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Register a new userG0.173-0.42: an X-ray and radio magnetized filament near the galactic center
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The recent detection of an X-ray filament associated with the radio filament G0.173-0.42 adds to four other nonthermal radio filaments with X-ray counterparts, amongst the more than 100 elongated radio structures that have been identified as synchrotron-emitting radio filaments in the inner couple of degrees of the Galactic center. The synchrotron mechanism has also been proposed to explain the emission from X-ray filaments. However, the origin of radio filaments and the acceleration sites of energetic particles to produce synchrotron emission in radio and X-rays remain mysterious. Using MeerKAT, VLA, Chandra, WISE and Spitzer, we present structural details of G0.173-0.42 which consists of multiple radio filaments, one of which has an X-ray counterpart. A faint oblique radio filament crosses the radio and X-ray filaments. Based on the morphology, brightening of radio and X-ray intensities, and radio spectral index variation, we argue that a physical interaction is taking place between two magnetized filaments. We consider that the reconnection of the magnetic field lines at the interaction site leads to the acceleration of particles to GeV energies. We also argue against the synchrotron mechanism for the X-ray emission due to the short $sim$30 year lifetime of TeV relativistic particles. Instead, we propose that the inverse Compton scattering mechanism is more likely to explain the X-ray emission by upscattering of seed photons emitted from a 10^6 solar luminosity star located at the northern tip of the X-ray filament.
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An elongated X-ray source with a strong K-shell line from He-like iron (Fe XXVI) is found at (RA, Dec)_{J2000.0}=(17h44m00s.0, -29D1340.9) in the Galactic center region. The position coincides with the X-ray thread, G359.55+0.16, which is aligned with the radio non-thermal filament. The X-ray spectrum is well fitted with an absorbed thin thermal plasma (apec) model. The best-fit temperature, metal abundance, and column density are 4.1^{+2.7}_{-1.8} keV, 0.58^{+0.41}_{-0.32} solar, and 6.1^{+2.5}_{-1.3}x10^{22} cm^{-2}, respectively. These values are similar to those of the largely extended Galactic center X-ray emission.
This paper reports the analysis procedure and results of simultaneous spectral fits of the Suzaku archive data for Sagittarius (Sgr) A East and the nearby Galactic center X-ray emission (GCXE). The results are that the mixed-morphology supernova remnant Sgr A East has a recombining plasma (RP) with Cr and Mn He$alpha$ lines, and a power-law component (PL) with an Fe I K$alpha$ line. The nearby GCXE has a $sim$1.5-times larger surface brightness than the mean GCXE far from Sgr A East, although the spectral shape is almost identical. Based on these results, we interpret that the origins of the RP and the PL with the Fe I K$alpha$ line are past big flares of Sgr A$^*$.
One of the most unique phenomena in the Galactic center region is the existence of numerous long and narrow filamentary structures within a few hundred parsecs of Sgr A$^{star}$. While more than one than one hundred radio filaments have been revealed by MeerKAT, about two dozens X-ray filaments have been discovered so far. In this article, we report our analysis on the deep Chandra and NuSTAR observations of a non-thermal X-ray filament, G0.13-0.11, which is located adjacent to the Radio arc. Chandra revealed a unique morphology of G0.13-0.11, which is an elongated (0.1 pc in width and 3.2 pc in length) structure slightly bended towards the Radio arc. A pulsar candidate ($Gamma sim 1.4$) is detected in the middle of the filament, with a tail of diffuse non-thermal X-ray emission on one side of the filament. The filament is detected by NuSTAR up to 79 keV, with the hard X-ray centroid consistent with the pulsar candidate. We found that the X-ray intensity decays along the filament farther away from the pulsar candidate, dropping to half of its peak value at 2.2 pc away. This system is mostly likely a Pulsar Wind Nebula interacting with ambient interstellar magnetic field, where the filaments are kinetic jets from PWN as recently proposed. The nature of this filament adds to complex origin of the X-ray filaments, which serve as powerful tools to probe local and global powerful particle accelerators in the Galactic center.
We report on multi-frequency, wideband radio observations of the Galactic Center magnetar (SGR 1745$-$2900) with the Green Bank Telescope for $sim$100 days immediately following its initial X-ray outburst in April 2013. We made multiple simultaneous observations at 1.5, 2.0, and 8.9 GHz, allowing us to examine the magnetars flux evolution, radio spectrum, and interstellar medium parameters (such as the dispersion measure (DM), the scattering timescale and its index). During two epochs, we have simultaneous observations from the Chandra X-ray Observatory, which permitted the absolute alignment of the radio and X-ray profiles. As with the two other radio magnetars with published alignments, the radio profile lies within the broad peak of the X-ray profile, preceding the X-ray profile maximum by $sim$0.2 rotations. We also find that the radio spectral index $gamma$ is significantly negative between $sim$2 and 9 GHz; during the final $sim$30 days of our observations $gamma sim -1.4$, which is typical of canonical pulsars. The radio flux has not decreased during this outburst, whereas the long-term trends in the other radio magnetars show concomitant fading of the radio and X-ray fluxes. Finally, our wideband measurements of the DMs taken in adjacent frequency bands in tandem are stochastically inconsistent with one another. Based on recent theoretical predictions, we consider the possibility that the dispersion measure is frequency-dependent. Despite having several properties in common with the other radio magnetars, such as $L_{textrm{X,qui}}/L_{textrm{rot}} lesssim 1$, an increase in the radio flux during the X-ray flux decay has not been observed thus far in other systems.
We report the discovery of a $1^circ$ scale X-ray plume in the northern Galactic Center (GC) region observed with Suzaku. The plume is located at ($l$, $b$) $sim$ ($0mbox{$.!!^circ$}2$, $0mbox{$.!!^circ$}6$), east of the radio lobe reported by previous studies. No significant X-ray excesses are found inside or to the west of the radio lobe. The spectrum of the plume exhibits strong emission lines from highly ionized Mg, Si, and S that is reproduced by a thin thermal plasma model with $kT sim 0.7$ keV and solar metallicity. There is no signature of non-equilibrium ionization. The unabsorbed surface brightness is $3times10^{-14}$ erg cm$^{-2}$ s$^{-1}$ arcmin$^{-2}$ in the 1.5-3.0 keV band. Strong interstellar absorption in the soft X-ray band indicates that the plume is not a foreground source but is at the GC distance, giving a physical size of $sim$100 pc, a density of 0.1 cm$^{-3}$, thermal pressure of $1times10^{-10}$ erg cm$^{-3}$, mass of 600 $M_odot$ and thermal energy of $7times10^{50}$ erg. From the apparent association with a polarized radio emission, we propose that the X-ray plume is a magnetized hot gas outflow from the GC.
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