Table 2 contains the same information as Table 1 for LETGS lines which occur above 37 Å. The extracted fluxes are as measured at Earth. Therefore they are not corrected for interstellar absorption which is of the order of 4% at 100 Å, 6% at 125 Å, 10% at 150 Å, and 15% at 175 Å. We added one Fe line (Fe X at 174.69 Å) that was observed in an offset observation of Procyon (obsID = 1224; 14.8 ksec). For that line the effective area was obtained by extrapolation. The line flux ratio of that line compared to the line at 171.075 Å in the offset observation was used to establish the flux value.
In both tables, we have compared the measured wavelengths
with the wavelengths in various atomic databases:
the MEKAL (Mewe et al. 1985, 1995) code, KELLY (Kelly 1987) and the
database of the National Institute of Standards and Technology (NIST), which is also available
on the web
.
We have also compared with a list of lines observed in the solar corona (Doschek & Cowan 1984, hereafter D&C).
Further we compare our measured iron lines with the results
from laboratory experiments such as the Lawrence Livermore National Laboratory's
Electron Beam Ion Trap (EBIT) (see Beiersdorfer et al. 1999 and Lepson et al. 2002 for Fe VIII-X and Lepson et al. 2000 for
Fe XII-XIII).
A number of lines in Table 2 (see note "d") are in close wavelength agreement to lines identified in EBIT.
Finally in Table 1 the fluxes, from the multi-temperature global fitting of Sect. 3.2, have been added.
Some possible line identifications have been omitted from Table 2, due to the absence of comparable lines belonging to the same multiplet or ion (Table 3) or due to ambiguity of the identification of lines in atomic databases (Kelly 1987). The latter concerns lines at 60.989 Å (Si VII, VIII, & IX) and 61.852 Å (Si VIII & IX).
Earlier benchmarks with a solar flare spectrum (Phillips et al. 1999) and with RGS and LETGS spectra of Capella
(Audard et al. 2001a; Mewe et al. 2001) have already shown that the
current atomic databases are lacking quite a number of spectral lines
for L-shell transitions of Ne, Mg, Si, and S, that appear
in the long-wavelength region above about 40 Å. This is illustrated by the many identifications present in the third
column (KELLY), which are absent in MEKAL. For the Fe L-shell Behar et al. (2001) have shown that the HULLAC atomic data
are fairly accurate.
LETGS | Line identificationsa | ||||||
MEKAL | KELLY | D&C | |||||
![]() |
fluxb | ![]() |
Ion | ![]() |
Ion | ![]() |
Ion |
39.276 | 0.63(14) | 39.300 | S XI | 39.300 | S XI | 39.30 | S XI |
39.264 | Si X | ||||||
39.305 | Si X | ||||||
40.263 | 2.29(36) | 40.270 | C V | 40.268 | C V | 40.27 | C V |
40.718 | 1.88(42) | 40.730 | C V | 40.731 | C V | 40.73 | C V |
41.475 | 1.07(29) | 41.470 | C V | 41.472 | C V | 41.47 | C V |
41.480 | Ar IX | 41.480 | Ar IX | ||||
42.543 | 1.29(28) | 42.530 | S X | 42.543 | S X | 42.53 | S X |
42.810 | 0.33(17) | - | 42.826 | Si XI | - | ||
