Diffuse Hard X-ray Sources Discovered with the ASCA Galactic Plane Survey

We found diffuse hard X-ray sources, G11.0+0.0, G25.5+0.0, and G26.6-0.1 in the ASCA Galactic plane survey data. The X-ray spectra are featureless with no emission line, and are fitted with both models of a thin thermal plasma in non-equilibrium ionization and a power-law function. The source distances are estimated to be 1-8 kpc, using the best-fit NH values on the assumption that the mean density in the line of sight is 1 H cm^-3. The source sizes and luminosities are then 4.5-27 pc and (0.8-23)x10^33 ergs/s. Although the source sizes are typical to supernova remnants (SNR) with young to intermediate ages, the X-ray luminosity, plasma temperature, and weak emission lines in the spectra are all unusual. This suggests that these objects are either shell-like SNRs dominated by X-ray synchrotron emission, like SN 1006, or, alternatively, plerionic SNRs. The total number of these classes of SNRs in our Galaxy is also estimated.Comment: 17 pages, 9 figures; to appear in Ap

Chandra Observations of A Galactic Supernova Remnant Vela Jr.: A New Sample of Thin Filaments Emitting Synchrotron X-Rays

A galactic supernova remnant (SNR) Vela Jr. (RX J0852.0$-$4622, G266.6$-$1.2) shows sharp filamentary structure on the north-western edge of the remnant in the hard X-ray band. The filaments are so smooth and located on the most outer side of the remnant. We measured the averaged scale width of the filaments ($w_u$ and $w_d$) with excellent spatial resolution of {\it Chandra}, which are in the order of the size of the point spread function of {\it Chandra} on the upstream side and 49.5 (36.0--88.8) arcsec on the downstream side, respectively. The spectra of the filaments are very hard and have no line-like structure, and were well reproduced with an absorbed power-law model with $\Gamma =$2.67 (2.55--2.77), or a {\tt SRCUT} model with $\nu_{rolloff}$ = 4.3 (3.4--5.3)$\times 10^{16}$ Hz under the assumption of $p=0.3$. These results imply that the hard X-rays are synchrotron radiation emitted by accelerated electrons, as mentioned previously. Using a correlation between a function ${\cal B} \equiv \nu_{rolloff}/w_d^2$ and the SNR age, we estimated the distance and the age of Vela Jr.: the estimated distance and age are 0.33 (0.26--0.50) kpc and 660 (420--1400) years, respectively. These results are consistent with previous reports, implying that ${\cal B}$--age relation may be a useful tool to estimate the distance and the age of synchrotron X-ray emitting SNRs.Comment: 19 pages, 8 figures, ApJ, in pres

Quantum squeezing generation versus photon localization in a disordered microcavity

We investigate theoretically the nonlinear dynamics induced by an intense pump field in a disordered planar microcavity. Through a self-consistent theory, we show how the generation of quantum optical noise squeezing is affected by the breaking of the in-plane translational invariance and the occurrence of photon localization. We find that the generation of single-mode Kerr squeezing for the ideal planar case can be prevented by disorder as a result of multimode nonlinear coupling, even when the other modes are in the vacuum state. However, the excess noise is a non-monotonous function of the disorder amplitude. In the strong localization limit, we show that the system becomes protected with respect to this fundamental coupling mechanism and that the ideal quadrature squeezing generation can be obtained

Fine Structures of Shock of SN 1006 with the Chandra Observation

The north east shell of SN 1006 is the most probable acceleration site of high energy electrons (up to ~ 100 TeV) with the Fermi acceleration mechanism at the shock front. We resolved non-thermal filaments from thermal emission in the shell with the excellent spatial resolution of Chandra. The thermal component is extended widely over about ~ 100 arcsec (about 1 pc at 1.8 kpc distance) in width, consistent with the shock width derived from the Sedov solution. The spectrum is fitted with a thin thermal plasma of kT = 0.24 keV in non-equilibrium ionization (NEI), typical for a young SNR. The non-thermal filaments are likely thin sheets with the scale widths of ~ 4 arcsec (0.04 pc) and ~ 20 arcsec (0.2 pc) at upstream and downstream, respectively. The spectra of the filaments are fitted with a power-law function of index 2.1--2.3, with no significant variation from position to position. In a standard diffusive shock acceleration (DSA) model, the extremely small scale length in upstream requires the magnetic field nearly perpendicular to the shock normal. The injection efficiency (eta) from thermal to non-thermal electrons around the shock front is estimated to be ~ 1e-3 under the assumption that the magnetic field in upstream is 10 micro G. In the filaments, the energy densities of the magnetic field and non-thermal electrons are similar to each other, and both are slightly smaller than that of thermal electrons. in the same order for each other. These results suggest that the acceleration occur in more compact region with larger efficiency than previous studies.Comment: 24 pages, 11 figures, Accepted for publication in ApJ, the paper with full resolution images in http://www-cr.scphys.kyoto-u.ac.jp/member/bamba/Paper/SN1006.pd

