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A slowly pulsating B-type star (SPB), formerly known as a 53 Persei variable, is a type of pulsating variable star. They may also be termed a long-period pulsating B star (LPB). As the name implies, they are 
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 (SPB) stars. The
main-sequence
In astronomy, the main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as HertzsprungāRussell diagrams after their co-developers, Ejnar ...
stars of spectral type B2 to B9 (3 to 9 times as massive as the Sun) 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
A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from emission or absorption of light in a narrow frequency range, compared with the nearby frequencies. Spectral lines are often used to ident ...
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 (SPB) stars. The General Catalogue of Variable Stars
The General Catalogue of Variable Stars (GCVS) is a list of variable stars. Its first edition, containing 10,820 stars, was published in 1948 by the Academy of Sciences of the USSR and edited by B. V. Kukarkin and P. P. Parenago. Second and thi ...
uses the acronym LPB for "comparatively long-period pulsating B stars (periods exceeding one day)", although this terminology is rarely seen elsewhere.
The similar Beta Cephei variable Beta Cephei variables, also known as Beta Canis Majoris stars, are variable stars that exhibit small rapid variations in their brightness due to pulsations of the stars' surfaces, thought due to the unusual properties of iron at temperatures of 200 ...
s 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
53 Piscium, abbreviated as 53 Psc, is a star in the zodiac constellation of Pisces. With an apparent magnitude of about 5.9, it is just barely visible to the naked eye. parallax measurements made by the Hipparcos spacecraft place the sta ...
, Nu Eridani
Nu Eridani (Ī½ Eri) is a star in the constellation Eridanus. It is visible to the naked eye with an apparent visual magnitude of 3.93. The distance to this star is roughly 520 light years, based upon an annual parallax shift of 0.0 ...
, Gamma Pegasi, HD 13745 (V354 Persei) and 53 Arietis
53 Arietis (abbreviated 53 Ari) is a variable star in the northern constellation of Aries. ''53 Arietis'' is the Flamsteed designation; it also bears the variable star designation UW Arietis. It is a B-type main sequence star with a stell ...
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.Notes
References
{{variable star topics *