VERA follow-up for possible
IceCube counterpart
TXS 0506+056
Kotaro Niinuma (Yamaguchi Univ.)
Collaborators:
Y. Tanaka (Hiroshima Univ.), H. Nagai, M. Honma (NAOJ), A. Doi(ISAS/JAXA), Y. Inoue (RIKEN), K. Murase (Pennsylvania State Univ.)and S. Yoshida (Chiba Univ.)

IceCube-170922A & TXS 0506+056

Radio catalog (NVSS@1.4 GHz) and IceCube positional error

1.1 deg

TXS 0506+056

2.1 deg

IceCube-170922A & TXS 0506+056

Radio catalog (NVSS@1.4 GHz) and IceCube positional error
Distance to TXS 0506+056:

1.1 deg

TXS 0506+056

0.1 - 300 GeV

20 deg

2.1 deg

Redshift of z = 0.3365±0.0010
determined by 10.4m Gran
Telescopio Canarias (Paiano etal., 2018)

Very Long Baseline InterferometryDAngular resolution

θ ~ λ / D (baseline length)θ < 1 mas

Acciari+09

Very Long Baseline InterferometryDAngular resolution

θ ~ λ / D (baseline length)θ < 1 mas

VLBI array in the world

Image credit: NRAO

Very Long Baseline Array(VLBA)• D: ~8,000 km• Frq.: 330 MHz - 86 GHz• NRAO

日韓VLBI観測網（KaVA）• D: ~3,000 km• Frq.: 22/43 GHz• NAOJ/KASIJapanese VLBI Network (JVN)• D: ~2,270 km• Frq.: 6/8/22 GHz• Universities（茨城、筑波、岐阜、大阪府立、山口、鹿児島）＋
NICT、NAOJ、JAXAVLBI observation of Blazars

43 GHz VLBA monitor of Blazar 3C279(Boston U. blazar monitor)VLBI observation of Blazars
Marscher+123

Optically thick region

Blazar core is ~10 pc (~105 Rs) far from BH

Estimated by indirect way (time-lag of LC, EVPA rotation)

BL Lac, PKS 1510-089, AO 0235+164, OJ 287 (Marscher+08, 10, Agudo+12)*Radio core at mm wavelength is a standing shock region

Radio (VLBI) property of TXS 0506+056
Radio corepc-scale jet(and limb-brightened)“VLBA-MOJAVE project”
http://www.physics.purdue.edu/astro/MOJAVE/sourcepages/0506+056.s
html

24.3 pc

Proper Motion of Blazar Jet

J4
J3
J2
J1J1
(t 0 ~ 2000.0 [yr])
J2
J3
J4

Modeling the jet structure using 2-D
Gaussians

vapp ~ 5.2 c
vapp << 1 c

GeV γ-ray & Radio light curve
201520162017

Fermi All-sky Variability Analysis (FAVA)[Jy]

The OVRO 40-Meter Telescope Monitoring Program
Blue line: IceCube-170922A

Intensive VERA observationof TXS 0506+056

What is the VERA?

VERA = VLBI Exploration of Radio Astrometry

One of Japanese VLBI arrays
Baseline length- Longest：2,270 km（MizusawaIshigaki）- Shortest：1,000 km（IrikiIshigaki）

Frequency (angularresolution)- 22GHz（~1.2 mas）
- 43GHz（~0.6 mas）

図．国内４カ所（岩手県奥州市、東京都小笠原村、鹿児島県薩摩川内市、沖縄県石垣市）に１基ずつ電波望遠鏡が置かれている。

VERA observationof TXS 0506+056
Observations- 2017/Sep/30, Oct/13, Nov/1,Nov/14（4 epochs）

Frequency- 22 GHzBeam size

- 1.2 x 0.8 (mas^2)

2015

2016

2017

VERA observations - Images
Score~0.4 Jy/b throughout 4epochs
Core + compact jet in south
direction- Consistent with previous
images in the VLBA archive

PreliminaryComparison with previous works
Core flux density shows anincrease as compared to thatin 2008, which is consistent
with the trend seen in the
single dish light curve(OVRO)No major change in flux(>15%) among 4 epochs of theVERA observations- Consistent with the single dishlight curve (OVRO)VLBAVERAProper Motion (Preliminary)

VERA image
2017 Sep 30

VLBA image
2017 Jun 17

Jet component seen in theVERA image is a mixture ofJ2, J3, and J4- No clear motion of J2+3+4
within 4 epochs of VERAobservations

No new-born component isobserved in the VERA image- vjet<55c if a new component wasejected with IceCube-170922A• No distance information was available when
the observations were triggered, somonitoring interval was not optimal.

[Jy]J4J3J2J1J2+3+4vapp ~ 3.9±0.4 c

J1(t 0 ~ 2002.0 [yr])J2 vapp ~ 0 c

J3 vapp ~ -2.1±1.1 c
J4VERA J3+4

vapp ~ 0 c
赤い点線: IceCube-170922A

Discussion & Summary
No major flux increase nor emergence of new moving
component 8-44 days after IceCube-170922A
Upper limit on the velocity of a possible moving component
associated with this event (<55c)
Continuing VLBI observations is essential to hunt a possible
emergence of new component- 2-3 years

ALMAShall we do ToO observations with ALMA next time?

- Now ALMA allows quick follow-up (<1 d) after the triggering.
- Resolution is poorer than VLBI, but mm/submm observations canprobe optically thinner part of jets.
- Anyone interested in submitting proposals for Cycle 6 (Deadline:April 19)?

backup

GeV γ-ray & Radio light curve
2015

2016

2017

No jet ejection associated with the activities
in 2015（from MOJAVE data）

ガンマ線:• IceCube eventの時期は（特に> GeVで）活動期• 最も明るいフレア時期（MJD~57920）
Fermi All-sky Variability Analysis (FAVA)
vapp ~ 3.9±0.4 c•J1 neutrino検出日（MJD 58018）(t 0 ~ 2002.0 [yr])J4J2•J3 静穏期（~0.3 Jy）に比べ２倍程度（~0.7cvapp ~ -2.1±1.1Jy）まで増光

J1The OVRO 40-Meter Telescope Monitoring Program

J3[Jy]

電波（15 GHz）
• IceCube eventの時期は2010年10月以
J2 vapp ~ 0
降では最も増光しているフェーズ
J4vapp ~ 0