12th East Asian VLBI Workshop (2019.09.24-26 @ Ibaraki Univ.)

Observed radio variabilities ofa magnetar XTE J1810-197
after its revived radio outburst
SUJIN EIE (NAOJ / Univ. of Tokyo)
Collaborators: T. Terasawa, M. Honma, T. Akahori, T. Oyama (NAOJ)
Y. Yonekura (Ibaraki Univ.) / M. Sekido, K. Takefuji (NICT)
H. Misawa, F. Tsuchiya (Tohoku Univ.) / T. Aoki (Yamaguchi Univ.)
T. Enoto (RIKEN, Kyoto Univ.) / S. Kisaka (Aoyama Gakuin Univ.)
1

!2Magnetar | Who are you?
• Pulsars mainly detected withintense short bursts,pulsations, outbursts
in X-ray, soft 𝞬-ray• Slow spin & Fast spin-down→ Relatively young ages(≲ 10000 yr)& Ultra-strong B fields(1014 - 1015 G)
Data is from the Australia Telescope National Facility (ATNF)
Pulsar Catalog (Manchester+05)
2019.09.26

12th East Asian VLBI Workshop (2019.09.24-26) @ Ibaraki Univ.

SUJIN EIE

!3

Magnetar | Who are you?
• X & 𝞬-ray

Spin-down
luminosity » luminosity

1039-47 erg s-1

1030-35 erg s-1(outbursts)

1033-36 erg s-1(persistent X-ray)(e.g. Turolla+15)→ Additional energy sources→ Magnetically powered(Duncan & Thompson 1992): Dissipation and decay ofsuper-strong internal
magnetic fields• 23 sources identified
2019.09.26

Data is from the Australia Telescope National Facility (ATNF)
Pulsar Catalog (Manchester+05)

12th East Asian VLBI Workshop (2019.09.24-26) @ Ibaraki Univ.

SUJIN EIE

!4Magnetar | Radio-loud• 4 sources detected in radio• No distinction between
radio-loud and radio-quiet.

NameP(s)B𝛕c(1014 G) (kyr)D(kpc)XTE J1810-1975.54

2.1

113.5

1E 1547.1-5408

2.07

3.00.69

4.5

PSR J1622-4950

4.33

2.7

4.0~9

SGR J1745-2900 3.76

2.3

4.3

8.3

(Kaspi & Beloborodov 2017)

Data is from the Australia Telescope National Facility (ATNF)
Pulsar Catalog (Manchester+05)
2019.09.26

12th East Asian VLBI Workshop (2019.09.24-26) @ Ibaraki Univ.

SUJIN EIE

!5Radio-loud | XTE J1810-197• Discovery in 2003 in X-ray (Ibrahim+04)

X-ray

X-ray

- Period: 5.54 s• Radio emission in 2004

(VLA; Halpern+05)

Credit: ROSAT/XMM/M. Roberts& Radio pulsations in 2006 (Parkes & GBT; Camilo+06)

0.69 GHz→ The first detected radio-loud magnetar!

• Flatter spectra (α ≈ -0.5 vs -1.8)(Camilo+07; Maron+00)→ Observable up to high radio freqs.

• Strong variations with time and freq.

Relative flux density• Distinct radio properties from ordinary

0.82 GHz
1.4 GHz
1.9 GHz
2.9 GHz
6.4 GHz
9.0 GHz14 GHz19 GHz: profile shape, intensity, polarization(e.g. Camilo+07, Levin+12, Lynch+15)

2019.09.26

42 GHz00.2(Camilo+06) pulse phase12th East Asian VLBI Workshop (2019.09.24-26) @ Ibaraki Univ.

0.4

SUJIN EIE

!6

Radio-loud | XTE J1810-197

Flux density (mJy)• No detectable radio pulsations from 10 years ago (Camilo+16)Radio obs.

Year
2019.09.26(Camilo+16)

12th East Asian VLBI Workshop (2019.09.24-26) @ Ibaraki Univ.

SUJIN EIE

!7

Radio-loud | XTE J1810-197• No detectable radio pulsations from 10 years ago (Camilo+16)• Reactivated!!

Radio obs.

