skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: DISCOVERY OF DIFFUSE HARD X-RAY EMISSION AROUND JUPITER WITH SUZAKU

Abstract

We report the discovery of diffuse hard (1-5 keV) X-ray emission around Jupiter in a deep 160 ks Suzaku X-ray Imaging Spectrometer data. The emission is distributed over {approx}16 x 8 Jovian radius and spatially associated with the radiation belts and the Io Plasma Torus (IPT). It shows a flat power-law spectrum with a photon index of 1.4 {+-} 0.2 with the 1-5 keV X-ray luminosity of (3.3 {+-} 0.5)x10{sup 15} erg s{sup -1}. We discussed its origin and concluded that it seems to be truly diffuse, although a possibility of multiple background point sources cannot be completely rejected with a limited angular resolution. If it is diffuse, the flat continuum indicates that X-rays arise by the nonthermal electrons in the radiation belts and/or the IPT. The synchrotron and bremsstrahlung models can be rejected from the necessary electron energy and X-ray spectral shape, respectively. The inverse-Compton scattering off solar photons by ultra-relativistic (several tens MeV) electrons can explain the energy and the spectrum but the necessary electron density is {approx}>10 times larger than the value estimated from the empirical model of Jovian charge particles.

Authors:
; ;  [1];  [2];  [3];  [4];  [5]
  1. Department of Physics, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji, Tokyo 192-0397 (Japan)
  2. Solar-Terrestrial Environment Laboratory, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601 (Japan)
  3. Department of Geophysics, Tohoku University, 6-3 Aoba, Aramaki, Aoba-ku, Sendai, Miyagi 980-8578 (Japan)
  4. Stanford Linear Accelerator Center, Standford University, 2575 Sand Hill Road, Menlo Park, CA 94025 (United States)
  5. Department of Physics, Nihon University, 1-8-14 Kanda Surugadai, Chiyoda, Tokyo 101-8308 (Japan), E-mail: ezoe@phys.metro-u.ac.jp
Publication Date:
OSTI Identifier:
21301352
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 709; Journal Issue: 2; Other Information: DOI: 10.1088/2041-8205/709/2/L178; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; BREMSSTRAHLUNG; COMPTON EFFECT; ELECTRON DENSITY; ELECTRONS; EMISSION; HARD X RADIATION; JUPITER PLANET; KEV RANGE 01-10; LUMINOSITY; MEV RANGE 10-100; PHOTONS; POINT SOURCES; RADIATION BELTS; RELATIVISTIC RANGE; SATELLITES; SPECTRA; SPECTROMETERS

