2015A&A...579A..87M


C.D.S. - SIMBAD4 rel 1.7 - 2019.11.15CET12:20:18

2015A&A...579A..87M - Astronomy and Astrophysics, volume 579A, 87-87 (2015/7-1)

Line absorption of He-like triplet lines by Li-like ions. Caveats of using line ratios of triplets for plasma diagnostics.

MEHDIPOUR M., KAASTRA J.S. and RAASSEN A.J.J.

Abstract (from CDS):

He-like ions produce distinctive series of triplet lines under various astrophysical conditions. However, this emission can be affected by line absorption from Li-like ions in the same medium. We investigate this absorption of He-like triplets and present the implications for diagnostics of plasmas in photoionisation equilibrium using the line ratios of the triplets. Our computations were carried out for the OVI and FeXXIV absorption of the OVII and FeXXV triplet emission lines, respectively. The fluorescent emission by the Li-like ions and continuum absorption of the He-like ion triplet lines are also investigated. We determine the absorption of the triplet lines as a function of Li-like ion column density and velocity dispersion of the emitting and absorbing medium. We find OVI line absorption can significantly alter the OVII triplet line ratios in optically-thin plasmas, by primarily absorbing the intercombination lines, and to a lesser extent, the forbidden line. Because of intrinsic line absorption by OVI inside a photoionised plasma, the predicted ratio of forbidden to intercombination line intensity for the OVII triplet increases from 4 up to an upper limit of 16. This process can explain the triplet line ratios that are higher than expected and that are seen in some X-ray observations of photoionised plasmas. For the FeXXV triplet, line absorption by FeXXIV becomes less apparent owing to significant fluorescent emission by FeXXIV. Without taking the associated Li-like ion line absorption into account, the density diagnosis of photoionised plasmas using the observed line ratios of the He-like ion triplet emission lines can be unreliable, especially for low-Z ions.

Abstract Copyright:

Journal keyword(s): techniques: spectroscopic - atomic processes - atomic data - X-rays: general

Simbad objects: 6

goto Full paper

goto View the reference in ADS

Number of rows : 6

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 M 77 GiP 02 42 40.771 -00 00 47.84 9.70 9.61 8.87 10.1 9.9 ~ 3991 2
2 Mrk 3 Sy2 06 15 36.458 +71 02 15.24 14.21 14.03 12.97     ~ 828 3
3 NGC 4051 Sy1 12 03 09.6098828919 +44 31 52.693714606   11.08 12.92 9.94   ~ 1954 1
4 NGC 4151 Sy1 12 10 32.5771747733 +39 24 21.057727323   12.18 11.48     ~ 3308 2
5 NGC 4593 Sy1 12 39 39.4435521178 -05 20 39.035028119   13.95 13.15     ~ 916 0
6 NGC 5548 Sy1 14 17 59.5401093128 +25 08 12.600227883   14.35 13.73     ~ 2336 0

    Equat.    Gal    SGal    Ecl

To bookmark this query, right click on this link: simbad:objects in 2015A&A...579A..87M and select 'bookmark this link' or equivalent in the popup menu


2019.11.15-12:20:18

© Université de Strasbourg/CNRS

    • Contact