119197153
Optical light curves of RS Oph (2006) and hydrogen burning turnoff
We report a coordinated multi-band photometry of the RS Oph 2006 outburst and highlight the emission line free y-band photometry that shows a mid-plateau phase at y ~ 10.2 mag from day 40 to day 75 after the discovery followed by a sharp drop of the final decline. Such mid-plateau phases are observed in other two recurrent novae, U Sco and CI Aql, and are interpreted as a bright disk irradiated by the white dwarf. We have calculated theoretical light curves based on the optically thick wind theory and have reproduced the early decline, mid-plateau phase, and final decline. The final decline is identified with the end of steady hydrogen shell-burning, which turned out at about day 80. This turnoff date is consistent with the end of a supersoft X-ray phase observed with Swift. Our model suggests a white dwarf mass of 1.35 \pm 0.01 M_\sun, which indicates that RS Oph is a progenitor of Type Ia supernovae. We strongly recommend the y-filter observation of novae to detect both the presence of a disk and the hydrogen burning turnoff. Observational data of y magnitudes are provided here together with other multi-wavelength light curve data.
117097765
Photometric and Spectroscopic Observations of V1280 Sco
Photometries of B, V, Rc, Ic, y, J, and Ks bands and low dispersion optical spectroscopic observations of Nova V1280 Sco, started soon after the outburst, are reported. We show that V1280 Sco is an Fe II nova and it is going through the historically slowest spectroscopic evolution. The rapid decline observed in the early phase was caused by formation of a dust shell. We estimate the abundances of CNO using the absorption lines on a spectrum at pre-maximum, and find over-abundances by [C/Fe] ~ 1.4, [N/Fe] > 2.0 and [O/Fe] ~ 1.1.
119301785
Five-year optical and near-infrared observations of the extremely slow nova V1280 Scorpii ,
We present optical (B, V, R c , I c and y) and near-infrared (J, H, and K s ) photometric and spectroscopic observations of a classical nova V 1280 Scorpii for five years from 2007 to 2011. Our photometric observations show a declining event in optical bands shortly after the maximum light, which took about 250 days to recover. This event was most probably caused by dust formation. The event was accompanied by a short (∼30 days) re-brightening episode (∼2.5 mag in V), which suggests that there had been some re-ignition of the surface nuclear burning. After 2008, the y band observations show a very long plateau at around y = 10.5 for more than 1000 days until April 2011 (∼1500 days after the maximum light). The nova had taken a very long time (∼50 months) to enter the nebular phase, according to a clear detection of both [O III] 4959 and 5007 and is still continuing to generate the wind caused by H-burning. This finding suggests that historically V1280 Sco is evolving at its slowest ever measured rate. The interval from the maximum light (2007 February 16) to the beginning of the nebular phase is longer than any previously known slow novae: V723 Cas (18 months), RR Pic (10 months), or HR Del (8 months). It suggests that the mass of a white dwarf in the V1280 Sco system might be 0.6 M ⊙ or lower. The distance, based on our measurements of the expansion velocity combined with the directly measured size of the dust shell, is estimated to be 1.1 ± 0.5 kpc.
118081065
Large Lepton-flavor Mixings from E8 Kodaira Singularity: Lopsided Texture via F-theory Family Unification
We show that a special type of colliding 7-brane configuration of a codimension-two singularity realizes not only a six-dimensional spectrum with exactly the same quantum numbers as that of the three-generation E7/(SU(5) x U(1)^3) coset family unification model, but also the three sets of nonchiral singlet pairs with precisely the correct U(1) charges needed for explaining the Yukawa hierarchies and large lepton-flavor mixings in a well-known seesaw scenario.
18439436
E10 symmetry in one-dimensional supergravity
We consider dimensional reduction of the eleven-dimensional supergravity to less than four dimensions. The three-dimensional E8(+8)/SO(16) nonlinear sigma model is derived by direct dimensional reduction from eleven dimensions. In two dimensions we explicitly check that the Matzner-Misner-type SL(2, R) symmetry, together with the E8, satisfies the generating relations of E9 under the generalized Geroch compatibility (hypersurface-orthogonality) condition. We further show that an extra SL(2,R) symmetry, which is newly present upon reduction to one dimension, extends the symmetry algebra to a real form of E10. The new SL(2,R acts on certain plane wave solutions propagating at the speed of light. To show that this SL(2,R) cannot be expressed in terms of the old E9 but truly enlarges the symmetry, we compactify the final two dimensions on a two-torus and confirm that it changes the conformal structure of this two-torus.
8428441
Wound D-branes in Gepner models
We propose a new prescription of how to represent D-branes in Gepner models in more general homology classes than those in the previous constructions. The central role is played by a certain projection acting on the Recknagel–Schomerus boundary states. Consequently, the boundary states are in most cases no longer a sum of products of N=2 Ishibashi states, but nevertheless preserve spacetime supersymmetry and satisfy the Cardy condition. We demonstrate these in the (k=1)3 Gepner model in detail, and construct boundary states for D-branes wound around arbitrary rigid 1-cycles on the corresponding 2-torus. We also emphasize the necessity of some angle-dependent transformations in identifying a proper free-field realization for each brane tilted at an angle. In particular, this is essential for the Witten index to give the correct intersection numbers between the different D-branes.