2006-10-27 (Protégé 3.2 build 342) Binaries:cataclysmic CataclyV* Variable stars showing outbursts caused by thermonuclear burst processes in their surface layers (novae) or deep in their interiors (supernovae). We use the term "novalike" for variables that show novalike outbursts caused by rapid energy release in the surrounding space (UG-type stars) and also for objects not displaying outbursts but resembling explosive variables at minimum light by their spectral (or other) characteristics. The majority of explosive and novalike variables are close binary systems, their components having strong mutual influence on the evolution of each star. It is often observed that the hot dwarf component of the system is surrounded by an accretion disk formed by matter lost by the other, cooler, and more extended component. CV* YSOs YSO Y*O IR IR Nova Novae Close binary systems with orbital periods from 0.05 to 230 days. One of the components of these systems is a hot dwarf star that suddenly, during a time interval from one to several dozen or several hundred days, increases its brightness by 7-19 mag in V, then returns gradually to its former brightness over several months, years, or decades. Small changes at minimum light may be present. Cool components may be giants, subgiants, or dwarfs of K-M type. The spectra of novae near maximum light resemble A-F absorption spectra of luminous stars at first. Then broad emission lines (bands) of hydrogen, helium, and other elements with absorption components indicating the presence of a rapidly expanding envelope appear in the spectrum. As the light decreases, the composite spectrum begins to show forbidden lines characteristic of the spectra of gas nebulae excited by hot stars. At minimum light, the spectra of novae are generally continuous or resemble the spectra of Wolf-Rayet stars. Only spectra of the most massive systems show traces of cool components. Some novae reveal pulsations of hot components with periods of approximately 100 s and amplitudes of about 0.05 mag in V after an outburst. Some novae eventually turn out to be eclipsing systems. According to the features of their light variations, novae are subdivided into fast, slow, very slow, and recurrent categories. No* *inAssoc *iA Explosion or Eruption process GinGroup GiG Star of Spectral Type B A high-mass X-ray binary (HMXB) is a binary star system where one of the components is a neutron star or a black hole. The other component is a massive star, usually a Be star or a blue supergiant. A fraction of the stellar wind of the companion star is captured by the compact star, and produces X-rays as it falls onto the compact object. In HMXB, the massive star dominates the emission of optical light. The compact object is the dominant source of X-rays. The massive stars are very luminous and therefore easily detected. One of the most famous HMXB is Cygnus X-1 which was the first stellar-mass black hole discovered. Soft-gamma rays emitters. HXB HMXB High Mass X-Ray Binary Gamma Doradus variables are variable stars which display variations in luminosity due to non-radial pulsations of their surface. The stars are typically young, early F or late A type main sequence stars, and typical brightness fluctuations are 0.1 magnitudes with periods on the order of one day. This is a relatively new class of variable stars, having been first characterised in the second half of the 1990s, and details on the underlying physical cause of the variations remains under investigation. Variable Star of gamma Dor type gD* gammaDor Pulsating Variable Star Pu* Pulsating variables are stars showing periodic expansion and contraction of their surface layers. The pulsations may be radial or nonradial. A radially pulsating star remains spherical in shape, while in the case of nonradial pulsations the star's shape periodically deviates from a sphere, and even neighboring zones of its surface may have opposite pulsation phases. Depending on the period value, on the mass and evolutionary status of the star, and on the scale of pulsational phenomena, different types of pulsating variables may be distinguished. PulsV* UV UV Hydrogen Low Surface brightness Galaxy LSB_G LSB Wavelength > 30 microns LMXB Low-mass X-ray binaries (LMXBs) are binary stars where one of the components is either a black hole or neutron star. The other component (donor) is usually filling its Roche lobe and therefore transfers mass to the compact star. The donor is less massive than the compact object, and can be on the main sequence, a degenerate dwarf (white dwarf), or an evolved star (red giant). Found in the Milky Way, external galaxies, and in globular clusters. A typical LMXB emits almost all of its radiation in X-rays, and typically less than one percent in visible light, so they are among the brightest