43.743 | 0.54(8) | 43.740 | Si XI | 43.763 | Si XI | 43.74 | Si XI |
44.014 | 0.43(8) | 44.020 | Si XII | 44.021 | Si XII | 44.02 | Si XII |
44.150 | 0.67(10) | 44.165 | Si XII | 44.165 | Si XII | 44.17 | Si XII |
44.218 | 0.52(10) | 44.249 | Si IX | 44.215 | Si IX | 44.22 | Si IX |
45.677 | 0.20(4) | 45.680 | Si XII | 45.692 | Si XII | 45.68 | Si XII |
45.684 | Si X | ||||||
46.283 | 0.25(7) | 46.300 | Si XI | 46.300 | Si XI | 46.30 | Si XI |
46.391 | 0.40(8) | 46.410 | Si XI | 46.401 | Si XI | 46.41 | Si XI |
47.242 | 0.46(8) | 47.280 | Mg X | 47.310 | Mg X | 47.31 | Mg X |
47.231 | Mg X | ||||||
47.249 | S IX | 47.25 | S IX | ||||
47.452 | 0.48(8) | 47.500 | S IX | 47.433 | S IX | 47.43 | S IX |
47.518 | S IX | ||||||
47.453 | Si XI | ||||||
47.642 | 0.49(8) | 47.654 | S X | 47.655 | S X | 47.65 | S X |
47.653 | Si XI | ||||||
47.774 | 0.34(7) | 47.793 | S X | 47.791 | S X | 47.79 | S X |
47.883 | 0.24(8) | 47.896 | Mg X | 47.905 | S X | 47.90 | Mg X |
47.899 | Si XI | ||||||
48.720 | 0.23(6) | 48.730 | Ar IX | 48.73 | Ar IX | 48.73 | Ar IX |
49.109 | 0.33(8) | - | 49.119 | S IX | 49.12 | S IX | |
49.207 | 1.44(14) | 49.220 | Si XI | 49.222 | Si XI | 49.22 | Si XI |
49.180 | Ar IX | 49.18 | Ar IX | 49.18 | Ar IX | ||
49.324 | 0.32(7) | - | 49.328 | S IX | - | ||
49.696 | 0.29(7) | - | 49.701 | Si X | - | ||
49.975 | 0.28(6) | 50.019 | Si VIIIc | 50.019 | Si VIII | - | |
50.327 | 0.51(8) | - | 50.333 | Si X | - | ||
50.520 | 1.68(15) | 50.530 | Si X | 50.524 | Si X | 50.53 | Si X |
50.686 | 1.30(14) | 50.690 | Si X | 50.691 | Si X | 50.69 | Si X |
52.306 | 0.75(11) | 52.300 | Si XI | 52.296 | Si XI | 52.30 | Si XI |
52.594 | 0.35(8) | 52.615 | Ni XVIII | 52.615 | Ni XVIII | - | |
52.611 | Si IX | ||||||
52.715 | 0.30(7) | 52.720 | Ni XVIII | 52.720 | Ni XVIII | 52.70 | S VIII |
52.772 | 0.30(7) | - | 52.756 | S VIII | - | ||
52.789 | S VIII | ||||||
52.898 | 0.30(7) | 52.911 | Fe XV | 52.911 | Fe XV | 52.87 | Fe XV |
54.133 | 0.56(13) | 54.118 | S VIII | 54.118 | S VIII | 54.12 | S VIII |
54.142 | Fe XVI | 54.142 | Fe XVI | 54.15 | Fe XVI | ||
54.180 | 0.31(10) | 54.180 | S IX | 54.175 | S IX | 54.18 | S IX |
54.546 | 0.54(13) | - | 54.571 | Si X | - | ||
54.566 | S VIII | ||||||
54.700 | 0.45(11) | 54.728 | Fe XVI | 54.728 | Fe XVI | 54.70 | Fe XVI |
55.094 | 0.68(15) | 55.060 | Mg IX | 55.060 | Mg IX | 55.06 | Mg IX |
55.094 | Si IX | 55.12 | Si IX | ||||
55.116 | Si IX | ||||||
55.096 | Si X | ||||||
55.270 | 0.88(25) | 55.272 | Si IX | 55.272 | Si IX | 55.27 | Si IX |
55.305 | Si IX | 55.31 | Si IX | ||||
55.359 | 2.14(27) | 55.356 | Si IX | 55.356 | Si IX | 55.36 | Si IX |
55.401 | Si IX | 55.40 | Si IX | ||||
56.037 | 0.19(11) | 56.000 | Ni XIII | 56.027 | Si IX | 56.03 | Si IX |
56.081 | S IX | 56.08 | S IX | ||||
56.836 | 0.20(8) | - | 56.804 | Si X | - | ||
57.741 | 0.80(35) | - | 57.736 | Mg VIII | - | ||
57.778 | Si IX | ||||||
57.856 | 0.78(35) | 57.880 | Mg X | 57.876 | Mg X | 57.88 | Mg X |
57.920 | Mg X | 57.920 | Mg X | 57.92 | Mg X | ||
