Slow Pulsing Spectral Class B Star

Slowly pulsating stars of spectral class B ( born slowly pulsating B-type star, SPB ), formerly called Perseus type 53, are a type of pulsating variable stars . They are stars of the main sequence of spectral class from B2 to B9 (3-9 times more massive than the Sun), pulsing with periods from half a day to five days, ^[1] but most of them have several periods of oscillation. ^{[2] The} stars exhibit variability both in the emission of radiation and in the profiles of spectral lines. Variations of stellar magnitude usually do not exceed 0.1, ^[1] which in most cases creates difficulties for detecting the variability of stars when observed by the eye. Variability increases with decreasing radiation wavelength, ^[2] therefore, variability is better detected in the ultraviolet part of the spectrum than in the optical range. The pulsations are not radial, that is, the star changes its shape rather than its volume; different parts of the star experience contraction and expansion simultaneously. ^[3]

These stars first identified astronomers Christoffel Waelkens and Fredy Rufener in a separate group in 1985 when searching and analyzing the variability of hot blue stars. Improving the methods of photometry made it possible to detect smaller changes in stellar magnitude, which allowed scientists to conclude that a larger proportion of variable hot stars. ^[4] By 1993, ten stars of this type were discovered, while the Waelkens were not sure that 53 Perseus really belonged to the type in question, therefore, he recommended calling the new type of stars slow pulsating B-stars. ^[2] The general catalog of variable stars uses the abbreviation LPB for long-period pulsating B-stars ( English long-period pulsating B stars ) with pulsation periods of more than a day, ^[5] although this term is rarely used in other sources. ^[6]

Similar variables of the Beta Cepheus type have shorter periods and pulsations in the p-mode , while SPB stars exhibit pulsations in the g-mode. ^[7] By 2007, 51 stars were confidently attributed to slow-pulsing B-stars, while another 65 stars belonged to this class in question. Six stars - Yota Hercules , 53 Pisces , Nude Eridanus , Gamma Pegasus , HD 13745 (V354 Perseus) and 53 Aries - show signs of variability in both the Beta Cepheus type and the SPB stars. ^[8] Slowly pulsating B-stars also include Altar V539 ^[1] and Gamma Fly . ^[9]