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
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).