Pulsar research at soft g-rays

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Pulsar research at soft g-rays

• Lucien Kuiper, Wim Hermsen Hans Bloemen

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Outline of presentation

• Introduction pulsars in a nutshell
• Overview current high-energy status (gt 10 keV)
• Concluding remarks

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• Pulsars (rapidly spinning neutron stars with high
  B-fields)
• can be grouped into three sub-classes
• I spin-down powered pulsars a) normal
  pulsars b) millisecond pulsars (old recycled
  systems)
• II accretion powered pulsars a) LMXB (incl.
  transient ms-pulsars) b) HMXB (Be-binaries
  (sub-)giant binaries) III magnetically powered
  pulsars (magnetars) AXPs/SGRs

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Spin-down powered (energetic) pulsars(Class Ia)

• CGRO (1991-2000 20 keV-30 GeV) heritage number
  of g-ray pulsars increased from 2 (CrabVela) to
  7 (10) all associated with young ( 100 ky) and
  energetic pulsars exception ms-pulsar PSR
  J02184232
• The only established galactic source population
  emittingg-rays over a wide (0.5 keV 10 GeV)
  energy band
• Inspite 30 year research we still do NOT know
  where the g-rays are produced in the
  magnetosphere (outer gap/polar cap) and
  whichphysical processes are acting
  (synchrotron, curvature, inverse Compton, photon
  splitting etc.)

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• At soft/medium g-ray energies (20 keV 30 MeV)
  only 4 pulsars were known (CGRO, RXTE, SAX
  all with very different pulse profile
  morphologies and spectra) a) PSR B053121
  PSR B1509-58 PSR B0540-69 (lt 10 kyr young)
  b) PSR B0833-45 (Vela pulsar) (middle aged lt 100
  kyr)

PSR B053121 (Crab) PSR
B1509-58 PSR B0540-69
?3s IBIS ISGRI 1 Ms
Note Vela very weak near 3s IBIS
ISGRI sensitivity limit
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Multi-wavelength profile collage of PSR
B0833-45 incl. IBIS ISGRI (2 Ms) 15-150 keV
profile (6.2s)
Comptel
EGRET
RXTE PCA
XMM
RXTE PCA
IBIS ISGRI
RXTE PCA
EGRET
XMM
OSSE
HE-profile morphology very complex! Statistics
still poor for 20 keV-10 MeV window ?
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• To understand the HE emission characteristics
  (pulse profile morphology changes vs. energy ?
  phase resolved spectroscopy double/triple peaked
  or asymmetric single peaked profiles) requires a
  significant increase of the number of g-ray
  pulsars
• Recent post-CGRO progress (Chandra/XMM/RXTE/INTEGR
  AL) Targetted (very) deep searches at the cores
  of SN-remnants or error boxes of unid. EGRET
  sources yielded the detection of several radio
  dim/quiet energetic pulsars emitting hard X-rays
  (gt 10 keV) e.g.

- PSR J19301852 (in G54.10.3 radio dim)- PSR
J1811-1925 (in G11.2-0.3 radio quiet)- PSR
J1846-0258 (in Kes 75 radio quiet)- PSR
J1617-5055 (near RCW 103)
PSR J19301852 in G54.10.3Chandra
PSR J1846-0258 in Kes 75
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• Pulsed emission has been detected up to 100 keV
  (RXTE HEXTE) from these 4 pulsars (Kuiper et
  al. 2005)!
• HE-pulse profile asymmetric single pulse similar
  to PSR B1509-58
• Pulsed spectra hard, similar to PSR B1509-58
  very likely reaching maximum luminosity at MeV
  energies

PSR J1846-0258 (Kes 75)RXTE HEXTE 20-100 keV
?3s IBIS ISGRI 1 Ms
These young energetic pulsars can be studied in
great detail over the softg-ray band with
instruments 10-50 x ISGRI sensitivity!
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Weaker hard X-ray emitting pulsars(all with hard
X-ray spectra)
- PSR J0537-6910 (LMC N157B radio quiet)- PSR
J020564 (in 3C58)- PSR J22296114 in 3EG
J22296122- PSR J1747-2958 (Mouse,
G359.23-0.82)- PSR J20213651 in 3EG J20213716
X-ray Pulse profiles
?3s IBIS ISGRI 1 Ms
HE-spectra (gt20 keV) below IBIS ISGRI
3s-limit,butcan be studied with instrument
10-50x more sensitive than IBIS ISGRI!
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Spin-down powered millisecond pulsars(Class Ib)

• Six (seven) systems show pulsed X-ray emission 2
  sub-classes
• I broad pulses soft spectra II small
  pulses hard spectra up to 20 keV
  
  g-rays from PSR J02184232! low X-ray
  luminosity high X-ray luminosity
  heated
  polar cap magnetospheric
  high Blc systems (Crab
  like) giant
  radio pulses
• 
  

X-rays 0.1-10 keV
?3s IBIS ISGRI 1 Ms
?GLAST?
The hard tails (gt20 keV) can be studied in
detailby instruments 10-50 x ISGRI sensitivity!
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Accretion powered millisecond pulsars (Class
IIa currently six members)

• The case IGR J002915934 Discovered in outburst
  during INTEGRAL GP scan
• Single symmetric pulse profile 2-150 keV
  pulsed emission detected up to 150 keV
• Total emission spectrum 5-200 keV thermal
  Comptonization spectrum on plasma
  
  with electron temperature of 50 keV
• Pulsed spectrum shows hardening towards higher
  energies Doppler boosting on Comptonized
  spectrum?

