Evidence for Solar-Wind Charge-Exchange X-Ray Emission from the Earth’s Magnetosheath

Fujimoto, Ryuichi; Mitsuda, Kazuhisa; McCammon, D.; Takei, Yoh; Bauer, Michael; Ishisaki, Yoshitaka; Porter, F. S.; Yamaguchi, Hiroya; Hayashida, Kentaro; Yamasaki, Noriko Y.

doi:10.1093/pasj/59.sp1.s133

Cited by 175 publications

(128 citation statements)

References 28 publications

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“…During the Suzaku observations of A2744 Northeast, XIS light curves were stable and the solar-wind proton flux measured by the ACE satellite, < 2 × 10 8 cm −2 s −1 , agree with that of the quiescent phase (Fujimoto et al 2007). Thus the present data is unlikely to be affected by the solar activity.…”

Section: Observation and Data Reductionsupporting

confidence: 73%

Search for the warm–hot intergalactic medium around A 2744 using Suzaku

Hattori

Ota

Zhang

et al. 2017

Publications of the Astronomical Society of Japan

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We present the results from the Suzaku satellite of the surrounding region of a galaxy cluster, A2744, at z = 0.3. To search for oxygen emission lines from the warm-hot intergalactic medium (WHIM), we analyzed X-ray spectra from two northeast regions 2.2-3.3 and 3.3-4.4 Mpc from the center of the cluster, which offers the first test on the presence of a WHIM near the typical accretion shock radius (∼ 2r 200 ) predicted by hydrodynamical simulations. For the 2.2-3.3 Mpc region, the spectral fit significantly (99.2% significance) improved when we include O VII and O VIII lines in the spectral model. A comparable WHIM surface brightness was obtained in the 3.3-4.4 Mpc region and the redshift of O VIII line is consistent with z = 0.3 within errors. The present results support that the observed soft X-ray emission originated from the WHIM. However, considering both statistical and systematic uncertainties, O VIII detection in the northeast regions was marginal. The surface brightness of the O VIII line in 10 −7 photons cm −2 s −1 arcmin −2 was measured to be 2.7 ± 1.0, 2.1 ± 1.2 for the 2.2-3.3, 3.3-4.4 Mpc regions, giving the upper limit on the baryon overdensity of δ = 319(< 443), 283(< 446), respectively. This is comparable with previous observations of cluster outskirts and their theoretical predictions. The future prospect for WHIM detection using the Athena X-IFU microcalorimeter is briefly discussed here. In addition, we also derived the ICM temperature distribution of A2744 to detect a clear discontinuity at the location of the radio relic. This suggests that the cluster has undergone strong shock heating by mass accretion along the filament.

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Section: Observation and Data Reductionsupporting

confidence: 73%

Search for the warm–hot intergalactic medium around A 2744 using Suzaku

Hattori

Ota

Zhang

et al. 2017

Publications of the Astronomical Society of Japan

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“…We checked the observation for contamination by solar wind charge exchange. The ACE SWEPAM 1 proton flux was less than 4 × 10 8 protons s −1 cm −2 which is typical of the quiescent Sun (e.g., Snowden et al 2004;Fujimoto et al 2007;Yoshino et al 2009), and the light curve accumulated in a 0.5−2 keV energy band (after soft proton flares removal) did not show any variability. The spectra of the out-of-field-of-view events of CCD 4 and 5 of MOS1 and CCD 5 of MOS 2 showed an anomalously high flux in the soft band (see ) so they were therefore excluded from our analysis.…”

Section: Observation and Data Reductionmentioning

confidence: 91%

Apparent high metallicity in 3–4 keV galaxy clusters: the inverse iron-bias in action in the case of the merging cluster Abell 2028