61.020 | 1.41(25) | 61.050 | Si VIII | 61.019 | Si VIII | 61.01 | Si VIII |
61.038 | Mg IX | ||||||
61.087 | 1.38(24) | - | 61.070 | Si VIII | 61.08 | Si VIII | |
61.088 | Mg IX | ||||||
61.578 | 0.52(17) | 61.600 | S VIII | 61.600 | S VIII | 61.60 | S VIII |
61.668 | 0.49(15) | - | 61.649 | Si IX | 61.66 | Si IX | |
61.843 | 0.67(11) | 61.841 | Si IX | 61.852 | Si IX | 61.84 | Si IX |
61.916 | 0.55(17) | 61.912 | Si VIII | 61.914 | Si VIII | 61.91 | Si VIII |
61.895 | Si VIII | 61.90 | Si VIII | ||||
62.748 | 0.53(17) | 62.755 | Mg IX | 62.751 | Mg IX | 62.76 | Mg IX |
62.699 | Fe XIIId | 62.694 | Fe XIII | ||||
62.849 | 0.38(11) | 62.879 | Fe XVI | 62.879 | Fe XVI | 62.88 | Fe XVI |
62.800 | Fe Xd | 62.8 | Fe X | ||||
63.161 | 0.64(13) | 63.153 | Mg X | 63.152 | Mg X | 63.15 | Mg X |
63.283 | 0.94(15) | 63.294 | Mg X | 63.295 | Mg X | 63.29 | Mg X |
63.390 | 0.38(8) | 63.314 | Mg X | 63.304 | S VIII | 63.40 | Mg VII |
63.396 | Mg VII | ||||||
63.720 | 0.58(11) | 63.719 | Fe XVI | 63.719 | Fe XVI | 63.71 | Fe XVI |
63.732 | Si VIII | 63.73 | Si VIII | ||||
63.921 | 0.39(10) | - | - | - | |||
64.135 | 0.44(11) | - | - | - | |||
65.677 | 0.38(11) | 65.672 | Mg X | 65.672 | Mg X | 65.67 | Mg X |
65.826 | 0.49(13) | 65.840 | Mg X | 65.847 | Mg X | 65.84 | Mg X |
65.822 | Ne VIII | ||||||
65.884 | 0.41(10) | 65.905 | Fe XIId | 65.905 | Fe XII | - | |
65.892 | Ne VIII | - | |||||
66.057 | 0.28(10) | 66.047 | Fe XIId | 66.047 | Fe XII | 66.04 | Fe XII |
66.255 | 0.64(14) | - | 66.259 | Ne VIII | - | ||
66.352 | 0.63(13) | - | 66.330 | Ne VIII | - | ||
67.161 | 0.48(11) | 67.132 | Mg IX | 67.135 | Mg IX | 67.13 | Mg IX |
67.255 | 0.87(18) | 67.233 | Mg IX | 67.239 | Mg IX | 67.22 | Mg IX |
67.291 | Fe XIId | ||||||
67.375 | 0.68(14) | 67.350 | Ne VIII | 67.382 | Ne VIII | 67.35 | Ne VIII |
69.646 | 2.03(21) | 69.658 | Si VIII | 69.632 | Si VIII | 69.66 | Si VIII |
69.660 | Fe XV | 69.66 | Fe XV | ||||
69.827 | 1.05(14) | 69.825 | Si VIII | 69.790 | Si VIII | 69.83 | Si VIII |
70.046 | 0.70(11) | 70.020 | Si VII | 70.027 | Si VII | 70.03 | Si VII |
70.010 | Fe XII | 70.01 | Fe XII | ||||
70.054 | Fe XV | 70.054 | Fe XV | 70.05 | Fe XV | ||
71.929 | 0.69(13 | - | 71.901 | Mg IX | 71.92 | Mg IX | |
71.955 | Si VII | ||||||
72.034 | 0.43(13) | 72.030 | Mg IX | 72.027 | Mg IX | 72.03 | Mg IX |
72.302 | 1.44(18) | 72.311 | Mg IX | 72.312 | Mg IX | 72.31 | Mg IX |
72.310 | Fe XI | 72.310 | Fe XI | ||||
72.668 | 0.73(14) | 72.663 | S VII | 72.663 | S VII | 72.66 | S VII |
72.871 | 0.58(15) | 72.850 | Fe IXd | 72.850 | Fe IX | - | |
73.478 | 0.47(11) | - | 73.470 | Ne VIII | - | ||
73.471 | Fe XV | 73.471 | Fe XV | 73.47 | Fe XV | ||
73.555 | 0.43(11) | 73.560 | Ne VIII | 73.563 | Ne VIII | 73.56 | Ne VIII |
74.860 | 1.10(18) | 74.854 | Mg VIII | 74.858 | Mg VIII | 74.85 | Mg VIII |
74.845 | Fe XIIId | 74.845 | Fe XIII | ||||
75.035 | 1.05(18) | 75.034 | Mg VIII | 75.034 | Mg VIII | 75.03 | Mg VIII |
75.978 | 0.47(11) | 76.006 | Fe Xd | 76.006 | Fe X | 76.02 | Fe X |
