Current progress in ESTEMA and relevant EAVN commissioning

Hiroshi Imai(Center for General Education/ Amanogawa Galaxy Astronomy Research Center,

Kagoshima University)On behalf of EAVN Evolved Stars SWG and ESTEMA team

Current members• EAVN Evolved Stars SWG

Hiroshi Imai, Se-Hyung Cho, Bo Zhang (co-chair), Youngjoo Yun, Dong-Hwan Yoon, Jaeheon Kim, Haneul Yang, D.-J. Kim, Lang Cui, J. Zhou, G. Wu, Gabor Orosz, Miyako Oyadomari, Akiharu Nakagawa, Ross Burns, Richard Dodson, Maria Rioja, James Chibueze Okwe, Yuanwei, Wu, Shuangjin Xu, Tomoaki Oyama, Yoshiaki Asaki, Naoko Matsumoto

• ESTEMA (EAVN Synthesis of Stellar Maser Animations)Hiroshi Imai, Youngjoo Yun, Bo Zhang (co-P.I.) , Se-Hyung Cho, Dong-Hwan Yoon, Jaeheon Kim, Haneul Yang, Dong-Jin Kim, Lang Cui, Jianjun Zhou, Gang Wu, Gabor Orosz, Miyako Oyadomari, Akiharu Nakagawa, Ross Burns, Richard Dodson, Maria Rioja, James Chibueze Okwe, Shuangjin Xu, Tomoaki Oyama, Yoshiaki Asaki, Jun-ichi Nakashima, Andrey M. Sobolev

Our goalsvisualization of dynamic stellar mass loss

SiO masers around TX Cam (Gonidakis et al. 2013)

Distance from star (stellar radius)

Shock waves in C-rich envelope (Höfner et al. 1995)

H2O maserregion

SiO maserregion

with shock waves

without shock waves

See alsoP24 (poster) by Se-Hyung ChoNext talk by YoungJoo Yun

How are materials on the stellar surface lifted up outward in a circumstellar envelope?

Anthares In CO line center(2.31 μm) (Ohnaka et al. 2017)

Höfner (2011)

Under periodic stellar pulsationand inhomogeneous mass ejection

€

Tenvelope = T*

R

R*

−2 / 5

T* ≈ 3000 K, R* ≈1-10 AU

Line overlapexcitation by Mid-IR H2O radiation

SiO maserlines(J→J-1,J=1,2,3,…;ν≈43×J[GHz])

How to collocate these maser line regions throughout stellar pulsation cycles?

Our challenges 1: simultaneous mapping of SiO maser transitions with H2O masers

Are we really watching true physical gas motions in these maser lines?

Quasi-optics for multi-band simultaneous observations

Yebes, ATCA (multi-antennas), NARIT(?), Effelsberg(?),...

Opened (2019)

In commissioning

VERAIn K/Q-bands

Commissioning of K/Q-band quasi-optics in VERA

Gain loss less than 10%(<uncertainty)by 20” beam offset(in Ishigakijima)

r19052b(W Hya and VX Sgr)

r19052a (S Per)

H2O masers

SiO masers

Source-frequencyphase-referencingtechnique should betested.

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Ulsan

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W Hya VX Sgr

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ESTEMA session (2 days x 4 hours/day)

• KaVA/EAVN: mapping H2O and SiO (43 GHz) masers à should be made in one day in future• KVN: band-to-band phase transfer calibration for SiO masers (43/86/129 GHz)• VERA: dual-beam astrometry and wide-band recording (for SiO v=3 and v=0 J=1à0 masers)

Our challenges 2: operating “hybrid” modeThree vex files for one-day block

Target sources of ESTEMA

Targeting biweekly (~20 sessions per year) snapshot (<4 hours with > 5 telescopes)

15 d15 d20 d20 d30 d60 d

Cadence

IRC-10151

Our challenges 3: time allocation with high cadence

15 d15 d20 d20 d30 d60 d

Cadence

IRC-10151

Negotiation in time allocation

Requesting ~550 hours/yr, ~2600 hours in totallAvoiding condensed LST zone (16—22 hours)lReducing to ~ 65% with K/Q-band simultaneous observations with VERAlReducing to ~ 50% by adding more telescopes (Nb, T6, Ur, Tl)

VLBI mapping of 16 circumstellar H2O maser sources - persistent clumps but changed distribution biases -

With full JVN(VERA+NRO+Takahagi+Tsukuba+Kashima(Imai et al. in preparation)

Contour peak: 120.5 Jy beam-1 km s-1

20 mas

S Per

Contour peak: 22.6 Jy beam-1 km s-1

20 mas

AP Lyn

50 mas

VY CMa

Contour peak: 129.6 Jy beam-1 km s-1

20 mas

R Crt

Contour peak: 871.8 Jy beam-1 km s-1

Contour peak: 43.9 Jy beam-1 km s-1R.A. offset

Contour peak: 103.6 Jy beam-1 km s-1R.A. offset

20 mas

RT VirS Crt

10 mas

Decl.

offs

etDe

cl. o

ffset

Decl.

offs

et

Decl.

offs

et

Contour peak: 86.4 Jy beam-1 km s-1

20 mas

IRC-10414

Contour peak: 5.2 Jy beam-1 km s-1

50 mas

W Hya

10 mas

RX Boo

Contour peak: 5.4 Jy beam-1 km s-1

Decl.

