Evidence for Episodic Accretion in Class I Source, IRAS 16316-1540 - - PowerPoint PPT Presentation

Evidence for Episodic Accretion in Class I Source, IRAS 16316-1540

Sung-Yong Yoon1, Jeong-Eun Lee1, Seokho Lee1, Sunkyung Park1

1Kyung Hee University

Contents

1.Introduction 1.1. Inner Region of Protoplanetary Disk 1.2. IGRINS Survey of Protoplanetary Disks 1.3. Characteristics of FU Orionis-type objects

• 2. Results

2.1. Spectra of Class I Objects 2.2. Class I & FU Ori-type Objects 2.3. Cross-correlation of IRAS 16316-1540 with FUors and Class I Sources 3.Analysis 3.1. Stellar Rotation vs. Disk Rotation 3.1.1. Standard Stars 3.1.2. Veiling 3.1.3. Chi-square test 3.2. Results of the Disk Rotation and Stellar Rotation 4.Summary & Future work

• 1. Introduction

1.1. Inner Region of Protoplanetary disk

Dullemond et al. (2010)

1.2. IGRINS Survey of Protoplanetary Disks

A part of Korea IGRINS Legacy program (PI : Jeong-Eun Lee). Spectroscopic observation of inner gaseous disks provides useful information about the formation process of star and planet, through line features that depend on accretion, wind, and rotation as well as timescale of gas dissipation and planet formation. The survey covers wide ranges of age, luminosity, and mass (from Class I to WTTS, and from low mass to Herbig Ae/Be and massive YSOs) It also covers FU Orionis-type objects (FUors) in which an

• utburst occurs.

1.2. IGRINS Survey of Protoplanetary Disks

Type Total Observed Remained MYSOs 4 3 1 Herbig Ae/Be 10 8 2 Class I 10 10 CTTS (Class II) 18 17 1 WTTS (Class III) 10 9 1 FUors 8 8 Total 60 55 5

1.2. IGRINS Survey of Protoplanetary Disks

Type Total Observed Remained MYSOs 4 3 1 Herbig Ae/Be 10 8 2 Class I 10 10 CTTS (Class II) 18 17 1 WTTS (Class III) 10 9 1 FUors 8 8 Total 60 55 5

1.3. Characteristics of FU Orionis- type objects

Hartmann & Kenyon (1996)

Large, sudden increases of brightness(≳ 4 mag) called outburst occur in the optical- wavelengths region in Classical T Tauri stars. The outbursts of FUors are believed as a result of enhanced accretion rate in circumstellar disk. “Double-peaked” or “boxy” absorption line profiles produced by Keplerian rotation of the disk. The varying spectral types with wavelengths;

• ptical and infrared spectra are consistent

with F-G (Teff ~ 7200-6500 K) and K-M supergiant (Teff ~ 3000-2000 K), respectively.

1.3. Characteristics of FU Orionis- type objects

Hartmann & Kenyon (1996) Hartmann et al. (2016)

Large, sudden increases of brightness(≳ 4 mag) called outburst occur in the optical- wavelengths region in Classical T Tauri stars. The outbursts of FUors are believed as a result of enhanced accretion rate in circumstellar disk. “Double-peaked” or “boxy” absorption line profiles produced by Keplerian rotation of the disk. The varying spectral types with wavelengths;

• ptical and infrared spectra are consistent

with F-G (Teff ~ 7200-6500 K) and K-M supergiant (Teff ~ 3000-2000 K), respectively.

• 2. Results

2.1. Spectra of Class I objects

2.2. Class I & FU Ori-type objects

2.3. Cross-correlation of IRAS 16316-1540 with FUors and Class I sources

Type Name Correlation r-value FUors 2MASS J06593158-0405277 0.74 10.769 FUors HBC 722 0.735 12.031 FUors FU Ori 0.709 10.892 Class I IRAS 18341-0113(N) 0.428 9.948 Class I IRAS 03301+3111 0.372 5.845

• 3. Analysis

3.1. Disk Rotation vs. Stellar Rotation

Stellar Rotation Disk Rotation

2.1.1. Standard Stars

We take the standard stars from IGRINS spectral library (Park et al. 2017, submitted). 87 standard stars Spectral type : G0 ~ M7 Luminosity Class : I ~ V

2.1.2. Veiling

Continuum excess of the disk weaken the depth of the absorption lines. It is called ‘veiling’. It is defined as the ratio of the intrinsic equivalent width (EW) to observed EW. EWi = (1 + rk)EWo

Hot spot Circumstellar disk Infalling gas 


• n magnetic field

Convolution with the disk/stellar 
 rotation profile of v sin i Interpolation Cross correlation X2 = Σ {(rkM - T)2 / σ2} ∂X2 / ∂rk = 0 Select a stellar template Comparison of the X2 values of entire stellar template Estimation of the spectral type of IRAS 16316-1540 2.1.3. Chi-square test

rk : veiling factor M : standard star T : IRAS 16316-1540

3.2. Results of the Disk Rotation and Stellar Rotation

Best fit result Spectral type : K5 V Disk (stellar) rotation velocity : ~ 40 km s-1 (~60 km s-1) Veiling (rk) : ~ 1

2.1358 Si I

−200 −100 100 200 Velocity (km s

• 1)

0.94 0.96 0.98 1.00 Relative Flux

K5V HD36003

2.2088 Na I

−100 100

2.2812 Mg I

−200 −100 100 200

Disk rotation Stellar rotation

• 4. Summary & Future work

The episodic accretion makes the broadened absorption lines with boxy or double-peaked profile which is produced by Keplerian disk. We found that the spectrum of Class I source, IRAS 16316-1540, shows broad absorption features similar to those of FUors. We could fit the broad absorption features of IRAS 16316-1540 with the K5 V template spectrum convolved with the disk rotation profile of about 40 km s

• 1.

It suggests that the episodic accretion can occur from the early stage of star formation and detect its signature using high-resolution spectrograph, IGRINS. We will study protoplanetary disks observed with IGRINS using statistical analysis to explore physical and chemical structure of the inner region of the disk.