Saint Mary's Faculty Articles and Other Works
http://library2.smu.ca:80/handle/01/21880
2018-01-21T00:40:56Zxi Tauri: a unique laboratory to study the dynamic interaction in a compact hierarchical quadruple system
http://library2.smu.ca:80/handle/01/27247
xi Tauri: a unique laboratory to study the dynamic interaction in a compact hierarchical quadruple system
Context. Compact hierarchical systems are important because the effects caused by the dynamical interaction among its members occur on a human timescale. These interactions play a role in the formation of close binaries through Kozai cycles with tides. One such system is xi Tauri: it has three hierarchical orbits: 7.14 d (eclipsing components Aa, Ab), 145 d (components Aa+Ab, B), and 51 yr (components Aa+Ab+B, C). Aims. We aim to obtain physical properties of the system and to study the dynamical interaction between its components. Methods. Our analysis is based on a large series of spectroscopic photometric (including space-borne) observations and long-baseline optical and infrared spectro-interferometric observations. We used two approaches to infer the system properties: a set of observation-specific models, where all components have elliptical trajectories, and an N-body model, which computes the trajectory of each component by integrating Newton’s equations of motion. Results. The triple subsystem exhibits clear signs of dynamical interaction. The most pronounced are the advance of the apsidal line and eclipse-timing variations.We determined the geometry of all three orbits using both observation-specific and N-body models. The latter correctly accounted for observed effects of the dynamical interaction, predicted cyclic variations of orbital inclinations, and determined the sense of motion of all orbits. Using perturbation theory, we demonstrate that prominent secular and periodic dynamical effects are explainable with a quadrupole interaction.
We constrained the basic properties of all components, especially of members of the inner triple subsystem and detected rapid low-amplitude light variations that we attribute to co-rotating surface structures of component B. We also estimated the radius of component B. Properties of component C remain uncertain because of its low relative luminosity. We provide an independent estimate of the distance to the system. Conclusions. The accuracy and consistency of our results make xi Tau an excellent test bed for models of formation and evolution of hierarchical
systems. Key words. binaries: close – binaries: spectroscopic – binaries: eclipsing – stars: kinematics and dynamics – stars: fundamental parameters –
supernovae: individual: xi Tauri
Publisher's Version/PDF
2016-10-01T00:00:00ZConstraining dust extinction properties via the VVV survey
http://library2.smu.ca:80/handle/01/27246
Constraining dust extinction properties via the VVV survey
Near-infrared color-excess and extinction ratios are essential for establishing the cosmic distance scale and probing the Galaxy, particularly when analyzing targets attenuated by significant dust. A robust determination of those ratios followed from leveraging new infrared observations from the VVV survey, wherein numerous bulge RR Lyrae and Type II Cepheids were discovered, in addition to BVJHK[subscript s](3.4 [right-facing arrow] 22) [micrometre] data for classical Cepheids and O stars occupying the broader Galaxy. The apparent optical color-excess ratios vary significantly with Galactic longitude (l), whereas the near-infrared results are comparatively constant with l and Galactocentric distance (E(J-3.5 [micrometre])E(J-K[subscript s]) = 1.28 [plus or minus] 0:03). The results derived imply that classical Cepheids and O stars display separate optical trends (R[superscript V],[subscript BV]) with l, which appear to disfavor theories advocating a strict and marked decrease in dust size with increasing Galactocentric distance. The classical Cepheid, Type II Cepheid, and RR Lyrae variables are characterized by A[subscript J]|E(J-K[subscript s])= R[subscript J,[subscript JKs]= 1.49 [plus or minus] 0:05 ([A[subscript Ks] |A[subscript J]= 0.33 [plus or minus] 0.02), whereas the O stars are expectedly impacted by emission beyond 3.6 [micrometre]. The mean optical ratios characterizing classical Cepheids and O stars are approximately R[subscript] V,[subscript BV] ~3.1 and R[subscript V],[subscript BV]~ 3.3, respectively.
