16893295
ASCA observations of two SNRs and NEI analysis
Based on the data from the ASCA observation of SNRs Kes79 and W49B, we present here the analysis of their X-ray spectra and morphologies. The Kes79 spectrum can be well fitted by a single NEI component, and the narrow-band images of that source show an inhomogeneous distribution of heavy elements. The heavy elements are richest in the positions S, SE and SW of Kes79, where there may exist interaction between shocks and molecular clouds implied by radio observations. For W49B we present here the non-equilibrium ionization (NEI) analysis based on its emission line diagnostics, and the spectral fit using two NEI components. The reverse shock in W49B may be still hot and we don't find evidence for a hotter blast wave in ASCA spectra.
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.
1162741
Low-Mass X-Ray Binary as the Progenitor of PSR J1713 + 0747
We have calculated the evolution of low-mass X-ray binaries that leads to the formation of the binary radio pulsars like PSR J1713+0747. We show that the mass transfer is most likely to be nonconservative, due to unstable disk accretion, to account for the mass of PSR J1713+0747, which is close to its initial value. We assume that part of the lost material from the binary may form a circumbinary disk, and find that it can significantly influence the mass transfer processes. We briefly discuss the implications of the circumbinary disks on the evolution of low-mass X-ray binaries and the formation of low-mass binary pulsars.
117111053
QUARK-ABNORMAL NEUTRON STARS
By using the equation of the state given by Freedman and MeLerran for quark state and that given by us for abnormal neutron state with abnormal protonsts, we have explored the models of stars with interior in quark state and outlayer in abnormal neutron state, and arrived at the conclusion that there possibly exist stable quark-abnormal neutron stars.
119458784
An Analysis of the X-Ray Emission from the Supernova Remnant 3C 397
The ASCA SIS and ROSAT PSPC spectral data of the supernova remnant 3C 397 are analyzed with a two-component nonequilibrium ionization model. In addition, the ASCA SIS0 and SIS1 spectra are fitted simultaneously in an equilibrium case. The resulting values of the hydrogen column density yield a distance of ~8 kpc to 3C 397. It is found that the hard X-ray emission, containing S and Fe Kα lines, arises primarily from the hot component, while most of the soft emission, composed mainly of Mg, Si, and Fe L lines and continuum, is produced by the cool component. The emission measures suggest that the remnant evolves in a cloudy medium and imply that the supernova progenitor might not be a massive early-type star. The cool component is approaching ionization equilibrium. The ages estimated from the ionization parameters and dynamics are all much greater than the previous determination. We restore the X-ray maps using the ASCA SIS data and compare them with the ROSAT HRI and the NRAO VLA Sky Survey 20 cm maps. The morphology with two bright concentrations suggests a bipolar remnant encountering a denser medium in the west.
18804785
Spitzer Imaging of nearby ULIRGs and their Progeny: Fine-Structure Elliptical Galaxies
We present results from two mid-infrared imaging programs of ultraluminous infrared galaxies (ULIRGs) and fine-structure elliptical galaxies. The former are known to nearly all be recent mergers between two gas-rich spiral galaxies, while the latter are also believed to be even more aged merger remnants. An examination of these two classes of objects, which may represent different stages of the same putative merger sequence, should reveal similarities in the distribution of their stellar populations and dust content consistent with that expected for time-evolution of the merger. The data reveal for the first time extended dust emission in the ULIRG galaxy bodies and along their tidal features. However, contrary to expectation, we find that the vast majority of the fine-structure elliptical galaxies lack such structured emission. This likely results from the optical selection of the elliptical sample, resulting in a population that reflects the IR-activity (or lack thereof) of optically selected interacting galaxies. Alternately, this may reflect an evolutionary process in the distribution of the dust content of the galaxy bodies.
118394364
Zitterbewegung and its significance for the Hawking radiation
The Hawking radiation can be viewed from very different perspectives, not all of which can be proved to be rigorously equivalent to one another. On the other hand, an old interest in the zitterbewegung (ZB) of the Dirac electron has recently been rekindled by the investigations on spintronics and graphene, etc. In this letter, we show that, if particles emitted by black holes are electrons or positrons, one can also regard the Hawking radiation as a ZB process.
116195444
The semileptonic decays $B_c^* \to \eta_c \ell \bar{\nu}_{\ell} $ with QCD sum rules
In this article, we calculate the $B_c^* \to \eta_c$ form-factors with the three-point QCD sum rules, then study the semileptonic decays $B_c^* \to \eta_c \ell \bar{\nu}_{\ell}$. The tiny decay widths may be observed experimentally in the future at the LHCb, while the $B_c^* \to \eta_c$ form-factors can be taken as basic input parameters in other phenomenological analysis.
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.
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