76.038 | 0.77(13) | - | - | - | |||
76.507 | 0.32(11) | 76.502 | Fe XVI | 76.502 | Fe XVI | 76.51 | Fe XVI |
76.862 | 0.55(13) | - | - | 76.87 | Fe XVI | ||
77.740 | 1.11(18) | 77.741 | Mg IX | 77.737 | Mg IX | 77.74 | Mg IX |
78.733 | 0.71(14) | 78.717 | Ni XI | 78.744 | Ni XI | 78.72 | Ni XI |
78.769 | Fe Xd | 78.769 | Fe X | ||||
79.483 | 0.58(13) | 79.488 | Fe XII | 79.488 | Fe XII | 79.49 | Fe XII |
80.017 | 0.38(11) | 80.022 | Fe XII | 80.022 | Fe XII | 80.02 | Fe XII |
80.236 | 0.54(14) | - | 80.255 | Mg VIII | - | ||
80.507 | 0.74(14) | 80.501 | Si VI | 80.501 | Si VI | 80.50 | Si VI |
80.510 | Fe XII | 80.510 | Fe XII | 80.51 | Fe XII | ||
80.751 | 0.54(14) | - | 80.725 | Si VI | - | ||
81.865 | 0.42(11) | - | 81.895 | Si VII | - | ||
82.420 | 0.48(11) | 82.430 | Fe IXd | 82.430 | Fe IX | 82.43 | Fe IX |
82.667 | 0.97(17) | 82.744 | Fe XII | 82.598 | Mg VIII | - | |
82.808 | 0.35(10) | 82.837 | Fe XII | 82.837 | Fe XII | - | |
82.822 | Mg VIII | ||||||
83.337 | 0.38(11) | - | 83.358 | Si VI | - | ||
83.600 | 0.55(15) | - | 83.587 | Mg VII | 83.59 | Mg VII | |
83.611 | Si VI | ||||||
83.764 | 0.47(17) | 83.766 | Mg VII | 83.766 | Mg VII | 83.77 | Mg VII |
83.935 | 0.46(11) | 83.959 | Mg VII | 83.959 | Mg VII | 83.96 | Mg VII |
83.910 | Mg VII | 83.91 | Mg VII | ||||
84.032 | 0.40(11) | - | 84.025 | Mg VII | 84.02 | Mg VII | |
84.292 | 0.40(11) | 84.292 | Ne VII | 84.292 | Ne VII | 84.29 | Ne VII |
84.212 | Ne VII | ||||||
84.433 | 0.39(11) | - | - | - | |||
85.448 | 0.38(11) | - | 85.477 | Fe XII | 85.47 | Fe XII | |
85.407 | Mg VII | 85.41 | Mg VII | ||||
86.765 | 1.13(17) | 86.772 | Fe XI | 86.772 | Fe XI | 86.77 | Fe XI |
86.876 | 0.55(17) | - | 86.847 | Mg VIII | - | ||
87.021 | 0.46(14) | 87.025 | Fe XI | 87.025 | Fe XI | 87.02 | Fe XI |
87.017 | Mg VIII | ||||||
88.087 | 1.68(20) | 88.092 | Ne VIII | 88.092 | Ne VIII | 88.08 | Ne VIII |
88.893 | 0.68(14) | - | - | - | |||
88.955 | 0.75(15) | - | 88.952 | Mg VI | - | ||
89.156 | 0.43(13) | 89.185 | Fe XI | 89.185 | Fe XI | 89.18 | Fe XI |
90.719 | 0.59(13) | - | 90.708 | Mg VII | - | ||
90.989 | 0.43(10) | 91.009 | Fe XIV | 91.009 | Fe XIV | - | |
90.955 | Fe XVIIe | ||||||
91.529 | 0.52(13) | 91.564 | Ne VII | 91.564 | Ne VII | 91.56 | Ne VII |
91.627 | 0.38(8) | - | - | - | |||
91.777 | 0.58(13) | 91.808 | Ni X | 91.790 | Ni X | 91.81 | Ni X |
92.155 | 0.51(13) | - | 92.123 | Mg VIII | - | ||
92.858 | 0.55(14) | - | 92.850 | Ne VII | - | ||
93.587 | 0.58(15) | - | - | - | |||
94.001 | 1.70(24) | 94.012 | Fe Xd | 94.012 | Fe X | 94.02 | Fe X |
95.339 | 0.90(18) | 95.374 | Fe X | 95.374 | Fe X | 95.37 | Fe X |
95.338 | Fe Xd | 95.338 | Fe X | - | |||
95.412 | 1.04(20) | 95.483 | Mg VI | 95.483 | Mg VI | 95.48 | Mg VI |
95.421 | Mg VI | 95.42 | Mg VI | ||||
95.997 | 1.46(20) | - | 96.022 | Si VI | 96.02 | Si VI | |
96.124 | 0.79(17) | 96.122 | Fe Xd | 96.122 | Fe X | 96.12 | Fe X |
96.804 | 0.71(18) | 96.788 | Fe Xd | 96.788 | Fe X | - | |
