Ennustetta seuraavalla rivillä on yksityiskohtaisia muuttuvia tähtiä koskevia tietoja (määrittelyt ovat peräisin muuttuvien tähtien yleisluettelosta GCVS):
| Koodi | Komponenttien fyysisiin ominaisuuksiin perustuva luokittelu |
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| ACV | Alpha2 Canum Venaticorum variables. These are main-sequence stars with spectral types B8p-A7p and
displaying strong magnetic fields. Spectra show abnormally strong lines of Si, Sr, Cr, and rare earths whose
intensities vary with rotation. They exhibit magnetic field and brightness changes (periods of 0.5-160 days or more).
The amplitudes of the brightness changes are usually within 0.01-0.1 mag in V. |
| ACVO | Rapidly oscillating Alpha2 CVn variables. These are nonradially pulsating, rotating magnetic
variables of Ap spectral type (DO Eri). Pulsation periods are in the range of 6-12 mmag (0.004-0.01 days), while
amplitudes of light variation caused by the pulsation are about 0.01 mag in V. The pulsational variations are
superposed on those caused by rotation. |
| ACYG | Variables of the Alpha Cygni type, which are nonradially pulsating supergiants of Bep-AepIa
spectral types. The light changes with amplitudes of the order of 0.1 mag often seem irregular, being caused by
the superposition of many oscillations with close periods. Cycles from several days to several weeks are observed.
|
| BCEPH | Variables of the Beta Cephei type (Beta Cep, Beta CMa), which are pulsating O8-B6 I-V stars with
periods of light and radial-velocity variations in the range of 0.1 - 0.6 days and light amplitudes from 0.01 to 0.3
mag in V. The light curves are similar in shape to average radial-velocity curves but lag in phase by a quarter of
the period, so that maximum brightness corresponds to maximum contraction, i.e., to minimum stellar radius. The
majority of these stars probably show radial pulsations, but some (V649 Per) display nonradial pulsations;
multiperiodicity is characteristic of many of these stars. |
| 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. |
| BY | BY Draconis-type variables, which are emission-line dwarfs of dKe-dMe spectral type showing
quasiperiodic light changes with periods from a fraction of a day to 120 days and amplitudes from several hundredths
to 0.5 mag in V. The light variability is caused by axial rotation of a star with a variable degree of nonuniformity
of the surface brightness (spots) and chromospheric activity. Some of these stars also show flares similar to those
of UV Cet stars, and in those cases they also belong to the latter type and are simultaneously considered eruptive
variables. |
| CEP | Cepheids. Radially pulsating, high luminosity (classes Ib-II) variables with periods in the range
of 1-135 days and amplitudes from several hundredths to 2 mag in V (in the B band, the amplitudes are greater).
Spectral type at maximum light is F; at minimum, the types are G-K. The longer the period of light variation, the
later is the spectral type. The maximum of the surface-layer expansion velocity almost coinciding with maximum light.
|
| CST | Nonvariable stars, formerly suspected to be variable and hastily designated. Further observations
have not confirmed their variability. |
| CW | Variables of the W Virginis type. These are pulsating variables of the galactic spherical component
(old disk) population with periods of approximately 0.8 to 35 days and amplitudes from 0.3 to 1.2 mag in V. They obey
a period-luminosity relation different from that for Delta Cep variables (see DCEP). For an equal period value, the W
Vir variables are fainter than the Delta Cep stars by 0.7 - 2 mag. The light curves of W Vir variables for some
period intervals differ from those of Delta Cep variables for corresponding periods either by amplitudes or by the
presence of humps on their descending branches, sometimes turning into broad flat maxima. W Vir variables are present
in globular clusters and at high galactic latitudes. |
| CWA | W Vir variables with periods longer than 8 days (W Vir). |
| CWB | W Vir variables with periods shorter than 8 days (BL Her). |
| DCEP | These are the classical Cepheids, or Delta Cep-type variables. Comparatively young objects that have
left the main sequence and evolved into the instability strip of the Hertzsprung-Russell (H-R) diagram, they obey
the well-known Cepheid period-luminosity relation and belong to the young disk population. DCEP stars are present in
open clusters. They display a certain relation between the shapes of their light curves and their periods. |
| DCEPS | These are Delta Cep variables having light amplitudes <0.5 mag in V (<0.7 mag in B) and almost
symmetrical light curves (M-m approx. 0.4 - 0.5 periods); as a rule, their periods do not exceed 7 days. They are
probably first-overtone pulsators and/or are in the first transition across the instability strip after leaving the
main sequence (SU Cas). Traditionally, both Delta Cep and W Vir stars are quite often called Cepheids because it is
often impossible to discriminate between them on the basis of the light curves for periods in the range 3 - 10 days.
