Radio Flare from Young
Stellar Objects
T. Umemoto (NAOJ), M. Saito, K. Nakanishi (ALMA),
N. Kuno(NRO), M. Tsuboi(JAXA/ISAS)
第11回高宇連研究会「多波長で探る高エネルギー現象」
2011年8月9日

早稲田大学

Magnetic Structures around YSOs

• Theoretical prediction• Angular momentum regulation of disks• Confine and accelerate outflows(Bouvier et al. 1993 , Montmerle et al. 2000)(Uchida & Shibata 1984 , Shu et al. 1997)• Observational evidence• X-ray from TTSs and protostars• Circular and linear polarizations(Koyama et al. 1996, Feigelson &Montmerle 1999)(Andre et al.1992, Phillips et al. 1996, Feigelson et al.

1998, Smith et al. 2003)• Non-thermal radio continuum from WTTS by VLBI

(Andre 1996)

X-ray from Star Forming Regions
Rho OphImanishi, Koyama, Tsuboi 2000 ApJ
Imanishi et al. 2003 PASJ

X-ray flare
red	 :	 0.5-2.0keV
blue	 :	 2.0-9.0keV

3

Optical image of Rho Oph cloud
0.5pc

Origin of Non-thermal RadioContinuum• gyrosynchrotron radiation from MeV electron with B~kG

similarity to solar flare

Lx - Lr correlation

EM ∝ B -5 T17/2
L= constant

EMYSO flare

Solar flareCorrelation between X-ray luminosity(Lx) and radio luminosity(Lr). Lx/Lr~10^15(Furuya et al. 2003, originated from Gudel 2002)& Yokoyama (1999)
Scaling law between temperature (Ｔ)Shibataand emission
measure (EM) (Shibata & Yokoyama 1999)

Flare by Magnetic Reconnection• Lager scale (R >10 Ro) flare by magnetic
reconnection (Montmerle et al. 2000)• 10^3〜10^6 times brighter than solar flare

Ｒｅｃｏｎｎｅｃｔｉｏｎ
Magnetic Filed• 10^2-10^4 times frequently
Ｒｅｃｏｎｎｅｃｔｉｏｎ

Magnetic Filed

Ｅｍｅｒｇｉｎｇ Ｆｌｕｘ
modified the figure of Shu et al. (1997)

GMR-A: WTTS in Orion

Menten et al. (2007)

Giant Radio Flare from GMR-A86GHzin Orion (418pc) (Kim et• WTTSal. 2008)160• Giant mm flare at 86GHz (Bower• just after X-ray flare• become more than 10 times•120

Flux (mJy)et al. , 2003) and at 2 & 3 mm (Furuyaet al. , 2003)

140

100

IR Spec
VLBA

22/43GHz

60
40

variable especially in higher
frequency

20

detected even after 70 days

IRX-ray80

brighter within a few hours• the emission at 22 or 43 GHz wasChandra
BIMA 86 GHz
BIMA 86 GHz ULNRO 150 GHz
NRO 100 GHzVLA 43 GHz
VLA 22 GHz
VLA 15 GHz

01015202530
UT Days in 2003

35

Light curve of GMR-A in mm wave, cm wave and Xray (Bower et al. 2003)40

Difficulties in Observations ofYSO Flares
Too weak: mJy/sub-mJy for the most time
➡ Intense flare rather at high frequency (Bower et al. 2003)

Highly variable: when flares occur?
➡ Periodic flare expected from binary orbit (Massi et al. 2002)

Short flare time within a few hours➡ Longer duration at 22/43 GHz (Bower et al. 2003; Umemoto et al. 2008)

Rapid response➡ Triggering by monitoring in real-time VLBI, X-ray, & optical

T Tauri Binary V773 Tau• WTTS in Taurus at d=148.4 pc (Lestrade et al. 1999)

2MASS image

V773 Tau Orbital Determination

No. 2, 2007

DYNAMICAL MASSES FOR PREYMAIN-SEQUENCE STARS• Keck I at K band &VLBA at 8.4 GHz(Boden et al. 2007)• P=51.1033 days
• T =53059.50 MJD• e=0.2708• i = 65.9 deg• M , M =1.54, 1.33 M
0Fig. 2.—Sample VLBA map from 2004 March 15. Here we give a contour
map of the total intensity continuum emission toward V773 Tau A from VLBA+
EB observations of 2004 March 15. Contours are at #3, 3, 4.5, 6, 7.5, 9, 12, anda image (0.1b mJy beam#1). The FWHM beam osize
15 ! of the rms noise in the(lower left) is 1:36 ; 0:50 mas at a position angle of #11.6% . The peak flux
density in the image is 0.55 mJy beam#1. V773 Tau A is offset in these data andimage as a calibrator (J0403+2600, not shown) served as the phase center. Thickplus signs are rendered at the predicted stellar separation based on our ‘‘V 2 andRV’’ orbit from Table 4 (i.e., no radio data included in the orbit modeling), registered to the center of the apparent primary position. The sizes of the plus signs
indicate the uncertainty in the separation estimate ($0.1 mas per axis).

