Slowly pulsating B-type star
A slowly pulsating B-type star (SPB), 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 (3 to 9 times as massive as the Sun) that pulsate with periods between approximately half a day and five days,[1] however within this most member stars have been found to have multiple periods of oscillations.[2] 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,[1] making it quite hard to observe variability with the naked eye in most cases. The variability increases with decreasing wavelength,[2] 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.[3]
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.[4] 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.[2]
The similar Beta Cephei variables have shorter periods and have p-mode pulsations, while the SPB stars show g-mode pulsations.[5] 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 (V354 Persei) and 53 Arietis had been found to exhibit both Beta Cephei and SPB variability.[6] Further examples of slowly pulsating B-type stars include V539 Arae,[1] and Gamma Muscae.[7]
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 (in days) |
Distance (in parsecs) |
---|---|---|---|---|
Gamma Pegasi | 2.84 | B2IV | [n 1] | 113 |
Zeta Pegasi | 3.41 | B8V | 0.96 | 63 |
Omicron Velorum | 3.63 | B3IV | 2.80 | 151 |
Iota Herculis | 3.80 | B3IV | 3.49 | 139 |
Gamma Muscae | 3.88 | B3V | 2.73 | 100 |
Tau Herculis | 3.90 | B5IV | 1.25 | 94 |
Nu Eridani | 3.92 | B2III | [n 1] | 207 |
Mu Eridani | 4.00 | B5IV | [n 2] | 160 |
Rho Lupi | 4.05 | B5V | 0.45 | 97 |
HD 105382 | 4.47 | B6IIIe | 1.30 | 134 |
Tau8 Eridani | 4.63 | B5V | 0.86 | 116 |
Nu Pavonis | 4.64 | B7III | 0.86 | 135 |
HY Velorum | 4.82 | B3IV | 1.55 | 148 |
HD 131120 | 5.01 | B7IIIp | 1.57 | 151 |
HR 5780 | 5.17 | B5V | 1.26 | 122 |
3 Vulpeculae | 5.19 | B6III | 1.26 | 120 |
12 Lacertae | 5.23 | B2III | [n 1] | 411 |
WZ Columbae | 5.29 | B9.5V | 1.38 | 131 |
V575 Persei | 5.30 | B5V | 166 | |
Xi Octantis | 5.31 | B6V | 1.77 | 151 |
40 Tauri | 5.33 | B5V | 1.53 | 196 |
25 Serpentis | 5.39 | B8III | 0.87 | 188 |
GU Eridani | 5.43 | B5IV | 1.87 | 200 |
HR 3600 | 5.54 | B5V | 132 | |
KL Velorum | 5.56 | B8 | 2.91 | 212 |
HD 1976 | 5.58 | B5IV | 1.06 | 307 |
V450 Carinae | 5.64 | B9III+B8V | 1.65 | 151 |
EO Leonis | 5.66 | B2V | 2.78 | 289 |
V539 Arae | 5.71 | B2/B3Vnn | [n 2] | 303 |
HD 128207 | 5.73 | B8V | 0.48 | 147 |
HD 27563 | 5.84 | B5III | 3.80 | 242 |
26 Canis Majoris | 5.90 | B2IV/V | 2.73 | 257 |
16 Monocerotis | 5.92 | B3V | 1.94 | 263 |
V335 Velorum | 5.93 | B.25III | 3.76 | 704 |
V869 Centauri | 5.96 | B9IV | 1.46 | 251 |
V363 Puppis | 5.97 | B2.5V+B9V | 0.70 | 278 |
V433 Aurigae | 5.99 | B2IV-V | 4.64 | 325 |
V1141 Tauri | 6.00 | B8IV-V | 0.62 | 170 |
HD 206540 | 6.05 | B5IV | 1.39 | 215 |
HR 1397 | 6.07 | B6IV | 1.26 | 198 |
V576 Persei | 6.09 | B7V | 0.84 | 159 |
V2100 Cygni | 6.11 | B5III | 2.61 | 239 |
HR 2517 | 6.15 | B2.5III | 2.56 | 2500 |
V492 Carinae | 6.18 | B3V | 1.06 | 370 |
HR 1328 | 6.20 | B9V | 0.38 | 121 |
V4199 Sagittarii | 6.26 | B5III | 1.24 | 240 |
HR 3562 | 6.26 | B3IV | 370 | |
V4198 Sagittarii | 6.28 | B8V | 1.19 | 186 |
V377 Lacertae | 6.32 | B7III | 2.62 | 305 |
DY Chamaeleontis | 6.32 | B8IV | 0.97 | 236 |
HR 2680 | 6.33 | B3V | [n 2] | 258 |
V473 Carinae | 6.35 | B5V | 0.95 | 218 |
V405 Lacertae | 6.37 | B5V | 1.02 | 170 |
HD 34798 | 6.39 | B5Vs | 1.28 | 263 |
HD 176582 | 6.40 | B5V | 1.58 | 292 |
V1377 Orionis | 6.41 | B3III | 1.01 | 476 |
HR 8768 | 6.42 | B2V | 3.25 | 326 |
GY Eridani | 6.42 | B3V | 1.33 | 220 |
QZ Velorum | 6.49 | B1IIIn | 1.03 | 813 |
V550 Lyrae | 6.49 | B3V | 1.69 | 379 |
HD 208727 | 6.50 | B8V | 0.32 | 330 |
HD 43317 | 6.61 | B3IV | [n 1] | 369 |
23 Sextantis | 6.64 | B3.2IV | [n 1] | 769 |
HD 33331 | 6.90 | B5III | 1.15 | 296 |
HD 163868 | 7.36 | B5Ve | [n 3] | 588 |
HD 163899 | 8.30 | B2Ib/II | 23.20 | |
HD 50209 | 8.36 | B9Ve | 0.67 | 694 |
Notes
- 1 2 3 4 5 Also a Beta Cephei variable
- 1 2 3 Also an Algol variable
- ↑ Also a shell star
References
- 1 2 3 Otero, S. A.; Watson, C.; Wils, P. "Variable Star Type Designations in the VSX". AAVSO Website. American Association of Variable Star Observers. Retrieved 11 May 2014.
- 1 2 3 Waelkens, Christoffel (1993). "Slowly Pulsating B Stars". In J. M. NEMEC (Ed), Jaymie M. Matthews. New Perspectives on Stellar Pulsation and Pulsating Variable Stars: IAU Colloquium 139. Cambridge University Press. pp. 180–82. ISBN 0521443822.
- ↑ John R. Percy (2007). Understanding Variable Stars. Cambridge University Press. pp. 137–38, 200–02. ISBN 0-521-23253-8.
- ↑ Waelkens, Christoffel; Rufener, Fredy (1985). "Photometric variability of mid-B stars". Astronomy & Astrophysics. 152 (1): 6–14. Bibcode:1985A&A...152....6W.
- ↑ Miglio, A. (2007). "Revised instability domains of SPB and β Cephei stars". Communications in Asteroseismology. 151: 48–56. arXiv:0706.3632. Bibcode:2007CoAst.151...48M. doi:10.1553/cia151s48. ISSN 1021-2043.
- ↑ de Cat, P. (2007). "Observational Asteroseismology of slowly pulsating B stars". Comm. in Asteroseismology. 150: 167–74. Bibcode:2007CoAst.150..167D. doi:10.1553/cia150s167.
- ↑ BSJ (5 March 2012). "Gamma Muscae". AAVSO Website. American Association of Variable Star Observers. Retrieved 21 December 2013.