Discovery of X–rays from Venus with Chandra

Dennerl, K.; Burwitz, V.; Englhauser, J.; Lisse, C. M.; Wolk, S. J.

doi:10.1051/0004-6361:20020097

Cited by 65 publications

(79 citation statements)

References 30 publications

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“…Adopting a total X-ray flux f x = 9 × 10 −14 erg cm −2 s −1 , a ratio f x / f opt = 5 × 10 −10 follows. This is similar to the value 2 × 10 −10 observed for Venus (Dennerl et al 2002a). In the case of X-ray fluorescence, the f x / f opt ratio of Mars is generally expected to exceed that of Venus, because the optical albedo of Mars is lower than that of Venus, while their X-ray albedos are comparable.…”

Section: Spectrum X-ray Flux and Luminositysupporting

confidence: 90%

“…4.5) was actually observed. The reason for the limb brightening and the different appearance of Mars in the three fluorescent lines is very similar to the case of Venus, and a discussion can be found in Dennerl et al (2002a). The close match between the simulated and observed morphology is an argument in favor of X-ray fluorescence as the dominant process responsible for the X-ray radiation of Mars.…”

supporting

confidence: 64%

“…The values for the photoabsorption cross sections were taken from Reilman & Manson (1979), supplemented by the following K-edge energies (see Dennerl et al 2002a for a discussion of these energies): E K C = 296.1 eV, E K N = 409.9 eV, E K O = 544.0 eV. From these values and the C, N, and O 2 Argon would produce a K α fluorescence line at 2.96 keV with a fluorescence yield y Ar = 0.118 (Krause 1979), which exceeds that of nitrogen by a factor of 20.…”

Section: Photoabsorption Cross Sectionsmentioning

confidence: 99%

“…The simulated images were synthesized with 20 km resolution perpendicular to the line of sight. Details about the simulation itself can be found in Dennerl et al (2002a). • (terminator, dashed lines) for the incident solar spectrum of Fig.…”

Section: Model Gridmentioning

confidence: 99%

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Discovery of X–rays from Mars with Chandra

Dennerl

2002

A&A

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107

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Abstract. On 4 July 2001, X-rays from Mars were detected for the first time. The observation was performed with the ACIS-I detector onboard Chandra and yielded data of high spatial and temporal resolution, together with spectral information. Mars is clearly detected as an almost fully illuminated disk, with an indication of limb brightening at the sunward side, accompanied by some fading on the opposite side. The morphology and the X-ray luminosity of ∼4 MW are fully consistent with fluorescent scattering of solar X-rays in the upper Mars atmosphere. The X-ray spectrum is dominated by a single narrow emission line, which is most likely caused by O-K α fluorescence. No evidence for temporal variability is found. This is in agreement with the solar X-ray flux, which was almost constant during the observation. In addition to the X-ray fluorescence, there is evidence for an additional source of X-ray emission, indicated by a faint X-ray halo which can be traced to about three Mars radii, and by an additional component in the X-ray spectrum of Mars, which has a similar spectral shape as the halo. Within the available limited statistics, the spectrum of this component can be characterized by 0.2 keV thermal bremsstrahlung emission. This is indicative of charge exchange interactions between highly charged heavy ions in the solar wind and exospheric hydrogen and oxygen around Mars. Although the observation was performed at the onset of a global dust storm, no evidence for dust-related X-ray emission was found.

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Section: Spectrum X-ray Flux and Luminositysupporting

confidence: 90%

supporting

confidence: 64%

Section: Photoabsorption Cross Sectionsmentioning

confidence: 99%

Section: Model Gridmentioning

confidence: 99%

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Discovery of X–rays from Mars with Chandra

Dennerl

2002

A&A

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107

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“…The flux f x (ϕ, i d ) can be obtained by modeling the individual scattering and absorption processes, as described in Dennerl et al (2002). We obtain L x (d) = (3.4 ± 0.4) MW for fluorescence of oxygen (lines CO2a and CO2b) and nitrogen (line N22) 5 .…”