Dissipation and detection of polaritons in ultrastrong coupling regime

We have investigated theoretically a dissipative polariton system in the ultrastrong light-matter coupling regime without using the rotating-wave approximation on system-reservoir coupling. Photons in a cavity and excitations in matter respectively couple two large ensembles of harmonic oscillators (photonic and excitonic reservoirs). Inheriting the quantum statistics of polaritons in the ultrastrong coupling regime, in the ground state of the whole system, the two reservoirs are not in the vacuum states but they are squeezed and correlated. We suppose this non-vacuum reservoir state in the master equation and in the input-output formalism with Langevin equations. Both two approaches consistently guarantee the decay of polariton system to its ground state, and no photon detection is also obtained when the polariton system is in the ground state.Comment: 18 pages, 3 figure

Constraints on cosmic-ray efficiency in the supernova remnant RCW 86 using multi-wavelength observations

Several young supernova remnants (SNRs) have recently been detected in the high-energy and very-high-energy gamma-ray domains. As exemplified by RX J1713.7-3946, the nature of this emission has been hotly debated, and direct evidence for the efficient acceleration of cosmic-ray protons at the SNR shocks still remains elusive. We analyzed more than 40 months of data acquired by the Large Area Telescope (LAT) on-board the Fermi Gamma-Ray Space Telescope in the HE domain, and gathered all of the relevant multi-wavelength (from radio to VHE gamma-rays) information about the broadband nonthermal emission from RCW 86. For this purpose, we re-analyzed the archival X-ray data from the ASCA/Gas Imaging Spectrometer (GIS), the XMM-Newton/EPIC-MOS, and the RXTE/Proportional Counter Array (PCA). Beyond the expected Galactic diffuse background, no significant gamma-ray emission in the direction of RCW 86 is detected in any of the 0.1-1, 1-10 and 10-100 GeV Fermi-LAT maps. In the hadronic scenario, the derived HE upper limits together with the HESS measurements in the VHE domain can only be accommodated by a spectral index Gamma <= 1.8, i.e. a value in-between the standard (test-particle) index and the asymptotic limit of theoretical particle spectra in the case of strongly modified shocks. The interpretation of the gamma-ray emission by inverse Compton scattering of high energy electrons reproduces the multi-wavelength data using a reasonable value for the average magnetic field of 15-25 muG. For these two scenarios, we assessed the level of acceleration efficiency. We discuss these results in the light of existing estimates of the magnetic field strength, the effective density and the acceleration efficiency in RCW 86.Comment: Accepted for publication in A&A; 10 pages and 4 figure

Thermal and Non-thermal X-Rays from the LMC Super Bubble 30 Dor C

We report on the discovery of thermal and non-thermal X-rays from the shells of the super bubble (SB) 30 Dor C in the Large Magellanic Cloud (LMC). The X-ray morphology is a nearly circular shell with a radius of about 40 pc, which is bright on the northern and western sides. The spectra of the shells are different from region to region. The southern shell shows clear emission lines, and is well fitted with a model of a thin-thermal plasma (kT = 0.21keV) in non-equilibrium ionization (NEI) plus a power-law component. This thermal plasma is located inside of the H alpha emission, which is the outer edge of the shell of the SB. The northern and western sides of the SB are dim in H alpha emission, but are bright in non-thermal (power-law) X-rays with a photon index of 2.1-2.9. The non-thermal X-ray shell traces the outer boundary of the radio shell. These features of thin-thermal and non-thermal X-rays are similar to those of SN 1006, a prototype of synchrotron X-ray shell, but the non-thermal component of 30 Dor C is about ten-times brighter than that of SN 1006. 30 Dor C is the first candidate of an extragalactic SB, in which energetic electrons are accelerating in the shell. The age is much older than that of SN 1006, and hence the particle acceleration time in this SB may be longer than those in normal shell-like SNRs. We found point-like sources associated with some of tight star clusters. The X-ray luminosity and spectrum are consistent with those of young clusters of massive stars. Point-like sources with non-thermal spectra are also found in the SB. These may be background objects (AGNs) or stellar remnants (neutron stars or black holes).Comment: 11 pages, 6 figures, Accepted for publication in ApJ, the paper with full resolution images in http://www-cr.scphys.kyoto-u.ac.jp/member/bamba/Paper/30DorC.pd

