X-ray emission from Saturn

Status Report From: e-Print archive
Posted: Monday, March 8, 2004

Astrophysics, abstract

From: Jan-Uwe Ness [view email]
Date: Wed, 14 Jan 2004 15:16:44 GMT   (639kb)
X-ray emission from Saturn

Authors: J.-U. Ness (1), J.H.M.M. Schmitt (1), S.J. Wolk (2), K. Dennerl (3), V. Burwitz (3) ((1) Hamburger Sternwarte, Universitaet Hamburg, Germany, (2) Chandra X-ray Center, Harvard-Smithsonian Center for Astrophysics, Cambridge, USA, (3) Max-Planck-Institut fuer extraterrestrische Physik, Garching, Germany)
Comments: 10 pages, 6 figures, accepted for publication in A&A

We report the first unambiguous detection of X-ray emission originating from Saturn with a Chandra observation, duration 65.5 ksec with ACIS-S3. Beyond the pure detection we analyze the spatial distribution of X-rays on the planetary surface, the light curve, and some spectral properties. The detection is based on 162 cts extracted from the ACIS-S3 chip within the optical disk of Saturn. We found no evidence for smaller or larger angular extent. The expected background level is 56 cts, i.e., the count rate is (1.6 +- 0.2) 10^-3 cts/s. The extracted photons are rather concentrated towards the equator of the apparent disk, while both polar caps have a relative photon deficit. The inclination angle of Saturn during the observation was -27 degrees, so that the northern hemisphere was not visible during the complete observation. In addition, it was occulted by the ring system. We found a small but significant photon excess at one edge of the ring system. The light curve shows a small dip twice at identical phases, but rotational modulation cannot be claimed at a significant level. Spectral modeling results in a number of statistically, but not necessarily physically, acceptable models. The X-ray flux level we calculate from the best-fit spectral models is 6.8 10^-15 erg/cm^2/s (in the energy interval 0.1-2keV), which corresponds to an X-ray luminosity of 8.7 10^14 erg/s. A combination of scatter processes of solar X-rays requires a relatively high albedo favoring internal processes, but a definitive explanation remains an open issue.
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