Observed and Physical Properties of Core-Collapse Supernovae

I use photometry and spectroscopy data for 24 Type II plateau supernovae to examine their observed and physical properties. This dataset shows that these objects encompass a wide range of ~5 mag in their plateau luminosities, their expansion velocities vary by x5, and the nickel masses produced in these explosions go from 0.0016 to 0.26 Mo. From a subset of 16 objects I find that the explosion energies vary between 0.6x and 5.5x10^51 ergs, the ejected masses encompass the range 14-56 Mo, and the progenitors' radii go from 80 to 600 Ro. Despite this great diversity several regularities emerge, which reveal that there is a continuum in the properties of these objects from the faint, low-energy, nickel-poor SNe 1997D and 1999br, to the bright, high-energy, nickel-rich SN 1992am. This study provides evidence that more massive progenitors produce more energetic explosions, thus suggesting that the outcome of the core collapse is somewhat determined by the envelope mass. I find also that supernovae with greater energies produce more nickel. Similar relationships appear to hold for Type Ib/c supernovae, which suggests that both Type II and Type Ib/c supernovae share the same core physics. When the whole sample of core collapse objects is considered, there is a continous distribution of energies below 8x10^51 ergs. Far above in energy scale and nickel production lies the extreme hypernova 1998bw, the only supernova firmly associated to a GRB.Comment: 25 pages, 7 figures, accepted for Part 1 of Astrophysical Journa

The Reddening-Free Decline Rate Versus Luminosity Relationship for Type Ia Supernovae

We develop a method for estimating the host galaxy dust extinction for type Ia supernovae based on an observational coincidence first noted by Lira (1995), who found that the B-V evolution during the period from 30-90 days after V maximum is remarkably similar for all events, regardless of light curve shape. This fact is used to calibrate the dependence of the B(max)-V(max) and V(max)-I(max) colors on the light curve decline rate parameter delta-m15, which can, in turn, be used to separately estimate the host galaxy extinction. Using these methods to eliminate the effects of reddening, we reexamine the functional form of the decline rate versus luminosity relationship and provide an updated estimate of the Hubble constant of Ho = 63.3 +- 2.2(internal) +- 3.5(external) km/s/Mpc.Comment: 32 pages, 10 figures, AJ 1999 in pres

Structural, electronic, and magneto-optical properties of YVO3_3

Optical and magneto-optical properties of YVO$_3$ single crystal were studied in FIR, visible, and UV regions. Two structural phase transitions at 75 K and 200 K were observed and established to be of the first and second order, respectively. The lattice has an orthorhombic $Pbnm$ symmetry both above 200 K as well as below 75 K, and is found to be dimerized monoclinic $Pb11$ in between. We identify YVO$_3$ as a Mott-Hubbard insulator with the optical gap of 1.6 eV. The electronic excitations in the visible spectrum are determined by three $d$-bands at 1.8, 2.4, and 3.3 eV, followed by the charge-transfer transitions at about 4 eV. The observed structure is in good agreement with LSDA+$U$ band structure calculations. By using ligand field considerations, we assigned these bands to the transitions to the $^4A_{2g}$, $^2E_{g} + ^2T_{1g}$, and $^2T_{2g}$ states. The strong temperature dependence of these bands is in agreement with the formation of orbital order. Despite the small net magnetic moment of 0.01 $\mu_B$ per vanadium, the Kerr effect of the order of $0.01^\circ$ was observed for all three $d$-bands in the magnetically ordered phase $T_{\text{N\'eel}}<116 K$. A surprisingly strong enhancement of the Kerr effect was found below 75 K, reaching a maximum of $0.1^\circ$. The effect is ascribed to the non-vanishing net orbital magnetic moment.Comment: Submitted to Phys. Rev.

SiFTO: An Empirical Method for Fitting SNe Ia Light Curves

We present SiFTO, a new empirical method for modeling type Ia supernovae (SNe Ia) light curves by manipulating a spectral template. We make use of high-redshift SN observations when training the model, allowing us to extend it bluer than rest frame U. This increases the utility of our high-redshift SN observations by allowing us to use more of the available data. We find that when the shape of the light curve is described using a stretch prescription, applying the same stretch at all wavelengths is not an adequate description. SiFTO therefore uses a generalization of stretch which applies different stretch factors as a function of both the wavelength of the observed filter and the stretch in the rest-frame B band. We compare SiFTO to other published light-curve models by applying them to the same set of SN photometry, and demonstrate that SiFTO and SALT2 perform better than the alternatives when judged by the scatter around the best fit luminosity distance relationship. We further demonstrate that when SiFTO and SALT2 are trained on the same data set the cosmological results agree.Comment: Modified to better match published version in Ap

Metamodelling in the information field

The article studies metamodelling in the information field. Specifics of metamodelling are described. Three basic interpretations of metamodelling are shown. The features of metamodelling in information technologies and information field are presented. A functional difference between the information space and the information field is specified. The article studies metarelations in the information field. Three information situations characterizing metarelations are considered: sequence, transformation, and generalization. The differences in metarelations between an object and a metamodel and between a model and a metamodel are described. The article shows the relation scheme in the system "object – model – metamodel". The scheme of metatheory formation is presented. The principles of metamodelling in the information field are revealed. The article proves that a metamodel in the information field is a model of information construction. A new concept of information metamodelling is introduced

