Cloudy in the microcalorimeter era: improved energies for K α transitions
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Cloudy in the microcalorimeter era: improved energies for K α transitions P. Chakraborty , G. J. Ferland , S.Bianchi , and M. Chatzikos University of KentuckyLexington, KY, USA Dipartimento di Matematica e Fisica, Universit`a degli Studi Roma Tre, via della Vasca Navale 84, I-00146 Roma, Italy
ABSTRACTX-ray missions with microcalorimeter technology will resolve spectral features with unprecedenteddetail. In this work, we improve the H-like K α energies for elements between 6 ≤ Z ≤
30 for therelease version of the spectral simulation code Cloudy to match laboratory energies. We update theionization potential ( I ion ) for these elements and add a fourth-order polynomial to the level energydifference. This brings the release version of Cloudy into a near-perfect agreement with NIST. Theupdated energies are ∼ Keywords:
High resolution Spectroscopy — X-ray astronomyINTRODUCTIONCloudy (Ferland et al. 2017) has long predicted intensities of X-ray lines due to its need to do physical simulations ofa non-equilibrium plasma. The original design for one and two-electron species took advantage of scaling relationshipsalong iso-electronic sequences. A series of papers, part of Ryan Porter’s thesis, reporting on this development includePorter et al. (2005) and Porter et al. (2012) on optical emission from He I and Porter & Ferland (2007) on X-rayemission from O VII. While the physics remains close to state of the art, the level energies and line wavelengthsderived in the older work had largely sufficient accuracy for the then-operational optical observatories and X-raymissions but not future missions.The available spectroscopic resolution has increased dramatically with the advent of microcalorimeter missions likeHitomi and the upcoming missions XRISM and Athena. We are now extending Cloudy to meet the spectroscopicchallenges of such missions as part of Priyanka Chakraborty’s thesis. The first papers focused on two-electron Fe K α emission. Chakraborty et al. (2020a) discussed line interlocking and Resonant Auger Destruction (Ross et al. 1978;Band et al. 1990; Ross et al. 1996; Liedahl 2005), and electron scattering escape (ESE) in the Fe XXV K α complex.Chakraborty et al. (2020b) discussed the Case A to B transition in H- and He- like iron. These atomic processes arevery sensitive to line wavelengths due to line overlap with nearby satellites (Mehdipour et al. 2015; Chakraborty et al.2020a) and require precise energies. This development is a work in progress and will be part of a future release ofCloudy. In the meantime, we have improved the treatment of levels and line energies in the release version of Cloudy,as described below. These improvements will be part of the C17.03 release in late 2020.RESULTSThe previous versions of Cloudy, through to C17.02, used ionization potentials ( I ion ) derived by Verner et al. (1996)with four significant digits. Level energies were then derived from the following equation: I n = I ion /n (1)and the K α energies were calculated from: E oldK α = I − I (2)The I ion ’s in equation 1, stored in the ‘phfit.dat’ file in the Cloudy data directory, were used to compute thephotoionization cross-sections in Verner et al. (1996). Although these values are reasonably accurate, microcalorimeter a r X i v : . [ a s t r o - ph . I M ] O c t observations require much better precision. We update the I ion ’s in ‘phfit.dat’ for H-like ions with those of NIST(Kramida et al. 2018), keeping up to the eighth significant digits. Our updated version of ‘phfit.dat’ will be includedin the C17.03 release.Following this, we generated a fourth-order polynomial for the energy correction (∆ E ) for better agreement withthe NIST K α energies: ∆ E = 0 . Z − . Z + 27 . Z − . Z + 570 .
59 (3)The updated energies ( E newK α ) for the K α transitions are given by the following equation: E newK α = E oldK α + ∆ E (4) R G S R G S
10 Atomic Number (Z) 3020 C h a n d r a M E G C h a n d r a H E G ( R G S ) X M M - N e w t o n XRISM
Athena
New with correctionOld | C l o u d y - N I S T | K α En e r g i e s ( i n e V ) −4 −3 Kα energies (eV)
Figure 1.
