Variable Stars - Types
Hills Observatory: 1 January 2013 to 26 May 2020
The information in these pages is taken from Centre de Données astronomiques de Strasbourg, in particular the fourth edition of the GCVS. Variability types are grouped according to the major astrophysical reasons for variability, viz., 1. Eruptive (FU, GCAS, I, IA, IB, IN, INA, INB, INT, IN(YY), IS, ISA, ISB, RCB, RS, SDOR, UV, UVN, WR) 2. Pulsating (ACYG, BCEP, BCEPS, CEP, CEP(B), CW, CWA, CWB, DCEP, DCEPS, DSCT, DSCTC, L, LB, LC, M, PVTEL, RR, RR(B), RRAB, RRC, RV, RVA, RVB, SR, SRA, SRB, SRC, SRD, SXPHE, ZZ, ZZA, ZZB) 3. Rotating (ACV, ACVO, BY, ELL, FKCOM, PSR, SXARI) 4. Cataclysmic (explosive and novalike) variables (N, NA, NB, NC, NL, NR, SN, SNI, SNII, UG, UGSS, UGSU, UGZ, ZAND) 5. Eclipsing binary systems (E, EA, EB, EW, GS, PN, RS, WD, WR, AR, D, DM, DS, DW, K, KE, KW, SD) 6. Intense variable X-ray sources (X, XB, XF, XI, XJ, XND, XNG, XP, XPR, XPRM) 7. Other symbols (BLLAC, CST, GAL, L:, QSO, S:, *, +) All of these classes include objects of a dissimilar nature that belong to different types of light variability. On the other hand, an object may be variable because of almost all of the possible reasons or becauseof any combination of them. If a variable belongs to several types of variability, the types are joined in the data field by a "+" sign, e.g. E+UG, UV+BY. Despite considerable success in understanding stellar variability processes, the classification adopted in the Catalogue is far from perfect. This is especially the case for explosive, symbiotic and novalike variables; X-ray sources; and peculiar objects. The new variability types (ZZO, AM, R, BE, LBV, BLBOO) have been added in the Name-Lists 67- 72 and in the GCVS vol.V. ZZO ZZ Cet type variables of the DO spectral type showing HeII and CIV absorbtion lines in their spectra. AM AM Her type variables; close binary systems consisting of a dK-dM type dwarf and of a compact object with strong magnetic field, characterized by variable linear and circular polarization of light. The total range of light variations may reach 4-5 mag V. R Close binary systems characterized by the presence of strong reflection (re- radiation) of the light of the hot star illuminating the surface of the cooler companion. Light curves are sinusoidal with the period equal to Porb, maximum brightness coinciding with the passage of the hot star in front of the companion. The eclipse may be absent. The range of light variation is about 0.5-1.0mag V (KV Vel). BE It becomes more and more clear that, although the majority of Be stars are photometrically variable, not all of them could be properly called GCAS variables. Quite a number of them show small-scale variations not necessarily related to shell events; in some cases the variations are quasi-periodic. By now we are not able to present an elaborated system of classification for Be variables, but we adopt a decision that in the cases when a Be variable cannot be readily described as a GCAS star we give simply BE for the type of variability. LBV For comparatively long-period pulsating B stars (periods exceeding one day), we introduce a provisional type LBV. BLBOO The so-called "anomalous Cepheids", i.e. stars with periods characteristic of comparatively long-period RRAB variables, but considerably brighter by luminosity (BL Boo = NGC 5466 V19).