119266949
MULTIBAND STUDIES OF THE OPTICAL PERIODIC MODULATION IN THE X-RAY BINARY SAX J1808.4–3658 DURING ITS QUIESCENCE AND 2008 OUTBURST
We report on time-resolved optical imaging of the X-ray binary SAX J1808.4-3658 during its quiescent state and 2008 outburst. The binary, containing an accretion-powered millisecond pulsar, has a large sinusoidal-like modulation in its quiescent optical emission. We employ a Markov chain Monte Carlo technique to fit our multi-band light curve data in quiescence with an irradiated star model, and derive a tight constraint of 50(-5)(+6) deg on the inclination angle i of the binary system. The pulsar and its companion are constrained to have masses of 0.97(-0.22)(+0.31) M-circle dot and 0.04(-0.01)(+0.02) M-circle dot (both 1 sigma ranges), respectively. The dependence of these results on the measurements of the companion's projected radial velocity is discussed. We also find that the accretion disk had nearly constant optical fluxes over a similar to 500 day period in the quiescent state our data covered, but started brightening 1.5 months before the 2008 outburst. Variations in modulation during the outburst were detected in our four observations made 7-12 days after the start of the outburst, and a sinusoidal-like modulation with 0.2 mag amplitude changed to have a smaller amplitude of 0.1 mag. The modulation variations are discussed. We estimate the albedo of the companion during its quiescence and the outburst, which was approximately 0 and 0.8 (for isotropic emission), respectively. This large difference probably provides additional evidence that the neutron star in the binary turns on as a radio pulsar in quiescence.
4503009
High-Resolution Imaging of Warm and Dense Molecular Gas in the Nuclear Region of the Luminous Infrared Galaxy NGC 6240
We present ~2'' resolution CO (3-2), HCO+(4-3), and 880 μm continuum images of the luminous infrared galaxy NGC 6240 obtained at the Submillimeter Array. We find that the spatially resolved CO (3-2), HCO + (4-3), and the 880 μm emission peaks between the two nuclear components that are both known to harbor AGNs. Our large velocity gradient (LVG) analysis performed on each velocity channel suggests that the peak of the molecular gas emission traced in our observations is warm (T = 20-100 K), dense (nH2 = 105.0-105.4 cm-3), and moderately optically thin (τ = 0.2-2) in the central 1 kpc. We also find large column densities of ~1023 cm-2. Such extreme conditions are observed over ~300 km s-1 centered around the CO-derived systemic velocity. The derived molecular gas mass from the CO (3-2) emission and a CO-to-H2 conversion factor commonly used for ULIRGs is (6.9 ± 1.7) × 109 M☉, and this is consistent with the mass derived from previous CO (2-1) observations. The gas is highly turbulent in the central kpc (ΔvFWZI ~ 1175 km s-1). Furthermore, possible inflow or outflow activity is suggested from the CO (3-2) velocity distribution. We tentatively state that 3.5 × 108 M☉ of isolated CO (3-2) emission seen west of the northern disk may be associated with outflows from starburst superwinds, but the gas outflow scenario from one of the central AGN is not completely ruled out. Piecing all of the information together, the central region of NGC 6240 harbors 2 AGNs, ~1010 M☉ of molecular gas mass, 5 × 107 M☉ of dust mass, and has possible evidence of inflow and outflow activity.
118345375
Graphene, neutrino mass and oscillation
A resolution of the Abraham-Minkowski dilemma is presented that other constant velocities can play the role of c in the theory of relativity. For example, in 2005 electrons of graphene were discovered to behave as if the coefficient is a Fermi velocity. Then we propose a conjecture for neutrinos to avoid the contradiction among two-component theory, negative rest mass-square and oscillation.
124130898
Study of the neutron-rich nucleus Si-36
Excited states of N=22 Si-36, populated in deep-inelastic processes produced by the interaction of a 215 MeV beam of S-36 ions with a Pb-208 target, were studied in the present work. gamma rays from the binary fragments detected using CLARA, an array of 25 Ge Clover detectors, were measured in coincidence with projectile-like fragments detected by PRISMA, a large solid angle magnetic spectrometer. Two new gamma-ray photopeaks at energies of 1442 and 842 keV were observed and tentatively assigned to the 4(+)-> 2(+) and 6(+)-> 4(+) transitions, respectively. The systematics of the level structures of N=22 isotones are presented, and a comparison is made of the behavior of Si, Mg, and S isotopes. The level structure of Si-36 is also compared with the results of sdpf shell model calculations.