The absolute value of the difference between NIST and Cloudy K α energies versus K α energies for H-like ions ofelements between 6 ≤ Z ≤
30. The x-axis on top shows the corresponding atomic numbers (Z). Red triangles show the differencebetween energies in the updated version of Cloudy (C17.03) and NIST. Green circles show the energy difference between theprevious versions of Cloudy (from ∼ Figure 1 shows the absolute values of the differences in K α energies between NIST and Cloudy for H-like ions versusK α energies for elements between 6 ≤ Z ≤
30. The red triangles and green circles show the difference with NIST forthe updated Cloudy (C17.03) energies and the old Cloudy energies appearing in C17.02 and before, respectively. Thefigure also shows the absolute values of the energy accuracy of current and future X-ray observatories. The solid anddashed magenta lines represent the energy accuracy of Chandra HEG and MEG, respectively . The solid and dotted https://cxc.harvard.edu/proposer/POG/html/chap8.html brown lines indicate the accuracy of RGS1 (1 st and 2 nd order) and RGS2 (1 st and 2 nd order) onboard XMM-Newton .The solid black and blue lines represent the energy accuracy of XRISM (Ishisaki et al. 2018) and Athena (Barret et al.2016), respectively. The updated K α energies in the revised Cloudy release (C17.03) are ∼ α energies ( E newK α ). These changes will be part of C17.03, and are now posted to the Cloudy user group . Updates onthe development of Cloudy are posted to its wiki .The improvement described here is made only for the K α energies for elements between Carbon (Z=6) and Zinc(Z=30) since it is negligible for lighter elements. The doublet splitting for the 2p levels is not included in this updatebut is part of the thesis work and will be incorporated into the next major release of Cloudy. This future version willread extensive data files from NIST instead of using the above correction.ACKNOWLEDGMENTSWe acknowledge support by NSF (1816537, 1910687), NASA (17-ATP17-0141, 19-ATP19-0188), and STScI (HST-AR-15018). MC also acknowledges support from STScI (HST-AR-14556.001-A). SB acknowledges financial supportfrom the Italian Space Agency (grant 2017-12-H.0) and from the PRIN MIUR project ‘Black Hole winds and theBaryonLife Cycle of Galaxies: the stone-guest at the galaxy evolution supper’, contract 2017-PH3WAT.REFERENCES Band, D. L., Klein, R. I., Castor, J. I., & Nash, J. K. 1990,ApJ, 362, 90, doi: 10.1086/169245Barret, D., Lam Trong, T., den Herder, J.-W., et al. 2016,in Society of Photo-Optical Instrumentation Engineers(SPIE) Conference Series, Vol. 9905, Space Telescopesand Instrumentation 2016: Ultraviolet to Gamma Ray,99052F, doi: 10.1117/12.2232432Chakraborty, P., Ferland, G. J., Chatzikos, M., Guzm´an,F., & Su, Y. 2020a, ApJ, 901, 68,doi: 10.3847/1538-4357/abaaab—. 2020b, ApJ, 901, 69, doi: 10.3847/1538-4357/abaaacFerland, G. J., Chatzikos, M., Guzm´an, F., et al. 2017,RMxAA, 53, 385. https://arxiv.org/abs/1705.10877Ishisaki, Y., Ezoe, Y., Yamada, S., et al. 2018, Journal ofLow Temperature Physics, 193, 991,doi: 10.1007/s10909-018-1913-4Kramida, A., Ralchenko, Y., Nave, G., & Reader, J. 2018,in APS Division of Atomic, Molecular and OpticalPhysics Meeting Abstracts, Vol. 2018, M01.004 Liedahl, D. A. 2005, in American Institute of PhysicsConference Series, Vol. 774, X-ray Diagnostics ofAstrophysical Plasmas: Theory, Experiment, andObservation, ed. R. Smith, 99–108,doi: 10.1063/1.1960918Mehdipour, M., Kaastra, J. S., & Raassen, A. J. J. 2015,A&A, 579, A87, doi: 10.1051/0004-6361/201526324Porter, R. L., Bauman, R. P., Ferland, G. J., & MacAdam,K. B. 2005, ApJL, 622, L73, doi: 10.1086/429370Porter, R. L., & Ferland, G. J. 2007, ApJ, 664, 586,doi: 10.1086/518882Porter, R. L., Ferland, G. J., Storey, P. J., & Detisch, M. J.2012, MNRAS, 425, L28,doi: 10.1111/j.1745-3933.2012.01300.xRoss, R. R., Fabian, A. C., & Brandt, W. N. 1996,MNRAS, 278, 1082, doi: 10.1093/mnras/278.4.1082Ross, R. R., Weaver, R., & McCray, R. 1978, ApJ, 219,292, doi: 10.1086/155776Verner, D. A., Ferland, G. J., Korista, K. T., & Yakovlev,D. G. 1996, ApJ, 465, 487, doi: 10.1086/177435 https://xmm-tools.cosmos.esa.int/external/xmm user support/documentation/uhb/rgs.html https://cloudyastrophysics.groups.io/g/Main/topics4