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Quark deconfinement in compact stars and GRBs structure

Quark deconfinement in compact stars and GRBs structure. Alessandro Drago University of Ferrara. Outline. What do we learn from the existence of stars of 2 M s ? Are hyperons excluded ? Are hybrid quark- hadron stars excluded ? Are quark stars excluded ?

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Quark deconfinement in compact stars and GRBs structure

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  1. Quark deconfinementin compact stars and GRBs structure Alessandro Drago University of Ferrara

  2. Outline • What do welearn from the existence of stars of 2 Ms? • Are hyperonsexcluded? • Are hybrid quark-hadronstarsexcluded? • Are quark starsexcluded? • Are radiismallerthanabout 10 km excluded by theory? • Two families co-existencehypothesis : hadronicstars and quark stars A. D., A. Lavagno and G. Pagliara; arXiv:1309.7263 • A few observational facts about long GRBs • Quiescent times: an open problem • The «quark deconfinement» interpretation • The magnetar model for GRBs(Usov92, Thompson 94, Metzger, Bucciantini et al) and howit can incorporate quark deconfinement to explain long quiescenttimes

  3. Whatdo welearnfrom the existence of stars of 2 Ms?

  4. Strangeness production • In heavyionexperimentsstrangeness can be producedonly by strong-interaction and therefore via associatedproduction (weakinteractiondoesnothave time to take place). The typicalfraction of strangenessislessthan 10% • In a compact star strangenessismainlyproduced by weakinteraction. Hyperons«normally» start appearingatdensitiesabove (2.5 – 3) r0 • Hyperonscan significantlysoften the EoS: isitpossible to have a 2 Ms compact star with hyperons? Yes, but…

  5. Hyperons in b-stablematter

  6. Hyperonicstars in a non-relativistic BHFwith parametrised 3-body forcesbetweenhyperonsVidana et al. Europhys.Lett. 94 (2011) 11002 Radius of a purelynucleonic star about 12 km stiffer and softer pure nucleonic EoS (curves 1 and 2) stiffer and softer hyperonic stars (curves 3 and 4) 3-body forces are notsufficent to reachtwo solar masses The centraldensityisvery large, 5 – 9 r0 A relativisticapproachcould be needed

  7. Borrowed from I. Vidana Radii for a 1.4 Mshyperonic star are about 12-14 km

  8. Basic questions Threshold for L: mn= mL Possibilities: • to reduce the mass of the nucleon, sincemn = (mn* 2 + Kf2) ½ + … • to increase the chemicalpotential of the L • How much can the mass of the nucleon be reduced? • How strongly repulsive can be the YNN, YYN, YYY three-body forces? Can it be much more repulsive than NNN three-body force at high density?

  9. Struggling with hybridstars Ippolito et al. Phys.Rev. D77 (2008) 023004 Zdunik and Haensel A&A, 551(2013) A61 Itisnotimpossible to satisfy the 2 Mslimit with a hybrid star but special limits on the parameters’ valueshave to be imposed Radius of a 1.4 Mshybrid star: 12-14 km

  10. Cold quark matter:a perturbative QCD approachKurkela, Romatschke, Vuorinen;Phys.Rev. D81 (2010) 105021 “ … equations of state including quark matter lead to hybrid star masses up to 2Ms, in agreement with current observations. For strange stars, we find maximal masses of 2.75Msand conclude that confirmed observations of compact stars with M > 2Ms would strongly favor the existence of stable strange quark matter”

  11. Passing the test with quark starsWeissenborn et al.; Astrophys.J. 740 (2011) L14 Itisnotparticularlydifficult to reachmasseslargerthan 2 Ms in the case of quark stars. In principleevenlargermasses can be obtained.

  12. A remarkconcerning «history»M.Alford, D.Blaschke, A.Drago, T.Klaehn, G.Pagliara, J.Schaffner-BielichNature, 445 (2007) E7 Radii for a 1.4 M s star largerthan 11 km Based on papers publishedbefore 2006

  13. AboutmassesandradiiHebeler, Lattimer, Pethick, Schwenk ApJ773(2013)11 Analysis based on politropicexpansion: R1.4 > 10 km Explicit model calculations indicate a evenslightlylargerlimit If a 2.4 M s star will be discovered, thenR1.4 > 12 km !