97.104 | 0.34(15) | 97.122 | Fe Xd | 97.122 | Fe X | 97.12 | Fe X |
97.486 | 0.78(17) | 97.502 | Ne VII | 97.502 | Ne VII | 97.50 | Ne VII |
98.091 | 1.58(25) | 98.115 | Ne VIII | 98.115 | Ne VIII | 98.13 | Ne VIII |
98.251 | 2.89(34) | 98.260 | Ne VIII | 98.260 | Ne VIII | 98.26 | Ne VIII |
100.57 | 1.05(24) | - | 100.597 | Mg VIII | - | ||
102.85 | 0.90(22) | 102.91 | Ne VIII | 102.911 | Ne VIII | 102.9 | Ne VIII |
103.07 | 1.68(27) | 103.08 | Ne VIII | 103.085 | Ne VIII | 103.1 | Ne VIII |
103.54 | 2.08(32) | 103.57 | Fe IXd | 103.566 | Fe IX | 103.6 | Fe IX |
103.88 | 0.72(22) | - | - | - | |||
104.67 | 0.68(21) | - | - | - | |||
104.78 | 0.86(21) | 104.81 | O VI | 104.813 | O VI | - | |
105.20 | 1.22(21) | 105.21 | Fe IXd | 105.208 | Fe IX | 105.2 | Fe IX |
106.18 | 1.03(20) | 106.19 | Ne VII | 106.192 | Ne VII | 106.2 | Ne VII |
111.23 | 1.49(28) | - | 111.198 | Ca X | - | ||
111.71 | 0.53(13) | 111.57 | Mg VI | 111.552 | Mg VI | 111.6 | Mg VI |
111.72 | Mg VI | 111.746 | Mg VI | 111.7 | Mg VI | ||
113.33 | 0.46(11) | - | 113.315 | Fe VIII | - | ||
113.77 | 0.60(20) | - | 113.763 | Fe VIII | - | ||
113.793 | Fe IX | ||||||
113.99 | 0.71(20) | - | 113.990 | Mg V | 114.0 | Mg V | |
114.029 | Mg V | ||||||
114.54 | 0.48(14) | - | 114.564 | Fe VIII | - | ||
114.88 | 0.66(17) | - | 114.785 | Mg V | 114.8 | Mg V | |
115.37 | 0.51(18) | 115.33 | Ne VII | 115.33 | Ne VII | - | |
- | 115.39 | Ne VII | - | ||||
115.80 | 0.77(20) | 115.83 | O VI | 115.826 | O VI | 115.8 | O VI |
115.89 | 0.46(17) | - | - | - | |||
116.70 | 1.54(25) | 116.69 | Ne VII | 116.693 | Ne VII | 116.7 | Ne VII |
116.87 | 0.54(14) | - | - | - | |||
117.20 | 0.54(20) | 117.20 | Fe VIIId | 117.197 | Fe VIII | - | |
117.66 | 0.80(20) | - | - | - | |||
119.31 | 0.46(13) | - | - | - | |||
120.31 | 0.60(15) | 120.33 | O VII | 120.331 | O VII | - | |
122.49 | 0.73(18) | 122.49 | Ne VI | 122.49 | Ne VI | 122.5 | Ne VI |
123.54 | 1.31(31) | - | - | - | |||
124.51 | 0.98(25) | - | - | - | |||
126.25 | 0.98(32) | - | 126.280 | Mg V | - | ||
127.53 | 0.98(25) | - | - | - | |||
127.69 | 1.44(29) | 127.66 | Ne VII | 127.663 | Ne VII | 127.7 | Ne VII |
129.86 | 1.07(34) | 129.83 | O VI | 129.871 | O VI | 129.9 | O VI |
130.92 | 1.78(39) | 130.94 | Fe VIIId | 130.941 | Fe VIII | 130.9 | Fe VIII |
131.21 | 1.78(35) | 131.24 | Fe VIIId | 131.240 | Fe VIII | 131.2 | Fe VIII |
134.21 | 1.43(41) | - | - | - | |||
135.48 | 0.97(35) | 135.52 | O V | 135.523 | O V | 135.5 | O V |
136.78 | 1.91(53) | - | - | - | |||
140.27 | 1.36(49) | - | - | - | |||
141.04 | 0.79(22) | 141.04 | Ca XII | 141.038 | Ca XII | 141.0 | Ca XII |
144.97 | 1.73(49) | 144.99 | Ni X | 144.988 | Ni X | 145.0 | Ni X |
147.27 | 1.12(35) | 147.27 | Ca XII | 147.278 | Ca XII | 147.3 | Ca XII |
148.36 | 11.3(10) | 148.40 | Ni XI | 148.402 | Ni XI | 148.4 | Ni XI |
150.08 | 5.08(60) | 150.10 | O VI | 150.1 | O VI | 150.1 | O VI |
151.52 | 2.36(39) | - | 151.548 | O V | - | ||
152.11 | 5.60(66) | 152.15 | Ni XII | 152.153 | Ni XII | 152.2 | Ni XII |
