Бета Cephei жұлдыздарының өзгеруі

Type of variable star
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 200,000 K in their interiors. These stars are usually hot blue white stars of spectral class B and should not be confused with Cepheid variables, which are named after Delta Cephei and are luminous supergiant stars.

[[File:BetaCepLightCurve. png|thumb|left|A light curve for Beta Cephei, plotted from TESS data The prototype of these variable stars, Beta Cephei, shows variation in apparent magnitude from +3.16 to +3.27 with a period of 4.57 hours. The point of maximum brightness occurs when the star is smallest and hottest. Their variation in brightness is much greater—up to 1 magnitude—in ultraviolet wavelengths. The pulsations of Beta Cephei variables are driven by the kappa mechanism and p mode pulsations. At a depth within the star where the temperature reaches 200,000 K, there is an abundance of iron. Iron at these temperatures will increase (rather than decrease) in opacity, resulting in the buildup of energy within the layer. This results in increased pressure that pushes the layer back out again, the cycle repeating itself in a matter of hours. This is known as the Fe bump or Z bump (Z standing for the star's metallicity). The similar slowly pulsating B stars show g mode pulsations driven by the same iron opacity changes, but in less massive stars and with longer periods.

American astronomer Edwin Brant Frost discovered the variation in radial velocity of Beta Cephei in 1902, initially concluding it was a spectroscopic binary. Paul Guthnick was the first to detect a variation in brightness, in 1913. Beta Canis Majoris and Sigma Scorpii were found to be variable not long afterwards, These variables were often called Beta Canis Majoris variables because Beta Canis Majoris was the most closely studied example in the first half of the 20th century, though its location in the southern sky meant that its lowness in the sky hampered observations. However, Beta Cephei was the first member of the class to be discovered and so they are generally called Beta Cephei variables—despite the similarity of name (and risk of confusion) with Cepheid variables. Cecilia Payne Gaposchkin and Sergei Gaposchkin catalogued 17 probable members of the class in their 1938 Variable Stars, though classified them with Delta Scuti variables. 16 Lacertae was another star extensively studied before 1952. Otto Struve studied these stars extensively in the 1950s, however research declined after his death. In 2021 β Cru became the first star of any kind to have its pulsation modes identified using polarimetric asteroseismology.

Designation (name)ConstellationDiscoveryMaximum Apparent magnitude (mV)Period (hours)Comment β CMa Canis Major 1909 (William Wallace Campbell) 1m.93 2m.00 6.031 B1II III Pulsations of 6.03, 6.00, and 4.74 hours. ξ1 CMa Canis Major B1II   ε Cen Centaurus 2m.29 2m.31 4.070 B1V   κ Cen Centaurus 3m.13 3m.14 2.288 B2IV   χ Cen Centaurus 4m.40 3m.16 3m.27 4.572 B2IIIe Prototype δ Cet Cetus Crux 2m.78 2m.84 3.625 B2IV ω1 Cyg Cygnus 4m.94 B2.5IV confirmed on hi res spectroscopy. 2m.29 2m.34 6.235 B1.5III   δ Lup Lupus 3m.36 3m.38 2.316 B2IV + B3V Triple star system; primary is a spectroscopic binary ι Lup BW Vul Vulpecula 6m.44 6m.68 4.8 B2IIIv Beta Cephei variable with largest change in radial velocity