Citation Formats

Ezoe, Y., Ishikawa, K., Ohashi, T., Miyoshi, Y., Terada, N., Uchiyama, Y., and Negoro, H. DISCOVERY OF DIFFUSE HARD X-RAY EMISSION AROUND JUPITER WITH SUZAKU. United States: N. p., 2010. Web. doi:10.1088/2041-8205/709/2/L178; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA).
Ezoe, Y., Ishikawa, K., Ohashi, T., Miyoshi, Y., Terada, N., Uchiyama, Y., & Negoro, H. DISCOVERY OF DIFFUSE HARD X-RAY EMISSION AROUND JUPITER WITH SUZAKU. United States. doi:10.1088/2041-8205/709/2/L178; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA).
Ezoe, Y., Ishikawa, K., Ohashi, T., Miyoshi, Y., Terada, N., Uchiyama, Y., and Negoro, H. 2010. "DISCOVERY OF DIFFUSE HARD X-RAY EMISSION AROUND JUPITER WITH SUZAKU". United States. doi:10.1088/2041-8205/709/2/L178; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA).
@article{osti_21301352,
title = {DISCOVERY OF DIFFUSE HARD X-RAY EMISSION AROUND JUPITER WITH SUZAKU},
author = {Ezoe, Y. and Ishikawa, K. and Ohashi, T. and Miyoshi, Y. and Terada, N. and Uchiyama, Y. and Negoro, H.},
abstractNote = {We report the discovery of diffuse hard (1-5 keV) X-ray emission around Jupiter in a deep 160 ks Suzaku X-ray Imaging Spectrometer data. The emission is distributed over {approx}16 x 8 Jovian radius and spatially associated with the radiation belts and the Io Plasma Torus (IPT). It shows a flat power-law spectrum with a photon index of 1.4 {+-} 0.2 with the 1-5 keV X-ray luminosity of (3.3 {+-} 0.5)x10{sup 15} erg s{sup -1}. We discussed its origin and concluded that it seems to be truly diffuse, although a possibility of multiple background point sources cannot be completely rejected with a limited angular resolution. If it is diffuse, the flat continuum indicates that X-rays arise by the nonthermal electrons in the radiation belts and/or the IPT. The synchrotron and bremsstrahlung models can be rejected from the necessary electron energy and X-ray spectral shape, respectively. The inverse-Compton scattering off solar photons by ultra-relativistic (several tens MeV) electrons can explain the energy and the spectrum but the necessary electron density is {approx}>10 times larger than the value estimated from the empirical model of Jovian charge particles.},
doi = {10.1088/2041-8205/709/2/L178; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA)},
journal = {Astrophysical Journal Letters},
number = 2,
volume = 709,
place = {United States},
year = 2010,
month = 2
}
  • The bright type I Seyfert galaxy NGC 3516 was observed by Suzaku twice, in 2005 October 12-15 and 2009 October 28-November 2, for a gross time coverage of 242 and 544 ks and a net exposure of 134 and 255 ks, respectively. The 2-10 keV luminosity was 2.8 Multiplication-Sign 10{sup 41} erg s{sup -1} in 2005 and 1.6 Multiplication-Sign 10{sup 41} erg s{sup -1} in 2009. The 1.4-1.7 keV and 1.7-10 keV count rates both exhibited peak-to-peak variations of a factor of {approx}2 in 2005 and {approx}4 in 2009. In both observations, the 15-45 keV count rate was less variable.more » The 2-10 keV spectrum in 2005 was significantly more convex than that in 2009. Through a count-count plot technique, the 2-45 keV signals in both sets of data were successfully decomposed in a model-independent way into two distinct broadband components. One is a variable emission with a featureless spectral shape, and the other is a non-varying hard component accompanied by a prominent Fe-K emission line at 6.33 keV (6.40 keV in the rest frame). The former was successfully fitted by an absorbed power-law model, while the latter requires a new hard continuum in addition to a reflection component from distant materials. The spectral and variability differences between the two observations are mainly attributed to long-term changes of this new hard continuum, which was stable on timescales of several hundreds of kiloseconds.« less
  • We present Suzaku X-ray observations along two edge regions of the Fermi Bubbles, with eight ≅ 20 ks pointings across the northern part of the North Polar Spur (NPS) surrounding the north bubble and six across the southernmost edge of the south bubble. After removing compact X-ray features, diffuse X-ray emission is clearly detected and is well reproduced by a three-component spectral model consisting of unabsorbed thermal emission (temperature kT ≅ 0.1 keV) from the Local Bubble, absorbed kT ≅ 0.3 keV thermal emission related to the NPS and/or Galactic halo (GH), and a power-law component at a level consistentmore » with the cosmic X-ray background. The emission measure (EM) of the 0.3 keV plasma decreases by ≅ 50% toward the inner regions of the northeast