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Radio Emissions of Magnetars & Observations at Nanshan

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. Anomalous X-ray Pulsar and Soft Gamma Repeaters.

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Radio Emissions of Magnetars & Observations at Nanshan

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  1. 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

  2. Anomalous X-ray Pulsar and Soft Gamma Repeaters • X-ray pulsators • p: 2-12 s • Period derivative：10-13 ~10-10 s s-1 • Lx >> Edot • Strong B: 1014 ~1015 G > Bcrit • No evidence for companion. • Magnetic energy powered • Magnetar model (Thompson & Duncom )

  3. 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

  4. AXP SGR • SGR (7+2) • 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 (9+3) • 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-1> spin-down luminosity • No companion, some associate with SNR

  5. 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 Hao’s talk.

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

  7. SGR 1900+14 • 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.

  8. 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

  9. 2 in 9 SGRs are detected to emit radio emission • Flux density: 100 uJy – 500 mJy, • Flux density decreased • Visible in several months

  10. 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

  11. Camilo et al 2007

  12. Flux density decreased significantly Lazaridis et al 2009

  13. Lazaridis et al 2007 Lazaridis et al 2008 S ~ν−0.5 (Camilo et al 2007 )

  14. 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

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

  16. Polarization Camilo et al 2007 • The radiation is highly linearly polarized, • Especially at high frequency, it is almost 100 per cent linearly polarized.

  17. Flux density is variable • Spectrum is different Camilo et al 2008

  18. 1E 2259+586 (See Malov’s talk) • Radio emission from two AXPs are reported by Malofeev • Mean duration of 120±20 ms, 1.7% • DM: 79±4 pc/cm−3 • Flux density < 150 mJy at 87 MHz (Malofeev 2005), • 35±25 mJy at 111 MHz (Malofeev 2007), • Estimated spectral index (S ~ν−α ) α> 2.5 • Estimated : S1500 < 0.05 mJy

  19. 4U 0142+61 (See Malov’s 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 >2.7, steep spectrum.

  20. 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,

  21. PSR J1622−4950 • A very high B ~ 2.8×1014 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.

  22. 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.

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

  24. 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)

  25. 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 • α = 5 (S/N threshold) • β = sqrt(π/2) ( one-bit digitization) • k: Boltzmann’ constant • Trec, Tspl, Tskyare noise • np = 2 number of polarization • τ = 1 ms, sampling interval • Δf = 320 MHz, BW • A = 490.87 m2 the area of antenna ESAMDIN et al 2008

  26. PSR B0525+21 • DM=50.94

  27. http://www.physics.mcgill.ca/~pulsar/magnetar/main.html H = soft gamma rays/hard X-rays (>10 keV); X = X-rays (1-10 keV); O = optical/near-infrared; I = mid to far infrared; R = radio, B = burst, F = Giant flare

  28. Single Pulse Search • 4U 0142+61 3*1 hr, negative • XTE J1810−197 5*1 hr, negative • 1E 2259+586 2*1 hr, negative

  29. Folding • 4U 0142+61 DM 27(5) pc cm−3 • 1E 2259+586 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

  30. Sumarry • Nondetection of single pulses with S1540>~4.8 Jy • Nondetection of 1-hr integrated pulses with S1540> ~ 0.26 mJy • Magnetar seems do not emit strong pulse sporadically in RRAT’s way. • We are looking forward the large telescope in Xinjiang!

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