2081456
Numerical solution for cosmological evolution of Newton's gravitational constant in superstring theories.
By using a computer to solve the ten-dimensional Einstein equations in superstring theories, we find that the present value for the time variation of Newton's gravitational constant is in the range of -1 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}11}$ to -6 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}12}$ ${\mathrm{yr}}^{\ensuremath{-}1}$ in the case of the flat internal potential, which confirms the previous perturbative estimate.
3131664
ANOMALOUS SILICATE DUST EMISSION IN THE TYPE 1 LINER NUCLEUS OF M81
We report the detection and successful modeling of the unusual 9.7 μm Si-O stretching silicate emission feature in the type 1 (i.e., face-on) LINER nucleus of M81. Using the Infrared Spectrograph (IRS) instrument on Spitzer, we determine the feature in the central 230 pc of M81 to be in strong emission, with a peak at ~10.5 μm. This feature is strikingly different in character from the absorption feature of the galactic interstellar medium, and from the silicate absorption or weak emission features typical of galaxies with active star formation. We successfully model the high signal-to-noise ratio IRS spectra with porous silicate dust using laboratory-acquired mineral spectra. We find that the most probable fit uses micron-sized, porous grains of amorphous silicate and amorphous carbon. In addition to silicate dust, there is weak polycyclic aromatic hydrocarbon (PAH) emission present (particularly at 11.3 μm, arising from the C-H out-of-plane bending vibration of relatively large PAHs of ~500-1000 C atoms) whose character reflects the low-excitation active galactic nucleus environment, with some evidence that small PAHs of ~100-200 C atoms (responsible for the 7.7 μm C-C stretching band) in the immediate vicinity of the nucleus have been preferentially destroyed. Analysis of the infrared fine structure lines confirms the LINER character of the M81 nucleus. Four of the infrared H_2 rotational lines are detected and fit to an excitation temperature of T ~ 800 K. Spectral maps of the central 230 pc in the [Ne II] 12.8 μm line, the H_2 17 μm line, and the 11.3 μm PAH C-H bending feature reveal arc- or spiral-like structures extending from the core. We also report on epochal photometric and spectroscopic observations of M81, whose nuclear intensity varies in time across the spectrum due to what is thought to be inefficient, sub-Eddington accretion onto its central black hole. We find that, contrary to the implications of earlier photometry, the nucleus has not varied over a period of two years at these infrared wavelengths to a precision of about 1%.
8434175
X-Ray Observation and Analysis of the Composite Supernova Remnant G327.1–1.1
Based on the data from the observation of the supernova remnant (SNR) G327.1-1.1 by the Advanced Satellite for Cosmology and Astrophysics (ASCA) and ROSAT, we find that G327.1-1.1 is a composite remnant with both a nonthermal emission component and a diffuse thermal emission component. The nonthermal component is well fitted by a power-law model with photon index Γ~2.2. This component is attributed to the emission from the synchrotron nebula powered by an undiscovered central pulsar. The thermal component has a temperature of about 0.4 keV. We attribute it to the emission from the shock-heat swept-up interstellar medium (ISM). Its age, explosion energy, and density of ambient medium are derived from the observed thermal component. Some characteristics of the synchrotron nebula are also derived. We have searched for the pulsed signal but have not found it. The soft X-ray (0.4-2 keV) and hard X-ray (2-10 keV) images are different, but they both elongate in the southeast-northwest direction. And this X-ray southeast-northwest elongation is in positional coincidence with the radio ridge in the Molonglo Observatory Synthesis Telescope (MOST) 843 MHz radio map. We present a possibility that the X-ray nonthermal emission mainly comes from the trail produced by a quickly moving undiscovered pulsar, and the long radio ridge is formed when the pulsar is moving out of the boundary of the plerionic structure.
839810
Discovery of a 692.5 s period in the X-ray Binary 4U 1820-30: an indication of a superhumper?
