Types of Stars  

In General > s.a. astronomy [X-ray]; history of astronomy; neutron stars [and pulsars]; star properties [masses].
* Classification: Stars are classified by their position on the HR diagram, in terms of L and T; Their mass and age and determined from those properties.
* Population I: Located in the galactic disk, they contain many heavy elements.
* Population II: In the nucleus and halo, spherically distributed, few heavy elements.
* Population III: Primordial, first-generation stars with almost no heavy elements; Probably dominated by very massive stars, because collapsing clouds with no heavy elements would not undergo fragmentation; 2007, No confirmed population III star known; The ones that are near enough to be seen may all have exploded long ago; One can look for them (statistically) using the cosmic IR background; > s.a. globular clusters.
* Binaries: Visual ones have P ~ 70 yr, ε ~ 0.5, sp class F5–G0; Spectroscopic ones P around 9d; Eclipsing ones P ~ 2–3 d, ε ~ 0, sp class B–A.
@ General references: Peletier a1210-proc [stellar populations]; Massey a1305-NAR [massive stars in the Local Group].
@ Individual stars: Wielen et al A&A-ap/00 [Polaris]; Kaler 02 [the 100 most interesting ones, r pw(02)oct]; Richichi & Roccatagliata A&A(05)ap [Aldebaran]; Martins a1404-ch [properties of very massive stars].
@ Binaries: Terrell et al 92 [pictorial atlas]; Verbunt ap/04-conf [and interferometry]; Lada ApJL(06)ap [binary/single rate]; Southworth a1201-conf [eclipsing]; Sana et al Sci(12)jul-a1207 [effect on evolution of massive stars]; news IfA(12)dec [how wide binary stars form]; Kochanek et al MNRAS(15)-a1405 [mergers]; news pt(19)jul [a 7-min white-dwarf eclipsing binary].
@ Compact binaries: Nelemans PT(06)jul; Postnov & Yungelson LRR(06) [evolution]; Benacquista & Downing LRR(13)-a1110 [in globular clusters]; Piran et al MNRAS(13)-a1204 [electromagnetic signatures of mergers]; Geier et al AN(12)-a1206 [unseen massive compact companions of underluminous stars].
@ The first stars: Larson in(00)ap/99; Larson & Bromm SA(01)dec; Beers Nat(03)ap; Bromm & Larson ARAA(04)ap/03; Scannapieco et al NAR(06)ap/05-proc [detection]; Naoz et al MNRAS(06)ap; Silk & Langer MNRAS(06)ap [usual mass range]; Tornatore et al MNRAS(07)-a0707 [fate of population III stars]; Johnson et al IAU(07)-a0802; Trenti et al ApJ(08)-a0807; Bromm et al Nat(09)may-a0905; Begelman MNRAS(10)-a0910 [supermassive]; Pettini PRS(11) [quasar absorption features]; Visbal et al Nat(12)jul-a1201; Wise a1201-proc [rev]; Frebel & Bromm PT(12)apr [in the outskirts of the Milky Way]; Glover a1209-ch; Whalen a1209-conf; Bromm RPP(13)-a1305; news pt(14)feb ["stellar archaeology"]; Maio a1606-proc; > s.a. early-universe cosmology.
@ Triple systems: Zasche et al a1407 [V819 Her, V2388 Oph, and V1031 Ori].

Variable Stars > s.a. astrophysics [star formation and evolution]; supernovae.
* Cepheids: Bright variable stars, with periods of days to weeks and a useful period-luminosity relationship.
* P Cygni Stars: Erratic stars, which emit mildly gas shells.
* RR Lyrae: Old, variable stars, distributed in the nucleus and in the halo of our galaxy.
* Wolf-Rayet: Erratic stars with strong He, He+ and N++ emission lines, from envelopes of ejected matter.
@ General references: Hoffmeister et al 85 [text]; Shears JBAA-a1109 [work by E E Markwick]; Handler et al IAU-a1111 [rev]; Percy et al a1202 [high-school student projects on RR Lyrae stars]; Feast & Whitelock IAU(13)-a1310 [and galactic astronomy].
@ Cepheids: Buchler IAP-ap/97 [rev]; Tanvir ap/98-in [as candles]; Lanoix et al MNRAS(99)ap [calibration]; Ngeow et al MNRAS(05)ap [non-linearity of P-L relation]; Macri ap/05-conf [in the Milky Way galaxy, Magellanic Clouds]; Storm ap/05-conf [and RR Lyrae, as distance indicators]; Vilardell et al A&A(07)-a0707 [in M31]; Kovacs a0802-proc [metallicity]; Madore & Freedman ApJ(09)-a0902 [slope of period-luminosity relation]; Bono et al ApJ(10)-a1004 [distance scale]; Williams & Saladyga 11; Learned et al CP(12) [the Cepheid galactic internet]; Pasachoff & Mativi TPT(20) [demonstrating the cosmic distance ladder]; > s.a. civilizations [communication].
@ Other variable stars: news sn(18)jan [Tabby's star flickers because of dust].

Other Types > s.a. star clusters; Brown Dwarves; White Dwarves.
* Strange stars: Objects consisting of strange matter, a soup of unbound up, down and strange quarks.
* Novae: Eruptions occurring in binary star systems containing a white dwarf star; There are an estimated 50 or so novae per year in the Milky Way galaxy, of which only 10 or so are discovered; The nearest ones can be seen with the naked eye.
@ Strange stars: Madsen PRL(98); Chakrabarty pw(00)feb [candidate]; Dey et al ap/00; Bombaci & Datta ApJL(00)ap [and GRBs]; Bombaci ap/00-conf; Bombaci et al ApJ(00)ap; Xu IAU-ap/02 [rev]; news sr(06)dec; news pw(10)oct [and dark matter].
@ Novae: Yang et al A&A(05)ap [Korean records]; Mukai a1407-proc [recurrent]; Mukai & Sokoloski PT(19)nov [better understanding].
@ Other: Leggett et al ap/04-proc [beyond M].
> Compact objects: see black holes; neutron stars.
> Hypothetical objects: see dark-matter phenomenology [dark stars]; matter [mirror stars]; astronomical objects [boson stars]; Q-Stars; solitons.

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