Spectroscopic Separation of Solar Wind Charge Exchange, Local Bubble, and Nearby Supernova Remnant X-rays:
Diffuse X-ray Spectrometer (DXS) Recent Results
Morgenthaler et al. AAS 2011 Boston Meeting Oral presentation #219.06
DXS
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DXS shown during its 1993 Shuttle flight
Authors/Acknowledgements • Jeffrey P. Morgenthaler (PSI) • Richard J. Edgar (Harvard-Smithsonian CfA) • Wilton T. Sanders (NASA HQ) • Randall K. Smith (Harvard-Smithsonian CfA) • Dimitra Koutroumpa (NASA/GSFC) • David B. Henley (University of Georgia) • Robin L. Shelton (University of Georgia) • Ina P. Robertson (University of Kansas) • Michael R. Collier (NASA/GSFC) • Thomas E. Cravens (University of Kansas)
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Original Wisconsin crew shown in red Particular thanks to Robin through whom I was introduced to the rest of the list
¼ keV Diffuse X-ray Background
• Old Paradigm: – “Local Bubble” – Solely Galactic
• New Paradigm: – Solar wind charge exchange mechanism (SWCX) – Local Bubble?
2 components of SWCX are particularly important Heliospheric SWCX relatively slow variation Geocoronal SWCX varies on time scales comparable to Shuttle flights Scratch chin, “we’ll get back to that.”
DXS was a dispersive spectrometer Short wavelength photons coming from this direction were collected at this end of the detector Long wavelength photons coming from that direction were collected at the other end of the detector In order to cover the entire free spectral range, DXS was rotated over a large angle
DXS Scan Path – RASS ¼ keV band map
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DXS scan path superimposed on the RASS ROSAT map centered on longitude 180° Blue regions = generic DXRB
DXS Diffuse X-ray Background
Local Bubble + Geocoronal SWCX + Heliospheric SWCX
150 eV 284 eV
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Here is a spectrum of the generic DXRB Astrophysical spectra did not fit well (Sanders et al. 2001) SWCX not considered in original DXS work
Isolating Geocoronal SWCX DX
S
Geocoronal SWCX Clean
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DXS count rate as a function of time over the 5-day Shuttle flight In my thesis I worried a lot about this: I demonstrated that these were photons coming from outside the insturment Now it is an opportunity “Clean” count rate is consistent with the RASS. Includes heliospheric SWCX and Galaxy, but not geocoronal SWCX Obviously the extra is geocoronal SWCX
Geocoronal SWCX +Heliospheric SWCX + Local Bubble
DXS Spectra, Geocoronal SWCX
Isolated Geocoronal SWCX!
150 eV 284 eV
Model = Robertson et al. (2006, 2010)
Total DXRB spectrum
SWCX with a hydrogen target
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Upper spectrum, generic DXRB from earlier slide Lower, spectrum geocoronal SWCX on – off Spectrum didn’t mean anything when I finished my thesis in 1998 Very excited when Ina Robertson handed me her geocoronal SWCX model and found that it threaded through most of the points! SWCX with a hydrogen target
Heliospheric SWCX Model Koutroumpa et al. 2009
SWCX with hydrogen and helium targets
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Solar wind onto hydrogen and helium targets
Heliospheric SWCX Model (Koutroumpa et al. 2009)
150 eV 284 eV
Total DXRB spectrum
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Convolved with DXS response matrix Room for Local Bubble emission at low energies
Heliospheric SWCX Model (Robertson et al. 2010)
284 eV 150 eV
Total DXRB spectrum
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Robertson et al. model similar
Conclusions/Future Research
• DXS measured geocoronal SWCX • Benchmark heliospheric SWCX models • Remove SWCX from any diffuse X-ray data • Isolate LISM X-ray spectrum • LISM ISM
Collapse previous figure into 1 D DXS counting rate as a function of Galactic longitude Cleaned ROSAT all-sky survey count rate compares nicely NO DOMINATED BY “LTE” (geocoronal SWCX)