1217

Periodic Radio Flare on V773 Tau• Most X-ray luminous flares• Lx~1033 erg/s (Skinner et al. 1997, Tsuboi et al. 1998)• Most radio luminous T Tauri star in Taurus-Auriga region (O’Neal et al. 1990)• Periodic radio flares at periastron: 〜orbital period of binary (Massi et al. 2002)• with ~3 days modulation in agreement with star rotation period
120

100

100

80

Effesberg (2.8 cm)
VLA (2 cm)

Flux Density (mJy)

Flux Density (mJy)

80

60

40

2060

40

20

00

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

Phase (Period =52 days)

52 days periodic time variation of V773 Tau (Massi et al. 2002)

011715

11720

11725

11730
11735
Julian Date [2440000 +]

11740

11745

11750

F ig. 4. D etails of F ig. 1 around 11730 J D . A t that epoch close

Observations of V773 Tau by NRO 45m• To obtain the spectral properties
which will provide physicalconditions of the flare• We conducted the multifrequency observations by using
Nobeyama Radio Observatory(NRO) 45m telescope• Continuum observations at 22,43, 86 GHz, simultaneously– Calibrator: J0418+380, J0433+53, NGC7027– On-off by the beam-switch at 15 Hz• Epoch: MJD=53364.60 - 53367.7– periastron passage at MJD=53366.1198
predicted by an orbital period of 51.1033 days

Nobeyama 45m Radio TelescopeMulti-frequency Observations ofV773 Tau
V773Tau Flux Variation
12022GHz flux
43GHz flux
86GHz flux

periastron passage

100Flux(mJy)8060• Multi-frequency observations at
22, 43, 86 GHz, simultaneously,by NRO 45m• Detected radio flare at all bands
just around periastron passage– The flux density became 4-10 times
brighter, then it rapidly decreased at 43& 86 GHz within an hour40

– on the contrary, 22GHz continuum wasdetected even 28 hours later
200
53365.053365.5

53366.053366.553367.0

1dayMJD

Flux variation of V773 Tau at periastron passage(Umemoto et al. 2010)• the flare will be predictable inaccordance with a binary orbital
period of 51.10 days

Spectra of V773 Tau at Flareat ﬂare

• It shows rising spectrum (∝ν0.7)(brighter at higher frequency)
at the flare

before ﬂare

• Descending spectrum(∝ν –0.9)
in an hour due to decreasing
flux at 86 GHz

after ﬂare

• The time scale of the variability
in the active phase ispresumably shorter at higher
frequencies• –＞high energy particles have

Change on spectra of V773 Tau at the ﬂare
(This work)

lost energy quicklyMillimeter Flare from V773 Taucoolingrise•

M. Massi et al.: Synchrotron emission froma T Tauri binary(90GHz)
systemMillimeter
flare

from radiation,
V773 Tauby IRAM
synchrotron
the emissionof each relati
with Lorentz factor γ moving in a magnetic fieldinterferometer (Massi et al.
is centered around a peak spectral frequency, ν02006)
Syrovatski1965) ofν0 = 1.8 × 106 Bγ2 Hz.

• It shows the very shortThis implies that, to reproduce the observed em90 GHz,
electrons
which the folloflare
timemust
as aexist
fewforhours
ship holds:

The temporal evolution of the flux density shot ~4.5h,
clearly
indicatesthat the emitting electron distrib
sible for the observed synchrotron emission, is su
104 .
Bγ2 = 5 ×similar
to X-ray flareriseFig. 2. V773 Tau A flare observed August 6, 2003 (Φ = 0.1) with thePlateau de Bure Interferometer at λ = 3 mm. The error bar corresponds
to 2σ.
Table
1. Flux
in November
2003.
ﬂare
at 3density
mm fromV773 Tau(Massi et al. 2006)
Day1314

S 1 mm (mJy)
5.0 ± 1.26.0 ± 1.2

S 3 mm (mJy)
3.0 ± 0.4
5.0 ± 0.3

tloss=2.31±0.19h
losses. In particular,
the derived e-folding time ofmm flare is of the same order of that measured by(1996)Ourfor cm
emissionat(aboutone hour).
This tresults86
GHz
areplies that the electrons must be at least partiallyconsistentwith
shortemittingregion, which
wouldthisotherwise
be rapidly
time equal to the size of the region divided by thdecay
at 90GHz
electrons:
20Rtime∗ /c ∼ 112 s. It is well-established•mm flareLight Curves of V773 Tau Flare
t=1.0 h1ht=4.6 h10h

