Slowly pulsating B-type star


A slowly pulsating B-type star, formerly known as a 53 Persei variable, is a type of pulsating variable star. As the name implies, they are main-sequence stars of spectral type B2 to B9 that pulsate with periods between approximately half a day and five days, however within this most member stars have been found to have multiple periods of oscillations. They display variability both in their light emission and in their spectral line profile. The variations in magnitude are generally smaller than 0.1 magnitudes, making it quite hard to observe variability with the naked eye in most cases. The variability increases with decreasing wavelength, thus they are more obviously variable in ultraviolet spectrum than visible light. Their pulsations are non-radial, that is, they vary in shape rather than volume; different parts of the star are expanding and contracting simultaneously.
These stars were first identified as a group and named by astronomers Christoffel Waelkens and Fredy Rufener in 1985 while looking for and analysing variability in hot blue stars. Improvements in photometry had made finding smaller changes in magnitude easier, and they had found that a high percentage of hot stars were intrinsically variable. They referred to them as 53 Persei stars after the prototype 53 Persei. Ten had been discovered by 1993, though Waelkens was unsure if the prototype was actually a member and recommended referring to the group as slowly pulsating B stars. The General Catalogue of Variable Stars uses the acronym LPB for "comparatively long-period pulsating B stars ", although this terminology is rarely seen elsewhere.
The similar Beta Cephei variables have shorter periods and have p-mode pulsations, while the SPB stars show g-mode pulsations. By 2007, 51 SPB stars had been confirmed with another 65 stars possible members. Six stars, namely Iota Herculis, 53 Piscium, Nu Eridani, Gamma Pegasi, HD 13745 and 53 Arietis had been found to exhibit both Beta Cephei and SPB variability.

List

The following list contains selected slowly pulsating B-type stars that are of interest to amateur or professional astronomy. Unless otherwise noted, the given magnitudes are in the V-band.
Star
Average
magnitude
Spectral
type
Period
Distance
Gamma Pegasi2.84B2IV113
Zeta Pegasi3.41B8V0.9663
Omicron Velorum3.63B3IV2.80151
Iota Herculis3.80B3IV3.49139
Gamma Muscae3.88B3V2.73100
Tau Herculis3.90B5IV1.2594
Nu Eridani3.92B2III207
Mu Eridani4.00B5IV160
Rho Lupi4.05B5V0.4597
HD 1053824.47B6IIIe1.30134
Tau8 Eridani4.63B5V0.86116
Nu Pavonis4.64B7III0.86135
HY Velorum4.82B3IV1.55148
HD 1311205.01B7IIIp1.57151
HR 57805.17B5V1.26122
3 Vulpeculae5.19B6III1.26120
12 Lacertae5.23B2III411
WZ Columbae5.29B9.5V1.38131
V575 Persei5.30B5V166
Xi Octantis5.31B6V1.77151
40 Tauri5.33B5V1.53196
25 Serpentis5.39B8III0.87188
GU Eridani5.43B5IV1.87200
HR 36005.54B5V132
KL Velorum5.56B82.91212
HD 19765.58B5IV1.06307
V450 Carinae5.64B9III+B8V1.65151
EO Leonis5.66B2V2.78289
V539 Arae5.71B2/B3Vnn303
HD 1282075.73B8V0.48147
HD 275635.84B5III3.80242
26 Canis Majoris5.90B2IV/V2.73257
16 Monocerotis5.92B3V1.94263
V335 Velorum5.93B.25III3.76704
V869 Centauri5.96B9IV1.46251
V363 Puppis5.97B2.5V+B9V0.70278
V433 Aurigae5.99B2IV-V4.64325
V1141 Tauri6.00B8IV-V0.62170
HD 2065406.05B5IV1.39215
HR 13976.07B6IV1.26198
V576 Persei6.09B7V0.84159
V2100 Cygni6.11B5III2.61239
HR 25176.15B2.5III2.562500
V492 Carinae6.18B3V1.06370
HR 13286.20B9V0.38121
V4199 Sagittarii6.26B5III1.24240
HR 35626.26B3IV370
V4198 Sagittarii6.28B8V1.19186
V377 Lacertae6.32B7III2.62305
DY Chamaeleontis6.32B8IV0.97236
HR 26806.33B3V258
V473 Carinae6.35B5V0.95218
V405 Lacertae6.37B5V1.02170
HD 347986.39B5Vs1.28263
HD 1765826.40B5V1.58292
V1377 Orionis6.41B3III1.01476
HR 87686.42B2V3.25326
GY Eridani6.42B3V1.33220
QZ Velorum6.49B1IIIn1.03813
V550 Lyrae6.49B3V1.69379
HD 2087276.50B8V0.32330
HD 433176.61B3IV369
23 Sextantis6.64B3.2IV769
HD 333316.90B5III1.15296
HD 1638687.36B5Ve588
HD 1638998.30B2Ib/II23.20
HD 502098.36B9Ve0.67694