Flux (10-10 erg s-1 cm-2)

Flux density (mJy)→ Strong radio flares (2018/12/08) (Lyne+ ATel #12284)→ X-ray was also confirmed (Gotthelf+19) RADIO RE-DETECTION
X-ray obs.
(MAXI)

Radio non-detection
Year2019.09.26(Camilo+16)

Time12th East Asian VLBI Workshop (2019.09.24-26) @ Ibaraki Univ.

(Gotthelf+19)
SUJIN EIE!8Objectives
Investigation of observational properties of
the re-activated radio emission
from XTE J1810-197• How does the emission vary in time/frequency domains?
• What have changed compared to the previous outburst?

2019.09.26

12th East Asian VLBI Workshop (2019.09.24-26) @ Ibaraki Univ.

SUJIN EIE!9Project team membersHonmaEnoto(NAOJ, UTokyo)- Overall supervision of magnetar research in radio(Kyoto Univ.)

RadioTerasawa

X-ray(NAOJ)- P.I. of ToO observations of Hitachi, Kashima, Iitate telescopes
Yonekura(Ibaraki Univ.)

Sekido & Takefuji(NICT)

Misawa & Tsuchiya(Tohoku Univ.)- Single-dish data analysis (initial)

Kisaka(Aoyama Gakuin Univ.)

Sujin

Akahori(NAOJ, UTokyo)(NAOJ)- P.I. of the ToO observations of VERA- VLBI data analysis Oyama Hirota(NAOJ)

2019.09.26

Theory(NAOJ)- Single-dish data analysis (main)- Development of pipelines- Analytic study of magnetar data

12th East Asian VLBI Workshop (2019.09.24-26) @ Ibaraki Univ.

SUJIN EIE

!10Observation | Facilities• VERA 20 m (4 stations) [NAOJ]@ 22 GHz• Hitachi 32 m [Ibaraki Univ.]@ 6 & 8 GHz• Kashima 34 m [NICT]@ 2 GHzata
Iitateantenna•dw
aR/shc31 m × 16.5 m × 2ope
01&sd
[Tohoku Univ.]nab5@ 325 MHz
2019.09.26

12th East Asian VLBI Workshop (2019.09.24-26) @ Ibaraki Univ.

SUJIN EIE

!11

Variability | Average pulse profiles

yranimilerP• Pulsed emission is generally becoming noisy (weak) with time.
• Strong single pulses are well-identified at 6 & 8 GHz• < 5σ in the last phase at 2 & 22 GHz• No detection at 0.3 GHz (< 5σ)2019.09.26

12th East Asian VLBI Workshop (2019.09.24-26) @ Ibaraki Univ.

SUJIN EIE!12Prospects | EAVN for magnetars
Transients
Fast Radio Bursts (FRBs)
Magnetars
Gamma-Ray Bursts(radio)
SupernovaePulsars
Ordinary radio pulsarsMilli-second pulsars
Pulsar wind nebulae…

…

An et al. 20182019.09.26

12th East Asian VLBI Workshop (2019.09.24-26) @ Ibaraki Univ.

SUJIN EIE

!13

Prospects | EAVN for magnetars• Magnetars can be observed > 20 GHz!
• Negligible impact of scattering and dispersion, etc.
• High-Sensitivity at sub-mm is required.
• Simultaneous multi-freq. capture can help better

understanding of variable characteristic of magnetar emission.

Pulsar & Magnetar

An et al. 20182019.09.26

12th East Asian VLBI Workshop (2019.09.24-26) @ Ibaraki Univ.

SUJIN EIE

!14Summary• Magnetar XTE J1810-197 was revived in radio band
after its 10-year of quiescent period.

• We performed multi-epoch, multi-frequency observations[2018.12 - 2019.06 (10 epochs) / 0.3 - 22 GHz (5 bands)]• We have developed our own pipeline for pulsar searching• The pulses were detectable at 2, 6, 8, 22 GHz.
(no detection at 0.3 GHz)

• The slow decay of the flux density after the re-activation

was observed at 2 GHz,
while faster decay directly started at 6, 8 GHz.
This frequency dependency is diﬀerent from the previous.

• Future theoretical interpretation will be done.
2019.09.26

12th East Asian VLBI Workshop (2019.09.24-26) @ Ibaraki Univ.

SUJIN EIE