3. B0

The line at 4200 is very much weaker than 4387. Si IV 4089 is stronger than Si III 4552. The blend near 4650 is sharply defined on the violet side.

TABLE 3
STANDARDS AT B0

Star	MKK	RA	DEC	m	HD	Notes
Cas....	B0 IV	00:50	+60° 11'	var	B0p	1
1 Ori...	B0 III	05:29	+ 9 25	4.5	B0
Ori.....	B0 I	05:31	- 1 16	1.8	B0
Ori....	B0 II	05:43	- 9 42	2.2	B0
Sco....	B0 IV	15:54	-22 20	2.5	B0
Sco....	B0 V	16:29	-28 1	2.9	B0	2
NOTES
1. Spectrograms taken on January 6, 1941. No emission lines visible.
2. The luminosity appears to be definitely lower than any other star in the table.

Luminosity differences are shown by the ratios 4009: 4089, 4072: 4089, and 4119: 4144. The line He II 4686 is present in class V.

Plate 7. Luminosity Effects at B0

High resolution image

Plate 8. AG Pegasi = BD 11 4673

High resolution image