However, these are distinct groups of entirely different objects in different evolutionary stages. One of the
significant spectral differences between W Vir stars and Cepheids is the presence, during a certain phase interval,
of hydrogen-line emission in the former and of Ca II H and K emission in the latter. |
| DSCT | Variables of the Delta Scuti type. These are pulsating variables of spectral types A0-F5 III-V
displaying light amplitudes from 0.003 to 0.9 mag in V (usually several hundredths of a magnitude) and periods from
0.01 to 0.2 days. The shapes of the light curves, periods, and amplitudes usually vary greatly. Radial as well as
nonradial pulsations are observed. The variability of some members of this type appears sporadically and sometimes
completely ceases, this being a consequence of strong amplitude modulation with the lower value of the amplitude not
exceeding 0.001 mag in some cases. The maximum of the surface layer expansion does not lag behind the maximum light
for more than 0.1 periods. DSCT stars are representatives of the galactic disk (flat component) and are
phenomenologically close to the SX Phe variables. |
| DSCTC | Low amplitude group of Delta Sct variables (light amplitude <0.1 mag in V). The majority of this
type's representatives are stars of luminosity class V; objects of this subtype generally are representative of the
Delta Sct variables in open clusters. |
| EA | Eclipsing binary systems. These are binary systems with orbital planes so close to the observer's
line of sight (the inclination i of the orbital plane to the plane orthogonal to the line of sight is close to 90 deg)
that the components periodically eclipse each other. Consequently, the observer finds changes of the apparent
combined brightness of the system with the period coincident with that of the components' orbital motion. (Note the
extra classification for eclipsing variables, given below) |
| EB | Beta Lyrae-type eclipsing systems. These are eclipsing systems having ellipsoidal components and
light curves for which it is impossible to specify the exact times of onset and end of eclipses because of a
continuous change of a system's apparent combined brightness between eclipses; secondary minimum is observed in all
cases, its depth usually being considerably smaller than that of the primary minimum; periods are mainly longer
than 1 day. The components generally belong to early spectral types (B-A). Light amplitudes are usually <2 mag in
V. (Note the extra classification for eclipsing variables, given below) |
| ELL | Rotating ellipsoidal variables (b Per, Alpha Vir). These are close binary systems with ellipsoidal
components, which change combined brightnesses with periods equal to those of orbital motion because of changes in
emitting areas toward an observer, but showing no eclipses. Light amplitudes do not exceed 0.1 mag in V. |
| EW | W Ursae Majoris-type eclipsing variables. These are eclipsers with periods shorter than 1 days,
consisting of ellipsoidal components almost in contact and having light curves for which it is impossible to specify
the exact times of onset and end of eclipses. The depths of the primary and secondary minima are almost equal or
differ insignificantly. Light amplitudes are usually <0.8 mag in V. The components generally belong to spectral
types F-G and later. (Note the extra classification for eclipsing variables, given below) |
| GCAS | Eruptive irregular variables of the Gamma Cas type. These are rapidly rotating B III-IVe stars
with mass outflow from their equatorial zones. The formation of equatorial rings or disks is often accompanied by
temporary fading. Light amplitudes may reach 1.5 mag in V. |
| I | Poorly studied irregular variables with unknown features of light variations and spectral types.
This is a very inhomogeneous group of objects. |
| IA | Poorly studied irregular variables of early (O-A) spectral type. |
| IB | Poorly studied irregular variables of intermediate (F-G) to late (K-M) spectral type. |
| IN | Orion variables. Irregular, eruptive variables connected with bright or dark diffuse nebulae or
observed in the regions of these nebulae. Some of them may show cyclic light variations caused by axial rotation.
