Towards an Understanding of the Isolated Neutron Star RX J1856.5-3754
Wynn HoKavli Institute for Particle Astrophysics and Cosmology
Stanford University
2005 Hubble Fellows Symposium – 7-8 April 2005
Physics from Neutron Star Surface Emission
(Yakovlev & Pethick 2004)
Equation of state Thermal evolution Surface composition Magnetic field
Lattimer & Prakash 2004,Courtesy of Page( )
Neutron Star Surface Emission
Atmosphere scale heightH 1 cm << R
Emission is anisotropic and polarized in magnetic field
Vacuum polarization important at B > BQ = me
2c3/eℏ = 4.4 1013 G
Atoms bound by magnetic field
RX J1856.5-3754
(Burwitz et al. 2003)
•Thermal emission
•No spectral features
•BB underpredicts optical by 7
•Atmosphere overpredicts by >> 1
•Two blackbodies
•kT=63 eV, R=4.4 km
•kT=26 eV, R=18.2 km
•No X-ray pulsations (1.3% limit)
RX J1856.5-3754
Model Spectra/ Observations
RX J1856.5-3754
(Burwitz et al. 2003)
•Thermal emission
•No spectral features
•BB underpredicts optical by 7
•Atmosphere overpredicts by >> 1
•Two blackbodies
•kT=63 eV, R=4.4 km
•kT=26 eV, R=18.2 km
•No X-ray pulsations (1.3% limit)
RX J1856.5-3754
Model Spectra/ Observations
Thin Atmospheres
Thin Atmospheres
Condensed Iron Surface Emission
105
Condensed Iron Surface Emission
105
RX J1856.5-3754
Model Spectra/ Observations
Collaborators
David L. Kaplan(Massachusetts Institute of Technology)
Philip Chang(University of California, Santa Barbara)
Matthew van Adelsberg and Dong Lai(Cornell University)
Alexander Y. Potekhin(Ioffe Physico-Technical Institute)
Gilles Chabrier(Ecole Normale Superieure de Lyon, CRAL)
RX J1856.5-3754
Effect of Redshift
Dim Isolated Neutron Stars
•Radio-quiet
•FX-ray / Foptical > 103
•Optical excess
•Blackbody fit to X-ray spectra
•kTBB 85 eV, RBB 6 km
DINS Period (s) PF T (eV) Eline (keV) EW (keV)
RX J1308.6+2127 10.3 15 % 86 0.3 0.15
RX J1605.3+3249 ? < 3-5 % 95 0.45 0.08
RX J0806.4-4123 11.4 6 % 96 0.41-0.46 0.06-0.03
RX J0420.0-5022 3.45 or 22.7 13 % 45 0.33 0.045
RX J0720.4-3125 8.4 11 % 85* 0.27 0.04
RX J2143.0+0654 9.4 4 % 101 0.7
(XMM-van Kerkwijk 2003)
RX J2143.0+0654
T (eV) χ2 / dof E (eV) σ (eV) τ
blackbody 101 1.36
blackbody+line 102 1.20 754 27 4.8
blackbody+edge 104 1.17 694 0.25
H atm (B=0 G) 29.8 1.94
H atm (B=1012 G) 47.3 1.99
H atm (B=1013 G) 50.0 2.19
(XMM-Zane et al. 2005)
line or edge?
