VARIABLE STARS
213
For 6 stars the agreement of L r is excellent; 4 give large positive re
siduals and 1 a negative residual. It is difficult to base any conclusion
on the table without examining the strength of the determination for each
star in detail. The probable errors refer only to L r (obs.); but L r (calc.) is
also subject to uncertainty arising in the determination of R 2 /a • I n some
cases the circumstances of the eclipse are more favourable for a determina
tion of the elements than in others. We discuss below the question whether
the calculated and observed values ought to agree without further cor
rection ; tentatively we are inclined to think that they should agree nearly,
and we must hope that the 5 outstanding residuals will be reduced when
improved data are obtained.
Table 28 a.
Reflection Effect in Eclipsing Variables.
No.
Star
T yP e
RJa
RJa
Lx
L r
(calc.)
L r
(obs.)
C-0
P.E.
1
SZ Her.
4-3
•318
•331
•800
•078
•030
+ -048
—
2
U Cep.
A
13-5
•191
•308
•838
•069
•043
+ -026
± -009
3
TV Cas.
B 9
6-9
•275
•302
•849
•068
•074
- -006
± -008
4
RZ Cas.
A
12-2
•253
•288
•902
•064
•063
+ -001
± -008
5
RT Per.
—
4-8
•309
•269
•863
•053
•022
+ -031
± -009
6
Z Dra.
—
12-8
•238
•263
•911
•053
•040
+ -013
± -006
7
RS Vul.
B 8
7-0
•201
•262
•804
•048
•078
- -030
—
8
R CMa.
F
13-2
•245
•236
•934
•046
•015
+ -031
—
9
ß Per.
B 8
11-6
•210
•239
•895
•043
•045
- -002
—
10
Y Cam.
A-F
20-0
•236
•225
•955
•041
•041
•000
—
11
RV Oph.
A
12-2
•125
•200
•825
•027
•018
+ -009
± -006
In this comparison we have made no discrimination between heat
reflection and light reflection. If a residual such as that in No. 5 is not
due to observational error, it signifies that the secondary in reflecting
the heat of the primary reduces its luminous efficiency to less than 50 per
cent. But in typical eclipsing variables we expect an increase rather than
a decrease of luminous efficiency. The primary is usually of type B or A
so that the original efficiency corresponds to a temperature above 10,000° ;
it is reflected from a star of lower surface brightness corresponding (as
judged from JflJJ to a temperature near 6000°. Not unless the tempera
ture of re-emission is below 4500° is there a loss of luminous efficiency.
Moreover, even if the temperature is below 4500° there is a compensating
gain, since the original radiation L 2 is now emitted at a higher temperature.
We should expect the residuals C-0 to be in general negative as in No. 7 ;
the puzzling thing about No. 7 is that it is the solitary exception and not
the general rule.
I think the fact that we have only one important negative residual