offs

et

50 mas

S CrB

Contour peak: 6.9 Jy beam-1 km s-1

20 mas

U Her

Contour peak: 27.0 Jy beam-1 km s-1

50 mas

VX Sgr

Contour peak: 437.3 Jy beam-1 km s-1R.A. offset R.A. offset

Decl.

offs

et

Decl.

offs

et

Contour peak: 420.3 Jy beam-1 km s-1

10 mas

R Aql

20 mas

RR Aql

Contour peak: 3.0 Jy beam-1 km s-1

Decl.

offs

et

Contour peak: 240.4 Jy beam-1 km s-1

20 mas

NML Cyg

20 mas

R Cas

Contour peak: 2.1 Jy beam-1 km s-1R.A. offset R.A. offset

Indicating importance of long-term monitoring of circumstellar H2O masers

TimevariationoftotalH2OmaserfluxtowardWHydrae(Shintani etal.2008)

What determines the extent and bias in H2O maser distribution?

DistributionextentofcompactH2OmasersaroundWHydrae(Imai,Nakagawa&Takaba 2019)

What determines the extent and bias in H2O maser distribution?

Phase lag of total H2O flux(Shintani et al. 2008)

Our decadal effortsØCommissioning works in KaVA/EAVN Evolved Stars SWG

üSince 2011 May üDemonstration of KaVA full-track / snap-shot imagingüDevelopment of scheme of hybrid observation modes

ØKaVA ESTEMA (Expanded Study on Stellar Masers)ü2015 November—2017 MarchüSnapshot imaging of ~40 stellar maser sources successfully detected

ØESTEMA (EAVN Synthesis of Stellar Maser Animations)üFrom 2018 MayüTargeting 6 stars (currently 2 stars) with different stellar pulsation

periods

S PerIn direct band-to-band

phase-transfer(Asaki et al. in prep.)

First KQW-band composite map of H2O and SiO masers

H2O (surviving over a decade)SiO v=1 J=1à0SiO v=2 J=1à0SiO v=1 J=2à1

Confidential

First KQW-band composite map of H2O and SiO masersS Per(Asaki et al. in prep.)

Ø Good assumption of maser distribution corresponding to true gas distribution

Ø Double SiOmaser rings

Ø Radial correlationamong H2O and SiO masers

Ø Episodicmass ejectionevery decade

Confidential

Venn diagram of VLBI fringe detections of KaVA ESTEMA circumstellar maser sources

H2O42

In scalar averaging

SiO J=1à0 54(v=2) 51(v=1)

9

16 SiOJ=2à1 27

152

SiO J=3à25

37

11

Image cube synthesis and statistical inspection still ongoing

80 stars in total(2015̶2017)

Ring (circle)-model fittingØKVN-KSP method using maser spot/feature maps

üInformation of maser emission distribution reduced to representative brightest peaks in the spots/features

ØEHT method finding azimuthal offset brightness peak üAvailable to a maser ring extremely biased, clumpy, and complicated?

ØESTEMA method finding the sharpest radial profile1.Determining the ring center at first using data of

a distribution of maser emission areas2.Estimating the ring size and widthChallenging to ring size accuracy better than 0.5 masExtension to ellipse fitting àfor masers around red supergiants

ESTEMA method

Demonstrated by Miyako Oyadomari

r18145a1 ch à 0.1 mas

D1 (5%̶95%)

D2 (5%̶50%)

Finding the minimum

Defined ring radius

Cum

ulat

ive

norm

alize

d flu

x

Demonstrated by Miyako Oyadomari

ESTEMA method r18145a1 ch à 0.1 mas

In 1000 trials in a Monte-Carlo simulation

Number of trials

Difference in the performances between SiO v=1 and v=2 J=1à0 maser lines

Preliminary

by Miyako Oyadomari

How to track true physical gas motions on sub-mass scale ?

See also talks byAkiharu Nakagawa(this session) and Haneul Yang and Shuangjing Xu (Astrometry session)

Very long time-domain astronomy with image cubes

FLASHING early science (Imai et al. 2020 PASJ Special Issue, submitted)-160 -80 0 80 160 240

LSR velocity [km/s]

0

1

00

2

00

3

00

4

00

0 -100

Decl.

offs

et (m

as)

R.A. offset (mas)

+

200 AUat 3.6 kpc

2006 Sep.ー2007 Feb.2009 May2019 March

New bipolar bulletejections

l Weekly̶monthly maser flaresl Decadal evolutionl Permanent turn off of a jet to become a planetary nebula

IRAS 18286-0959(water fountain from

a dying star)

Summary and future perspectivesØCommissioning to deliver the full set of circumstellar H2O and SiO

maser animationsH2O, SiO (v=0, 1, 2, 3, J=1à0 / v=1 J=2à1, J=3à2 / 29SiO v=0, J=1à0)Toward synchronized operation of VERA (K/Q) and Nobeyama

(K/Q/W) with KaVA/EAVN/ and the Global AllianceØKaVA ESTEMA: statistical analyses based on snap-shot image

cubes from ~20 starsüAstrometric registration ongoing üComparisons with latest data: Gaia DR2, VLTI, NESS, ALMA…

ØESTEMA: legacy animations of circumstellar H2O and SIO masersüTracing dynamic mass loss events on week scale