Controlled vortex formation at nanostructured superconductor/ferromagnetic junctions

Stability and transport properties of superconducting/insulating/ferromagnetic nanostructures are decisively affected by vortex formation in the superconductor. Herein, the emergence of such vortices due to finite size and geometric effects is studied using a Landau–Ginzburg approach coupled to the magnetic layer via its stray field. Numerical simulations based on the finite-element method evidence that magnetic vortices can be induced and coupled to each others upon appropriate nanostructuring of the magnetic films. These findings are of immediate relevance to transport properties of such structures

Vortex ring and helical current formation in superconductors driven by a THz‐field‐induced toroidal vector potential

Herein, the vortex dynamics in a type II superconducting torus driven by a curl-free vector potential corresponding to a toroidal moment is studied, which is triggered within picoseconds in an enclosed semiconductor by polarization-structured THz vector field pulses. Numerical simulations of the time-dependent Ginzburg–Landau equation in the presence of the toroidal vector potential evidence the formation of vortex ring structures that depend on the toroidal moment strength with a behavior resembling the Little–Parks effect. Applying in addition a static external magnetic flux density, the induced textures in the superconducting phase can be stabilized and steered to form stripe domains with corresponding helical supercurrent density

Supercurrent induced by chiral coupling in multiferroic/superconductor nanostructures

We study the transport and the superconducting dynamics in a layer of type II superconductor (SC) with a normal top layer that hosts a helical magnetic ordering that gives rise to spin-current-driven ferroelectric polarization. Proximity effects akin to this heterostructure result in an anisotropic supercurrent transport and modify the dynamic properties of vortices in the SC. The vortices can be acted upon and controlled by electric gating or other means that couple to the spin ordering in the top layer, which, in turn, alter the superconducting/helical magnet coupling characteristics. We demonstrate, using the time dependent Ginzburg–Landau approach, how the spin helicity of the top layer can be utilized for pinning and guiding the vortices in the superconducting layer

Tracking Advanced Planetary Systems (TAPAS) with HARPS-N. V.: A Massive Jupiter orbiting the very low metallicity giant star BD+03 2562 and a possible planet around HD~103485

We present two evolved stars from the TAPAS (Tracking Advanced PlAnetary Systems) with HARPS-N project devoted to RV precision measurements of identified candidates within the PennState - Torun Centre for Astronomy Planet Search. Evolved stars with planets are crucial to understand the dependency of the planet formation mechanism on the mass and metallicity of the parent star and to study star-planet interactions. The paper is based on precise radial velocity (RV) measurements, for HD 103485 we collected 57 epochs over 3317 days with the Hobby-Eberly Telescope and its High Resolution Spectrograph and 18 ultra-precise HARPS-N data over 919 days. For BD+03 2562 we collected 46 epochs of HET data over 3380 days and 19 epochs of HARPS-N data over 919 days. We present the analysis of the data and the search for correlations between the RV signal and stellar activity, stellar rotation and photometric variability. Based on the available data, we interpret the RV variations measured in both stars as Keplerian motion. Both stars have masses close to Solar (1.11 and 1.14), very low metallicities ([Fe/H]=-0.50 and -0.71), and, both have Jupiter planetary mass companions (m sin i=7 and 6.4 Mj), in close to terrestrial orbits (1.4 and 1.3~au), with moderate eccentricities (e=0.34 and 0.2). However, we cannot totally exclude that the signal in the case of HD~103485 is due to rotational modulation of active regions. Based on the current data, we conclude that BD+03 2562 has a bona fide planetary companion while for HD 103485 we cannot totally exclude that the best explanation for the RV signal modulations is not the existence of a planet but stellar activity. If, the interpretation remains that both stars have planetary companions they represent systems orbiting very evolved stars with very low metallicities, a challenge to the conditions required for the formation of massive giant gas planets.Comment: Acepted A&A 12 pages, 11 figure

A Planetary Mass Companion to the K0 Giant HD 17092

We report the discovery of a substellar-mass companion to the K0-giant HD 17092 with the Hobby-Eberly Telescope. In the absence of any correlation of the observed 360-day periodicity with the standard indicators of stellar activity, the observed radial velocity variations are most plausibly explained in terms of a Keplerian motion of a planetary-mass body around the star. With the estimated stellar mass of 2.3Msun, the minimum mass of the planet is 4.6MJ. The planet's orbit is characterized by a mild eccentricity of e=0.17 and a semi-major axis of 1.3 AU. This is the tenth published detection of a planetary companion around a red giant star. Such discoveries add to our understanding of planet formation around intermediate-mass stars and they provide dynamical information on the evolution of planetary systems around post-main sequence stars.Comment: 13 pages, 3 figures, 2 tables. Submitted to Ap

Between the Literary and the Visual: Inter-Artistic Approaches to African-American Art History

A stubborn truism vexes African-American art history: the canon of black American literature is viewed as more established and robust than that of black American visual arts. This misconception has more to do with conventional disciplinary divisions, than it does with either the quantity or quality of black visual expression. Segregating the literary from the visual --and assigning these to English and Art History departments, respectively--has obscured the originally inter-artistic nature of much black cultural expression as well as the terms of its early reception and critique. African-American artists have repeatedly worked in black literary contexts--from Aaron Douglas\u27s illustrations for Alain Locke\u27s The New Negro to Glenn Ligon\u27s painted excerpts from Ralph Ellison and Richard Pryor. At the same time, many (nonblack) literary critics have been enthusiastic interpreters of black visual arts. Theater critic and novelist Carl Van Vechten promoted the painters of the Harlem Renaissance; Sidney Hirsch, one of Vanderbilt University\u27s influential literary modernists, discovered black folk sculptor William Edmondson; and French poststructuralist Roland Barthes famously used a photograph by James Van Der Zee to explain his concept of the photographic punctum. This panel seeks papers that take stock of this prodigious overlap between the literary and the visual arts. Participants are invited to address how literature and literary criticism may productively inform African-American art history, to recount the specific historical circumstances that compel this approach, and to consider broadly how attention to inter-artistic histories might helpfully reform both approaches to and canons of black cultural expression

UVSat: a concept of an ultraviolet/optical photometric satellite

Time-series photometry from space in the ultraviolet can be presently done with only a few platforms, none of which is able to provide wide-field long-term high-cadence photometry. We present a concept of UVSat, a twin space telescope which will be capable to perform this kind of photometry, filling an observational niche. The satellite will host two telescopes, one for observations in the ultraviolet, the other for observations in the optical band. We also briefly show what science can be done with UVSat.Comment: 6 pages, 2 figures, accepted for publication in the Proceedings of the PAS (Proc. of the 2nd BRITE Science conference, Innsbruck