In the Spectrum-Luminosity diagram, they are found in the area of the main sequence and subgiants. They are probably
young objects that, during the course of further evolution, will become light-constant stars on the zero-age main
sequence (ZAMS). The range of brightness variations may reach several magnitudes. In the case of rapid light
variations having been observed (up to 1 mag in 1-10 days), the letter "S" is added to the symbol
for the type (INS). |
| INA | Orion variables of early spectral types (B-A or Ae). They are often characterized by occasional
abrupt Algol-like fadings (T Ori). |
| INB | Orion variables of intermediate and late spectral types, F-M or Fe-Me (BH Cep, AH Ori). F-type
stars may show Algol-like fadings similar to those of many INA stars; K-M stars may produce flares along with
irregular light variations. |
| INT | Orion variables of the T Tauri type. Stars are assigned to this type on the basis of the following
(purely spectroscopic) criteria: spectral types are in the range Fe-Me. The spectra of most typical stars resemble
the spectrum of the solar chromosphere. The feature specific to the type is the presence of the flourescent emission
lines Fe II 4046, 4132 A (anomalously intense in the spectra of these stars), emission lines [Si II] and [O I], as
well as the absorption line Li I 6707 A. These variables are usually observed only in diffuse nebulae. If it is not
apparent that the star is associated with a nebula, the letter "N" in the symbol for the type may be
omitted, e.g., IT (RW AUR). |
| IN(YY) | Some Orion variables (YY Ori) show the presence of absorption components on the redward sides of
emission lines, indicating the infall of matter toward the stars' surfaces. In such cases, the symbol for the type
may be accompanied by the symbol "YY". |
| IS | Rapid irregular variables having no apparent connection with diffuse nebulae and showing light
changes of about 0.5 - 1.0 mag within several hours or days. |
| L | Slow irregular variables. The light variations of these stars show no evidence of periodicity,
or any periodicity present is very poorly defined and appears only occasionally. Like for the type I, stars are
often attributed to this type because of being insufficiently studied. Many type L variables are really semiregulars
or belong to other types. |
| LB | Slow irregular variables of late spectral types (K, M, C, S); as a rule, they are giants (CO Cyg).
This type is also ascribed, in the GCVS, to slow red irregular variables in the case of unknown spectral types and
luminosities. |
| LBV | For comparatively long-period pulsating B stars (periods exceeding one day). |
| LC | Irregular variable supergiants of late spectral types having amplitudes of about 1 mag in V (TZ Cas).
|
| M | Mira (Omicron) Ceti-type variables. These are long-period variable giants with characteristic
late-type emission spectra (Me, Ce, Se) and light amplitudes from 2.5 to 11 mag in V. Their periodicity is well
pronounced, and the periods lie in the range between 80 and 1000 days. Infrared amplitudes are usually less than in
the visible and may be <2.5 mag. For example, in the K band they usually do not exceed 0.9 mag. If the amplitudes
exceed 1 - 1.5 mag , but it is not certain that the true light amplitude exceeds 2.5 mag, the symbol
"M" is followed by a colon, or the star is attributed to the semiregular class with a colon following
the symbol for that type (SR). |
| NL | Novalike variables, which are insufficiently studied objects resembling novae by the characteristics
of their light changes or by spectral features. This type includes, in addition to variables showing novalike outbursts,
objects with no bursts ever observed; the spectra of novalike variables resemble those of old novae, and small light
changes resemble those typical for old novae at minimum light. However, quite often a detailed investigation makes it
possible to reclassify some representatives of this highly inhomogeneous group of objects into other types. |
| PVTEL | Variables of the PV Telescopii type. These are helium supergiant Bp stars with weak hydrogen lines
and enhanced lines of He and C. They pulsate with periods of approximately 0.1 to 1 days, or vary in brightness with
an amplitude of 0.1 mag in V during a time interval of about a year. |
| RCB | Variables of the R Coronae Borealis type. These are hydrogen-poor, carbon- and helium-rich,
high-luminosity stars belonging to the spectral types Bpe-R, which are simultaneously eruptive and pulsating
variables. They show slow nonperiodic fadings by 1-9mag in V lasting from a month or more to several hundred days.