objects in the X-ray sky, but relatively faint in visible light. The apparent magnitude is typically around 15 to 20. The brightest part of the system is the accretion disk around the compact object. The orbital periods of LMXBs range from ten minutes to hundreds of days. Soft-gamma rays emitters. Low Mass X-Ray Binary LXB Star A stellar object: proto-star, star in the main sequence, evolved star or stellar remnant * Stars Star of Spectral Type G Variable Star of delta sct type PulsV*delsct 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. Delta Sct stars are representatives of the galactic disk (flat component) and are phenomenologically close to the SX Phe variables. Sub-type: - 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. dS* A star that is part of a double star *i* *in** Stars:early-type Star of the early spectral types Radio Rad component of the spacevelocity Variable Star of RR Lyr type RR* RRLyr 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. If these changes are periodic, they are called the "Blazhko effect." 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. Sub-types: - RR Lyrae variables showing two simultaneously operating pulsation modes, the fundamental tone with the period P0 and the first overtone, P1 (AQ Leo). The ratio P1/P0 is approximately 0.745; - 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; - 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). blu Blue_test Blue_objects Blue HI (neutral) region HI HI X X GinCl Galaxy in Cluster of Galaxies GiC Associations Assoc* Association of Stars AS* 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. Varaible Star of BY Dra type BYDra BY* Range allowing the description of the existence of a (noticeable) continuum for a given object Variable Star of Irregular type Ir* Stars showing variations of irregular (non-periodic) type. Mostly (?) of eruptive type. Irregular_V* CH Envelope-type Star CH* CH* HVC (High Velocity Cloud) EmG EmG Emission-line galaxy gam gamma High_z_G HzG Galaxy with high redshift Measured observational parameters/properties RS* Variable of RS CVn type RSCVn 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. Galaxies Galaxy G Process implying an observed variability smm Radio(sub-mm) OVV Optically Violently Variable Object OVV Helium s'applique aux objets étendus ( Gal/nebula) Pre-main sequence star pr* pMS* Any class in Morgan Keeman's spectral classification FU* Orion variables (eruptive) of the FU Orionis type. Characterized by gradual increases in brightness by about 6 mag in several months, followed by either almost complete constancy at maximum that is sustained for long periods of time or slow decline by 1-2 mag. Spectral types at maximum are in the range Ae(alpha) - Gpe(alpha). After an outburst, a gradual development of an emission spectrum is observed and the spectral type becomes later. These variables probably mark one of the evolutionary stages of T Tauri-type Orion variables, as evidenced by an outburst of one member, V1057 Cyg, but its decline (2.5 mag in 11 years) commenced immediately after maximum brightness was attained. All presently known FU Ori variables are coupled with reflecting cometary nebulae. FUOr* Variable Star of FU Ori type Wavelength < 10 microns Star of Luminosity Class V Radio(m) mR PairG 2 TOP concept PaG Variable stars with nonuniform surface brightness and/or ellipsoidal shapes, whose variability is caused by axial rotation with respect to the observer. The nonuniformity of surface brightness distributions may be caused by the presence of spots or by some thermal or chemical inhomogeneity of the atmosphere caused by a magnetic field whose axis is not coincident with the rotation axis. Rotationally Variable Star Ro* RotV* *inNeb *iN SBG Starburst Galaxy StarburstG Psr Pulsars Pulsar Optically variable pulsars (CM Tau), which are rapidly rotating neutron stars with strong magnetic fields, radiating in the radio, optical, and X-ray regions. Pulsars emit narrow beams of radiation, and periods of their light changes coincide with rotational periods (from 0.004 to 4 s), while amplitudes of the light pulses reach 0.8 mag. Pulsar (Extra-solar) Planet Candidate Pl? Planet? SCG Super Cluster Of Galaxies SuperClG 3 Compact_Gr_G CGG Radio(mm) mm near IR emission, age around 10^6years Dwarf Nova (U Geminorum-type variable star) DwarfNova 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. DN* 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 withine 0.01-0.1 mag in V. Sub-type: - 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. Variable Star of alpha2 CVn type RotV*alf2CVn a2* Silicium Em* Stars:Emission Em* Emission-line Star Open_clusters OpCl OpC Star of Spectral Type A Variable Star of Orion type Orion_V* Or* 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. This type may be