We describe the latest release of AtomDB, version 2.0.2, a database of atomic data and a plasma modeling code with a focus on X-ray astronomy. This release includes several major updates to the fundamental atomic structure and process data held within AtomDB, incorporating new ionization balance data, state-selective recombination data, and updated collisional excitation data for many ions, including the iron L-shell ions from Fe +16 to Fe +23 and all of the hydrogen-and helium-like sequences. We also describe some of the effects that these changes have on calculated emission and diagnostic line ratios, such as changes in the temperature implied by the He-like G-ratios of up to a factor of 2.

Most supermassive black holes (SMBHs) are accreting at very low levels and are difficult to distinguish from the galaxy centers where they reside. Our own Galaxy's SMBH provides a uniquely instructive exception, and we present a close-up view of its quiescent X-ray emission based on 3 mega-second of Chandra observations. Although the X-ray emission is elongated and aligns well with a surrounding disk of massive stars, we can rule out a concentration of low-mass coronally active stars as the origin of the 1 arXiv:1307.5845v2 [astro-ph.HE]

An arbitrary unknown quantum state cannot be precisely measured or perfectly replicated. However, quantum teleportation allows faithful transfer of unknown quantum states from one object to another over long distance, without physical travelling of the object itself. Long-distance teleportation has been recognized as a fundamental element in protocols such as large-scale quantum networks and distributed quantum computation. However, the previous teleportation experiments between distant locations were limited to a distance on the order of 100 kilometers, due to photon loss in optical fibres or terrestrial free-space channels. An outstanding open challenge for a global-scale "quantum internet" is to significantly extend the range for teleportation. A promising solution to this problem is exploiting satellite platform and space-based link, which can conveniently connect two remote points on the Earth with greatly reduced channel loss because most of the photons' propagation path is in empty space. Here, we report the first quantum teleportation of independent single-photon qubits from a ground observatory to a low Earth orbit satellite - through an up-link channel - with a distance up to 1400 km. To optimize the link efficiency and overcome the atmospheric turbulence in the up-link, a series of techniques are developed, including a compact ultra-bright source of multi-photon entanglement, narrow beam divergence, high-bandwidth and high-accuracy acquiring, pointing, and tracking (APT). We demonstrate successful quantum teleportation for six input states in mutually unbiased bases with an average fidelity of 0.80+/-0.01, well above the classical limit. This work establishes the first ground-to-satellite up-link for faithful and ultra-long-distance quantum teleportation, an essential step toward global-scale quantum internet.Comment: 16 pages, 3 figure

Starting in 2012, we began an unprecedented observational program focused on the supermassive black hole in the center of our Galaxy, Sgr A * , utilizing the High Energy Transmission Gratings Spectrometer (HETGS) instrument on the Chandra X-ray Observatory. These observations will allow us to measure the quiescent Xray spectra of Sgr A * for the first time at both high spatial and spectral resolution. The X-ray emission of Sgr A * , however, is known to flare roughly daily by factors of a few to ten times over quiescent emission levels, with rarer flares extending to factors of greater than 100 times quiescence. Here were report an observation performed on 2012 February 9 wherein we detected what is the highest peak flux and fluence flare ever observed from Sgr A * . The flare, which lasted for 5.6 ks and had a decidedly asymmetric profile with a faster decline than rise, achieved a mean absorbed 2-8 keV flux of (8.5 ± 0.9) × 10 −12 erg cm −2 s −1 . The peak flux was 2.5 times higher, and the total 2-10 keV emission of the event was approximately 10 39 erg. Only one other flare of comparable magnitude, but shorter duration, has been observed in Sgr A * by XMM-Newton in 2002 October. We perform spectral fits of this Chandra observed flare, and compare our results to the two brightest flares ever observed with XMM-Newton. We find good agreement among the fitted spectral slopes (Γ ∼ 2) and X-ray absorbing columns (N H ∼ 15 × 10 22 cm −2 ) for all three of these events, resolving prior differences (which are most likely due to the combined effects of pileup and spectral modeling) among Chandra and XMM-Newton observations of Sgr A * flares. We also discuss fits to the quiescent spectra of Sgr A * .