154.14 | 2.73(42) | 154.18 | Ni XII | 154.175 | Ni XII | 154.2 | Ni XII |
155.56 | 1.36(28) | - | - | - | |||
156.14 | 1.66(32) | - | 156.140 | Ne V | - | ||
156.38 | 1.29(31) | - | - | - | |||
157.68 | 2.76(42) | 157.73 | Ni XIII | 157.730 | Ni XIII | 157.7 | Ni XIII |
158.33 | 2.08(35) | 158.38 | Ni X | 158.377 | Ni X | 158.4 | Ni X |
158.78 | 1.47(34) | - | 158.770 | Ni XIII | - | ||
159.24 | 1.03(27) | - | 159.300 | Si X | 159.1 | Ar XIII | |
159.58 | 1.83(43) | - | - | - | |||
159.93 | 3.09(43) | 159.94 | Ni X | 159.977 | Ni X | 159.9 | Ni X |
159.97 | Ni XIII | 159.97 | Ni XIII | ||||
162.56 | 2.94(83) | 162.56 | N V | 162.556 | N V | - | |
164.11 | 3.53(74) | 164.15 | Ni XIII | 164.146 | Ni XIII | 164.1 | Ni XIII |
167.43 | 3.9(10) | 167.49 | Fe VIII | 167.486 | Fe VIII | 167.5 | Fe VIII |
167.59 | 3.9(12) | 167.66 | Fe VIII | 167.656 | Fe VIII | - | |
168.13 | 7.4(13) | 168.17 | Fe VIII | 168.172 | Fe VIII | 168.2 | Fe VIII |
168.51 | 5.4(13) | 168.54 | Fe VIII | 168.545 | Fe VIII | 168.5 | Fe VIII |
168.90 | 5.0(18) | 168.93 | Fe VIII | 168.929 | Fe VIII | 168.9 | Fe VIII |
171.04 | 114(8) | 171.08 | Fe IX | 171.075 | Fe IX | 171.1 | Fe IX |
174.49 | 118(24) | 174.53 | Fe X | 174.53 | Fe X | 174.5 | Fe X |
In Table 4 results for temperatures T (in MK), emission measures EM, and abundances are given.
Statistic 1
uncertainties are given in parentheses.
The emission measure is defined as
,
where V is the volume contributing
to the emission and for solar abundances the hydrogen density
.
The temperatures and emission measures of all spectra show a dominant region between 1 and 2.5 MK. The two dominant temperature
components are about 1.2 and 2.3 MK. Using EUVE, Schmitt et al. (1996) derived a DEM with a peak temperature of 1.6 MK based on
Fe-lines only. This is in satisfactory agreement with our results.
The total emission measures summed over all temperature components
are about
cm-3 for LETGS and
cm-3 for RGS+MOS.
These are similar to the
total EM of
cm-3 found by Schmitt et al. (1996).
The determination of abundances is complicated by several factors. The many weak L-shell lines, which are absent
in the atomic code (see difference between Col. "MEKAL'' and "KELLY'' of Table 2) can produce a "pseudo-continuum''
(see e.g. Fig. 2a between 42 and 58 Å), which bias the determination of the real but very weak continuum.
Several fits to the LETGS spectrum were made: a) to the total spectrum, b) to the total spectrum with selected lines in the
wavelength range from 40 to 100 Å, to limit the influence of the inaccuracy of atomic data of Ne-, Mg-, and Si- L-shell lines, and
c) to a line spectrum with lines of Table 1 and lines with a statistical significance 4
in the wavelength range
above 40 Å (see Table 5). During our investigations the absolute (relative to H)
abundances turned out to be very sensitive to the selected group of elements introduced in the fit procedure. This is especially true
for the elements Ar and Ca.
