A mercury–manganese star (also HgMn star) is a type of chemically peculiar star with a prominent spectral line at 398.4 nm, due to absorption from ionized mercury.Mercury–manganese star . The Internet Encyclopedia of Science, David Darling. Accessed on line August 14, 2008. These stars are of spectral type B8, B9, or A0, corresponding to surface temperatures between about 10,000 and 15,000 K, with two distinctive characteristics: An atmospheric excess of elements like phosphorus, manganese, gallium, strontium, yttrium, zirconium, platinum and mercury. A lack of a strong dipole magnetic field.
Their rotation is relatively slow, and as a consequence their atmosphere is relatively calm. It is thought, but has not been proven, that some types of atoms sink under the force of gravity, while others are lifted towards the exterior of the star by radiation pressure, making a heterogeneous atmosphere.
List The following table includes the brightest stars in this group.
NameBayer or Flamsteed designationSpectral typeNames, spectral types and apparent magnitudes taken from SIMBAD, except as noted.Apparent visual magnitude Alpheratz α Andromedae B8IVmnp 2.06 Gienah Corvi γ Corvi A B8III 2.59 Maia 20 Tauri B8III 3.87 χ Lupi B9IV 3.96 MulipheinMuliphein , Stars, Jim Kaler. Accessed on line August 14, 2008. γ Canis Majoris B8II 4.10 φ Herculis B9mnp 4.23 π1 Bootis B9p 4.91 HIP 79098 B9IVn 5.88 ι Coronae Borealis A0p 4.98 κ Cancri A B8IIImnp 5.24 14 Sagittae B9p 5.89 Dabih MinorDabih , Stars, Jim Kaler. Accessed on line August 14, 2008. β Capricorni B B9.5III/IV 6.10 HD 30963 B9 III 7.23 Nath β Tauri B7III 1.65λ1 Sculptoris A B9.5V6.61 53 Aurigae A B9 Mn 5.74
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