divided into the following subtypes: - Rapid light variations observed (up to 1 mag in 1-10 days), - Orion variables of early spectral types (B-A or Ae). They are often characterized by occasional abrupt Algol-like fadings (T Ori); - 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; K-M stars may produce flares along with irregular light variations; - 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. - 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. Planetary_Nebulae 2 PN PN A planetary nebula is a nebula surrounding a stellar remnant (white dwarf) Star of Spectral Type K BCG BlueCompG Blue Compact Galaxy ClG ClG 3 Clusters_of_galaxies Star of Spectral Type F Star of Luminosity Class II DkNeb DNe A white dwarf or a stellar remnant Stars:white_dwarf WD* WD* 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. Delta Cep stars are present in open clusters. They display a certain relation between the shapes of their light curves and their periods. Sub-type: - 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. deltaCep cC* Classical Cepheid (delta Cep type) Sub-stellar su* ? Unknown Object of Unknown nature RV* Variable Star of RV Tau type 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. Two subtypes are recognized: - RV Tauri variables that do not vary in mean magnitude (AC Her); - 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). PulsV*RVTau H2G HII_G HII Galaxy any component of a stellar object SB Binaries:spectroscopic SB* Cataclysmic Variable Star DQ Her type DQHer DQ* OH/IR OH* OH/IR Envelope-type Star NIR IR<10µ Multiple_Stars Double or multiple star ** A system of two or more distinct stars 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. Ellipsoidal Variable Star RotV*Ell El* Quasar QSO QSOs QSO Any component of a galaxy red Red pulsWD* ZZ* Pulsating White Dwarf Star of Luminosity Class IV EB* Binaries:eclipsing Eclipsing Binary 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. EB* Eruptive variables are stars varying in brightness because of violent processes and flares occurring in their chromospheres and coronae. The light changes are usually accompanied by shell events or mass outflow in the form of stellar winds of variable intensity and/or by interaction with the surrounding interstellar medium. Eruptive Variable Star Er* Eruptive* rG RadioG Object which main particularity is to feature a variability Stars:variable component of the spacevelocity AGB* AG* Asymptotic Giant Branch Star 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. Symbiotic Star Symbiotic* Sy* FIR IR>30µ Radio(cm) cm HII (inonized) region HII HII HII_regions Proplyd C* Carbon Star C* Eclipsing Binary of W UMa type EB*WUMa WU* 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. Seyfert_2 Seyfert 2 Galaxy Sy2 Star of Luminosity Class I RfNeb RNe Nova-like 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. NL* 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. Mira Mi* Variable Star of Mira Cet type BLLac BL Lac-type Object BLL BL_Lac_objects AGN AGN AGN Active Galaxy Nucleus HB* HB* Horizontal Branch Star Portion of an astronomical object which is not an astronomical object itself Peculiar Stellar Object Any astronomical object LINER LINER-type Active Galaxy Nucleus LIN post-AGB* Post-AGB Star pA* GiP GinPair SuperNovae SuperNova SN* SN Rapid_Irreg_V* Variable Star with rapid variations RI* Rapid irregular variables (class: eruptive) having no apparent connection with diffuse nebulae and showing light changes of about 0.5 - 1.0 mag within several hours or days. There is no strict boundary between rapid irregular and Orion variables. If a rapid irregular star is observed in the region of a diffuse nebula, it is considered an Orion variable. To attribute a variable to this type (R.I.), it is necessary to take much care to be certain that its light changes are really not periodic. Sub-types: - Rapid irregular variables of the early spectral types, B-A or Ae; - Rapid irregular variables of the intermediate and late spectral types, F-M and Fe-Me. *inCl *iC An individual star located in a star cluster XB* Close binary systems that are sources of strong, variable X-ray emission and which do not belong to or are not yet attributed to any other type of variable stars. One of the components of the system is a hot compact object (white dwarf, neutron star, or possibly a black hole). X-ray emission originates from the infall of matter onto the compact object or onto an accretion disk surrounding the compact object. In turn, the X-ray emission is incident upon the atmosphere of the cooler companion of the compact object and is reradiated in the form of optical high-temperature radiation (reflection effect), thus making that area of the cooler companion's surface an earlier spectral type. XB High Velocity Star HV* HV*