Part 2 — TABLE XXIII
Reading edition
M = +7 +8.8 +9.2 +11.0 +13.2
+6 +13.3
+5 +3.5 +5.0 +7.4 +9.6
+4 +10.0 +10.8
+3 -1.8 +0.5 +3.8 +6.7
+2 +6.7 +7.0 +7.6 +10.0
+1 -7.2 -3.8 +0.2 +3.2
0 +3.5 +3.4 +3.2 +3.0
1 -12.9 -8.2 -3.2 -0.3
-2 +0.3 -0.2 -1.4 -3.7
-3 -12.1 -7.3 -3.8
-4 -2.8 -4.2 -5.8 -10.0
M = +6 -2.0 -1.4
+5 -1.5 -0.5 0.0 +1.0
+4 +1.2 +1.3
+3 +1.8 +3.3 +4.4 +4.5
+2 +5.0 +3.0
+1 +4.8 +6.5 +7.8 +7.6
0 +6.5 +4.7
-1 +8.6 +9.3 +11.0 +11.0
-2 +12.0 +8.6 +8.6 +8.2
M = +6 -18.1
+5 -3.7 -5.8 -9.6 -14.7
+4 -15.3
+3 -1.0 -3.3 -6.6 -11.0
+2 -12.4
+1 +1.7 -0.6 -3.7 -7.5
0 -9.4
-1 +4.5 +2.0 -0.9 -4.0
-2 -6.6
-3 +7.2 +4.7 +2.0 -0.2
M = +6 +7.4 +6.2
+5 +6.2
+4 +4.3 +3.0
+3 +3.0
+2 +1.3 0.0
+1 0.0
0 0.0 -2.0
1 +2.6
-2 +2.0 +0.7
-3 +5.2
The preceding table contains a transcription of the reduction-curve material given by Harper and Young for the four pairs of lines mentioned. Tabulated quantities are the “step differences” for the classes at the heads of the columns, and the absolute magnitudes contained in the first column.
Presumably the irregularities of the observed curves have been smoothed out in forming the reduction table, but the figures will certainly give an indication of the direction in which a given line is affected by absolute magnitude.
The predicted effect of lowered pressure upon the lines involved is contained in the table that follows:
Line Source Max. Effect of lowered pressure
4071 Fe (sub) weakened throughout
4077 Sr+ (ult) strengthened in , weakened in and
4215 Sr+ (ult) strengthened in , weakened in and
4247 Sc+ (?) strengthened throughout range
4250 Fe (sub) weakened throughout
4455 Ca (sub) weakened throughout
4494 Fe (sub) weakened throughout
The predicted changes in the line ratios with lowered pressure are therefore as follows:
The ratio behaves in exact accordance with prediction, and which decreases and then increases again, offers no evidence for or against the theory. The two remaining ratios, involving the two Sr+ lines, display a lack of agreement with theory for the and classes, apparently owing to the strengthening of the Sr+ lines with high luminosity, even at temperatures higher than those at which they attain maximum intensity. The strengthening of Sr+ with high luminosity is one of the best-attested facts of observational astrophysics, and it is a serious deficiency in theory if the observed behavior of the lines in the hotter stars cannot be explained. The question will be further discussed presently.
The material obtained by the writer, and summarized in a preceding chapter,[422] may be used in making a test of the predicted pressure effects by means of direct estimates. As was pointed out above, the lines of a giant are stronger than those of a dwarf, owing to the greater photospheric depth in the former. The practical difficulty of making comparable estimates upon sharp and somewhat hazy lines must also be considered in the discussion of the results. Clearly some numerical correction is required, in order to allow for the Stewart effect, and this has been done in a somewhat arbitrary manner in forming Table XXIV. It is assumed that the mean increase in intensity for such lines as are strengthened will be equal to the mean decrease in intensity for such lines as are weakened. For each spectral class this assumption provides a correcting factor, which never exceeds one scale unit.
The table that follows contains the material derived from the measures enumerated in Chapter VIII, and from other sources, bearing on the intensity differences between giants and dwarfs of the same spectral class. All the available estimates have been used. Successive columns give the line, the atom, the predicted behavior, and the observed difference in the sense giant-dwarf, for the Classes , , , , , and . The symbols , , and , following the atom, denote ultimate, neutral, and enhanced lines, respectively. The number of stars contributing to each entry will be seen from the list on p. 119, Chapter VIII. The notation is as follows: 0 = no change; ± 0 = between 0 and 1; ± 1 = between 1 and 2; ± 2 = between 2 and 3; and so on. The values for are taken from Menzel’s measures[423] of Indi and Tauri, “the scale of intensities being (0) no difference, (1) a little stronger (2) much stronger, (3) very much stronger.” The signs from Menzel’s table are reversed, in accordance with the notation used in the present table. In the column headed are the signs indicating the direction in which the corresponding lines are affected in that class,[424] for which quantitative measures have not been published. The letters “” and “” in the column headed refer to strengthening or weakening of lines, as observed by Baxandall[425] in a comparison of the solar spectrum with that of Capella. Baxandall’s estimates are inserted to supplement the present material. The numerous gaps in the table result from the difficulty of seeing the fainter lines in the dwarf spectrum.