Physics 663
Par t icle Physics Phenomenology
J une 4, 2002
Physics 663, lecture 13
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Quar k St ar s
• Recent obser vat ions by t he Chandr a X-r ay t elescope have
been int er pr et ed by some as evidence f or quar k st ar s
• Compact st ar s
• Theor y of quar k st ar s
• The Chandr a dat a
• GRBs?
Physics 663, lecture 13
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ast r o-ph/ 0204159
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Compact St ar s/ Obj ect s
• Est ablished:
– whit e dwar f s
– neut r on st ar s
– black holes
• Hypot hesized
– quar k st ar s
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Theor y of Quar k St ar s
• Baade and Zwicky pr oposed in 1934 t hat t he explanat ion of
super novae was t he t r ansit ion wit hin t he cor e of t he st ar of
or dinar y st ar t o neut r on st ar
• I n such a st at e, t he neut r ons ar e bound 10 t imes mor e
st r ongly by t he f or ce of gr avit y (Nat ur e’s weakest f or ce)
t han a nucleon is bound wit hin a nucleus by t he st r ong f or ce
• The st ar r eleases in seconds 10 t imes as much ener gy as it
has r eleased dur ing it ’s ent ir e exist ence
• The r esult ing neut r on st ar is nor mally t hought of as a body
of closely packed neut r ons, but car ef ully st udy of t he t heor y
of t hese st ar s leads one t o conclude t hey ar e much mor e
complex
Glendenning, ast r o-ph/ 9707351
Physics 663, lecture 13
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QCD Phase Diagr am
•
µ is t he chemical
pot ent ial, simply r elat ed
t o mat t er densit y
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Theor y of Quar k St ar s
• As a neut r on st ar spins down, it becomes denser , and it s
pr oper t ies will evolve
Glendenning, astro-ph/9707351
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Theor y of Quar k St ar s
Glendenning, astro-ph/9707351
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Theor y of Quar k St ar s
• Compr ession br ings t he possibilit y f or t he dist r ibut ion of
t he bar yon char ge over as many species as possible, including
hyper ons and quar ks
• At low densit y, neut r ons decay t o pr ot ons and elect r ons and
maint ain t he pr oper equilibr ium
• At higher densit ies, t he Fer mi ener gy incr eases, and
neut r ons can decay int o hyper ons (t his pr ocess is f avor ed by
t he Pauli pr inciple since in br ings in addit ional species of
par t icles)
Glendenning, astro-ph/9707351
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Theor y of Quar k St ar s
• Bar yon number is conser ved but
not lept on number
– neut r inos have car r ied away lept on
number
• Deep wit hin t he st ar , t he negat ive
char ge is car r ied by hyper ons, not
elect r ons
Glendenning, astro-ph/9707351
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Theor y of Quar k St ar s
Glendenning, astro-ph/9707351
Physics 663, lecture 13
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Quar k St ar s or
Hybr id St ar s
Glendenning, astro-ph/9707351
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Hybr id St ar s
Glendenning, astro-ph/9707351
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Signal f or
Hybr id St ar s
Glendenning, Pei, and Weber, astro-ph/9705235
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Signal f or Hybr id St ar s
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Chandr a Obser vat ions
• Two st ar s st udied by Chandr a ar e inconsist ent wit h t he
expect ed pr oper t ies of neut r on st ar s
– one is t oo cold
– one is t oo small
RX J 1856.5-3754
Physics 663, lecture 13
3C58
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Chandr a
• Launched J uly 23, 1999
• designed t o obser ved X-r ays
HRC
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RX J 1856.5-3754
• Combining Chandr a and HST
dat a r eveals
– X-r ay spect r um well descr ived
by T ~ 700,000 K blackbody
– dist ance ar gued t o be ~ 140 pc
– r adius = 3.8 - 8.2 km
• t oo small f or a neut r on st ar
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3C58
• Remnant of super nova obser ved in 1181
AD by J apanese and Chinese
• a r apidly r ot at ing neut r on st ar
embedded in a cloud of high ener gy
par t icles.
• Chandr a dat a r evealed t hat t he neut r on
st ar , or pulsar , is r ot at ing about 15
t imes a second, and is slowing down at
t he r at e of about 10 micr oseconds per
year .
• X-r ays obser ved f r om ext ended r egion
of high ener gy par t icles over 20 light year s
– sur pr isingly f ast cooling
– T ~ 10 6 K (since no BB f r om cor e)
• (would have expect ed 2 x 10 6 K)
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SAX J 1808.4-3658
• SAX J 1808.4-3658 is a millisecond X-r ay pulsar
• discover ed in 1996 wit h t he Wide Field Camer a on boar d t he
BeppoSAX
• Li et al have pr oposed t hat SAX J 1808.4-3658 is a “st r ange
st ar ” (pr l 83, 3776, 1999), ”a compact obj ect made ent ir ely
of deconf ined u,d,s quar k mat t er (st r ange mat t er )”
• This conclusion der ives f r om deducing t he mass and r adius
of SAX J 1808.4-3658 and not ing it is inconsist ent wit h t he
par amet er s f or neut r ons st ar s, and mor e consist ent wit h
st r ange st ar s
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Quar k St ar s and Gamma Ray Bur st s
• Quar k st ar s have been pr oposed as t he inner engines f or
GRBs
• I n a r ecent paper (Ouyed and Sannino ast r -ph/ 0103022)
quar k st ar s ar e pr oposed as a possible candidat e f or t he
GRBs
• The onset of exot ic phases of quar k mat t er at t he sur f ace
of such st ar s - color super conduct ivit y
• Par t icles (light glue balls) which ar e unst able t o phot on
decay pr ovide a nat ur al mechanism f or f ir eball gener at ion
• The model can r epr oduce t he GRB f eat ur es
– episodic act ivit y
– t wo dist inct cat egor ies of bur st s (shor t and long)
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Conclusion
• Quar k st ar s and Hybr id st ar s ar e expect ed t o exist
• Recent obser vat ions f r om Chandr a have been int er pr et ed as
possible signs of such obj ect s
• These obser vat ions ar e cont r over sial
• Fut ur e ast r ophysical dat a may pr ovide an avenue f or
invest igat ion of t he pr oper t y of dense quar k and hyper on
mat t er
• Per haps t he GRBs will be r elat ed t o t he exist ence of quar k
st ar s?
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