Long-period variable
A long-period variable (LPV) is a type of pulsating cool giant variable star with periods from a few days to a thousand or more, sometimes poorly defined, and sometimes irregular. Long-period variables have spectral class F and redwards, but most are red giants and AGB giants, meaning spectral class M, S or C. They are usually deep orange or red.
The following well defined variable star classes used to be counted into the LPV category,[1] although in common usage often referring simply to Mira variables:[2]
- Mira variables, long rather regular pulsation periods in the range between 80 to 1000 days and grand light variations, from 2.5 magnitudes up to 11;
- semiregular variables (SR), the periods in the same range as Miras, but lower amplitude and often irregularities that makes the period determination hard;
- slow irregular variables (L), stars similar to the semiregulars, but whose period cannot be determined, because of the irregularity of the light change;
- OGLE small amplitude red giants (OSARGs),[3][4] forming several series having periods from a few days up to several hundred days and amplitudes of at most a few tenths of a magnitude.
The AAVSO LPV Section covers the Mira, SR, and L stars, but also RV Tauri variables, another type of large cool slowly varying star. This includes SRc and Lc stars which are respectively semi-regular and irregular cool supergiants. Recent researches have increasingly focused on the long period variables as only AGB and possibly red giant tip stars. The recently-classified OSARGs are by far the most numerous of these stars, comprising a high proportion of red giants.
References
- ↑ Xiong, D. R.; Deng, L.; Cheng, Q. L. (1998). "Turbulent Convection and Pulsational Stability of Variable Stars. I. Oscillations of Long‐Period Variables". The Astrophysical Journal 499: 355. arXiv:astro-ph/9710053. Bibcode:1998ApJ...499..355X. doi:10.1086/305601.
- ↑ Tuthill, P. G.; Haniff, C. A.; Baldwin, J. E. (1999). "Surface imaging of long-period variable stars". Monthly Notices of the Royal Astronomical Society 306 (2): 353. Bibcode:1999MNRAS.306..353T. doi:10.1046/j.1365-8711.1999.02512.x.
- ↑ Soszynski; Udalski; Szymanski; Kubiak; Pietrzynski; Wyrzykowski; Szewczyk; Ulaczyk et al. (2009). "The Optical Gravitational Lensing Experiment. The OGLE-III Catalog of Variable Stars. IV. Long-Period Variables in the Large Magellanic Cloud". Acta Astronomica 59 (239). arXiv:0910.1354. Bibcode:2009AcA....59..239S.
- ↑ Masaki Takayama; Hideyuki Saio; Yoshifusa Ita (2013). "On the pulsation modes of OGLE small amplitude red giant variables in the LMC". arXiv:1303.7059 [astro-ph.SR].
External links
| ||||||||||||||||||||||||||||||||||||||||||||||||||
