The ASCA X-ray spectrum of the powerful radio galaxy 3C109

We report the results from an ASCA X-ray observation of the powerful Broad Line Radio Galaxy, 3C109. The ASCA spectra confirm our earlier ROSAT detection of intrinsic X-ray absorption associated with the source. The absorbing material obscures a central engine of quasar-like luminosity. The luminosity is variable, having dropped by a factor of two since the ROSAT observations 4 years before. The ASCA data also provide evidence for a broad iron emission line from the source, with an intrinsic FWHM of ~ 120,000 km/s. Interpreting the line as fluorescent emission from the inner parts of an accretion disk, we can constrain the inclination of the disk to be $> 35$ degree, and the inner radius of the disk to be $< 70$ Schwarzschild radii. Our results support unified schemes for active galaxies, and demonstrate a remarkable similarity between the X-ray properties of this powerful radio source, and those of lower luminosity, Seyfert 1 galaxies.Comment: MNRAS in press. 7 pages, 5 figures in MNRAS LaTex styl

Orbital Characteristics of the Subdwarf-B and F V Star Binary EC~20117-4014(=V4640 Sgr)

Among the competing evolution theories for subdwarf-B (sdB) stars is the binary evolution scenario. EC~20117-4014 (=V4640~Sgr) is a spectroscopic binary system consisting of a pulsating sdB star and a late F main-sequence companion (O'Donoghue et al. 1997), however the period and the orbit semi-major axes have not been precisely determined. This paper presents orbital characteristics of the EC 20117-4014 binary system using 20 years of photometric data. Periodic Observed minus Calculated (O-C) variations were detected in the two highest amplitude pulsations identified in the EC 20117-4014 power spectrum, indicating the binary system's precise orbital period (P = 792.3 days) and the light-travel time amplitude (A = 468.9 s). This binary shows no significant orbital eccentricity and the upper limit of the eccentricity is 0.025 (using 3 $\sigma$ as an upper limit). This upper limit of the eccentricity is the lowest among all wide sdB binaries with known orbital parameters. This analysis indicated that the sdB is likely to have lost its hydrogen envelope through stable Roche lobe overflow, thus supporting hypotheses for the origin of sdB stars. In addition to those results, the underlying pulsation period change obtained from the photometric data was $\dot{P}$ = 5.4 ($\pm$0.7) $\times$ $10^{-14}$ d d$^{-1}$, which shows that the sdB is just before the end of the core helium-burning phase

Interfacial mechanism in the anomalous Hall effect of Co/Bi2_2O3_3 bilayers

Oxide interfaces are a source of spin-orbit coupling which can lead to novel spin-to-charge conversion effects. In this work the contribution of the Bi$_2$O$_3$ interface to the anomalous Hall effect of Co is experimentally studied in Co/Bi$_2$O$_3$ bilayers. We evidence a variation of 40% in the AHE of Co when a Bi$_2$O$_3$ capping layer is added to the ferromagnet. This strong variation is attributed to an additional source of asymmetric transport in Co/Bi$_2$O$_3$ bilayers that originates from the Co/Bi$_2$O$_3$ interface and contributes to the skew scattering.Comment: 7 pages, 4 figure

Electron-phonon interaction in transition metal diborides TB_2 (T=Zr, Nb, Ta) studied by point-contact spectroscopy

The electron-phonon interaction (EPI) in transition metal diborides TB_2 (T=Zr, Nb, Ta) is investigated by point-contact (PC) spectroscopy. The PC EPI functions were recovered and the EPI parameters lambda<0.1 were estimated for all three compounds. Common and distinctive features between the EPI functions for those diborides are discussed also in connection with the superconductivity in MgB_2.Comment: V2: minor changes, Ref.[21] added, publ. in PR

RE J2248-511 - Not all variable, ultrasoft, X-ray AGN have narrow Balmer lines

We present ASCA data on RE J2248-511, extending existing optical and soft X-ray coverage to 10 keV, and monitoring the soft component. These data show that, despite a very strong ultrasoft X-ray excess below 0.3 keV and a soft 0.3--2 keV spectral index in earlier ROSAT data, the hard X-ray spectrum (alpha~ -0.8; 0.6-10 keV) is typical of type 1 AGN, and the soft component has since disappeared. Optical data taken at two different epochs show that the big blue bump is also highly variable. The strength of the ultrasoft X-ray component and the extreme variability in RE J2248-511 are reminiscent of the behaviour observed in many narrow line Seyfert 1s (NLS1s). However, the high energy end of the ROSAT spectrum, the ASCA spectrum and the Balmer line full widths at half maximum of ~3000 km/s in RE J2248-511, are typical of normal Seyfert 1 AGN. The change in the soft X-ray spectrum as observed in the ROSAT and ASCA data is consistent with the behaviour of Galactic Black Hole Candidates (GBHCs) as they move from a high to a low state, ie. a fall in the ultrasoft component and a hardening of the X-ray continuum. This GBHC analogy has also been proposed for NLS1s. Alternatively, the variability may be caused by opacity changes in a hot, optically-thin corona which surrounds a cold, dense accretion disc; this was first suggested by Guainazzi et al. for 1H0419-577, an object which shows remarkably similar properties to RE J2248-511.Comment: 10 pages, 4 figures. Accepted for Monthly Notices of RA

