hmm..> Nancy and Jeremy, hmm..> hmm..> Are there any astrophysical lines whose energy hmm..> (wavelength) you would say is known to 1 part hmm..> in 30000 ? Is there any line which is or will hmm..> be defined as a "standard" in the 0.9 to 1.5 keV hmm..> range? hmm..> hmm..> -Dan hmm..> Date: Wed, 9 Jul 1997 16:18:41 -0400 From: jdrake@duncan.harvard.edu (Jeremy Drake) Message-Id: <199707092018.QAA19820@duncan> To: dd Subject: Re: emmission line Cc: bhouse@duncan.harvard.edu X-Sun-Charset: US-ASCII Status: R Hello Dan, That's a good question and one I was trying to find the answer to last year (I append Jack Sugar's e-mail reply below). The "simple" lines (H-like) are the ones that will be known with most accuracy through calculations. The limit for run-of-the-mill lines (eg Fe L) are going to be governed by how accurate the empirical energy levels and wavelengths are, unless you want to believe someone's theoretical work to that accuracy, which I would strongly suggest is not a good idea. 1/30000 is pushing it, partly I think just because many of the lab X-ray spectrometers used for some of that work don't generally have that high resolving power. Before my office was moved, I had a couple of papers (cited in Sugar e-mail) that has some definitive wavelengths to fairly high accuracy, but not quite 1/30000. Also, while this figure is 10km/s in radial velocity terms which will be well-known for stars, there are likely to be line shifts of much larger amplitude that will prevent us from getting to this number for in-orbit calibration, even if the line wavelengths are known to good accuracy. So, I think 30,000 is too optimistic for in-orbit. Nancy also pointed out the fine structure compliations (message appended below in case you didn't get it), which will degrade the accuracy of centroids a bit. Cheers, JEremy ----- Begin Included Message ----- >From SUGAR@ENH.NIST.GOV Tue Oct 15 11:58:25 1996 From: SUGAR@ENH.NIST.GOV Date: Tue, 15 Oct 1996 11:57:32 -0400 (EDT) Subject: x-ray line wavelengths To: jdrake@duncan.harvard.edu X-PS-Qualifiers: /LEFT_MARGIN=6/SIZE=11 X-VMS-To: IN%"jdrake@duncan.harvard.edu" MIME-version: 1.0 Content-transfer-encoding: 7BIT Dear Dr. Drake, In reply to your e-mail note of Oct. 8 regarding the accuracy of wavelengths of L-shell transitions in cosmically abundant elements, we have improved the experimental accuracy of spectral lines of highly-ionized elements of the Fe-period, namely, Cr, Fe, and Ni. I am sending you reprints of the articles on this work. The paper by Reader et al. in JOSA B 11, 1930 (1994) contains Fe XXIV lines at 30-32 A and 6-11 A is measured with an accuracy of +-0.002 to 0.004 A. For Fe lines in the range of 91-263 A given by Sugar and Rowan, JOSA B 12, 1404 (1995) the accuracy is +- 0.005 A. For similar data on Cr and Ni see references see Sugar et al. JOSA B 10, 13 (1993) and JOSA B 9, 344 (1992). Of course He-like and H-like ions are calculated with much greater accuracy. Regards, Jack Sugar ----- End Included Message ----- ----- Begin Included Message ----- >From bhouse@head-cfa.harvard.edu Wed Jul 9 15:25:16 1997 To: jdrake@cfa.harvard.edu cc: bhouse@head-cfa.harvard.edu Subject: what I know about lines Date: Wed, 09 Jul 1997 15:25:13 -0400 From: Nancy Brickhouse Brad Wargelin and co-authors have recently submitted a paper on the 7 to 9 Angstrom spectral region. They use the Mg and Na H-like Lyman series and He-like K series, and state that the theoretical wavelengths are accurate to better than .0001 Angstrom. The references they cite are Garcia and Mack (1965, J. Opt. Soc. Am., 55, 654), Safranova (1986, private communication) and they also use the new version of Kelly (1987). The experimental wavelengths (from my version of Kelly, which is 1982, there is a newer version) are good to better than .002 Angstroms, so the theory is expected to be much better. So the answer is yes, but there may be a pragmatic problem, because of fine structure or other line blending. If you wanted to use Ne X Ly alpha (12.132 Angstrom) there are two fine structure lines which are .006 Angstroms apart which you can't resolve. There would be other lines from the series like Ne X Ly beta at 10.24 Angstroms. That had about 200 counts in the Capella simulation at 100 ks. But that's where the missing Fe is a big question. Then the lines get progressively weaker, so Ne X Ly gamma (9.71 A) has only about 50 counts. ----- End Included Message -----