Radio Emissions of Magnetars

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Radio Emissions of Magnetars Observations at
Nanshan
Xinjiang Astronomical Observatory Yuan Jianping,
Wang Na, Liu Zhiyong

• Outline
• Introduction of magnetar
• Radio emissions of Magnetars
• Observations of Magnetars at Nanshan

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Anomalous X-ray Pulsar and Soft Gamma Repeaters

• X-ray pulsators
• p 2-12 s
• Period derivative10-13 10-10 s s-1
• Lx gtgt Edot
• Strong B 1014 1015 G gt Bcrit
• No evidence for companion.
• Magnetic energy powered
• Magnetar model (Thompson Duncom )

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Some Major Unsolved Problems

• Wood, Thompson 2006
• What is the birth rate of AXP and SGRs
• What fractions of NS go through a phase of strong
  B activity
• Why are the periods clustered in an interval of 2
  -12 s
• Are SGRs and AXPs fundamentally NS
• What is the initial spin period of magnetars
• What is the evolutionary sequence of magnetar
• Do the magnetars and high B-field radio pulsars
  form a continuum of magnetic activity

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AXP SGR

• SGR (72)
• Spin period (2 -12 s)
• Period derivative 10-13 10-10
• No companion
• X-ray and soft gamma-ray emission.
• 3 sources have Giant flares, 1044 erg s-1
  (Mereghetti 2000)

• AXP (93)
• Spin period (2 - 12 s)
• Period derivative 10-10 10-13 s s-1
• Characteristic age 103 105yr
• X-ray luminosity 1034 1035 erg s-1gt spin-down
  luminosity
• No companion, some associate with SNR

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Emission Mechanisms

• Persistent emission it can be induced by
  twisting of the external B caused by the motions
  of the star interior (mereghetti 2008)
• Bursts and flares are explained in terms of
  magnetic reconnections (Lyubarsky 2002),
  fast-mode breakdown model (Heyl Hernquist 2005)
• See Tong Haos talk.

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• radio quite?
• Their radio detection started 10 years ago.

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SGR 190014

• A fading radio source within the X-ray box of it.
  (Frail 1999)
• A short-lived cloud of ionized gas, powered by
  relativistic particles ejected at the time of
  intense burst of HE photons.

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SGR 1806-20

• Giant gamma ray flare on 27 Dec 2004
• Radio emission Jan 2005, was suggested arises
  from the debris ejected during the explosion

Cameron et al. Nat. 2005
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• 2 in 9 SGRs are detected to emit radio emission
• Flux density 100 uJy 500 mJy,
• Flux density decreased
• Visible in several months

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XTE J1810-197

• Transient X-ray outburst began 2003. P 5.54 s
  (Ibrahim et al 2004)
• Radio emission (Halpern et al 2005), P 5.54 s
  (Camilo et al 2006),

Camilo et al 2006
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Camilo et al 2007
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• Flux density decreased significantly

Lazaridis et al 2009
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Lazaridis et al 2007
Lazaridis et al 2008
S ?-0.5 (Camilo et al 2007 )
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AXP 1E 1547-5408 (PSR J1550-5418)

• Radio signals P 2 s (Camilo et al 2007)
• DM 830 pc cm-3

Camilo et al 2007
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• Single pulses profiles
• The average profile

Camilo et al 2007
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Polarization
Camilo et al 2007

• The radiation is highly linearly polarized,
• Especially at high frequency, it is almost 100
  per cent linearly polarized.

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• Flux density is variable
• Spectrum is different

Camilo et al 2008
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1E 2259586 (See Malovs talk)

• Radio emission from two AXPs are reported by
  Malofeev
• Mean duration of 12020 ms, 1.7
• DM 794 pc/cm-3
• Flux density lt 150 mJy at 87 MHz (Malofeev 2005),
• 3525 mJy at 111 MHz (Malofeev 2007),
• Estimated spectral index (S ?-a ) agt 2.5
• Estimated S1500 lt 0.05 mJy

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4U 014261 (See Malovs talk)

• X-ray pulsar with a P of 8.7 s (Israel 1994)
• DM 27(5) pc cm-3
• S111, 30(20)mJy (Malofeev 2010)
• Large flux-density fluctuation were observed.
• Spectral index gt2.7, steep spectrum.

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PSR J1622-4950

• Discovered in HTRU survey, with a P of 4.326 s
  DM 820 pc cm3
• A greatly varying flux density, 6 with 24 h
• Profile changes shape on short timescales.
• Pdot is fluctuating within a factor of 2,

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PSR J1622-4950

• A very high B 2.81014 G, the highest B of any
  radio pulsar known to date.
• Appears to have an inverted spectrum
• similar to two AXPs
• a magnetar, the first to be discovered via its
  radio emission
• The x-ray counterpart be in quiescence
• Highlights unprecedented features of the emission
  of the magnetars across radio band.

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• Totally, 5 in 12 AXPs are reported to emit radio
  emission.
• The discoveries provided an exciting new spectral
  window on magnetar physics
• Another link between magnetar and radio pulsar.
• Average pulse profile change significant
• Spectrum are different from radio pulsar.
• Flux density is variable
• Mechanism appears to have a different origin or
  perhaps multiple origins, compared to the normal
  radio pulsars.

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• The radio emission isn't stable, repeated
  observations are warranted
• Is radio emission related to X-ray behavior?
• Do they have narrow radio emissions?

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Observations at Nanshan

• Nanshan 25m radio telescope
• Central frequency 1540 MHz
• BW 320 MHz, 125 channels
• Single pulse mode
• 1 bit sample every 1 ms
• July, 2009 Dec, 2010
• 3600 s (1h)

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Single Pulse Search

• De-dispersed at a set of trial DM ranging from 0
  to 1000 pc cm-3, spacing is 1 pc cm-3
• Flux density limit 4.8 Jy

• a 5 (S/N threshold)
• ß sqrt(p/2) ( one-bit digitization)
• k Boltzmann constant
• Trec, Tspl, Tsky are noise
• np 2 number of polarization
• t 1 ms, sampling interval
• ?f 320 MHz, BW
• A 490.87 m2 the area of antenna
• ESAMDIN et al 2008

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PSR B052521

• DM50.94

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http//www.physics.mcgill.ca/pulsar/magnetar/main
.html
Name P dP / dt e-11 Activity
4U 014261 8.6883297 0.196 H X O I, B
XTE 1810-197 5.539 0.81 H X R, B, transient
1E 2259586 6.9789 0.048 H X O, B
H soft gamma rays/hard X-rays (gt10 keV) X
X-rays (1-10 keV) O optical/near-infrared I
mid to far infrared R radio, B burst, F
Giant flare
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Single Pulse Search

• 4U 014261 31 hr, negative
• XTE J1810-197 51 hr, negative
• 1E 2259586 21 hr, negative

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Folding

• 4U 014261 DM 27(5) pc cm-3
• 1E 2259586 DM 79(4) pc cm-3
• XTE J1810-197 DM 178 pc cm-3
• Dedispersed with reported DM and folded with
  catalog period.
• Negative.
• For XTE J1810-197
• Flux density decreased.
• It would be detectable when it is in activity

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Sumarry

• Nondetection of single pulses with S1540gt4.8 Jy
• Nondetection of 1-hr integrated pulses with
  S1540gt 0.26 mJy
• Magnetar seems do not emit strong pulse
  sporadically in RRATs way.
• We are looking forward the large telescope in
  Xinjiang!