Birth of quark stars

Giuseppe Pagliara
Dipartimento di Fisica e Scienzedella Terra, Universita' diFerrara & INFN Ferrara, Italy

Supernovae & Gamma-ray-bursts in Kyoto 2013

Are quark stars massive enough?

Alford et al Nature 2006

Kurkela et al 2010

Before the discoveries of the two 2Msun stars!!

Weissenborn et al 2011

Within a simple
parametrization:

Two EoSs which provide amaximum mass of 2Msun

E/A=860 MeV(set1)
E/A=930 MeV(set2)

Different QSs binding
energy MB-MG

Conversion of aneutron star into aquark star

The process is similar
to the thermonuclear
burning inside a whitedwarf during a Type Ia
supernova, need for
multidimensional
numerical simulations

Importance of turbulence &hydrodynamical instabilities-) Horvath et al 1988-) Lugones et al 1994, Cho et al 1994-) Tokareva et al 2006-) Drago et al 2007

Herzog, Roepke 2011, useof the 3+1D hydrocode for
SNIa to simulate theconversion of a neutronstar and study the different
possible combustion modesHydro simulations
Input from microphysics:1) EoS of hadronic matter & quark
matter at finite temperature: at themoment both beta-stable, lepton
number not conserved :-(2) Detonation or deflagration &laminar burning velocity: at themoment only deflagration has beentested based on the results of Drago etal 2007 where a strong deflagration
has been found in all the cases.

Condition for exothermic
combustion

3+1D code developped byHillebrandt and collaborators forthe study of SNIa adapted, by use ofan effective relativistic potential, forhandling the large compactness ofNSs, ( see Roepke et al A&A2005)
Best resolution 10m.

Conversion of a 1.4 Msunstar-) Rayleigh-Taylor
instabilities develop andthe conversion occurs ontime scales of ms.
-) The burning stops
before the whole hadronicmatter has converted (theprocess is no more
exothermic, about 0.5
Msun of unburnedmaterial)-) A succesfull conversion
need a small E/A, noconversion is possible
with set2 (the one with alarger E/A=smaller
binding energy)

Herzog, Roepke 2011, G.P. Herzog, Roepke 2013

Temperature profiles after the combustion
The huge energy
released in theburning leads to asignificant heatingof the star, few tensof MeV in thecenter.

Steep gradient of thetemperature
Since the burning occurs on time scales of the order of ms, it isdecoupled from the cooling (typical time scales of the order ofseconds)

Temperature profiles as initial conditions for the cooling diffusion equation
Heat transport equation due toneutrino diffusion

Assumption: quark matter isformed already in beta
equilibrium, no lepton number
conservation imposed in theburning simulation, no lepton
number diffusion

Diffusion is dominated byscattering of non-degenenerate
neutrinos off degenerate quarks

Steiner et al 2001Expected smaller coolingtimes with respect to hot
neutron stars

Reddy et al 2003

Luminosity
curves similar tothe protoneutronstars neutrino
luminosities.
Possiblecorrections due tolepton number
conservation...

Phenomenology I: such a neutrinosignal could be detected for eventsoccurring in our galaxy (possible
strong neutrino signal lacking theoptical counterpart if the conversion
is delayed wrt the SN)

Phenomenology II: connection withdouble GRBs within the protomagnetar
modelAnalysis of QLMXBs Guillot etal 2013

See also Lattimer-Steiner 2013 – larger radii for the same objects, above
11kmVery compact objects (withoutstrangeness obtained via theinclusion of Delta resonances)
Shurhoff et al, APJ 2010

-)Very compactobjects: hadronicstars containing
Delta and hyperons-) Hadronic stars
are metastable anddecay into quarkstars-) Massive stars(M>1.5Msun) would
be quark stars.
Different properties
concerning cooling,
crust oscillations...

A. Drago, A. Lavagno and G.P. ArXiv: 1309.7263
See talk by A. Drago next week

Conclusion: if the existence of 2.4 Msun stars and of stars
with radii smaller than 10 km are confirmed, that would
strongly favor the hypothesis of two families of CSs

Appendix

Open questions: Seeding ofquark matter

Are all CSs QSs ?: Merger of strangestars

MIT60: 8 × 10-5Msun, MIT80 no ejecta. By
assuming a galactic merger rate of 10-4(-5) /year,
mass ejected: 10-8(-9) Msun/year. Constraints on thestrangelets flux (for AMS02)
A. Bauswein et al PRL (2009)

Nucleation(many papers!! done by many people of this workshop!!)

Hot stars: thermalnucleation

As expected: strong
dependence onsurface tension andoverpressure

Cold stars: quantum
nucleation, WKB appr.

Mintz et al 2010

Recent estimates of σ ∼ 5−15
MeV/fm^2 in 2 and 3 flavor
quark meson models (Palhareset al 2010, Mintz et al 2013),
nucleation is likely to occur.
Values of 100 MeV/fm^2 ofLugones (see previousdiscussions)Frozen flavor composition?

Tiny amount of hyperons alreadyallows nucleation (statisticalfluctuations of the density for adrop of 2-3 fm allow to form betastable quark matter)

Palhares Fraga 2010

Q*It shifts the nucleation threshold toconsiderably higher densities

Open questions related to theburning
1) Deflagration or detonation (in thenumerical simulations of burning this is
an input )2) Full GR3) Lepton number conservation
4) Effect of magnetic field (Lugones et al 2002)
asymmetric combustion… and of course EoS!!!

Deflagration to detonation transition in QSs?

Lugones et al 1994 –Niebergal et al 2010

Also in SNIa this is still
an open question:
detonations do occur inthese systems but in thesimulations one forces theDDT to take place at anarbitrary chosen instantand location

If it works, Quarknova model of Ouyed
and collaborators

Roepke & collaborators 2013

- Double humped SN- r-processes-...

Appendix2

Drago et al 2007