Models of hydrostatic atmospheres of at high

Thijs van Putten1 Anna Watts1, Caroline D’Angelo1, Matthew Baring2, Chryssa Kouveliotou3 1University of Amsterdam, 2Rice University, 3NASA/Marshall Space Flight Center

arXiv:1208.4212

October 30 2012, Fermi Symposium, Monterey

image © Don Dixon Magnetars

✤ Neutron with inferred dipole magnetic field B ~ 1013-1016 G.

✤ Exhibit pulses (X-ray & radio), soft gamma ray bursts (~1040 erg s-1) and giant flares (~1044 erg s-1).

image © NASA

Magnetar atmosphere models Thijs van Putten October 30 2012 model

✤ What is the equation of state?

✤ How and where is the emission created?

✤ What is the magnetic field configuration?

Thompson & Duncan (1995)

Magnetar atmosphere models Thijs van Putten October 30 2012 A peculiar magnetar burst

Fermi GBM light curve of August 2008 burst from SGR 0501+4516.

Light curve and black body fits of X2127 (Smale 2001)

Magnetar atmosphere models Thijs van Putten October 30 2012 Photospheric Radius Expansion in magnetars?

✤ PRE in magnetars seems qualitatively possible (Watts et al. 2010) if magnetars have:

✤ Emission from optically thick region

✤ A critical

✤ cooling with expansion

✤ Opacity increasing with radius

Fermi GBM light curve of August 2008 burst from SGR 0501+4516. ✤ Observing it would constrain EoS, B and the emission location.

Magnetar atmosphere models Thijs van Putten October 30 2012 Nonmagnetic models

0.9999

✤ PRE requires sequence of extended stable atmospheres.

✤ Nonmagnetic models made by 0.9998

Paczynski & Anderson (1986). Luminosity / Eddington luminosity 0.0002 0.1 1 10 100 Atmosphere height (km) ✤ Stable nonmagnetic atmospheres exist up to r = 200 km.

dP GM L r 0.0001 ⇢ 2 1 dr ' r ! Lcr ' Gas pressure / total

0.1 1 10 100 Atmosphere height (km)

Magnetar atmosphere models Thijs van Putten October 30 2012 We find: No hydrostatic magnetar atmospheres with photospheric height > 10 m.

Nonmagnetic case Our result

Magnetar atmosphere models Thijs van Putten October 30 2012 Magnetar atmosphere models Thijs van Putten October 30 2012 Opacity in a super strong magnetic field

BRIEF ARTICLE

THE AUTHOR

0 Thomson scattering -2

✤ Two photon polarizations: O-mode ] -1

g -4 (E∥B) and E-mode (E⊥B) 2

-6

10 keV -8 log Opacity [cm O Th 1 keV ' -10 2 2 ! T 0.1 keV -12 E Th 2 2 ' !C / B 11 12 13 14 15 16 log Magnetic field strength [G]

E-mode Rosseland mean scattering opacity

Magnetar atmosphere models Thijs van Putten October 30 2012

1 Atmosphere models

E O 5 / P

g 4 T 2 3  / B2 2 T 1 Lcr 

] ; log T [keV] P /

-3 1

[g cm 0 L/Lcr =1 6 Pg / P log -1 0.01 0.1 1 10 Atmosphere height [m]

Magnetar atmosphere models Thijs van Putten October 30 2012 Conclusions

✤ Hydrostatic extended magnetar atmospheres do not exist in open field line regions.

✤ Photospheric Radius Expansion cannot occur in magnetars.

✤ Spectral models of magnetar bursts considering two distinct components attributed to the E- and O-mode may have to be reconsidered.

✤ Future work: what does happen when L reaches Lcr in a magnetar atmosphere?

Magnetar atmosphere models Thijs van Putten October 30 2012