1. 서울대학교 물리천문학부 천문학전공 초기우주천체연구단 윤용민
SWIFT J
서울대학교 물리천문학부 천문학전공 초기우주천체연구단
윤용민

2. Brief introduction
Swift J was first detected by the Swift Burst Alert Telescope (BAT) at 12:57:45 UT on 28 March 2011.
The source was assumed to be a gamma-ray burst and was named GRB110328A.
Redshift : 0.35
A. J. Levan et al. (2011)

3. There are two models to explain this phenomenon.
1. Main sequence star was tidally disrupted by 106 – 107 M◉ BH and its debris accreted into the central BH.
2. White dwarf star was tidally disrupted by ~ 104 M◉ BH.

4. Procedure Flux decay ∝ 𝒕 − 𝟓 𝟑
Finding out the fraction of bulge component using HST images.
CQUEAN(g, r, i, z, Y band) and UKIRT(J, H, K band) data
→ SED fitting → determining stellar mass of the bulge fraction.
Finding out the mass of the central black hole.
Analyzing the light curve of 1.5 years period.
Flux decay ∝ 𝒕 − 𝟓 𝟑
M. Limousin et al. (2008)

5. Current Progress 1. WFC3 UVIS F606W image observed in 2011.12.02
2. WFC3 IR F160W image observed in

6. 2D fitting by GALFIT to decompose the bulge component.
1. One component fitting :
de Vaucouleurs(Bulge), Exponential(Disk)
2. Two component fitting :
Bulge + Disk, Bulge + PSF, Disk + PSF
3. Three component fitting
Bulge + Disk + PSF
The models which have small chi-square value and reasonable parameters are selected as good fitting models.

7. Good fitting models of the optical image.
1. Single bulge component model (de Vaucouleurs profile)
de Vaucouleurs profile (Bulge)
Magnitude
22.66
Effective radius
0.24(arcsec)
Axis ratio
0.97

8. 2. Bulge + PSF Model Total magnitude : 22.63
de Vaucouleurs profile (Bulge)
Magnitude
22.66
Effective radius
0.27(arcsec)
Axis ratio
0.98
PSF component
Magnitude
26.59
Total magnitude : 22.63

9. Good fitting models of the IR image.
1. Bulge + PSF Model
de Vaucouleurs profile (Bulge)
Magnitude
21.50
Effective radius
0.15(arcsec)
Axis ratio
0.96
PSF component
Magnitude
22.75
Total magnitude : 21.20

10. 2. Bulge + Disk + PSF Model Total magnitude : 21.22
de Vaucouleurs profile (Bulge)
Magnitude
22.08
Effective radius
0.11(arcsec)
Axis ratio
0.72
Exponential profile (Disk)
Magnitude
22.92
Effective radius
0.41(arcsec)
Axis ratio
0.82
PSF component
Magnitude
22.41
Total magnitude : 21.22

11. Future work CQUEAN(g, r, i, z, Y band) and UKIRT(J, H, K band) data
→ SED fitting → determining stellar mass of the bulge fraction.
Finding out the mass of the central black hole.
→ Determining the disrupted star’s identity
A. J. Levan et al. (2011)

12. Thank you