• Fitting by exponential decay • Fitting to the decay part by exponential•

e-folding time：1.0 hour at 86GHz••

e-folding time：4.6 h at 22GHz
different from and longer than that at 86 GHz

Synchrotron Radiation• We follow an analysis similar to that presented in Massi etal. (2006)• Magnetic field strength required to produce cyclotron

emission at 86GHz is 30 kG >> 1-3 kG on surface for TTSs
(Bower et al. 2003)→synchrotron radiation• Maximum spectral frequency (Hz) (Ginzburg & Syrovatski 1965)
ν0 = 1.8 × 106 Bγ 2(1)• If synchrotron losses are responsible for the observed
decay (τs, in hours)(Blumenthal & Gould 1970)•5
2.2×10B2γ =τs(2)Physical Parametersmm(90GHz)
flaremm(86GHz)
flareradio(22GHz)
flare

decay time τ(h)

2.31

1.0

4.6

B(G)

56

9757

γ30

2215

distance (R*)

3.8(8.3a)3.1(6.8a)3.7(8.2a)reference

Massi et al. (2006)

this work

this work(a) in solar radius assuming R*=2.2 Ro by Boden et al. (2007)->the emitting regions at mm and 22GHz are very similar

Interacting Magnetospheres Modelmission from a T Tauri binary systemvevel.

s,autyetn-963• Interaction of magnetospheres

just before peri-astron passage,raise• Flare by reconnection of magnetic
fields- at mm wavelength impulsive

flare by accelerated electrons

after that• magnetosphere was filled withFig. 5. Sketch of the binary system with the orbit parameters of Welty(1995). One star with helmet streamers is shown at different positions
alongorbit. Interbinarycollisions
may occur at periastronpassage
Flare theoccurredby interactionof magnetospheresaround peri(see text).
astoron passage (Massi et al. 2006)

formed at the top of a coronal loop, as in the case of the Sun,
could interact with the corona of the other star and could produce the strong radio flares observed around periastron passage

energetic electrons- the emission at 22 GHz by lessenergetic electrons comesfrom the same region

Evaporation Model of Solar Flare
Intensity

microwave (GHz)

Shimojyo (2004)

ＨαUV

softＸray (keV)

hardＸray(>20keV)
時間→timewhether the evaporation model is approved evenat large scale (10Ro) YSO flares ?

e 2: left: VLA monitoring of V773 Tau folded with the orbital period 51.075 days. Phase 0 (1,2) r

NRO45m-Suzaku Joint Observations

VLA monitoring zoomed in at a periastron on Julian Day 11731. The separation between cons
et al. 2002)(Suzaku PI: Yohko Tsuboi)• observation of V773 Tau•••

at periastron
expected giant flare at
X-ray with Lx=1034 erg
an order of magnitudelarger than previous one
detectable non-thermal
hard X-ray(>10keV)
comparing X-rayintensity variation withradio→whether the gigantic flares
are still on empirical relation?

Multi-wavelength Observations• Simultaneous observationsof V773 Tau in Xray, Radio,and Optical & Infrared• around periastron in which giant
flare will be occurred, 3 days of2011 Feb.17, 18, 19.

• Suzaku X-ray satellite、NRO
45m radio telescope, and many
Optical and Infrared telescopes• Results...
22

Collaborator• X-ray: Suzaku•

Y. Tsuboi, R. Iizuka, K. Matsumura•

T. Umemoto, T. Hitora, K. Ninuma,Y.Yonekura,T.Oyama, H. Misawa• Radio: NRO45m,VERA, JVN etc• Optical & Infrared: Nishi-Harima, Okayama,Bisei, Kamiyama, Gunma, Ishigaki etc•

T. Niwa, N. Tokimasa, D. Nogami, T. Kuramoto, K. Ayani,
M.Isogai, H. Takahashi, K. Kinugasa, H. Hanayama,
H.Fukushima, H. Maehara, O. Oshima, K. Nagai

23

Radio Observations of V773 Tau• Multi-frequency observations at22, 43, 86 GHz, simultaneously, byNRO 45m

No significant data for Flarebecause of bad weather

Detected flareat X-ray and Optical!

Nobeyama 45m radio telescopeSummary• Using the NRO 45m telescope, we detected the radio flarefrom V773 Tau at 22, 43, and 86 GHz just around theperiastron passage which is expected from a binary orbital
period.

• The radio flare has occurred just before the periastronpassage, so our results are likely consistent with the modelthat the flares are caused by interaction of magnetoshperes• From simultaneous observations of V773 Tau in Xray,Radio, and Optical & Infrared, the X-ray and optical flares
were detected around the periastron passage. But nosignificant radio data was obtained because of bad weather.

• We are planning the next simultaneous observations inRadio, and Optical & Infrared in this autumn or winter.