X-Ray Synchrotron Emitting Fe-Rich Ejecta in SNR RCW 86

Supernova remnants may exhibit both thermal and nonthermal X-ray emission. We present Chandra observations of RCW 86. Striking differences in the morphology of X-rays below 1 keV and above 2 keV point to a different physical origin. Hard X-ray emission is correlated fairly well with the edges of regions of radio emission, suggesting that these are the locations of shock waves at which both short-lived X-ray emitting electrons, and longer-lived radio-emitting electrons, are accelerated. Soft X-rays are spatially well-correlated with optical emission from nonradiative shocks, which are almost certainly portions of the outer blast wave. These soft X-rays are well fit with simple thermal plane-shock models. Harder X-rays show Fe K alpha emission and are well described with a similar soft thermal component, but a much stronger synchrotron continuum dominating above 2 keV, and a strong Fe K alpha line. Quantitative analysis of this line and the surrounding continuum shows that it cannot be produced by thermal emission from a cosmic-abundance plasma; the ionization time is too short, as shown both by the low centroid energy (6.4 keV) and the absence of oxygen lines below 1 keV. Instead, a model of a plane shock into Fe-rich ejecta, with a synchrotron continuum, provides a natural explanation. This requires that reverse shocks into ejecta be accelerating electrons to energies of order 50 TeV. We show that maximum energies of this order can be produced by radiation-limited diffusive shock acceleration at the reverse shocks.Comment: ApJ, accepted; full resolution images in http://spider.ipac.caltech.edu/staff/rho/rcw86chandra.p

Gravity and Electromagnetism with Y(R)F2Y(R)F^2-type Coupling and Magnetic Monopole Solutions

We investigate $Y(R) F^2$-type coupling of electromagnetic fields to gravity. After we derive field equations by a first order variational principle from the Lagrangian formulation of the non-minimally coupled theory, we look for static, spherically symmetric, magnetic monopole solutions. We point out that the solutions can provide possible geometries which may explain the flatness of the observed rotation curves of galaxies.Comment: 10 page

A Spatial and Spectral Study of Nonthermal Filaments in Historical Supernova Remnants: Observational Results with Chandra

The outer shells of young supernova remnants (SNRs) are the most plausible acceleration sites of high-energy electrons with the diffusive shock acceleration (DSA) mechanism. We studied spatial and spectral properties close to the shock fronts in four historical SNRs (Cas A, Kepler's remnant, Tycho's remnant, and RCW 86) with excellent spatial resolution of {\it Chandra}. In all of the SNRs, hard X-ray emissions were found on the rims of the SNRs, which concentrate in very narrow regions (so-called "filaments"); apparent scale widths on the upstream side are below or in the order of the point spread function of {\it Chandra}, while 0.5--40 arcsec (0.01--0.4 pc) on the downstream side with most reliable distances. The spectra of these filaments can be fitted with both thermal and nonthermal (power-law and {\tt SRCUT}) models. The former requires unrealistic high temperature (\ga2 keV) and low abundances (\la1 solar) for emission from young SNRs and may be thus unlikely. The latter reproduces the spectra with best-fit photon indices of 2.1--3.8, or roll-off frequencies of (0.1--28)$\times 10^{17}$ Hz, which reminds us of the synchrotron emission from electrons accelerated via DSA. We consider various physical parameters as functions of the SNR age, including the previous results on SN 1006 \citep{bamba2003b}; the filament width on the downstream side increases with the SNR age, and the spectrum becomes softer keeping a nonthermal feature. It was also found that a function, that is the roll-off frequency divided by the square of the scale width on the downstream side, shows negative correlation with the age, which might provide us some information on the DSA theory.Comment: 23 pages, 23 figures, accepted by Ap