We present the analysis of a deep Chandra observation of a ∼ 2L * late-type galaxy, ESO 137-002, in the closest rich cluster A3627. The Chandra data reveal a long ( 40 kpc) and narrow tail with a nearly constant width (∼ 3 kpc) to the southeast of the galaxy, and a leading edge ∼ 1.5 kpc from the galaxy center on the upstream side of the tail. The tail is most likely caused by the nearly edge-on stripping of ESO 137-002's interstellar medium (ISM) by ram pressure, compared to the nearly face-on stripping of ESO 137-001 discussed in our previous work. Spectral analysis of individual regions along the tail shows that the gas throughout it has a rather constant temperature, ∼ 1 keV, very close to the temperature of the tails of ESO 137-001, if the same atomic database is used. The derived gas abundance is low (∼ 0.2 solar with the single-kT model), an indication of the multiphase nature of the gas in the tail. The mass of the X-ray tail is only a small fraction (< 5%) of the initial ISM mass of the galaxy, suggesting that the stripping is most likely at an early stage. However, with any of the single-kT , double-kT and multi-kT models we tried, the tail is always "over-pressured" relative to the surrounding intracluster medium (ICM), which could be due to the uncertainties in the abundance, thermal vs. non-thermal X-ray emission, or magnetic support in the ICM. The Hα data from the Southern Observatory for Astrophysical Research (SOAR) show a ∼ 21 kpc tail spatially coincident with the X-ray tail, as well as a secondary tail (∼ 12 kpc long) to the east of the main tail diverging at an angle of ∼ 23 • and starting at a distance of ∼ 7.5 kpc from the nucleus. At the position of the secondary Hα tail, the X-ray emission is also enhanced at the ∼ 2σ level. We compare the tails of ESO 137-001 and ESO 137-002, and also compare the tails to simulations. Both the similarities and differences of the tails pose challenges to the simulations. Several implications are briefly discussed.

It has been proposed that the charge exchange (CX) process at the interface between hot and cool interstellar gases could contribute significantly to the observed soft X-ray emission in star forming galaxies. We analyze the XMM-Newton/RGS spectrum of M82, using a newly developed CX model combined with a single-temperature thermal plasma to characterize the volume-filling hot gas. The CX process is largely responsible for not only the strongly enhanced forbidden lines of the Kα triplets of various He-like ions, but also good fractions of the Lyα transitions of C vi (∼ 87%), O viii and N vii ( 50%) as well. In total about a quarter of the X-ray flux in the RGS 6-30Å band originates in the CX. We infer an ion incident rate of 3 × 10 51 s −1 undergoing CX at the hot and cool gas interface, and an effective area of the interface as ∼ 2 × 10 45 cm 2 that is one order of magnitude larger than the cross section of the global biconic outflow. With the CX contribution accounted for, the best fit temperature of the hot gas is 0.6 keV, and the metal abundances are approximately solar. We further show that the same CX/thermal plasma model also gives an excellent description of the EPIC-pn spectrum of the outflow Cap, projected at 11.6 kpc away from the galactic disk of M82. This analysis demonstrates that the CX is potentially an important contributor to the X-ray emission from starburst galaxies and also an invaluable tool to probe the interface astrophysics.

Magnetic skyrmions, a kind of localized spin texture topologically protected in magnetic materials, characterized by smaller size and much lower manipulating current density in comparison with ferromagnetic domain walls, are highlighted as potential information carriers for high-density magnetic storage devices. For technological applications, the stabilization of skyrmions in a temperature range around room temperature under a low magnetic field is essential. Here, we demonstrate the formation of magnetic biskyrmions in a low magnetic field at room temperature in a centrosymmetric hexagonal MnPdGa magnet via Lorentz transmission electron microscopy in combination with transport and magnetic measurements. High-density biskyrmions are generated at 300 K in a magnetic field of 0.15 T. In addition, biskyrmions can be generated from ferromagnetic domains and partly remained at zero field when the magnetic field is decreased. A large topological Hall resistivity is observed near room temperature. Furthermore, a wide temperature and magnetic-field window for biskyrmions is deduced from transport and magnetic properties. The simultaneous features of high-density and low magnetic field near room temperature in a single-component material make MnPdGa a promising candidate for future skyrmion-based topological spintronic applications.

4U 1822−371 is one of the proto-type accretion disk coronal sources with an orbital period of about 5.6 hours. The binary is viewed almost edge-on at a high inclination angle of 83 degrees, which makes it a unique candidate to study binary orbital and accretion disk dynamics in high powered X-ray sources. We observed the X-ray source in 4U 1822−371 with the Chandra High Energy Transmission Grating Spectrometer (HETGS) for almost nine binary orbits. X-ray eclipse times provide an update of the orbital ephemeris. We find that our result follows the quadratic function implied by previous observations; however, it suggests a flatter trend. Detailed line dynamics also confirm a previous suggestion that the observed photo-ionized line emission originates from a confined region in the outer edge of the accretion disk near the hot spot. Line properties allow us to impose limits on the size of accretion disk, the central corona, and the emission region. The photo-ionized plasma is consistent with ionization parameters of log ξ > 2, and when combined with disk size and reasonable assumptions for the plasma density, this suggests illuminating disk luminosities which are over an order of magnitude higher than what is actually observed. That is, we do not directly observe the central emitting X-ray source. The spectral continua are best fit by a flat power law with a high energy cut-off and partial covering absorption (N H ranging from 5.4-6.3 × 10 22 cm −2 ) with a covering fraction of about 50%. We discuss some implications of our findings with respect to the photo-ionized line emission for the basic properties of the X-ray source.