Difference between revisions of "Variable Stars"

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==Classification==
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=Classification=
  
 
Variable stars may be either ''intrinsic'' or ''extrinsic''.
 
Variable stars may be either ''intrinsic'' or ''extrinsic''.
  
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==Intrinsic Variable Stars==
 
*'''Intrinsic variable stars''': stars where the variability is being caused by changes in the physical properties of the stars themselves. This category can be divided into three subgroups.
 
*'''Intrinsic variable stars''': stars where the variability is being caused by changes in the physical properties of the stars themselves. This category can be divided into three subgroups.
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**Eruptive variables, stars who experience eruptions on their surfaces like flares or mass ejections.
 
**Pulsating variables, stars whose radius alternately expands and contracts as part of their natural evolutionary ageing processes.
 
**Pulsating variables, stars whose radius alternately expands and contracts as part of their natural evolutionary ageing processes.
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**Eruptive variables, stars who experience eruptions on their surfaces like flares or mass ejections.
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**Cataclysmic or explosive variables, stars that undergo a cataclysmic change in their properties like [[nova]]e and [[supernova]]e.  Interacting binary systems with white dwarfs or stars showing large amplitude outbursts.
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**Cataclysmic or explosive variables, stars that undergo a cataclysmic change in their properties like [[nova]]e and [[supernova]]e.
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*'''Extrinsic variable stars''': stars where the variability is caused by external properties like rotation or eclipses. There are two main subgroups.
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1. Eruptive
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**Eclipsing binaries, [[double star]]s where, as seen from [[Earth]]'s vantage point the stars occasionally eclipse one another as they orbit.
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          FU, GCAS, I, IA, IB, IN, INA, INB, INT, IT, IN(YY), IS, ISA, ISB, RCB, RS, SDOR, UV, UVN, WR
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**Rotating variables, stars whose variability is caused by phenomena related to their rotation. Examples are stars with extreme "sunspots" which affect the apparent brightness or stars that have fast rotation speeds causing them to become ellipsoidal in shape.
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2. Pulsating
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          ACYG, BCEP, BCEPS, CEP, CEP(B), CW, CWA, CWB, DCEP, DCEPS, DSCT, DSCTC, GDOR, L, LB, LC, M, PVTEL, RPHS, RR, RR(B), RRAB, RRC, RV, RVA, RVB, SR, SRA, SRB, SRC, SRD, SXPHE, ZZ, ZZA, ZZB
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3. Cataclysmic (explosive and novalike) variables
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          N, NA, NB, NC, NL, NR, SN, SNI, SNII, UG, UGSS, UGSU, UGZ, ZAND
  
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These subgroups themselves are further divided into specific types of variable stars that are usually named after their prototype. For example, dwarf novae are designated ''U Geminorum'' stars after the first recognized star in the class, ''U Geminorum''.
 
  
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=Intrinsic=
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==Extrinsic Variable Stars==
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[[image:HR-vartype.svg|right|thumb|400px|Intrinsic variable types in the Hertzsprung–Russell diagram]]
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*'''Extrinsic variable stars''': stars where the variability is caused by external properties like rotation or eclipses. There are two main subgroups.
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Intrinsic Variable stars are stars which vary their light output, where the variability is being caused by changes in the physical properties of the stars themselves. These stars provide information about the internal structure of stars and provide astronomers with informational to support models of stellar evolution.  
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**Eclipsing binaries, double stars where, as seen from Earth's vantage point the stars occasionally eclipse one another as they orbit.
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==Pulsating Stars==
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Pulsating variable stars experience periodic expansion and contraction of the surface layers of the stars.  Pulsating variables actually increases and decreases in size periodically, creating light curves which give clues to the interior processes of the stars. Pulsating variables are also valuable in distance measurements to the stars.  The four primary classifications of pulsating variables includes Cephids, RR Lyrae, RV Tauri, and Long-Period Variables.
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===Cepheids===
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====Type I Classical====
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4. Eclipsing binary systems
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          E, EA, EB, EW, GS, PN, RS, WD, WR, AR, D, DM, DS, DW, K, KE, KW, SD
  
