NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Coronal Emission from dG Halo StarsThe halo dG star HD 114762 was observed with the XMM-Newton satellite on 28-29 June 2004, during orbit 834, and the data were processed using the XMM-Newton Science Analysis System (SAS), version 6.0.0. Somewhat surprisingly, the target was NOT detected during this approx.30 ks exposure, which yielded instead a count rate upper limit of less than 0.0041 cts/s. We computed an X-ray flux upper limit by assuming a Raymond-Smith thermal spectrum of coronal temperature 1 million degrees K, typical of quiet old stars, a hydrogen column density of 2-10$^{19)$ cm$^{-2)$ and sub-solar abundances of 0.2. Our calculated X-ray luminosity upper limit in the 0.25-7.8 keV band is L$_x < 4.95 $\time$10$^{26)$ erg/s, where we have assumed a stellar distance of 28 pc. This relatively low upper limit has implications for the capability of metal poor stars to host solar-like dynamos, as we will report in a forthcoming paper (now in preparation).
Document ID
20050185212
Acquisition Source
Headquarters
Document Type
Contractor or Grantee Report
Authors
Mushotzky, Richard
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Harnden, F. R.
(Smithsonian Astrophysical Observatory Cambridge, MA, United States)
Date Acquired
August 23, 2013
Publication Date
June 1, 2005
Subject Category
Astronomy
Funding Number(s)
CONTRACT_GRANT: NNG04GM96G
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
Document Inquiry

Available Downloads

There are no available downloads for this record.
No Preview Available