Neutron - PowerPoint Presentation

Slide1

Neutron Stars: Insights into their Formation, Evolution & Structure from theirMasses and Radii

Feryal OzelUniversity of Arizona

In collaboration with T. Guver, M. Baubock, L. Camarota, P. Wroblewski, A. Santos Villarreal; G. Baym, D. Psaltis, R. Narayan, J. McClintock

Supernovae and Gamma Ray Bursts in KyotoSlide2

Neutron Star MassesUnderstand stellar evolution & supernova explosions

Find maximum

neutron star mass  Dense Matter EoSGR testsGW signals Slide3

Neutron Star Masses

Rely on pulsars/neutron stars in binaries

Group byData Quality: Number of measurements, type of errorsSource type:

Double NS,

Recycled NS, NS with

High Mass Companion

Total

of

6 pairs of double

neutron

stars

(12)

and

9 NS+WD systems with

precisely

measured

masses

31 more neutron stars

with

reasonably

well determined

m

asses Slide4

NS Mass MeasurementsÖzel et al. 2012

Current Record

Holders: M= 1.97±0.04 M Demorest et al. 2010 M= 2.01±0.04 M Antoniadis et al. 2013 Slide5

NS Mass DistributionsÖzel et al. 2012Slide6

NS Mass DistributionsI. Lifetime of accretion/recycling shifts the mean 0.2 M upII. There is no evidence for the effect of the maximum mass on the distribution

III. Double Neutron Star mass distribution is peculiarly narrowSlide7

Why is the DNS

distribution so narrow?Slide8

Black Hole Masses

Determine velocity amplitude K, orbital period P, mass function f

4U 1543-47

Radial Velocity (km s

-1

)

Time (HJD-2,450,600+)

+ Varying

levels of

data on inclination

and mass ratio

from

Orosz

et al. 1998 Slide9

Masses of Stellar Black Holes

Özel

, Psaltis, Narayan, & McClintock 2010Slide10

Parameters of the Distribution

Cutoff mass ≥ 5 M

Fast decay at high mass endNot dominated by a particular group of sources Özel et al. 2010

See also

Bailyn

et al. 1998

Farr et al. 2011Slide11

Neutron Stars and Black HolesÖzel et al. 2012Slide12

Failed Supernovae?Kochanek 2013Woosley & Heger 2012Lovegrove & Woosley 2013

PROGENITOR MASS

~16-25 MFailed SNeDirect collapseEject H envelopeBH Mass = He core mass < 15 M

Successful

SNe

No fallback

NS remnant

> 25 M



Significant pre-SN

mass loss

Slide13

NS Radii – What is the Appeal?

Image credit:

Chandra X-ray ObservatoryThe Physics of Cold Ultradense MatterNS/BHs divisionSupernova mechanismGRB durationsGravitational waves Slide14

EoS Mass-Radius Relation

P

ρ

The

pressure at three

fiducial

densities capture the

characteristics

of all equations of state

This

reduces

~infinite

parameter problem to 3

parameters

Ö

zel

&

Psaltis

2009, PRD, 80,103003

Read et al. 2009, PRD Slide15

Özel

& Psaltis 2009, PRD

≥ 3 Radius measurements achieve a faithful recovery of the

EoS

Data simulated

using the

FPS EoS



Mass-Radius Measurement to

EoS

:

a formal inversionSlide16

Measuring Neutron Star RadiiComplications:The radius and mass measurements are coupled

Need sources where we see the neutron star surface, the whole neutron star surface, and nothing but the neutron star surfaceSlide17

Low Mass X-ray BinariesTwo windows onto the neutron star surface during periods of quiescence and bursts

Modified Julian Date - 50000

ASM Counts s

-1

Low magnetic fields (B<10

9

G)

Expectation for uniform emission from surface Slide18

Radii from Quiescent LMXBs

in Globular Clusters

Five Chandra observations of U24 in NGC 6397 Guillot et al. 2011

Heinke

et al.

2006; Webb

&

Barret

2007;

Guillot

et al. 2011 Slide19

Evolution of Thermonuclear BurstsSlide20

Constant, Reproducible Apparent Radii

4U 1728-34

Level of systematic uncertainty < 5% in apparent radiiSlide21

Two Other Measurements: Distances and Eddington Limit

F

rad

F

grav

Time (s)Slide22

Measuring the Eddington Limit

4U 1820-30

Guver, Wroblewski, Camarota, & Ozel 2010, ApJ Slide23

Pinning Down NS RadiiG

lobular cluster source EXO 1745-248

Özel et al. 2009, ApJ, 693, 1775Slide24

Current Radius Measurements Remarkable agreement in radii between different spectroscopic measurementsR ~ 9-12 km

Majority of the 10 radii smaller than vanilla nuclear EoS AP4

predictionsCan already constrain the neutron star EoSSlide25

The Pressure of Cold Ultradense Matter

Ö

zel, Baym, & Guver 2010, PRD, 82, 101301Slide26

ConclusionsNuclear EoS that fit low-density data too stiff at high densitiesIndication for new degrees of freedom in NS matterNS-BH mass gap and narrow DNS distribution point to new aspects of supernova mechanismSlide27
Slide28

Additional SlidesSlide29

The Futurea NASA Exploreran ESA M3 missionSlide30

Is the low-mass gap due to a selection effect?

Transient

black holesFollow-up criterion:1 Crab in outburstIf L ~ M, could lead to a low-mass gapSlide31

But it is not a selection effect…

Brighter sources

are nearby onesSlide32

Persistent SourcesBowen emission line blend technique, @ 4640 A Applied mostly to neutron star binaries, which are persistent (Steeghs & Casares 2002)Slide33

Steeghs & Casares 2002Slide34

Persistent SourcesBowen emission line blend technique Applied so far to neutron star binaries, which are persistentCan help address if sample of transients introduces a selection effectSlide35

Highest Mass Neutron Star

Measurement of the

Shapiro delay in PSR J1614-2230 with the GBTDemorest et al. 2010Slide36

Highest Mass Neutron Star

M= 1.97±0.04 M

Slide37

SAX J1748.9-2021Slide38

Baubock et al. 2012

GR Effects at Moderate SpinsSlide39

Neutron Star Surface Emission Low magnetic fields Plane parallel atmospheres

Radiative equilibrium

Non-coherent scattering Possible heavy elementsfrom Madej et al. 2004 Majczyna et al 2005Ozel et al. 2009Suleimanov et al. 2011Slide40

Effects of Pile-up on X7 spectrumSlide41

Spectra are well-described by Comptonized atmosphere modelsAnalysis of the Burst Spectra

4U 1636-536

26 d.o.f.1712 spectraSlide42

Is There A Stiff EoS in 4U 1724-307?

The source used by Suleimanov et al. 2011Slide43

Redshift MeasurementM/R from spectral lines:

Cottam et al. 2003, Nature

2ME = E0

(

)

R

1

These lines do not come from the stellar surface

Lin, Ozel, Chakrabarty, Psaltis 2010, ApJ