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====Type II W Virginis====
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**Rotating variables, stars whose variability is caused by phenomena related to their rotation. Examples are stars with extreme "sunspots" which affect the apparent brightness or stars that have fast rotation speeds causing them to become ellipsoidal in shape.
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===RR Lyrae===
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===RV Tauri===
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===Long-Period Variables (LPVs)===
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====Mira Type====
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====Semiregular====
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==Eruptive (cataclysmic stars)==
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===Supernovae===
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===Novae===
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===Recurrent Novae===
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===Dwarf Novae===
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===Symbiotic Stars===
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===R Coronae Borealis===
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=Extrinsic=
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==Eclipsing Binaries==
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==Rotating Variables==
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=Variable Star Resources=
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[http://www.aavso.org American Association of Variable Star Observers] - (AAVSO) is a non-profit worldwide scientific and educational organization of amateur and professional astronomers who are interested in stars that change in brightness—variable stars.
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[http://arxiv.org/archive/astro-ph arXiv.org Astrophysics] - An e-print service in the fields of physics, mathematics, computer science, quantitative biology, quantitative finance and statistics maintained Cornell University.
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[http://www.adsabs.harvard.edu Astrophysics Data System] - The ADS maintains three bibliographic databases containing more than 10.8 million records: Astronomy and Astrophysics, Physics, and arXiv e-prints.
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[http://www.britastro.org/vss The British Astronomical Association: Variable Star Section] - The VSS was formed in 1890, the year the BAA was founded, with the aim of collecting and analysing observations of variable stars.
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5. Rotating
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          ACV, ACVO, BY, ELL, FKCOM, PSR, SXARI
  
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[http://http://www.konkoly.hu/IBVS/IBVS.html Konkoly Observatory, Hungary - Variable Stars] - The Information Bulletin on Variable Stars is a bulletin of the Commissions  27 and 42 of the International Astronomical Union, published by the Konkoly Observatory, Budapest, Hungary.
 
  
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[http://www.rasnz.org.nz Royal Astronomical Society of New Zealand] - The RASNZ has links to [http://www.variablestarssouth.org Variable Stars South], a group focused on Variable Stars in the Southern skies.
 
  
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[http://simbad.u-strasbg.fr/Simbad The SIMBAD astronomical database] provides basic data, cross-identifications, bibliography and measurements for astronomical objects outside the solar system.
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6. intense variable X-ray sources (X, XB, XF, XI, XJ, XND, XNG, XP, XPR,
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            XPRM, XM),
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7. other symbols (BLLAC, CST, GAL, L:, QSO, S, *, +, :).
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8. the new variability types (ZZO, AM, R, BE, LBV, BLBOO, EP, SRS, LPB)

Latest revision as of 21:02, 18 May 2014

A variable star is a star where its brightness as seen from Earth fluctuates. The study of variable stars involves the recording of its magnitude, and how that fluctuates over time. The plotting of a variable star's magnitude vs. time is known as a light curve. The light curve plotting of variable stars combined with the study of supernovae events help physicists understand the formation of the universe.


Classification

Variable stars may be either intrinsic or extrinsic.

Intrinsic Variable Stars

  • Intrinsic variable stars: stars where the variability is being caused by changes in the physical properties of the stars themselves. This category can be divided into three subgroups.
    • Eruptive variables, stars who experience eruptions on their surfaces like flares or mass ejections.
    • Pulsating variables, stars whose radius alternately expands and contracts as part of their natural evolutionary ageing processes.
    • Cataclysmic or explosive variables, stars that undergo a cataclysmic change in their properties like novae and supernovae. Interacting binary systems with white dwarfs or stars showing large amplitude outbursts.

1. Eruptive 

          FU, GCAS, I, IA, IB, IN, INA, INB, INT, IT, 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, GDOR, L, LB, LC, M, PVTEL, RPHS, RR, RR(B), RRAB, RRC, RV, RVA, RVB, SR, SRA, SRB, SRC, SRD, SXPHE, ZZ, ZZA, ZZB

3. Cataclysmic (explosive and novalike) variables 

          N, NA, NB, NC, NL, NR, SN, SNI, SNII, UG, UGSS, UGSU, UGZ, ZAND


Extrinsic Variable Stars

  • Extrinsic variable stars: stars where the variability is caused by external properties like rotation or eclipses. There are two main subgroups.
    • Eclipsing binaries, double stars where, as seen from Earth's vantage point the stars occasionally eclipse one another as they orbit.

4. Eclipsing binary systems 

          E, EA, EB, EW, GS, PN, RS, WD, WR, AR, D, DM, DS, DW, K, KE, KW, SD
    • Rotating variables, stars whose variability is caused by phenomena related to their rotation. Examples are stars with extreme "sunspots" which affect the apparent brightness or stars that have fast rotation speeds causing them to become ellipsoidal in shape.

5. Rotating 

         ACV, ACVO, BY, ELL, FKCOM, PSR, SXARI


6. intense variable X-ray sources (X, XB, XF, XI, XJ, XND, XNG, XP, XPR, 

           XPRM, XM),

7. other symbols (BLLAC, CST, GAL, L:, QSO, S, *, +, :). 8. the new variability types (ZZO, AM, R, BE, LBV, BLBOO, EP, SRS, LPB)

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