（ 1: Kobe University, 2: Nagoya University, 3: NAOJ)

☆Abstract☆

We obtained a high spatial resolution (FWHM ~ 0.1”) near-infrared image of XZ Tau, a 0.3” separated binary system, using Subaru/CIAO. A jet-like structure (Jet1 of Fig 5) was detected at northeast side of the binary. It is possibly driven from the secondary. Previous HST observations of the binary showed a shock (bubble structure of Fig 3) created by another jet (Jet2 of Fig 5) from the primary.

1. Introduction

1.1 Motivation・ Many T Tauri stars (~1 Myr) have protoplanetary disks

and bipolar jets.

・ The observations have focused mainly on single T Tauri stars.

・ More than half of T Tauri stars are binaries. (Ghez et al)

A limited number of studies have so far examined the disks and the jets around binary systems. (e.g., UY Aur; Hioki et al. 2007)

1.2 CIAO － Coronagraphic Imager with Adaptive Optics ・ Mask has ~2% transmission for the central star.

・ A pupil Lyot stop reduce the diffracted light.

⇒CIAO is effective for the detection of protoplanetary disks and jets around the stellar vicinity.

1.3 XZ Tau (Classical T Tauri Binary)・ Location: Taurus star forming region (L1551; d~140 pc, Elias 1978 ）・ Separation: ~0”.3 (=40 AU; Haas et al. 1990)・ Mass: 0.4 Msun (Primary), 0.3 Msun (Secondary) （ Hartigan & Kenyon 2003 ）

1.4 Previous Study of XZ Tau

①Detection of a bipolar jet （ Mundt et al. 1988, 1990 ）

⇒Blue-shifted (northeast side) & red-shifted (southwest side)

②HST/WFPC2 Observations（ Fig 3; Krist et al. 1997, 1999, Coffey et al. 2004 ）

⇒A bubble of emission nebulosity was detected to north (P.A. ~20 deg) of the binary system.

Its structure is the following:

　・ The bubble extending with time　・ [S II], Hα, and [O I] emission lines　・ The bubble = Shock created by collision between circumstellar material and jet from the primary?? ・ Accretion from the circumstellar disk around the primary is very active （ White & Ghez 2001). 　・ The primary is an EXor, which periodically undergo outbursts （ Coffey et al. 2004 ） .

2 ． ObservationsDate: 2005 Nov 9, 2007 Dec 16

Instrument: Subaru/ CIAO

FOV: 22” by 22”

Wavelength: H-band (1.6 um), [Fe II]

PSF-reference stars were obtained before and after XZ Tau observations.

　 3 ． Reduction (IRAF)　① Dark subtraction　② Flat-fielding by twilight flat　③ Hot and bad pixel removal　

　④ Sky subtraction

　

　⑤ Shift each frame to adjust the position of the stars

　⑥ Rotation of PSF-reference stars to adjust the position angle of the spider 　

　　　　⑦ Combining XZ Tau frames subtracted their PSFs

Tomonori Hioki1 (otopen@kobe-u.ac.jp), Yoichi Itoh1, Yumiko Oasa1, Misato Fukagawa2, SDPS Team3

Fig2 Coronagraph structure

4. Result

4.1 　 Jet from the secondary

Fig5 presents that the jet (Jet1) drive from the secondary in the direction of P.A.~54 deg.

4.2 　 H-band Magnitude, Separation, Position Angle

On the other hand, it is thought that the secondary is equable compared with the primary.

⇒Does the secondary drive the jet? or not??

Brightness r ∝ -4

● ： Northeast

○ ： Southwest

Limiting

magnitude

<Northeast side>①Extending to ~ 300 AU from the secondary②Surface brightness ∝ r ^-4 (r : distance from the secondary)If the structure is scattering from the central binary, its brightness ∝ r^-3.

Therefore,

[1] the more it is distant from the stars, the optically thinner or [2] it emits not only by scattering but also by emission lines (such as [Fe II]).

<Southwest side>Outstanding structure is not seen. ⇒The jet is probably obscured by a circumbinary disk (if any) in the plane perpendicular to the jet.

Fig1 Circumstellar disk and jet of HH30 (HST/WFPC2; Burrows et al. 1996 ）

Jet

Disk

Fig3 XZ Tau image taken by HST/WFPC2 （ R-band; Krist et al. 1999 ）

Fig5 Coronagraphic image of XZ Tau

Fig6 Brightness of the northeast (●) and southwest (○) jets from the secondary

5. Discussion5.1 　 Jet? or Reflection Nebulae?It is possibility that the jet-like structure is scattering from the central binary.

⇒We also carried out the [Fe II] observations in 2007 Dec.

5.2 Result of [Fe II] image

Fig7 [Fe II] coronagraphic image of the XZ Tau binary (ex time: 1280 s)

Was a weak [Fe II] emission detected??

If it is real, the jet-like structure corresponds to the jet from the secondary. Because forbidden lines are indicative of the jet from young stellar objects.

But…

This image is the result of simplified reduction. More detailed reduction is needed!!

Mask size [arcsec]

Ex time [sec]

FWHM[arcsec]

XZ Tau 0.6 720 0.1

PSF-ref 0.6 228 0.1

Fig4 Raw image of XZ Tau

1” = 140 AU

北

東

Blue ： Separation ~0.3” (=42 AU)Red ： Angular velocity ~1.2 deg/yr

⇒Orbital period ~300 yrs Total mass ~0.8 M sun

　　 (assuming its orbit is circular)

Blue: Secondary ( ～ 0.6 mag up)Red ： Primary （～ 1.3 mag down)

These variations may originate from: ・ variable accretion rate to the stars・ rotation of the secondary with hot spots on its surface.

The variation of the primary possibly contributes to its outburst.

E

N

1”=140 AU

●●

Secondary

Primary