  14. First «conclusion» • Itispossible to reachtwo solar masses with hyperonic and with hybridstars, although tight limits on the parameters’ spacehave to be imposed. • The two solar mass constraint can be satisfied more easily with quark stars (butitisunlikelythat ALL compact stars are quark stars). • The radii of a 1.4 Ms star are largerthanabout (10 ― 10.5) km ifall compact stars are eithernucleonic or hadronic or hybridstars. If a 2.4 Ms star existsthenradiismallerthanabout 12 km are ruled out ifall compact starsbelong to one family.

  15. Are radiismallerthan 10 km ruled out by microphysics?(and whatif a 2.4 Mswill be discovered?)

  16. Analysis of 5 QLMXBs Lattimer and Steiner 1305.3242 Guillot et al. ApJ772(2013)7

  17. Guillot et al. ApJ772(2013)7analysis of 5 QLMXBs

  18. The role of delta resonancesSchurhoff, Schramm, DexheimerApJ 724 (2010) L74 The delta-nucleon mass splitting atnuclearmattersaturation can be tested via electron-nucleus scattering and thereforecannot be increasedalmostarbitraryas for the Lambda-nucleon mass splitting. Itcouldtherefore be difficult to eliminate delta resonances (and the associate softening) from compact stars!

  19. How to have small radii and large masseswith twotypes of compact starsA.D., A. Lavagno, G. Pagliara arXiv:1309.7263 The hadronic star willnottransforminto a quark star till the moment in which hyperons start appearing, or slightlylater. In this way stars with radii of the order of 10 km or smaller are possible and those stars are mainly made of nucleons and Δ-resonances. The mostheavystars wouldinstead be quark stars. Stars with a mass smallerthanabout 1.5 Mswould be composed of nucleons and of Dresonances. Theirpropertiesconcerning e.g. stability under rapidrotationwould be similar to purelynucleonicstars. Theywouldalso have a crust. Most of the features of supermassivestarswouldinstead differ from those of normalneutronstars.

  20. Signatures of a two family scenario • The energyreleased in the conversionfrom hadrons to quarksistypicallyof the order of 1053 erg, large enough to produce a neutrino fluxable to revitalize a failed SN explosion. • A fewGRBscould be associated with the conversion from hadrons to quarks. In particularGRBsnotassociated with a SN can exist. AlsosuggestsGRBs with «two» activeperiods. • The radius of the most massive starsisexpected to be large instead of relatively small. • The most massive starsshould be anomalousconcerning e.g.: • «crust» vibration • Cooling • Caracteristic of an outburstassociated with mass accretion • … • A few (rare) stars with small masses and small radii can exist • Stars with a mass significantlylargerthan 2 Ms can exist

  21. What can welearn from measuringthe radii of compact stars? • Ifallmeasuredradiiwill be of the order of about 12 km wewill be able to excludecertainsolutions (e.g. the onesbased on verystiffphenomenologicalEOSsatlow-moderate densities). • «Exotica» will likely be present in at least the more heavy stars. • Therewillbe no needto speculate about the existence of quark stars. • Ifinsteadatleast a fewstarswill be found to haveradii of the order of 10 km or smaller, thanmostlikelythere are two families of compact stars • The mostheavyobjectswill be quark stars. • Stars of normal mass willnotcontainsignificantamount of hyperons or strange quarks. Theywillbehavesimilarly to nucleonicstars. • LOFT and NICER should be able to distinguishbetweenthesetwopossibilities

  22. Conclusions • The possible co-existence of two families of compact starsissuggested by recentanalysis of theirmasses and radii, butbetter data for the radii are needed. • The transition from a hadronic star to a quark star releasesabout 1053 erg, mainly in neutrinos. Thisenergy (together with the oneassociated with the rotation of the star) can be sufficient to power a GRB. • The time structure of long GRBssuggests the existence of long quiescenttimes (from seconds up to a fewhundredseconds) separating «two» activeperiods. Quark deconfinement in the compact star can be at the origin of the secondactiveperiod. Possibility to integrate thismechanisminto the proto-magnetar model. • Also the possibleexistenceof GRBsnotassociated with a SN can be explained by the mechanismbased on quark deconfinement.

  23. M-R relations and parameters’ value Kosov, Fuchs, Marmyanov, Faessler, PLB 421 (1998) 37

  24. Composition of matterwithout and with D-resonances D-resonances can take the place of hyperons, pushing the hyperons’ threshold to largerdensities

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