These changes are superposed on cyclic pulsations with amplitudes up to several tenths of a magnitude and periods
in the range 30-100 days. |
| RR | Variables of the RR Lyrae type, which are radially-pulsating giant A-F stars having amplitudes
from 0.2 to 2 mag in V. Cases of variable light-curve shapes as well as variable periods are known. Traditionally,
RR Lyrae stars are sometimes called short-period Cepheids or cluster-type variables. The majority of these stars
belong to the spherical component of the Galaxy; they are present, sometimes in large numbers, in some globular
clusters, where they are known as pulsating horizontal-branch stars. Like Cepheids, maximum expansion velocities of
surface layers for these stars practically coincide with maximum light. |
| RRAB | RR Lyrae variables with asymmetric light curves (steep ascending branches), periods from 0.3 to
1.2 days, and amplitudes from 0.5 to 2 mag in V; |
| RRC | RR Lyrae variables with nearly symmetric, sometimes sinusoidal, light curves, periods from 0.2 to
0.5 days, and amplitudes not greater than 0.8 mag in V (SX UMa). |
| RS | Eruptive variables of the RS Canum Venaticorum type. This type is ascribed to close binary
systems with spectra showing Ca II H and K in emission, their components having enhanced chromospheric activity
that causes quasi-periodic light variability. The period of variation is close to the orbital one, and the
variability amplitude is usually as great as 0.2 mag in V (UX Ari). They are X-ray sources and rotating variables.
RS CVn itself is also an eclipsing system. |
| RV | Variables of the RV Tauri type. These are radially pulsating supergiants having spectral types
F-G at maximum light and K-M at minimum. The light curves are characterized by the presence of double waves with
alternating primary and secondary minima that can vary in depth so that primary minima may become secondary and
vice versa. The complete light amplitude may reach 3-4 mag in V. Periods between two adjacent primary minima
(usually called formal periods) lie in the range 30-150 days (these are the periods appearing in the Catalogue). |
| RVA | RV Tauri variables that do not vary in mean magnitude (AC Her). |
| RVB | RV Tauri variables that periodically (with periods from 600 to 1500 days and amplitudes up to 2
mag in V) vary in mean magnitude (DF Cyg, RV Tau). |
| SDOR | Variables of the S Doradus type. These are eruptive, high-luminosity Bpec-Fpec stars showing
irregular (sometimes cyclic) light changes with amplitudes in the range 1-7 mag in V. They belong to the brightest
blue stars of their parent galaxies. As a rule, these stars are connected with diffuse nebulae and surrounded by
expanding envelopes (P Cyg, Eta Car). |
| SR | Semiregular variables, which are giants or supergiants of intermediate and late spectral types
showing noticeable periodicity in their light changes, accompanied or sometimes interrupted by various irregularities.
Periods lie in the range from 20 to &qt;2000 days, while the shapes of the light curves are rather different and variable,
and the amplitudes may be from several hundredths to several magnitudes (usually 1-2 mag in V). |
| SRA | Semiregular late-type (M, C, S or Me, Ce, Se) giants displaying persistent periodicity and usually
small (<2.5 mag in V) light amplitudes (Z Aqr). Amplitudes and light-curve shapes generally vary and periods are in
the range of 35-1200 days. Many of these stars differ from Miras only by showing smaller light amplitudes. |
| SRB | Semiregular late-type (M, C, S or Me, Ce, Se) giants with poorly defined periodicity (mean cycles
in the range of 20 to 2300 days) or with alternating intervals of periodic and slow irregular changes, and even with
light constancy intervals (RR CrB, AF Cyg). Every star of this type may usually be assigned a certain mean period
(cycle), which is the value given in the Catalogue. In a number of cases, the simultaneous presence of two or more
periods of light variation is observed. |
| SRC | Semiregular late-type (M, C, S or Me, Ce, Se) supergiants (Mu Cep) with amplitudes of about 1 mag
and periods of light variation from 30 days to several thousand days. |
| SRD | Semiregular variable giants and supergiants of F, G, or K spectral types, sometimes with emission
lines in their spectra. Amplitudes of light variation are in the range from 0.1 to 4 mag, and the range of periods is
from 30 to 1100 days (SX Her, SV UMa). |
| SXARI | SX Arietis-type variables. These are main-sequence B0p-B9p stars with variable-intensity He I and
Si III lines and magnetic fields. They are sometimes called helium variables. Periods of light and magnetic field
changes (about 1 day) coincide with rotational periods, while amplitudes are approximately 0.1 mag in V. These stars
are high-temperature analogs of the ACV variables. |
