Astronomy:PV Telescopii variable
PV Telescopii variable is a type of variable star that is established in the General Catalogue of Variable Stars with the acronym PVTEL. This class of variables are defined as "helium supergiant Bp stars with weak hydrogen lines and enhanced lines of He and C".[1] That is, the hydrogen spectral lines of these stars are weaker than normal for a star of stellar class B, while the lines of helium and carbon are stronger. The prototype for this category is HD 168476, also known as PV Telescopii, which undergoes small but complex luminosity variations and radial velocity fluctuations.[2] The PV Tel stars are extremely hydrogen-deficient compared to other B-class stars and vary in luminosity on time scales ranging from a few hours to several years.[3] As of 2008, there are twelve confirmed PV Tel variables in the General Catalogue of Variable Stars.[1]
PV Telescopii variables are subdivided into three distinct types on the basis of spectral type: type I represents late B and A stars, type II represents O and early B, and type III represents F and G stars. The type III stars are always carbon-rich and hydrogen-deficient, while the type I and II stars do not necessarily have an excess of carbon. The hotter types pulsate more quickly than the cooler types.[4]
List
The following list contains selected PV Telescopii variable that are of interest to amateur or professional astronomy. Unless otherwise noted, the given magnitudes are in the V-band.[citation needed]
| Star |
Maximum magnitude |
Minimum magnitude |
Type | Spectral type |
|---|---|---|---|---|
| Upsilon Sagittarii | 4.43 | 4.65 | I[n 1] | F2p |
| HD 182040 | 6.95 | 7.17 | III | C... |
| HM Librae | 7.42 | 7.63 | III | C |
| KS Persei | 7.60 | 7.85 | I | A5Iap |
| PV Telescopii | 9.24 | 9.40 | I | B5p |
| BD +1 4381 | 9.47 | 9.60 | I | F |
| CD -35 11760 | 9.62 | 9.83 | I | B4Ibe |
| HD 160641 | 9.78 | 10.08 | II | sdOC9.5II-III_He40 |
| DN Leonis | 9.91 | 10.00 | II | Bp |
| HD 124448 | 9.94 | 10.03 | II | B3p |
| NO Serpentis | 10.27 | 10.39 | I | B |
| V1920 Cygni | 10.30 | 10.41 | I | B2/3 |
| CPD -58 2721 | 10.40 | 10.60 | I | B+... |
| BD -9 4395 | 10.44 | 10.63 | II | B |
| LS IV -1 2 | 10.95 | 11.05 | I | OB+ |
Notes
- ↑ also a spectroscopic binary, possibly eclipsing
References
- ↑ 1.0 1.1 Jeffery, C. Simon (March 2008). "Variable Star Designations for Extreme Helium Stars". Information Bulletin on Variable Stars 5817 (1). Bibcode: 2008IBVS.5817....1J.
- ↑ Walker, H. J.; Hill, P. W. (August 1985). "Radial velocities for the hydrogen-deficient star HD 168476, several helium-strong and helium-weak stars". Astronomy and Astrophysics Supplement Series 61: 303–311. Bibcode: 1985A&AS...61..303W.
- ↑ Jeffery, C. S.; Heber, U. (July 1992). "The extreme helium star BD-9 deg 4395". Astronomy and Astrophysics 260 (1-2): 133–150. Bibcode: 1992A&A...260..133J.
- ↑ Otero, S. A.; Watson, C.; Wils, P.. "Variable Star Type Designations in the VSX". AAVSO Website. American Association of Variable Star Observers. http://www.aavso.org/vsx/index.php?view=about.vartypes. Retrieved 19 July 2014.
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