6241544
Wind Accretion and State Transitions in Cygnus X-1
We present the results of a spectroscopic monitoring program (from 1998 to 2002) of the Hα emission strength in HDE 226868, the optical counterpart of the black hole binary Cyg X-1. The feature provides an important probe of the mass-loss rate in the base of the stellar wind of the supergiant star. We derive an updated ephemeris for the orbit based on radial velocities measured from He I λ6678. We list net equivalent widths for the entire Hα emission/absorption complex, and we find that there are large variations in emission strength over both long (years) and short (hours to days) time spans. There are coherent orbital phase-related variations in the profiles when the spectra are grouped by Hα equivalent width. The profiles consist of (1) a P Cygni component associated with the wind of the supergiant, (2) emission components that attain high velocity at the conjunctions and that probably form in enhanced outflows both toward and away from the black hole, and (3) an emission component that moves in antiphase with the supergiant's motion. We argue that the third component forms in accreted gas near the black hole and that the radial velocity curve of the emission is consistent with a mass ratio of MX/Mopt ≈ 0.36 ± 0.05. We find that there is a general anticorrelation between the Hα emission strength and X-ray flux (from the Rossi X-Ray Timing Explorer All Sky Monitor) in the sense that when the Hα emission is strong (Wλ < -0.5 A) the X-ray flux is weaker and the spectrum harder. On the other hand, there is no correlation between Hα emission strength and X-ray flux when Hα is weak. We argue that this relationship is not caused by wind X-ray absorption nor by the reduction in Hα emissivity by X-ray heating. Instead, we suggest that the Hα variations track changes in wind density and strength near the photosphere. The density of the wind determines the size of X-ray ionization zones surrounding the black hole, and these in turn control the acceleration of the wind in the direction of the black hole. During the low/hard X-ray state, the strong wind is fast and the accretion rate is relatively low, while during the high/soft state, the weaker, highly ionized wind attains only a moderate velocity and the accretion rate increases. We argue that the X-ray transitions from the normal low/hard to the rare high/soft state are triggered by episodes of decreased mass-loss rate in the supergiant donor star.
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.
14918025
Water abundance in molecular cloud cores
We present Submillimeter Wave Astronomy Satellite (SWAS) observations of the 110 → 101 transition of ortho-H2O at 557 GHz toward 12 molecular cloud cores. The water emission was detected in NGC 7538, ρ Oph A, NGC 2024, CRL 2591, W3, W3OH, Mon R2, and W33 and was not detected in TMC-1, L134N, and B335. We also present a small map of the H2O emission in S140. Observations of the H218O line were obtained toward S140 and NGC 7538, but no emission was detected. The abundance of ortho-H2O relative to H2 in the giant molecular cloud cores was found to vary between 6 × 10-10 and 1 × 10-8. Five of the cloud cores in our sample have previous H2O detections; however, in all cases the emission is thought to arise from hot cores with small angular extents. The H2O abundance estimated for the hot core gas is at least 100 times larger than in the gas probed by SWAS. The most stringent upper limit on the ortho-H2O abundance in dark clouds is provided in TMC-1, where the 3 σ upper limit on the ortho-H2O fractional abundance is 7 × 10-8.
119232297
Subaru Constraint on Circular Polarization in I-Band Emission from the Magnetar 4U 0142+61
We present the first imaging circular polarimetry of the anomalous X-ray pulsar (AXP) 4U 0142+61 at optical wavelengths. The AXP is the only magnetar that has been well studied at optical and infrared wavelengths, and is known to have a complicated broad-band spectrum over the wavelength range. The optical polarimetric observation was carried out with the 8.2-m Subaru telescope at the I-band. From the observation, the degree of circular polarization, V, was measured to be V = 1.1 +/- 2.0%, or vertical bar V vertical bar <= 4.3% (90% confidence). The relatively large uncertainty was due to the faintness of the source (I = 23.4-24.0). Considering the currently suggested models for optical emission from magnetars, our result is not sufficiently conclusive to discriminate the models. We suggest that because linear polarization is expected to be strong in the models, linear polarimetry of this magnetar should be conducted.
119397253
Evidence for superdeformation in Dy-149,Dy-150: Onset of the collapse of the Z=66 deformed shell closure?
An experiment has been performed to search for superdeformed (SD) states in Dy-149,Dy-150. While no evidence for discrete superdeformed states has been observed, a superdeformed ridge with a separation of Delta E-gamma=52 keV with a total intensity of 1.8+/-0.5% that of Dy-150 has been observed. An upper limit of 0.8% (0.9%), of the intensity of Dy-150 (Dy-149), is placed for observation of the most intense discrete line states. The relative weakness in the SD population is suggested to be due to a rapid decrease in the depth of the superdeformed minimum, as one moves away from doubly magic Dy-152.
119922132
Transport beam line for ultraslow monoenergetic antiprotons
A beam line for the transportation of slow antiprotons from a multiring electrode trap to an experimental chamber is described. The beam line is equipped with a three-stage differential pumping system in order to maintain a pressure lower than 1×10−12 Torr in the trap region while simultaneously having a pressure of around 1×10−6 Torr in the chamber. Tests have shown that 105 positive ions per trapping cycle were successfully extracted at 250 eV from the trap positioned in a superconducting solenoid. The ions were then further transported through three small apertures to the target area located 3.5 m downstream of the trap. Results from the first delivery of a 250 eV antiproton beam are described.