| SXPHE | Phenomenologically, these resemble DSCT (Delta Sct) variables and are pulsating subdwarfs of the
spherical component, or old disk galactic population, with spectral types in the range A2-F5. They may show several
simultaneous periods of oscillation, generally in the range 0.04-0.08 days, with variable-amplitude light changes
that may reach 0.7 mag in V. These stars are present in globular clusters. |
| UG | U Geminorum-type variables, quite often called dwarf novae. They are close binary systems consisting
of a dwarf or subgiant K-M star that fills the volume of its inner Roche lobe and a white dwarf surrounded by an
accretion disk. Orbital periods are in the range 0.05-0.5 days. Usually only small, in some cases rapid, light
fluctuations are observed, but from time to time the brightness of a system increases rapidly by several magnitudes
and, after an interval of from several days to a month or more, returns to the original state. Intervals between two
consecutive outbursts for a given star may vary greatly, but every star is characterized by a certain mean value of
these intervals, i.e., a mean cycle that corresponds to the mean light amplitude. The longer the cycle, the greater
the amplitude. These systems are frequently sources of X-ray emission. The spectrum of a system at minimum is
continuous, with broad H and He emission lines. At maximum these lines almost disappear or become shallow
absorption lines. Some of these systems are eclipsing, possibly indicating that the primary minimum is caused by
the eclipse of a hot spot that originates in the accretion disk from the infall of a gaseous stream from the K-M
star. According to the characteristics of the light changes, U Gem variables may be subdivided into three types:
SS Cyg, SU UMa, and Z Cam. |
| UGSS | SS Cygni-type variables (SS Cyg, U Gem). They increase in brightness by 2-6 mag in V in 1-2 days
and in several subsequent days return to their original brightnesses. The values of the cycle are in the range 10
days to several thousand. |
| UGSU | SU Ursae Majoris-type variables. These are characterized by the presence of two types of
outbursts called "normal" and "supermaxima". Normal, short outbursts are similar to those
of UGSS stars, while supermaxima are brighter by 2 mag, are more than five times longer (wider), and occur several
times less frequently. During supermaxima the light curves show superposed periodic oscillations (superhumps),
their periods being close to the orbital ones and amplitudes being about 0.2-0.3 mag in V. Orbital periods are
shorter than 0.1 days; companions are of dM spectral type. |
| UGZ | Z Camelopardalis-type stars. These also show cyclic outbursts, differing from UGSS variables by
the fact that sometimes after an outburst they do not return to the original brightness, but during several cycles
retain a magnitude between maximum and minimum. The values of cycles are from 10 to 40 days, while light amplitudes
are from 2 to 5 mag in V. |
| UV | Eruptive variables of the UV Ceti type, these are K Ve-M Ve stars sometimes displaying flare
activity with amplitudes from several tenths of a magnitude up to 6 mag in V. The amplitude is considerably greater
in the ultraviolet spectral region. Maximum light is attained in several seconds or dozens of seconds after the
beginning of a flare; the star returns to its normal brightness in several minutes or dozens of minutes. |
| UVN | Flaring Orion variables of spectral types Ke-Me. These are phenomenologically almost identical to
UV Cet variables observed in the solar neighbourhood. In addition to being related to nebulae, they are normally
characterized by being of earlier spectral type and greater luminosity, with slower development of flares (V389 Ori).
They are possibly a specific subgroup of INB variables with irregular variations superimposed by flares. |
| XI | X-ray irregulars. Close binary systems consisting of a hot compact object surrounded by an
accretion disk and a dA - dM-type dwarf. These display irregular light changes on time scales of minutes and hours,
and amplitudes of about 1 mag in V. Superposition of a periodic variation because of orbital motion is possible
(V818 Sco); |
| XNG | X-ray, novalike (transient) systems with an early-type supergiant or giant primary component and
a hot compact object as a companion. Following the main component's outburst, the material ejected by it falls onto
the compact object and causes, with a significant delay, the appearance of X rays. The amplitudes are about 1-2 mag
in V (V725 Tau); |
| ZAND | Symbiotic variables of the Z Andromedae type. They are close binaries consisting of a hot star, a
star of late type, and an extended envelope excited by the hot star's radiation. The combined brightness displays
irregular variations with amplitudes up to 4 mag in V. A very inhomogeneous group of objects. |