The Tully-Fisher relation of intermediate redshift field and cluster galaxies from Subaru spectroscopy

We have carried out spectroscopic observations in 4 cluster fields using Subaru's FOCAS multi-slit spectrograph and obtained spectra for 103 bright disk field and cluster galaxies at $0.06 \le z \le 1.20$. Seventy-seven of these show emission lines, and 33 provide reasonably-secure determinations of the galaxies' rotation velocity. The rotation velocities, luminosities, colours and emission-line properties of these galaxies are used to study the possible effects of the cluster environment on the star-formation history of the galaxies. Comparing the Tully-Fisher relations of cluster and field galaxies at similar reshifts we find no measurable difference in rest-frame $B$-band luminosity at a given rotation velocity (the formal difference is $0.18\pm0.33$mag). The colours of the cluster emission line galaxies are only marginally redder in rest-frame $B-V$ (by $0.06\pm0.04$mag) than the field galaxies in our sample. Taken at face value, these results seem to indicate that bright star-forming cluster spirals are similar to their field counterparts in their star-formation properties. However, we find that the fraction of disk galaxies with absorption-line spectra (i.e., with no current star formation) is larger in clusters than in the field by a factor of $\sim3$--5. This suggests that the cluster environment has the overall effect of switching off star formation in (at least) some spiral galaxies. To interpret these observational results, we carry out simulations of the possible effects of the cluster environment on the star-formation history of disk galaxies and thus their photometric and spectroscopic properties. Finally, we evaluate the evolution of the rest-frame absolute $B$-band magnitude per unit redshift at fixed rotation velocity.Comment: 21 pages, 13 figures, accepted for publication in MNRA

Magnetostriction of a Superconductor: -Results from the Critical-State Model

In many cases, the critical-state theory can be treated as a suffi ciently accurate approximation for the modelling of the magnetic properties of superconductors. In the present work, the magnetostrictive hysteresis is computed for a quite general case of the modified Kim-Anderson model. The results obtained reproduce many features of the giant magnetostriction (butterfly-shaped curves) reported in the literature for measurements made on single-crystal samples of the high-temperature superconductor $Bi_2Sr_2CaCu_2O_8$. It is shown that addition of a contribution to the magnetostriction in the superconducting state which is of similar origin as in the normal state, offers a broader phenomenological interpretation of the complex magnetostriction hysteresis found in such heavy-fermion compounds as $UPt_3$, $URu_2Si_2$ or $UBe_{13}$.Comment: 9 LaTeX pages, 4 Postscript figures, WWW version available at http://is.dal.ca/~zkoziol/super.htm

Single grain (LRE)-Ba-Cu-O superconductors fabricated by top seeded melt growth in air

We have recently reported a practical processing method for the fabrication in air of large, single grain (LRE)-Ba-Cu-O [where LRE Nd, Sm, Eu and Gd] bulk superconductors that exhibit high Tc and high Jc. The process is based initially on the development of a new type of generic seed crystal that can promote effectively the epitaxial nucleation of any (RE)-Ba-Cu-O system and, secondly, by suppressing the formation of (LRE)/Ba solid solution in a controlled manner within large LRE-Ba-Cu-O grains processed in air. In this paper we investigate the degree of homogeneity of large grain Sm-Ba-Cu-O superconductors fabricated by this novel process. The technique offers a significant degree of freedom in terms of processing parameters and reproducibility in the growth of oriented single grains in air and yields bulk samples with significantly improved superconducting and field-trapping properties compared to those processed by conventional top seeded melt growth (TSMG)

Detection of the linear radical HC4N in IRC+10216

We report the detection of the linear radical HC4N in the C-rich envelope of IRC+10216. After HCCN, HC4N is the second member of the allenic chain family HC_(2n)N observed in space. The column density of HC4N is found to be 1.5 10**12 cm**(-2). The abundance ratio HC2N/HC4N is 9, a factor of two larger than the decrement observed for the cyanopolyynes HC$_(2n+1)N/HC_(2n+3)N. Linear HC_4N has a 3-Sigma electronic ground state and is one of the 3 low-energy isomeric forms of this molecule. We have searched for the bent and ringed HC4N isomers, but could only derive an upper limit to their column densities of about 3 10**(12) cm**(-2).Comment: Preprint of 10 page