For these reasons no consistent absolute values of the abundances could be obtained. However, abundance ratios
turn out to be much more robust. Therefore the abundance values are
normalized to oxygen, and are given relative to their solar photospheric values (Anders & Grevesse 1989), except for iron.
For Fe we use log
is 7.51 (see Drake et al. 1995) instead of 7.67 (Anders & Grevesse 1989). Here
log
is the logarithmic of the Fe-abundance relative to log
.
The abundances presented in Table 4 are derived assuming the same abundances for the three temperature components.
These are averaged over the different fits, together with their least-squares-fit standard deviations (within parentheses).
![]() |
present | ion | missing | ion |
93.587 | 93.616 | FeVIII | 93.469 | FeVIII |
108.077 | FeVIII | |||
98.583 | 98.548 | FeVIII | 98.371 | FeVIII |
103.88 | 103.937 | FeXVIII | 93.923 | FeXVIII |
103.88 | 103.904 | MgV | 110.859 | MgV |
We obtain abundance values between 0.7 and 2.4 relative to oxygen (e.g., some enhancement for Ne and Si). However, apart from statistical errors these values are also sensitive to systematic errors, due to changes in values of the solar photospheric abundances, where uncertainties of a factor of 2 cannot be excluded (e.g., Prieto et al. 2001; Grevesse & Sauval 1998). So we cannot obtain indications for a significant FIP effect (enhancement of elements with a low First Ionization Potential) as found for the solar corona (e.g., Feldman et al. 1992). This confirms the conclusions by Drake et al. (1995), based on relative abundances from EUVE observations. The abundances of C and N, relative to O are somewhat higher than the values obtained in the solar photosphere (Anders & Grevesse 1989). In the EUVE observations by Drake et al. (1995) no suitable C- and N-lines were present to constrain (relative) abundances.
Values for ,
given in Table 4, have been obtained by fitting to the O VII and N VI triplet lines. The C V lines have been omitted from this
procedure because their intensities are sensitive for the stellar UV-radiative field, mimicing higher densities
(Ness et al. 2001; Porquet et al. 2001).
Parameter | LETGS | RGS+MOS |
log ![]() |
18.06b | 18.06b |
T1 [MK] | 0.63(.10) | - |
T2 [MK] | 1.21(.07) | 1.65(.15) |
T3 [MK] | 2.26(.12) | 2.68(.22) |
EM1 [1050 cm-3] | 0.41(.14) | - |
EM2 [1050 cm-3] | 2.45(.27) | 3.0(.20) |
EM3 [1050 cm-3] | 1.72(.29) | 0.9(.18) |
![]() |
1.4 +1.5-0.6 | 1.5 +2.0-0.6 |
![]() |
0.2 +0.8-0.2 | - |
O/H | 0.68(0.38) | 0.76(0.33) |
C/O | 1.38(.24) | 1.45(.29) |
N/O | 1.33(.10) | 1.47(.5) |
O/O | 1.0 | 1.0 |
Ne/O | 1.49(.21) | 1.53(.27) |
Mg/O | 1.1(.5) | - |
Si/O | 1.56(.36) | - |
S/O | 0.69(.15) | - |
Fe/O | 0.97(.31) | 1.47(.22) |
Ni/O | 2.39(.27) | - |
|
As a result we find a dominant emission measure of
the order of 1050 cm-3 between 1-3 MK. The total emission measures are
cm-3 for RGS+MOS
and
cm-3 for LETGS (in line with the multi-temperature fitting).
Figure 3 allows us to conclude that there is no significant amount of EM at
4 MK in the corona of Procyon. Schmitt et al. (1996) give
an upper limit of 6 MK, based on EUVE observations.
The EM observed at different times as well as lines fluxes in Table 1 show no significant variability.
Figure 4 shows fit residuals of parts of the LETGS spectrum fitted using this temperature-dependent emission measure modeling, i.e. applying the model of Fig. 3 (LETGS). From Fig. 4a we recognize large deviations in residual due to model insufficiencies and a pseudo-continuum (most fit residuals positive) due to the lack of weaker lines in current atomic databases in this wavelength range. Clear from Fig. 4b are the succeeding large positive and negative residuals around 148 and 171 Å, due to wavelength deviations of lines in the spectrum and the model.
