14349816
The Near-infrared Counterpart to the Anomalous X-ray Pulsar 1e 1048.1−5937
We report our discovery of the likely near-infrared counter part to the anomalous X-ray pulsar (AXP) 1E 1048.1−5937, using observations from the 6.5 m Baade (Magellan I) te lescope in Chile. We derived a precise position for the X-ray source using archival data from t heChandra X-Ray Observatory. Since this position is inconsistent with a position reported earlier from XMM-Newton, we conservatively considered eight optical and near-infrared sources within both error circles as cand id te counterparts, although we also show that the XMM-Newton observation likely suffered from attitude reconstruction problems. Two of the infrared objects have unusual colors, and one of these has colors consistent with t hose of the identified counterparts of two other AXPs. The latter object is the only source detected within the Chandra error circle, and we identify it as the counterpart to 1E 1048.1 −5937. This is the first AXP counterpart detected in multiple i nfrared bands, with magnitudes J=21.7(3),H=20.8(3), andK=19.4(3). There is marginal evidence for spectral flattenin g at longer wavelengths. Subject headings: pulsars: individual (1E 1048.1 −5937) — stars: neutron
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
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
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.
118614871
THE LIKELY ORBITAL PERIOD OF THE ULTRACOMPACT LOW-MASS X-RAY BINARY 2S 0918-549
We report the discovery of the likely orbital period of the ultracompact low-mass X-ray binary (LMXB) 2S 0918-549. Using time-resolved optical photometry carried out with the 8 m Gemini South Telescope, we obtained a 2.4 hr long, Sloan r' light curve of 2S 0918-549 and found a periodic, sinusoidal modulation at 17.4 +/- 0.1 minutes with a semiamplitude of 0.015 +/- 0.002 mag, which we identify as the binary period. In addition to 4U 0513-40 in the globular cluster NGC 1851 and the Galactic disk source 4U 1543-624, 2S 0918-549 is the third member of the ultracompact LMXBs that have orbital periods around 18 minutes. Our result verifies the suggestion that 2S 0918-549 is an ultracompact binary based on its X-ray and optical spectroscopic properties. Given that the donor in 2S 0918-549 has been suggested to be either a C-O or He white dwarf, its likely mass and radius are around 0.024-0.029 M-circle dot and 0.03-0.032 R-circle dot, respectively, for the former case and 0.034-0.039 M-circle dot and 0.033-0.035 R-circle dot for the latter case. If the optical modulation arises from X-ray heating of the mass donor, its sinusoidal shape suggests that the binary has a low inclination angle, probably around 10 degrees.
119229485
Classification study of WISE infrared sources: identification of candidate asymptotic giant branch stars
In the Wide-field Infrared Survey Explorer (WISE) all-sky source catalog there are 76 million mid-infrared point sources that were detected in the first three WISE bands and have association with only one 2MASS near-IR source within 3′′. We search for their identifications in the SIMBAD database and find 3.2 million identified sources. Based on these known sources, we establish three criteria for selecting candidate asymptotic giant branch (AGB) stars in the Galaxy, which are three defined zones in a color-color diagram, Galactic latitude |b| ≤ 20°, and “corrected” WISE third-band W3 c ≤11. Applying these criteria to the WISE+2MASS sources, 1.37 million of them are selected. We analyze the WISE third-band W3 distribution of the selected sources, and further establish that W3≤8 is required in order to exclude a large fraction of normal stars from them. We therefore find 0.47 million candidate AGB stars in our Galaxy from the WISE source catalog. Using W3 c , we estimate their distances and derive their Galactic distributions. The candidates are generally distributed around the Galactic center uniformly, with 68% (1-σ) of them within approximately 8 kpc. We discuss the idea that optical spectroscopy can be used to verify the C-rich AGB stars in our candidates, and thus a fraction of them (~10%) will be good targets for the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) survey that is planned to start in fall of 2012.
119791200
Zero-Point Time of Quantum Fields
Based on the first principles and without resorting to any additional assumption, a new physical quantity describing the space-time position of particle-number center of quantum fields is introduced, which can be regarded as a generalized Noether charge related to the symmetry under a local gauge transformation. As an interesting result, one can show that quantum fields have a zero-point time, which is related to the zero-point energy of quantum fields via the Heisenberg uncertainty principle.
8540093
Analysis of the Y(4140) and related molecular states with QCD sum rules
In this article, we assume that there exist scalar ${D}^{\ast}{\bar {D}}^{\ast}$, ${D}_{s}^{\ast}{\bar{D}}_{s}^{\ast}$, ${B}^{\ast}{\bar {B}}^{\ast}$ and ${B}_{s}^{\ast}{\bar{B}}_{s}^{\ast}$ molecular states, and study their masses using the QCD sum rules. The numerical results indicate that the masses are about (250–500) MeV above the corresponding D*–${\bar{D}}^{\ast}$, Ds*–${\bar {D}}_{s}^{\ast}$, B*–${\bar{B}}^{\ast}$ and Bs*–${\bar {B}}_{s}^{\ast}$ thresholds, the Y(4140) is unlikely a scalar ${D}_{s}^{\ast}{\bar{D}}_{s}^{\ast}$ molecular state. The scalar $D^{\ast}{\bar{D}}^{\ast}$, $D_{s}^{\ast}{\bar{D}}_{s}^{\ast}$, $B^{\ast}{\bar{B}}^{\ast}$ and $B_{s}^{\ast}{\bar{B}}_{s}^{\ast}$ molecular states maybe not exist, while the scalar ${D'}^{\ast}{\bar{D}}^{\prime\ast}$, ${D}_{s}^{\prime\ast}{\bar{D}}_{s}^{\prime\ast}$, ${B}^{\prime\ast}{\bar{B}}^{\prime\ast}$ and ${B}_{s}^{\prime\ast}{\bar{B}}_{s}^{\prime\ast}$ molecular states maybe exist.
15172685
SEARCH FOR MID-INFRARED FLUX VARIATIONS FROM THE ANOMALOUS X-RAY PULSAR 4U 0142+61
We report on our Spitzer observations of the anomalous X-ray pulsar 4U 0142+61, made following a large X-ray burst that occurred on 2007 February 7. To search for mid-infrared flux variations, four imaging observations were carried out at 4.5 and 8.0 μm with the Infrared Array Camera from February 14 to 21. No significant flux variations were detected, and the average fluxes were 32.1 ± 2.0 μJy at 4.5 μm and 59.8 ± 8.5 μJy at 8.0 μm, consistent with those obtained in 2005. The nondetection of variability is interesting in light of reported rapid variability from this source in the near-infrared but consistent with the fact that the source already went back to its quiescent state before our observations began, as indicated by contemporaneous X-ray observations. In order to understand the origin of the near-infrared variability, frequent, simultaneous multiwavelength observations are needed.
119216177
Radiative Transitions Among the Vector and Scalar Heavy Quarkonium States with Covariant Light-Front Quark Model
In this article, we study the radiative transitions among the vector and scalar heavy quarkonium states with the covariant light-front quark model. In calculations, we observe that the radiative decay widths are sensitive to the constituent quark masses and the shape parameters of the wave-functions, and reproduce the experimental data with suitable parameters.
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.