Radio Emissions of Magnetars &Observations at Nanshan

Xinjiang Astronomical ObservatoryYuan 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 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 )

GPPdotB 193.3 10

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

AXP SGR

• 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

• 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)

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.

• radio quite?

• Their radio detection started ~ 10 years ago.

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.

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

2 in 9 SGRs are detected to emit radio emissionFlux density: 100 uJy – 500 mJy,Flux density decreasedVisible in several months

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

Camilo et al 2007

• Flux density decreased significantly

Lazaridis et al 2009

Lazaridis et al 2008

S ~ν−0.5

(Camilo et al 2007 )

Lazaridis et al 2007

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

Camilo et al 2007

Single pulses profilesThe average profile

Polarization

Camilo et al 2007

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

• Flux density is variable

• Spectrum is different

Camilo et al 2008

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

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.

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,

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.

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.

• The radio emission isn't stable, repeated observations are warranted

• Is radio emission related to X−ray behavior?

• Do they have narrow radio emissions?

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)

• 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, Tsky are 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

Single Pulse Search

PSR B0525+21

DM=50.94

http://www.physics.mcgill.ca/~pulsar/magnetar/main.html

Name P dP / dt e−11 Activity

4U 0142+61 8.6883297 0.196 H X O I, B

XTE 1810−197 5.539 0.81 H X R, B, transient

1E 2259+586 6.9789 0.048 H X O, B

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

Single Pulse Search

• 4U 0142+61 3*1 hr, negative

• XTE J1810−197 5*1 hr, negative

• 1E 2259+586 2*1 hr, negative

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

1.Flux density decreased.

2.It would be detectable when it is in activity

Sumarry

Nondetection of single pulses with S1540>~4.8 JyNondetection of 1-hr integrated pulses with S1540> ~

0.26 mJyMagnetar seems do not emit strong pulse sporadically

in RRAT’s way.We are looking forward the large telescope in Xinjiang!