![]() |
Figure 3:
EM (
![]() ![]() |
For the short-wavelength region this is done for all lines (Table 1), while for the longer wavelength range only
lines with a statistical significance 4
were used. For the latter the fluxes have been compared with
the 3-T model as well as with the results from the DEM model. The values are given in Table 5.
This table shows generally a good agreement between the observed flux and the 3-T flux and the flux from the DEM-modeling, summed over
the T-bins.
Most striking are the deviations for the Fe VIII lines around 131 and 168 Å. This is definitely due to a large deficiency
in the atomic data used. From atomic physics grounds the line at 168.13 Å is the stronger, as observed in the
spectrum and in laboratory experiments (Wang et al. 1984), but in our code this line turns out to be the
weakest
. Another interesting
feature is the contamination of the forbidden C V line - which is often used for density diagnostics - with Ar IX. Another clear
example of blending is the line at 74.860 Å which contains Mg VIII and Fe XIII.
LETGS | Line identifications | |||
Observed | Model | |||
![]() |
![]() |
3-T fluxb | DEM-fluxb | Ion |
18.972 1.83(15) | 18.973 | 1.93 | 1.80 | N VII |
21.597 3.01(25) | 21.602 | 3.35 | 2.94 | N VII |
24.790 0.80(14) | 24.781 | 0.76 | 0.70 | N VII |
33.731 4.02(32) | 33.736 | 4.64 | 4.19 | C VI |
40.263 2.29(36) | 40.270 | 2.03 | 1.40 | C V |
40.718 1.88(42) | 40.730 | 1.33 | C V | |
41.475 1.07(29) | 41.470 | 0.68 | C V | |
41.480 | 0.28 | 0.31 | Ar IX | |
43.743 0.54(8) | 43.740 | 0.54 | 0.94 | Si XI |
44.150 0.67(10) | 44.165 | 0.64 | 0.66 | Si XII |
47.242 0.46(8) | 47.280 | 0.19 | 0.17 | Mg X |
47.452 0.48(8) | 47.500 | 0.61 | 0.60 | S IX |
47.642 0.49(8) | 47.654 | 0.20 | 0.31 | S X |
49.207 1.44(14) | 49.220 | 0.43 | 0.95 | Si XI |
49.180 | 0.41 | 0.37 | Ar IX | |
50.520 1.68(15) | 50.530 | 1.48 | 1.55 | Si X |
50.686 1.30(14) | 50.690 | 1.50 | 1.58 | Si X |
52.306 0.75(11) | 52.300 | 0.45 | 0.74 | Si XI |
61.020 1.41(25) | 61.050 | 2.51 | 1.98 | Si VIII |
61.087 1.38(24) | Si VIIIc | |||
63.283 0.94(15) | 63.294 | 1.07 | 0.93 | Mg X |
69.646 2.03(21) | 69.658 | 0.85 | 0.67 | Si VIII |
69.660 | 1.14 | 1.11 | Fe XV | |
74.860 1.10(18) | 74.854 | 0.51 | 0.57 | Mg VIII |
74.845 | 0.26 | 0.40 | Fe XIII | |
75.035 1.05(18) | 75.034 | 0.52 | 0.57 | Mg VIII |
77.740 1.11(18) | 77.741 | 0.42 | 0.37 | Mg IX |
86.765 1.13(17) | 86.772 | 0.71 | 0.45 | Fe XI |
88.087 1.68(20) | 88.092 | 2.33 | 1.62 | Ne VIII |
98.251 2.89(34) | 98.260 | 3.02 | 2.37 | Ne VIII |
105.20 1.22(21) | 105.21 | 0.32 | 0.19 | Fe IX |
130.92 1.78(39) | 130.94 | 0.29 | 0.20 | Fe VIII |
131.21 1.78(35) | 131.24 | 0.41 | 0.29 | Fe VIII |
148.36 11.3(10) | 148.40 | 11.0 | 15.5 | Ni XI |
150.08 5.08(60) | 150.10 | 2.8 | 2.63 | O VI |
152.11 5.60(66) | 152.15 | 2.9 | 6.0 | Ni XII |
167.43 3.9(10) | 167.49 | 3.9 | 2.64 | Fe VIII |
167.59 3.9(12) | 167.66 | 4.0 | 2.74 | Fe VIII |
168.13 7.4(13) | 168.17 | 0.3 | 0.20 | Fe VIII |
168.51 5.4(13) | 168.54 | 2.0 | 1.42 | Fe VIII |
168.90 5.0(18) | 168.93 | 1.3 | 0.71 | Fe VIII |
171.04 114(8) | 171.08 | 100 | 78 | Fe IX |
|
Copyright ESO 2002