Transverse optical plasmons in layered superconductors

We discuss the possible existance of transverse optical plasma modes in superlattices consisting of Josephson coupled superconducting layers. These modes appear as resonances in the current-current correlation function, as opposed to the usual plasmons which are poles in the density-density channel. We consider both bilayer superlattices, and single layer lattices with a spread of interlayer Josephson couplings. We show that our model is in quantitative agreement with the recent experimental observation by a number of groups of a peak at the Josephson plasma frequency in the optical conductivity of La$_{1.85}$Sr$_{0.15}$CuO$_4$Comment: Proceedings of LT21, in press, 4 pages, Latex with LTpaper.sty and epsfig.sty, 2 postscript figure

Theory of c-axis Josephson tunneling in d-wave superconductors

The temperature and angular dependence of the c-axis Josephson current and the superfluid density in layered d-wave superconductors are studied within the framework of an extended Ambegaokar-Baratoff formalism. In particular, the effects of angle-dependent tunneling matrix elements and Andreev scattering at grain boundaries are taken into account. These lead to strong corrections of the low-temperature behavior of the plasma frequency and the Josephson current. Recent c-axis measurements on the cuprate high-temperature superconductors HgBa_2CaCu_{1+\delta} and Bi_2Sr_2CaCu_2O_{8+\delta} can therefore be interpreted to be consistent with a d-wave order parameter.Comment: Revtex, 4 pages with 4 eps figures, to appear in PRB R

Formation of Millisecond Pulsars from Accretion Induced Collapse and Constraints on Pulsar Gamma Ray Burst Models

We study accretion induced collapse of magnetized white dwarfs as an origin of millisecond pulsars. We apply magnetized accretion disk models to the pre-collapse accreting magnetic white dwarfs and calculate the white dwarf spin evolution. If the pulsar magnetic field results solely from the flux-frozen fossil white dwarf field, a typical millisecond pulsar is born with a field strength $\sim 10^{11}-10^{12}G$. The uncertainty in the field strength is mainly due to the uncertain physical parameters of the magnetized accretion disk models. A simple correlation between the pulsar spin $\Omega_*$ and the magnetic field $B_*$, $(\Omega_*/10^4s^{-1})\sim (B_{*}/10^{11}G)^{-4/5}$, is derived for a typical accretion rate \sim 5\times 10^{-8}M_{\sun}/yr. This correlation remains valid for a wide pre-collapse physical conditions unless the white dwarf spin and the binary orbit are synchronized prior to accretion induced collapse. We critically examine the possibility of spin-orbit synchronization in close binary systems. Using idealized homogeneous ellipsoid models, we compute the electromagnetic and gravitational wave emission from the millisecond pulsars and find that electromagnetic dipole emission remains nearly constant while millisecond pulsars may spin up rather than spin down as a result of gravitational wave emission. We also derive the physical conditions under which electromagnetic emission from millisecond pulsars formed by accretion induced collapse can be a source of cosmological gamma-ray bursts. We find that relativistic beaming of gamma-ray emission and precession of gamma-ray emitting jets are required unless the dipole magnetic field strengths are $>10^{15}$G; such strong dipole fields are in excess of those allowed from the accretion induced collapse formation process except in spin-orbit synchronization.Comment: 36 pages, AASLATEX, 4 ps figures, Ap

Massive stars exploding in a He-rich circumstellar medium. IV. Transitional Type Ibn Supernovae

We present ultraviolet, optical and near-infrared data of the Type Ibn supernovae (SNe) 2010al and 2011hw. SN 2010al reaches an absolute magnitude at peak of M(R) = -18.86 +- 0.21. Its early light curve shows similarities with normal SNe Ib, with a rise to maximum slower than most SNe Ibn. The spectra are dominated by a blue continuum at early stages, with narrow P-Cygni He I lines indicating the presence of a slow-moving, He-rich circumstellar medium. At later epochs the spectra well match those of the prototypical SN Ibn 2006jc, although the broader lines suggest that a significant amount of He was still present in the stellar envelope at the time of the explosion. SN 2011hw is somewhat different. It was discovered after the first maximum, but the light curve shows a double-peak. The absolute magnitude at discovery is similar to that of the second peak (M(R) = -18.59 +- 0.25), and slightly fainter than the average of SNe Ibn. Though the spectra of SN 2011hw are similar to those of SN 2006jc, coronal lines and narrow Balmer lines are cleary detected. This indicates substantial interaction of the SN ejecta with He-rich, but not H-free, circumstellar material. The spectra of SN 2011hw suggest that it is a transitional SN Ibn/IIn event similar to SN 2005la. While for SN 2010al the spectro-photometric evolution favours a H-deprived Wolf-Rayet progenitor (of WN-type), we agree with the conclusion of Smith et al. (2012) that the precursor of SN 2011hw was likely in transition from a luminous blue variable to an early Wolf-Rayet (Ofpe/WN9) stage.Comment: 23 pages, 11 figures, 6 tables. Accepted by MNRA

Observation of out-of-phase bilayer plasmons in YBa_2Cu_3O_7-delta

The temperature dependence of the c-axis optical conductivity \sigma(\omega) of optimally and overdoped YBa_2Cu_3O_x (x=6.93 and 7) is reported in the far- (FIR) and mid-infrared (MIR) range. Below T_c we observe a transfer of spectral weight from the FIR not only to the condensate at \omega = 0, but also to a new peak in the MIR. This peak is naturally explained as a transverse out-of-phase bilayer plasmon by a model for \sigma(\omega) which takes the layered crystal structure into account. With decreasing doping the plasmon shifts to lower frequencies and can be identified with the surprising and so far not understood FIR feature reported in underdoped bilayer cuprates.Comment: 7 pages, 3 eps figures, Revtex, epsfi