feryal ozel university of arizona
DESCRIPTION
Neutron Stars: Insights into their Formation , Evolution & Structure from their Masses and Radii. Supernovae and Gamma Ray Bursts in Kyoto. Feryal Ozel University of Arizona. In collaboration with T. Guver , M. Baubock , L. Camarota , P. Wroblewski , - PowerPoint PPT PresentationTRANSCRIPT
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 Kyoto
Neutron Star Masses Understand stellar evolution & supernova
explosions
Find maximum neutron star mass Dense Matter EoS
GR tests
GW signals
Neutron Star MassesRely on pulsars/neutron stars in binaries
Group by
Data Quality: Number of measurements, type of errors
Source 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 withreasonably well determined masses
NS Mass Measurements
Özel 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
NS Mass Distributions
Özel et al. 2012
NS Mass DistributionsI. Lifetime of accretion/recycling shifts the mean 0.2 M up
II. There is no evidence for the effect of the maximum mass on the distribution
III. Double Neutron Star mass distribution is peculiarly narrow
Why is the DNS distribution so narrow?
Black Hole MassesDetermine velocity amplitude K, orbital period P, mass function f
4U 1543-47
Radi
al V
eloc
ity (k
m s-
1 )
Time (HJD-2,450,600+)
+ Varying levels of data on inclination and mass ratio
from Orosz et al. 1998
Masses of
Stellar Black Holes
Özel, Psaltis, Narayan, & McClintock 2010
Parameters of the Distribution• Cutoff mass ≥ 5 M
• Fast decay at high mass end
• Not dominated by a particular group of sources
Özel et al. 2010
See also Bailyn et al. 1998Farr et al. 2011
Neutron Stars and Black Holes
Özel et al. 2012
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 SNeNo fallbackNS remnant
> 25 M
Significant pre-SN mass loss
NS Radii – What is the Appeal?
Image credit:Chandra X-ray Observatory
The Physics of Cold Ultradense Matter
NS/BHs divisionSupernova mechanismGRB durationsGravitational waves
EoS Mass-Radius RelationP
ρ
The pressure at three fiducial densities capture the characteristics of all equations of state
This reduces ~infinite parameter problem to 3 parameters
Özel & Psaltis 2009, PRD, 80,103003Read et al. 2009, PRD
Özel & Psaltis 2009, PRD ≥ 3 Radius measurements achieve a faithful recovery of the EoS
Data simulatedusing the FPS EoS
Mass-Radius Measurement to EoS:
a formal inversion
Measuring Neutron Star Radii
Complications:
1. The radius and mass measurements are coupled
2. Need sources where we see the neutron star surface, the whole neutron star surface, and nothing but the neutron star surface
Low Mass X-ray BinariesTwo windows onto the neutron star surface
during periods of quiescence and bursts
Modified Julian Date - 50000
AS
M C
ount
s s-1
• Low magnetic fields (B<109 G)• Expectation for uniform emission from surface
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
Evolution of Thermonuclear Bursts
Constant, Reproducible Apparent Radii 4U 1728-34
Level of systematic uncertainty < 5% in apparent radii
Two Other Measurements: Distances and Eddington Limit
Frad
Fgrav
Time (s)
Measuring the Eddington Limit4U 1820-30
Guver, Wroblewski, Camarota, & Ozel 2010, ApJ
Pinning Down NS Radii
Globular cluster source EXO 1745-248Özel et al. 2009, ApJ, 693, 1775
Current Radius Measurements Remarkable
agreement in radii between
different spectroscopic
measurements
R ~ 9-12 km
Majority of the 10 radii smaller than
vanilla nuclear EoS
AP4predictions
Can already constrain the neutron star
EoS
The Pressure of Cold Ultradense Matter
Özel, Baym, & Guver 2010, PRD, 82, 101301
Conclusions• Nuclear EoS that fit low-density data too stiff
at high densities
• Indication for new degrees of freedom in NS matter
• NS-BH mass gap and narrow DNS distribution point to new aspects of supernova mechanism
Additional Slides
The Future
a NASA Explorer
an ESA M3 mission
Is the low-mass gap due to a selection effect?
Transient black holes
Follow-up criterion:1 Crab in outburst
If L ~ M, could lead to a low-mass gap
But it is not a selection effect…
Brighter sources are nearby ones
Persistent Sources• Bowen emission line blend technique, @ 4640 A • Applied mostly to neutron star binaries, which are
persistent (Steeghs & Casares 2002)
Steeghs & Casares 2002
Persistent Sources• Bowen emission line blend technique• Applied so far to neutron star binaries, which are
persistent• Can help address if sample of transients
introduces a selection effect
Highest Mass Neutron Star
Measurement of the Shapiro delay in PSR J1614-2230 with the GBT
Demorest et al. 2010
Highest Mass Neutron Star
M= 1.97±0.04 M
SAX J1748.9-2021
Baubock et al. 2012
GR Effects at Moderate Spins
Neutron Star Surface Emission
• Low magnetic fields• Plane parallel atmospheres• Radiative equilibrium
• Non-coherent scattering• Possible heavy elements
from Madej et al. 2004 Majczyna et al 2005
Ozel et al. 2009Suleimanov et al. 2011
Effects of Pile-up on X7 spectrum
Spectra are well-described by Comptonized atmosphere models
Analysis of the Burst Spectra
4U 1636-53626 d.o.f.1712 spectra
Is There A Stiff EoS in 4U 1724-307?The source used by Suleimanov et al. 2011
Redshift MeasurementM/R from spectral lines:
Cottam et al. 2003, Nature
2ME = E0 ( )
R1
These lines do not come from the stellar surface Lin, Ozel, Chakrabarty, Psaltis 2010, ApJ