Optical detection of spin transport in non-magnetic metals

We determine the dynamic magnetization induced in non-magnetic metal wedges composed of silver, copper and platinum by means of Brillouin light scattering (BLS) microscopy. The magnetization is transferred from a ferromagnetic Ni80Fe20 layer to the metal wedge via the spin pumping effect. The spin pumping efficiency can be controlled by adding an insulating but transparent interlayer between the magnetic and non-magnetic layer. By comparing the experimental results to a dynamical macroscopic spin-transport model we determine the transverse relaxation time of the pumped spin current which is much smaller than the longitudinal relaxation time

The Optical Polarization and Warm Absorber in IRAS 17020+4544

We report the detection of ionized absorption in the ASCA spectrum of the narrow-line Seyfert 1 galaxy IRAS 17020+4544. Subsequent optical spectropolarimetry revealed high polarization increasing from 3% in the red to 5% in the blue, indicating electron or dust scattering as a likely origin. The broad emission line H$\alpha$ is somewhat less polarized than the continuum, supporting a location of the polarizing material within the AGN. The Balmer line decrement and reddened optical spectrum support the presence of a dusty warm absorber in this object. We compared the broad band optical polarization and ionized X-ray absorption of a collection of Seyfert 1 and 1.5 galaxies, excluding classes of objects that are likely to have significant neutral X-ray absorption. Warm absorber objects are generally more likely to have high optical polarization than objects with no detected ionized absorption. This result lends additional support to the idea that the warm absorber is associated with dust and implies either that dust transmission is responsible for at least part of the polarization or that the polarization is revealed because of the dimming of the optical spectrum. Spectropolarimetry of Seyfert 1s generally locates the scattering material inside the narrow-line region and often close to or within the broad line region, consistent with estimates of the location of the dusty warm absorber.Comment: 11 pages using (AASTeX) aaspp4.sty and 3 Postscript figures. Accepted for publication in Astrophysical Journal Letter

Tuning the spin Hall effect of Pt from the moderately dirty to the superclean regime

We systematically measure and analyze the spin diffusion length and the spin Hall effect in Pt with a wide range of conductivities using the spin absorption method in lateral spin valve devices. We observe a linear relation between the spin diffusion length and the conductivity, evidencing that the spin relaxation in Pt is governed by the Elliott-Yafet mechanism. We find a single intrinsic spin Hall conductivity ($\sigma_{SH}^{int}=1600\pm150\: \Omega^{-1}cm^{-1}$) for Pt in the full range studied which is in good agreement with theory. For the first time we have obtained the crossover between the moderately dirty and the superclean scaling regimes of the spin Hall effect by tuning the conductivity. This is equivalent to that obtained for the anomalous Hall effect. Our results explain the spread of the spin Hall angle values in the literature and find a route to maximize this important parameter.Comment: 11 pages, 4 figure

Occultation Mapping of the Central Engine in the Active Galaxy MCG -6-30-15

The colossal power output of active galactic nuclei (AGN) is believed to be fueled by the accretion of matter onto a supermassive black hole. This central accreting region of AGN has hitherto been spatially unresolved and its structure therefore unknown. Here we propose that a previously reported `deep minimum' in the X-ray intensity of the AGN MCG-6-30-15, was due to a unique X-ray occultation event and that it probes structure of the central engine on scales < 1e14 cm, or 1.4e-7 arcseconds. The data are consistent with a bright central source surrounded by a less intense ring, which we identify with the inner edge of an accretion disk. These may be the first direct measurements of the spatial structure and geometry of the accreting black-hole system in an active galaxy.If the ring of X-ray emission is identified with the inner edge of an accretion disk, upper limits on the BH mass can be derived. Our occultation interpretation is controversial in the sense that X-ray variability in AGNs is normally attributed to intrinsic physical changes in the X-ray emission region, such as disk or coronal instabilities.Comment: 15 pages, 2 Figures. Latex with separate postscript figure files. Accepted for publication in ApJ Letter