Growth-related profiles of remanent flux in bulk melt-textured YBaCuO crystal magnetized by pulsed fields

We have studied the remanent magnetic flux distribution in bulk melt-textured YBa2Cu3O7 (YBCO) crystals after their magnetization in quasi-static and pulsed magnetic fields up to 6T. It has been shown that, provided that the magnetic pulse is sharp enough and its amplitude much exceeds the twice penetration magnetic field, the pulse magnetization technique becomes extremely sensitive to the sample inhomogeneities. Using this method with appropriate parameters of the magnetic pulse, we have particularly demonstrated that the growth of YBCO crystals in the growth sectors (GSs) responds for a macroscopic arrangement of weaks links -- they mostly appear inside of GSs, but not along the GS boundaries.Comment: 8 pages in LaTeX2e, 5 figures. Revised version, submitted to Supercond. Sci. Techno

Momentum dependence of the energy gap in the superconducting state of optimally doped Bi2(Sr,R)2CuOy (R=La and Eu)

The energy gap of optimally doped Bi2(Sr,R)2CuOy (R=La and Eu) was probed by angle resolved photoemission spectroscopy (ARPES) using a vacuum ultraviolet laser (photon energy 6.994 eV) or He I resonance line (21.218 eV) as photon source. The results show that the gap around the node at sufficiently low temperatures can be well described by a monotonic d-wave gap function for both samples and the gap of the R=La sample is larger reflecting the higher Tc. However, an abrupt deviation from the d-wave gap function and an opposite R dependence for the gap size were observed around the antinode, which represent a clear disentanglement between the antinodal pseudogap and the nodal superconducting gap.Comment: Submitted as the proceedings of LT2

Do Kepler superflare stars really include slowly-rotating Sun-like stars ? - Results using APO 3.5m telescope spectroscopic observations and Gaia-DR2 data -

We report the latest view of Kepler solar-type (G-type main-sequence) superflare stars, including recent updates with Apache Point Observatory (APO) 3.5m telescope spectroscopic observations and Gaia-DR2 data. First, we newly conducted APO3.5m spectroscopic observations of 18 superflare stars found from Kepler 1-min time cadence data. More than half (43 stars) are confirmed to be "single" stars, among 64 superflare stars in total that have been spectroscopically investigated so far in this APO3.5m and our previous Subaru/HDS observations. The measurements of $v\sin i$ (projected rotational velocity) and chromospheric lines (Ca II H\&K and Ca II 8542\AA) support the brightness variation of superflare stars is caused by the rotation of a star with large starspots. We then investigated the statistical properties of Kepler solar-type superflare stars by incorporating Gaia-DR2 stellar radius estimates. As a result, the maximum superflare energy continuously decreases as the rotation period $P_{\mathrm{rot}}$ increases. Superflares with energies $\lesssim 5\times10^{34}$ erg occur on old, slowly-rotating Sun-like stars ($P_{\mathrm{rot}}\sim$25 days) approximately once every 2000--3000 years, while young rapidly-rotating stars with $P_{\mathrm{rot}}\sim$ a few days have superflares up to $10^{36}$ erg. The maximum starspot area does not depend on the rotation period when the star is young, but as the rotation slows down, it starts to steeply decrease at $P_{\mathrm{rot}}\gtrsim$12 days for Sun-like stars. These two decreasing trends are consistent since the magnetic energy stored around starspots explains the flare energy, but other factors like spot magnetic structure should also be considered.Comment: 71 pages, 31 figures, 10 tables. Accepted for publication in The Astrophysical Journal (on March 29, 2019

Fabrication of micro-structures for optically driven micromachines using two-photon photopolymerization of UV curing resins

Two-photon photopolymerization of UV curing resins is an attractive method for the fabrication of microscopic transparent objects with size in the tens of micrometers range. We have been using this method to produce three-dimensional structures for optical micromanipulation, in an optical system based on a femtosecond laser. By carefully adjusting the laser power and the exposure time we were able to create micro-objects with well-defined 3D features and with resolution below the diffraction limit of light. We discuss the performance and capabilities of a microfabrication system, with some examples of its products.Comment: 12 pages, 10 figure