Publisher's Version/PDF
2016-09-01T00:00:00ZCrystal structure of 2-chloro-1,3-(2,6-diisopropylphenyl)- 4,5-dihydro-1H-imidazol-3-ium tetrakis- (3,5-trifluoromethylphenyl)borate
http://library2.smu.ca:80/handle/01/27245
Crystal structure of 2-chloro-1,3-(2,6-diisopropylphenyl)- 4,5-dihydro-1H-imidazol-3-ium tetrakis- (3,5-trifluoromethylphenyl)borate
The title compound, C [subscript 27] H[subscript 38]ClN[subscript 2 superscript
+].C[subscript 32]H[subscript 12]BF[subscript 24]-, was synthesized by reacting the
product formed from a previous reaction between 1,3-bis(2,6-diisopropylphenyl)
imidazolinium-2-carboxylate (SIPrC[subscript 2]), and SOCl[subscript 2], with sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (NaBARF). In the cation, the
imidazole ring is in a half-chair conformation and the formerly carbene carbon
atom is bonded in a distorted trigonal–planar geometry with N—C—Cl angles of
122.96 (16) and 122.21 (16)[degrees symbol] and an N—C—N angle of 114.83 (18)[degrees symbol]. In the crystal, weak C—H[dot dot dot]F hydrogen bonds link the cations and anions, forming a three-dimensional network. In addition, a short Cl[dot dot dot]F contact of 3.213 [1 10-billionth of metre] and several short F[dot dot dot] F contacts less than the sum of the van der Waals radii [1.47 A [1 10-billionth of metre]+ 1.47 A [1 10-billionth of metre]= 2.94 [1 10-billionth of metre] ] are observed. The F atoms of two of the CF[superscript 3] groups were refined as disordered over four sets of sites.
Publisher's Version/PDF
2016-10-01T00:00:00ZPreliminary study of the [superscript 10]Li nucleus via one-neutron transfer
http://library2.smu.ca:80/handle/01/27244
Preliminary study of the [superscript 10]Li nucleus via one-neutron transfer
The structure of the [superscript 10]Li unbound nucleus is a subject of large interest and its description is nowadays a matter of debate. We have investigated this system using the d([superscript 9]Li,p)[superscript 10]Li one-neutron transfer reaction at 100 MeV in inverse kinematics. The experiment was performed at the ISACII facility at TRIUMF laboratory. The excitation energy spectrum has been reconstructed by measuring the emitted protons at backward angles and the [superscript 9]Li at forward angles.
Publisher's Version/PDF; Proceedings paper from the 12th International Conference on Nucleus-Nucleus Collisions, Catania, Italy, June 21-26, 2015.
2016-01-01T00:00:00ZThe structure of superqubit states
http://library2.smu.ca:80/handle/01/27169
The structure of superqubit states
Superqubits provide a supersymmetric generalisation of the conventional qubit in quantum information theory. After a review of their current status, we address the problem of generating entangled states. We introduce the global unitary supergroup UOSp((3[superscript n] + 1)/2|(3[superscript n] - 1)/2) for an n-superqubit system, which contains as a subgroup the local unitary supergroup [UOSp](2|1)][superscript n]. While for 4 > n > 1 the bosonic subgroup in UOSp((3[superscript n] + 1)/2|(3[superscript n] - 1)/2) does not contain the standard global unitary group SU(2[superscript n]), it does have an USp(2[superscript n]) [subset] SU (2[superscript n]) subgroup which acts transitively on the n-qubit subspace, as required for consistency with the conventional multi-qubit framework. For two superqubits the UOSp(5|4) action is used to generate entangled states from the "bosonic" separable state |00>.
Preprint
2015-08-01T00:00:00ZEvidence of Soft Dipole Resonance in 11Li with Isoscalar Character
http://library2.smu.ca:80/handle/01/27163
Evidence of Soft Dipole Resonance in 11Li with Isoscalar Character
The first conclusive evidence of a dipole resonance in 11Li having isoscalar character observed from inelastic scattering with a novel solid deuteron target is reported. The experiment was performed at the newly commissioned IRIS facility at TRIUMF. The results show a resonance peak at an excitation energy of 1.03 [plus or minus] 0.03 MeV with a width of 0.51 [plus or minus] 0.11 MeV (FWHM). The angular distribution is consistent with a dipole excitation in the distorted-wave Born approximation framework. The observed resonance energy together with shell model calculations show the first signature that the monopole tensor interaction is important in 11Li. The first ab initio calculations in the coupled cluster framework are also presented.