bubble, with no accompanying temperature change. However, such a jump in the EM is not clearly seen in the south bubble data. While it is unclear whether the NPS originates from a nearby supernova remnant or is related to previous activity within or around the Galactic center, our Suzaku observations provide evidence that suggests the latter scenario. In the latter framework, the presence of a large amount of neutral matter absorbing the X-ray emission as well as the existence of the kT ≅ 0.3 keV gas can be naturally interpreted as a weak shock driven by the bubbles' expansion in the surrounding medium, with velocity v {sub exp} ∼ 300 km s{sup –1} (corresponding to shock Mach number M≃1.5), compressing the GH gas to form the NPS feature. We also derived an upper limit for any non-thermal X-ray emission component associated with the bubbles and demonstrate that, in agreement with the aforementioned findings, the non-thermal pressure and energy estimated from a one-zone leptonic model of its broadband spectrum, are in rough equilibrium with that of the surrounding thermal plasma.« less
  • We present the direct imaging discovery of an extrasolar planet, or possible low-mass brown dwarf, at a projected separation of 55 {+-} 2 AU (1.''058 {+-} 0.''007) from the B9-type star {kappa} And. The planet was detected with Subaru/HiCIAO during the SEEDS survey and confirmed as a bound companion via common proper motion measurements. Observed near-infrared magnitudes of J = 16.3 {+-} 0.3, H = 15.2 {+-} 0.2, K{sub s} = 14.6 {+-} 0.4, and L' = 13.12 {+-} 0.09 indicate a temperature of {approx}1700 K. The galactic kinematics of the host star are consistent with membership in the Columbamore » Association, implying a corresponding age of 30{sup +20}{sub -10} Myr. The system's age, combined with the companion photometry, points to a model-dependent companion mass {approx}12.8 M{sub Jup}. The host star's estimated mass of 2.4-2.5 M{sub Sun} places it among the most massive stars ever known to harbor an extrasolar planet or low-mass brown dwarf. While the mass of the companion is close to the deuterium burning limit, its mass ratio, orbital separation, and likely planet-like formation scenario imply that it may be best defined as a 'super-Jupiter' with properties similar to other recently discovered companions to massive stars.« less
  • We present the first dedicated X-ray study of the supernova remnant (SNR) G32.8−0.1 (Kes 78) with Suzaku. X-ray emission from the whole SNR shell has been detected for the first time. The X-ray morphology is well correlated with the emission from the radio shell, while anti-correlated with the molecular cloud found in the SNR field. The X-ray spectrum shows not only conventional low-temperature (kT ∼ 0.6 keV) thermal emission in a non-equilibrium ionization state, but also a very high-temperature (kT ∼ 3.4 keV) component with a very low ionization timescale (∼2.7 × 10{sup 9} cm{sup −3} s), or a hard nonthermal component with a photon index Γmore » ∼ 2.3. The average density of the low-temperature plasma is rather low, of the order of 10{sup −3}–10{sup −2} cm{sup −3}, implying that this SNR is expanding into a low-density cavity. We discuss the X-ray emission of the SNR, also detected in TeV with H.E.S.S., together with multi-wavelength studies of the remnant and other gamma-ray emitting SNRs, such as W28 and RCW 86. Analysis of a time-variable source, 2XMM J185114.3−000004, found in the northern part of the SNR, is also reported for the first time. Rapid time variability and a heavily absorbed hard-X-ray spectrum suggest that this source could be a new supergiant fast X-ray transient.« less
  • We searched for redshifted O emission lines from the possible warm-hot intergalactic medium (WHIM) surrounding the cluster of galaxies A2218 at z = 0.1756 using the XIS instrument on Suzaku. This cluster is thought to have an elongated structure along the line of sight based on previous studies. We studied systematic uncertainties in the spectrum of the Galactic emission and in the soft X-ray response of the detectors due to the contamination building up on the XIS filters. We detected no significant redshifted O lines, and set a tight constraint on the intensity with upper limits for the surface brightnessmore » of O{sub VII} and O{sub VIII} lines of 1.1 x 10{sup -7} and 3.0 x 10{sup -7} photons cm{sup -2} s{sup -1} arcmin{sup -2}, respectively. These upper limits are significantly lower than the previously reported fluxes from the WHIM around other clusters of galaxies. We also discuss the prospect for the detection of the WHIM lines with Suzaku XIS in the future.« less