework of a synchrotron self compton modelComment: 5 pages, 2 figures, publishe