Gastaldello¹,

Ettori²,

Balestra³

et al. 2010

A&A

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Context. Recent work based on a global measurement of the ICM properties finds evidence for an increase in the iron abundance in galaxy clusters with temperatures around 2−4 keV up to a value about 3 times higher than is typical of very hot clusters Z Fe 0.25 Z . Aims. We have started a study of the metal distribution in nearby X-ray luminous poor galaxy clusters in the temperature range 3−4 keV with measured high abundances. Our study aims at spatially resolving the metal content of the central regions of the ICM, in particular characterizing how our measurements are biased by the diagnostics adopted and by the possible multi-temperature nature of the projected observed spectra. We report here on a 42 ks XMM-Newton observation of the first object in the sample, the cluster Abell 2028. Methods. We selected interesting regions of the ICM to analyze the spatially resolved structure of projected temperature and abundance, thereby producing two-dimensional maps. Results. The XMM-Newton observation of the first object of the sample, the cluster Abell 2028, reveals the complex structure of the cluster over a scale of ∼300 kpc, showing an interaction between two subclusters in cometary-like configurations. Cold fronts have been detected at the leading edges of the two substructures. The core of the main subcluster is likely hosting a cool corona. We show that a one-component fit for this region returns a biased high metallicity. The inverse iron bias is caused by the behavior of the fitting code in shaping the Fe-L complex. In the presence of a multi-temperature structure of the ICM, the best-fit metallicity turns out to be artificially higher when the projected spectrum is modeled with a single temperature component, while it is not related to the presence of both Fe-L and Fe-K emission lines in the spectrum. After accounting for the inverse iron bias, the overall abundance of the cluster is consistent with the one typical of hotter, more massive clusters. Conclusions. We caution against interpreting high abundances inferred when fitting a single thermal component to spectra derived from relatively large apertures in 3−4 keV clusters, because the inverse iron bias can be present. Most of the inferences trying to relate high abundances in 3−4 keV clusters to fundamental physical processes will probably have to be revised.

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“…the charge exchange mechanism in the earth vicinity in interplanetary space (see e.g. Cox 1998;Cravens 2000;Fujimoto et al 2007). For the RGS the X-ray background can be treated as an extended source.…”

Section: X-ray Backgroundmentioning

confidence: 99%

Calibration and in-orbit performance of the reflection grating spectrometer onboardXMM-Newton

Vries

Herder

Gabriel

et al. 2015

A&A

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Context. XMM-Newton was launched on 10 December 1999 and has been operational since early 2000. One of the instruments onboard XMM-Newton is the reflection grating spectrometer (RGS). Two identical RGS instruments are available, with each RGS combining a reflection grating assembly and a camera with charge-coupled devices to record the spectra. Aims. We describe the calibration and in-orbit performance of the RGS instrument. By combining the preflight calibration with appropriate inflight calibration data including the changes in detector performance over time, we aim at profound knowledge about the accuracy in the calibration. This will be crucial for any correct scientific interpretation of spectral features for a wide variety of objects. Methods. Ground calibrations alone are not able to fully characterize the instrument. Dedicated inflight measurements and constant monitoring are essential for a full understanding of the instrument and the variations of the instrument response over time. Physical models of the instrument are tuned to agree with calibration measurements and are the basis from which the actual instrument response can be interpolated over the full parameter space. Results. Uncertainties in the instrument response have been reduced to <10% for the effective area and <6 mÅ for the wavelength scale (in the range from 8 Å to 34 Å). The remaining systematic uncertainty in the detection of weak absorption features has been estimated to be 1.5%. Conclusions. Based on a large set of inflight calibration data and comparison with other instruments onboard XMM-Newton, the calibration accuracy of the RGS instrument has been improved considerably over the preflight calibrations.

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Evidence for Solar-Wind Charge-Exchange X-Ray Emission from the Earth’s Magnetosheath

Cited by 175 publications

References 28 publications

Search for the warm–hot intergalactic medium around A 2744 using Suzaku

Search for the warm–hot intergalactic medium around A 2744 using Suzaku

Apparent high metallicity in 3–4 keV galaxy clusters: the inverse iron-bias in action in the case of the merging cluster Abell 2028

Calibration and in-orbit performance of the reflection grating spectrometer onboardXMM-Newton

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