Section: Luminosity Of the Disk And Halomentioning

confidence: 99%

First observation of Mars with XMM-Newton

Dennerl

Lisse

Bhardwaj

et al. 2006

A&A

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117

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In the first observation of Mars with XMM-Newton, on 20−21 November 2003, this planet is clearly detected as an X-ray source. High resolution X-ray spectroscopy with the Reflection Grating Spectrometer (RGS) confirms that the X-ray radiation from Mars is composed of two different components: one due to fluorescent scattering of solar X-rays in its upper atmosphere and the other one due to solar wind charge exchange in its exosphere. Close to Mars, the RGS spectrum is dominated by two pronounced CO 2 fluorescence lines at 23.5 Å and 23.7 Å. Fluorescence from N 2 at 31.5 Å is also observed. With increasing distance from Mars, these lines fade, while numerous (∼12) emission lines become prominent at the positions expected for de-excitation of highly ionized C, N, O, and Ne atoms, strongly resembling a cometary X-ray spectrum. The He-like O 6+ multiplet is resolved and is dominated by the spin-forbidden magnetic dipole transition 2 3 S 1 → 1 1 S 0 , confirming charge exchange as the origin of the emission, while the resonance line 2 1 P 1 → 1 1 S 0 increases in intensity closer to Mars, where the density of the exosphere is higher. The high spectral dispersion and throughput of XMM-Newton / RGS make it possible to produce X-ray images of the Martian exosphere in individual emission lines, free from fluorescent radiation. They show extended emission out to ∼8 Mars radii, with morphological differences between individual ions and ionization states. This is the first definite detection of charge exchange induced X-ray emission from the exosphere of another planet, providing a direct link to cometary X-ray emission.

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Chandra X‐ray Observatory

Weisskopf

2003

Encyclopedia of Space Science and Technology

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The Chandra X‐ray Observatory (originally called the Advanced X‐ray Astrophysics Facility—AXAF) is the X‐ray component of NASA's “Great Observatory” Program. Chandra is a NASA facility that provides scientific data to the international astronomical community in response to scientific proposals for using it. The Observatory is the product of the efforts of many organizations in the United States and Europe. The Great Observatories also include the Hubble Space Telescope for space‐based observations of astronomical objects primarily in the visible portion of the electromagnetic spectrum, the now defunct Compton Gamma‐Ray Observatory that was designed to observe gamma‐ray emission from astronomical objects, and the soon‐to‐be‐launched Space Infrared Telescope Facility (SIRTF). The Chandra X‐ray Observatory (hereafter CXO) is sensitive to X rays in the energy range from below 0.1 to above 10.0 keV, corresponding to wavelengths from 12 to 0.12 nanometers. The relationships among the various parts of the electromagnetic spectrum, sorted by characteristic temperature and the corresponding wavelength are illustrated in this article. X‐ray astronomy is an extremely important field because it has been found that all categories of astronomical objects (or a subset thereof), from comets to quasars, emit X‐rays. Thus learning how and why these objects produce X‐rays are fundamental to our understanding of the way astronomical systems work. This, together with the large amounts of energy required to produce X‐rays, makes their study interesting and exciting. A second reason that the field is so important is that the vast bulk of the matter in the Universe that we can directly observe through the electromagnetic radiation that it emits is in the very hot (temperatures of millions of degrees) X‐ray emitting gas that fills the space between galaxies in clusters of galaxies, the largest collections of matter in the Universe. The CXO is the prime method of gaining new information about the X‐ray emission seen in the Universe. The CXO was named in honor of the late Indian‐American Nobel laureate, Subrahmanyan Chandrasekhar, nicknamed “Chandra” which means “moon” or “luminous” in Sanskrit. He was one of the foremost astrophysicists of the twentieth century and, in 1983, was awarded the Nobel prize for his studies of the physical processes important to the structure and evolution of stars. The observatory and its instrumentation are discussed. Scientific results are detailed CXO's role in solving the mystery of gamma ray bursts is also discussed.

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Discovery of X–rays from Venus with Chandra

Cited by 65 publications

References 30 publications

Discovery of X–rays from Mars with Chandra

Discovery of X–rays from Mars with Chandra

First observation of Mars with XMM-Newton

Chandra X‐ray Observatory

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