Publisher's version/PDF
2015-05-12T00:00:00ZSpectroscopy of [superscript 9][subscript lambda]Li by electroproduction
http://library2.smu.ca:80/handle/01/27141
Spectroscopy of [superscript 9][subscript lambda]Li by electroproduction
Background: In the absence of accurate data on the free two-body hyperon-nucleon interaction, the spectra of hypernuclei provides information on the details of the effective hyperon-nucleon interaction.
Purpose: To obtain a high-resolution binding-energy spectrum for the [superscript 9]Be(e,e'K[superscript plus])[superscript 9][lambda] Li reaction.
Method: Electroproduction of the hypernucleus [superscript 9][lambda] Li has been studied for the first time with sub-MeV energy resolution in Hall A at Jefferson Lab on a [superscript 9]Be target. In order to increase the counting rate and to provide unambiguous kaon identification, two superconducting septum magnets and a ring imaging Cherenkov detector were added to the Hall A standard equipment.
Results: The cross section to low-lying states of [superscript 9][lambda] Li is concentrated within 3 MeV of the ground state and can be fit with four peaks. The positions of the doublets agree with theory while a disagreement could exist with respect to the relative strengths of the peaks in the doublets. The [lambda] separation energy, B[subscript lambda], of 8.36 [plus or minus] 0.08 (stat.) [plus or minus]0.08 (syst.) MeV was measured, in agreement with an earlier experiment.
Publisher's version/PDF
2015-03-04T00:00:00ZPhotoproduction of the [omega] meson on the proton near threshold
http://library2.smu.ca:80/handle/01/27075
Photoproduction of the [omega] meson on the proton near threshold
An experimental study of [omega] photoproduction on the proton was conducted by using the Crystal Ball and TAPS multiphoton spectrometers together with the photon tagging facility at the Mainz Microtron MAMI. The [gamma] p [right arrow] [omega] p differential cross sections are measured from threshold to the incident-photon energy E[subscript gamma] = 1.40 GeV (W = 1.87 GeV for the center-of-mass energy) with 15-MeV binning in E[subscript gamma] and full production-angle coverage. The quality of the present data near threshold gives access to a variety of interesting physics aspects. As an example, an estimation of the [omega]N scattering length [alpha subscript omega]p is provided.
Publisher's version/PDF
2015-04-30T00:00:00ZSeparated response functions in exclusive, forward [pi superscript plus or minus] electroproduction on deuterium
http://library2.smu.ca:80/handle/01/27074
Separated response functions in exclusive, forward [pi superscript plus or minus] electroproduction on deuterium
Measurements of forward exclusive meson production at different squared four-momenta of the exchanged virtual photon, Q[superscript 2], and at different four-momentum transfer, t, can be used to probe QCD’s transition from meson-nucleon degrees of freedom at long distances to quark-gluon degrees of freedom at short scales. Ratios of separated response functions in [pi superscript]− and[pi superscript]+ electroproduction are particularly informative. The ratio for transverse photons may allow this transition to be more easily observed, while the ratio for longitudinal photons provides a crucial verification of the assumed pole dominance, needed for reliable extraction of the pion form
factor from electroproduction data.
Publisher's version/PDF
2015-01-07T00:00:00ZSimultaneous analysis of the elastic scattering and breakup channel for the reaction [superscript 11]Li + [superscript 208]Pb at energies near the Coulomb barrier
http://library2.smu.ca:80/handle/01/27070
Simultaneous analysis of the elastic scattering and breakup channel for the reaction [superscript 11]Li + [superscript 208]Pb at energies near the Coulomb barrier
We present a detailed analysis of the elastic scattering and breakup channel for the reaction of [superscript 11]Li on [superscript 208]Pb at incident laboratory energies of 24.3 and 29.8 MeV, measured at the radioactive ion beam facility of TRIUMF, in Vancouver, Canada. A large yield of [superscript 9]Li fragments was detected by four charged particle telescopes in a wide angular range. The experimental angular and energy distributions of these [superscript 9]Li fragments have been compared to coupled-reaction-channel and continuum-discretized coupled-channel calculations. The large production of [superscript 9]Li fragments at small angles can be explained by considering a direct breakup mechanism, while at medium-large angles a competition between direct breakup and neutron transfer to the continuum of the [superscript 208]Pb target was observed.
Publisher's version/PDF
2015-10-15T00:00:00Z