The Be/X-ray Transient V0332+53: Evidence for a tilt between the orbit and the equatorial plane?

We present optical and infrared observations of BQ Cam, the optical counterpart to the Be/X-ray transient system V0332+53. BQ Cam is shown to be an O8-9Ve star, which places V0332+53 at a distance of ~7 kpc. H-alpha spectroscopy and infrared photometry are used to discuss the evolution of the circumstellar envelope. Due to the low inclination of the system, parameters are strongly constrained. We find strong evidence for a tilt of the orbital plane with respect to the circumstellar disc (pressumably on the equatorial plane). Even though the periastron distance is only ~ 10 R_*, during the present quiescent state the circumstellar disc does not extend to the distance of periastron passage. Under these conditions, X-ray emission is effectively prevented by centrifugal inhibition of accretion. The circumstellar disc is shown to be optically dense at optical and infrared wavelengths, which together with its small size, is taken as an indication of tidal truncation.Comment: 9 pages, 3 figures, uses mn.sty and epsfig Accepted for publication in MNRA

Induced fission of 240Pu

We study the fission dynamics of 240Pu within an implementation of the Density Functional Theory (DFT) extended to superfluid systems and real-time dynamics. We demonstrate the critical role played by the pairing correlations. The evolution is found to be much slower than previously expected in this fully non-adiabatic treatment of nuclear dynamics, where there are no symmetry restrictions and all collective degrees of freedom (CDOF) are allowed to participate in the dynamics.Comment: 8 pages, 4 figures, talk given at The 6th International Conference on Fission and Properties of Neutron-Rich Nuclei, Sanibel Island, Florida, November 6-2 (2016

The X-ray Transient XTE J2012+381

We present optical and infrared observations of the soft X-ray transient (SXT) XTE J2012+381 and identify the optical counterpart with a faint red star heavily blended with a brighter foreground star. The fainter star is coincident with the radio counterpart and appears to show weak H alpha emission and to have faded between observations. The RXTE/ASM lightcurve of XTE J2012+381 is unusual for an SXT in that after an extended linear decay, it settled into a plateau state for about 40 days before undergoing a weak mini-outburst. We discuss the nature of the object and suggest similarities to long orbital period SXTs.Comment: 5 pages, 7 postscript figures included, uses mn.sty. Accepted for publication in MNRA

Real time description of fission

Using the time-dependent superfluid local density approximation, the dynamics of fission is investigated in real time from just beyond the saddle to fully separated fragments. Simulations produced in this fully microscopic framework can help to assess the validity of the current approaches to fission, and to obtain estimate of fission observables. In this contribution, we concentrate on general aspects of fission dynamics.Comment: Proceedings of the "15th Varenna Conference on Nuclear Reaction Mechanisms," Varenna, Italy, June 201

Magnetoresistance in Disordered Graphene: The Role of Pseudospin and Dimensionality Effects Unraveled

We report a theoretical low-field magnetotransport study unveiling the effect of pseudospin in realistic models of weakly disordered graphene-based materials. Using an efficient Kubo computational method, and simulating the effect of charges trapped in the oxide, different magnetoconductance fingerprints are numerically obtained in system sizes as large as 0.3 micronmeter squared, containing tens of millions of carbon atoms. In two-dimensional graphene, a strong valley mixing is found to irreparably yield a positive magnetoconductance (weak localization), whereas crossovers from positive to a negative magnetoconductance (weak antilocalization) are obtained by reducing disorder strength down to the ballistic limit. In sharp contrast, graphene nanoribbons with lateral size as large as 10nm show no sign of weak antilocalization, even for very small disorder strength. Our results rationalize the emergence of a complex phase diagram of magnetoconductance fingerprints, shedding some new light on the microscopical origin of pseudospin effects.Comment: 8 pages, 5 figure

High Redshift Candidates and the Nature of Small Galaxies in the Hubble Deep Field

We present results on two related topics: 1. A discussion of high redshift candidates (z>4.5), and 2. A study of very small galaxies at intermediate redshifts, both sets being detected in the region of the northern Hubble Deep Field covered by deep NICMOS observations at 1.6 and 1.1 microns. The high redshift candidates are just those with redshift z>4.5 as given in the recent catalog of Thompson, Weymann and Storrie-Lombardi, while the ``small galaxy'' sample is defined to be those objects with isophotal area <= 0.2 squ. arcsec and with photometric redshifts 1<z<4.5. Of the 19 possible high redshift candidates listed in the Thompson et al. catalog, 11 have (nominal) photometric redshifts less than 5.0. Of these, however, only 4 are ``robust'' in the sense of yielding high redshifts when the fluxes are randomly perturbed with errors comparable to the estimated measuring error in each wave band. For the 8 other objects with nominal photometric redshifts greater than 5.0, one (WFPC2 4--473) has a published spectroscopic redshift. Of the remaining 7, 4 are robust in the sense indicated above. Two of these form a close pair (NIC 586 and NIC 107). The redshift of the object having formally the highest redshift, at 6.56 (NIC118 = WFPC2 4--601), is problematic, since F606W and F814W flux are clearly present, and the nature of this object poses a dilemma. (abridged)Comment: 44 pages, 12 figures, to appear in ApJ v591, July 10, 200