118521941
Relativistic quantum effects of Dirac particles simulated by ultracold atoms
Quantum simulation is a powerful tool to study a variety of problems in physics, ranging from high-energy physics to condensed-matter physics. In this article, we review the recent theoretical and experimental progress in quantum simulation of Dirac equation with tunable parameters by using ultracold neutral atoms trapped in optical lattices or subject to light-induced synthetic gauge fields. The effective theories for the quasiparticles become relativistic under certain conditions in these systems, making them ideal platforms for studying the exotic relativistic effects. We focus on the realization of one, two, and three dimensional Dirac equations as well as the detection of some relativistic effects, including particularly the well-known Zitterbewegung effect and Klein tunneling. The realization of quantum anomalous Hall effects is also briefly discussed.
119548246
Subarcsecond Resolution Mid-Infrared Observations of Super Star Clusters in the Antennae (NGC 4038/4039)*
We present ground-based subarcsecond mid-infrared imaging and spectroscopy of young super star clusters in the overlap region of the merging galaxies NGC 4038/4039 (the Antennae) obtained with the VLT Imager and Spectrometer for mid-InfraRed (VISIR). With its unprecedented spatial resolution, VISIR begins for the first time to resolve the H II/photodissociation region complexes around the star-forming regions. In the N-band spectra of two young star clusters, unexpectedly low polycyclic aromatic hydrocarbon (PAH) emission is observed, compared to what is seen with the Infrared Space Observatory and with the Spitzer Space Telescope. We conclude that a large fraction of the PAH emission cannot be directly associated with the super star clusters but originates from an extended region of at least 215 pc radius around the clusters. In the distribution of [Ne II] 12.81 μm emission, a highly obscured cluster is discovered that does not have an optical or near-infrared counterpart.
54712303
Constructive Renormalization of the 2-Dimensional Grosse–Wulkenhaar Model
We study a quartic matrix model with partition function $$Z=\int d\ M\exp \mathrm{Tr}\ (-\Delta M^2-\frac{\lambda }{4}M^4)$$Z=∫dMexpTr(-ΔM2-λ4M4). The integral is over the space of Hermitian $$(\varLambda +1)\times (\varLambda +1)$$(Λ+1)×(Λ+1) matrices, the matrix $$\Delta $$Δ, which is not a multiple of the identity matrix, encodes the dynamics and $$\lambda >0$$λ>0 is a scalar coupling constant. We proved that the logarithm of the partition function is the Borel sum of the perturbation series and hence is a well-defined analytic function of the coupling constant in certain analytic domain of $$\lambda $$λ, by using the multi-scale loop vertex expansions. All the non-planar graphs generated in the perturbation expansions have been taken care of on the same footing as the planar ones. This model is derived from the self-dual $$\phi ^4$$ϕ4 theory on the 2-dimensional Moyal space also called the 2-dimensional Grosse–Wulkenhaar model. This would also be the first fully constructed matrix model which is non-trivial and not solvable.
303237
Discovery of Pulsations in the X-Ray Transient 4U 1901+03
We describe observations of the 2003 outburst of the hard-spectrum X-ray transient 4U 1901+03 with the Rossi X-Ray Timing Explorer (RXTE). The outburst was first detected in 2003 February by the All-Sky Monitor and reached a peak 2.5-25 keV flux of 8 × 10-9 ergs cm-2 s-1 (around 240 mcrab). The only other known outburst occurred 32.2 yr earlier, likely the longest currently known recurrence time for any X-ray transient. Proportional Counter Array (PCA) observations over the 5 month duration of the 2003 outburst revealed a 2.763 s pulsar in a 22.58 days orbit. The detection of pulsations down to a flux of 3 × 10-11 ergs cm-2 s-1 (2.5-25 keV), along with the inferred long-term accretion rate of 8.1 × 10-11 M☉ yr-1 (assuming a distance of 10 kpc), suggests that the surface magnetic field strength is below ~5 × 1011 G. The corresponding cyclotron energy is thus below 4 keV, consistent with the nondetection of resonance features at high energies. Although we could not unambiguously identify the optical counterpart, the lack of a bright IR candidate within the 1' RXTE error circle rules out a supergiant mass donor. The neutron star in 4U 1901+03 probably accretes from the wind of a main-sequence OB star, like most other high-mass binary X-ray pulsars. The almost circular orbit (e = 0.036) confirms the system's membership in a growing class of wide, low-eccentricity systems in which the neutron stars may have received much smaller kicks as a result of their natal supernova explosions.
119390755
The X-Ray Position and Infrared Counterpart of the Eclipsing X-Ray Pulsar OAO 1657–415
We have measured the precise position of the 38 s eclipsing X-ray pulsar OAO 1657-415 with the Chandra X-Ray Observatory: (J2000) = 17h00m4890, (J2000) = -4139216, error radius = 05. Based on the previously measured pulsar mass function and X-ray eclipse duration, this 10.4 day high-mass X-ray binary is believed to contain a B supergiant companion. Deep optical imaging of the field did not detect any stars at the Chandra source position, setting a limit of V > 23. However, near-infrared imaging revealed a relatively bright star (J = 14.1, H = 11.9, Ks = 10.7) coincident with the Chandra position, and we identify this star as the infrared counterpart of OAO 1657-415. The infrared colors and magnitudes and the optical nondetections for this star are all consistent with a highly reddened B supergiant (AV = 20.4