SLIDE 1
X-ray emission from the young pulsar J1357-6429 and similar objects
Slava Zavlin (NASA/MSFC) Neutron Star Crust and Surface: Observations and Models INT, Seattle, June 25-29, 2007
SLIDE 2 Thermal vs. Nonthermal emission in pulsars of different ages
Young active (~1 kyr): Middle-aged (~100 kyr): Old (>1 Myr): nonthermal radiation thermal component from thermal emission from dominates; the whole surface; hot polar caps; Crab, B1509-58, B0656+14, B1055-15, millisecond PSRs, B0540-69 Geminga B0950+08
Nonthermal (magnetospheric) emission, ~ dE/dt ~ t-β , β ~ 2—4 NSs cool down from T≈1011 K (at birth) to 0.2-2 MK in 0.1-1 Myr
SLIDE 3
Crab
τ ≈ τc = P/[2dP/dt] = 1.3 kyr , dE/dt ≈ 5×1038 ergs/s, d ≈ 2.0 kpc
T∞ < 2.1 MK (for R∞=13 km, M=1.4 Msol — Tennant et al. 2001)
J0205+6449
τ ≈ 0.8 kyr, τc = 5.4 kyr , dE/dt ≈ 3×1037 ergs/s, d ≈ 3.2 kpc
T∞ < 1.1 MK (Slane et al. 2004)
Nonthermally emitting pulsars: Pulsars with dominating thermal X-ray flux: Vela (Pavlov et al. 2001)
τc = 11.0 kyr , dE/dt ≈ 7×1036 ergs/s, d ≈ 0.3 kpc
J1119-6127 (Gonzalez et al. 2005)
τc = 1.6 kyr , dE/dt ≈ 2×1036 ergs/s, d ≈ 8.4 kpc
SLIDE 4
Multiwavelength spectrum of the Vela pulsar
thermal nonthermal
SLIDE 5
PSR J1119-6127: XMM-Newton
nontherm therm
SLIDE 6
PSR J1357-6429:
τc = 7.3 kyr , P = 166 ms, dE/dt ≈ 3×1038 ergs/s, d ≈ 2.5 kpc
(Camilo et al. 2004)
τ = 2 τc [n-1]-1 < 15 kyr (for n = 1—2), ∆P/P = -2.4×10-6 ⇒
⇒ a young neutron star XMM-Newton EPIC: 12/15 ks (August 2005), spectral analysis Chandra HRC-I: 31 ks (November 2005), imaging & timing
SLIDE 7
PSR J1357-6429: Chandra HRC-I
SLIDE 8
PSR J1357-6429: Chandra HRC-I The elongated “tail” — a pulsar jet (?), like those generated by Crab, Vela, Geminga, PSRs B1757-24, B1957+20
(Weisskopf et al. 2000; Pavlov et al. 2003, 2006; Kaspi et al. 2001, Stappers et al. 2003)
SLIDE 9
PSR J1357-6429: Chandra HRC-I fp = 63 ± 15% Radio ephemeris valid for April-December 2005
(Camilo 2007)
Signal detection: 99.8%
SLIDE 10
Spectrum of PSR J1357-6429: single PL model — Γ = 2.1 ± 0.4, LX = 2×1032 ergs/s = 7×10-5 dE/dt An additional thermal component — required at a 4.5σ level
SLIDE 11
PSR J1357-6429: XMM-Newton
EPIC-pn EPIC-MOS therm nontherm
SLIDE 12
NS atmosphere models: magnetized, B = 1010—1013 G, nonmagnetic, B = 0
SLIDE 13
Angular dependence of radiation from a magnetized NS atmosphere: “pencil“-like structure along B “fan“-like structure at larger angles
r B r r
SLIDE 14
NS atmosphere vs. blackbody model Tbb / Tatm ≈ 2-3 Aatm / Abb ≈ 50-200
SLIDE 15
PL component — Γ = 1.2 ± 0.3, LX = 1×1032 ergs/s = 5×10-5 dE/dt Thermal component — blackbody spectrum: T∞ = 1.7 ± 0.2 MK, R∞ = 2.5 ± 0.5 km, L∞ = 4×1032 ergs/s NS magnetized atmosphere models:
(Pavlov et al. 1995; Zavlin 2007)
T = 1.0 ± 0.1 MK @ R = 10 km, Latm = 7×1032 ergs/s T∞ = [1—2GM/c2R]1/2 T L∞ = [1—2GM/c2R] Latm ≈ 0.5Latm Two-component modeling of the X-ray spectrum of PSR J1357-6429:
SLIDE 16
Blackbody fitting results: radiation from small hot area (polar caps) on the NS surface? Problems: too large radius, R∞ ≈ 2.5 km >> Rpc = (2π R3 /cP)1/2 = 0.3 km too large pulsed fraction, fp > 50%, for isotropic emission NS atmosphere model results: radiation from the whole NS surface the large fp ⇒ nonuniform surface temperature ⇒ ⇒ a “mean” temperature of 1 MK
SLIDE 17
PSR
τc/τtrue
Tmean (NSA; R=10-12 km) T∞ R∞ kyr MK MK km J1119-6127 1.6 1.6 2.4 3.4 J1357-6429 7.3 1.0 1.7 2.5 Vela 11.0 0.9 1.6 2.8 B1706-44 17.5 1.0 2.0 1.8 J0538+2817 620/30 1.1 2.1 1.7 B2334+61 40.9 0.9 1.5 2.8
putative PSR in IC443:
CXU J0617..... 30-40? 0.8 1.4 2.4
(Kramer et al. 2003; McGowan et al. 2004; Zavlin 2007)
J1119-6127: fp > 65% (Gonzalez et al. 2005) J0538+2817: strong dependence of pulse profile on photon energy ⇒
(Zavlin & Pavlov 2004)
⇒ anisotropic emission & nonuniform temperature
SLIDE 18
NS cooling models vs. observations Cooling curves with and without proton superfluidity (Yakovlev & Pethick 2004)
SLIDE 19
Conclusions:
group of (at least) 6 young and pulsars with τ=1—40 kyr with X-ray thermal flux dominating at softer energies even possessing strong magnetic fields, these are hot enough, > 1 MK, to have an atmosphere plausible interpretation involves NS atmosphere models, but requires inhomogeneous distributions of surface temperature (and magnetic field) more advanced analysis should include both spectral and pulse profile modeling (too many unknowns) Thermally emitting older pulsars, τ > 100 kyr, Geminga, PSRs B0656+14, B1055-52, radio-quiet NSs....: they are much colder , ~ 0.5 MK ⇒ atmospheres may not exist...