Need for high statistics measurements at energies
50 keV
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Anomalous X-ray pulsars (Class III)

• Anomalous X-ray pulsars (status before early
  2004)- No rotation powered pulsar! LX gtgt
  Lsd- No X-ray pulsar in LMXB/HMXB steady
  spin-down no apparent (no accretion-powered
  pulsar) optical counterpart no
  periodic Doppler delay in X-ray timing
• Characteristics
• Pulse periods 5 -12 s
• Steady spin-down like rotation powered pulsars
  (glitches observed also)
• X-ray luminosities 1034-36 erg/s (steady, but
  outbursts also detected transient AXPs)
• (very) soft X-ray (0.5-10 keV) spectra BB
  (0.35 0.6 keV) PL (2 4)
• Similar to Soft Gamma-Ray Repeaters Magnetars
  (neutron stars (glitches (out)bursts) with B
  1014-15 Gauss powered
  by decay of
  B-field)
• Young population concentrated along galactic
  plane some embedded in Supernova remnants

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AXP Discovery Ps
B1014 G Persistent 1E2259586
(SNR) 1981 6.98 0.61E1048-594 1985 6.45
5.04U 0142614 1993 8.69 1.31RXS
J1708-4009 1997 11.00 4.61E1841-045
(SNR) 1997 11.77 7.1CXOU J0100-721
(SMC) 2002 8.02 3.9 Transients AX
J1845-026 1998 6.97 ?XTE J1810-197 2003 5.5
4 2.6
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HE-Picture changed dramatically by the detection
of point-sources at AXPlocations at energies
above 20 keV in IBIS ISGRI skymaps 1E
1841-045,1RXS J1708-4009, 4U 0142614!

• Pulsed nature of gt20 keV emission
• Pulsed fraction ? 100
• Emission is very hard!

HEXTE 4.2s 3.1s 2.7s
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High-energy spectra Kes 73 and AXP 1E 1841-045
(Kuiper, Hermsen Mendez, 2004, ApJ 613, 1173)
4) Pulsed 1E 1841-045 RXTE/HEXTE g 0.940.16
1) Kes 73 1E 1841-045 XMM-Newton
?
?
?
2) Total 1E 1841-045 Chandra (Morii et al.
2003)
5) Kes 73 (?) 1E 1841-045 IBIS ISGRI
?
?
?
6) Kes 73 (?) 1E 1841-045 CGRO COMPTEL
3) Pulsed 1E 1841-045 RXTE/PCA
HE-spectrum of 1E 1841-045 must break above 100
keV!This can be studied in detail with an
instrument 10-50 x more sensitive than IBIS ISGRI
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4U0142614
4U0142614
5.7s
3.4s
2.1s
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4U0142614
? ChandraDCPulsed
? IBIS ISGRIDCPulsed
?
?
?
? ASCA GIS Pulsed
? RXTE HEXTEPulsed
?
?
?
? RXTE PCAPulsed
? CGRO COMPTELDCPulsed
Very hard soft g-ray spectrum up to 200 keV
beyond drastic break!The transition can be
studied in detail with an instrument 10-50 x
ISGRI/COMPTEL sensitivity!
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1E2259586 (CTB 109) RXTE PCA/HEXTE
Screened PCU-2 exposure747 ks!
5.2s
3.1s
Onset hard tail!
10.6s
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1E2259586 (CTB 109)
1) Total Chandra ACIS (S.K. Patel ApJ 563,
2001)
3) Pulsed RXTE/HEXTE
1
3
4) Total INTEGRAL (Kuiper et al. 2005)
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2
2) Pulsed RXTE PCA
INTEGRAL 3ssensitivity for 6Ms(Ao1Ao2Ao3)
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Conclusion

• In the soft g-ray band drastic spectral
  changes/pulse morphologychanges (e.g. Vela/Crab)
  occur for any type of pulsar. Therefore
• Improving the instrument sensitivity by more than
  a factor of 10 in the soft g-ray band will boost
  our understanding of the physics acting in the
  various types of pulsars enormously!

Young spin-downpowered pulsars
AXPs
Hopefully such a soft g-ray mission will be
selected in near futureto significantly increase
our knowledge of pulsars in general!