The X-ray source 4U 1820−30 in the globular cluster NGC 6624 is known as the most compact binary among the identified X-ray binaries. Having an orbital period of 685.0 s, the source consists of a neutron star primary and likely a 0.06–0.08 M⊙ white dwarf secondary. Here we report on far-ultraviolet (FUV) observations of this X-ray binary, made with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope. From our Fourier spectral analysis of the FUV timing data, we obtain a period of 692.5±1.1 s, which is significantly different from the orbital period. The light curve folded at this period can be described by a sinusoid, with a fractional semiamplitude of 6.3%. While the discovered FUV period may be consistent with a hierarchical triple system model considered for 4U 1820−30, we suggest that it could instead be the indication of the binary being a superhump source. The X-ray and FUV periods would be the orbital and superhump periods, respectively, indicating a 1% superhump excess and a white-dwarf/neutron-star mass ratio around 0.06. We discuss possible methods for further identification of 4U 1820−30 as a superhump source. Subject headings: binaries: close — stars: individual (4U 1820−30) — X-rays: binary — stars: lowmass — stars: neutron
122884461
On the composition laws of Beltrami-Liouville theories and 2D quantum gravity☆
Abstract We present the composition laws or cocycle conditions of the Liouville theory and Beltrami-Liouville theory as well as the quantum gravity in two dimensions. We show that for the 2D gravity, their special cases give rise to the composition laws of Polyakov's light-cone action and that of the geometric action of the Virasoro group. By means of the composition laws, we give the gravitational Ward identities and a relation between the actions of the Liouville theory and the topological gravity and find that the principal action of the 2D topological gravity is a coboundary which should obey a cocylce condition in the Liouville complex.
119069538
Search for gamma-ray emission from four accreting millisecond pulsars with Fermi/LAT
We report our search for -ray emission in the energy range from 100 MeV to 300 GeV from four Accreting Millisecond Pulsars (AMPs), SAX J1808.4 3658, IGR J00291+5934, XTE J1814 338, and XTE J0929 314. The data are from four-year observations carried out by Large Area Telescope (LAT) onboard the Fermi -ray Space Telescope. The AMPs were not detected, and their -ray luminosity upper limits we obtain are 5.1 × 10 33 ergs s −1 for SAX J1808.4 3658, 2.1 × 10 33 ergs s −1 for IGR J00291+5934, 1.2 × 10 34 ergs s −1 for XTE J1814 338, and 2.2 × 10 33 ergs s −1 for XTE J0929 314. We compare our results with -ray irradiation luminosities required for producing optical modulations seen from the companions in the AMPs, which has been suggested by Takata et al. (2012), and our upper limits have excluded -ray emission as the heating source in these systems except XTE J0929 314, the upper limit of which is not deep enough. Our results also do not support the model proposed by Takata et al. (2012) that relatively strong -ray emission could arise from the outer gap of a high-mass neutron star controlled by the photon-photon pair-creation for the AMPs. Two AMPs, SAX J1808.4 3658 and IGR J00291+5934, have the measurements of their spin-down rates, and we derive the upper limits of their -ray conversion efficiencies, which are 57% and 3%, respectively. We discuss the implications to the AMP systems by comparing the efficiency upper limit values with that of 20 -ray millisecond pulsars (MSP) detected by Fermi and the newly discovered transitional MSP binary J1023+0038. Subject headings: pulsars: general – stars: neutron – binaries: close – gamma rays: stars
119184301
The Zb(10610) and Zb(10650) as axial-vector tetraquark states in the QCD sum rules
Abstract In this article, we study the axial-vector mesons Z b ( 10 610 ) and Z b ( 10 650 ) with the C γ μ – C γ 5 type and C γ μ – C γ ν type interpolating currents, respectively, by carrying out the operator product expansion to the vacuum condensates up to dimension 10. In calculations, we explore the energy scale dependence of the QCD spectral densities of the hidden bottom tetraquark states in detail for the first time, and suggest a formula μ = M X / Y / Z 2 − ( 2 M b ) 2 with the effective mass M b = 5.13 GeV to determine the energy scales. The numerical results favor assigning the Z b ( 10 610 ) and Z b ( 10 650 ) as the C γ μ – C γ 5 type and C γ μ – C γ ν type hidden bottom tetraquark states, respectively. We obtain the mass of the J PC = 1 + + hidden bottom tetraquark state as a byproduct, which can be compared to the experimental data in the futures. Furthermore, we study the strong decays Z b ± ( 10 610 ) → ϒ π ± , η b ρ ± with the three-point QCD sum rules, the decay widths also support assigning the Z b ( 10 610 ) as the C γ μ – C γ 5 type hidden bottom tetraquark state.