1. Gamma-Ray Bursts Xue-Feng Wu 2014, June 6, Nanjing
3rd International Collaboration Meeting on Antarctic Survey Telescopes
Gamma-Ray Bursts
Xue-Feng Wu
Chinese Center for Antarctic Astronomy,
Purple Mountain Observatory,
Chinese Academy of Sciences
2014, June 6, Nanjing

2. What are gamma-ray bursts (GRBs)

3. isotropic distribution in the sky
cosmological origin?

4. compact stellar objects: black hole, neutron star?
GRB light curves
morphology
complicated & irregular
duration
～ ms s,
or even longer
variability timescale
δt ～ 1ms, even ～ 0.1ms
size of the emission region
R < c δt ~ 300km
compact stellar objects: black hole, neutron star?

5. GRB prompt emission spectra
non-thermal:
synchrotron or inverse Compton?

6. GRB prompt emission spectra -continued
Thermal Component
Extra High Energy Component
GRB090902B
GRB090926A
broadened
Planck function
Abdo et al. 2009, ApJ, 706, L138
Ackermann et al. 2011, ApJ, 729, 114
If this spectral break is due to γγ annihilation (optical depth ~1) ,
then the Lorentz factor can be estimated as !
fastest bulk motion
in the universe!

7. classification: long soft vs short hard
short GRBs
long GRBs
2 s
Kulkarni et al. 2000

8. discovery of afterglows from long GRBs
one of the breakthroughs of the year 1997, Science magazine
the first afterglow (from GRB970228)
t -1.3
BeppoSAX
Costa et al., 1997, Nature, 387, 783

9. first redshift measurement for long GRBs
absorption lines in
afterglow spectrum
host galaxy emission lines
GRB
z=0.835
(t~2.3day)
(t~6-11months)
Bloom et al., 2001, ApJ, 554, 678
Metzger et al., 1997, Nature, 387, 878

10. first optical flash
one of the breakthroughs of the year 1999, Science magazine
GRB
GRB
ROTSE
Akerlof et al., 1999, Nature, 398, 400

11. brightest GRB optical afterglows
Bloom et al., 2009, ApJ
GRB
Peak Magnitude
redshift
Peak Absolute Magnitude
Luminosity in unit of the brightest SN
080319B
5.3
0.937
-38
1.6e6
130427A
7.03
0.34
-34
2.5e4
990123
8.9
1.6
-36.38
2.25e5
061007
10.3
1.261
-34.44
3.7e4
Vestrand et al., 2013, Science

12. GRB 140311A: early optical afterglow by Zadko telescope
Why early optical afterglow observations are important:
To determine the initial Lorentz factor;
To estimate the type and density of circum-burst environment (ISM, or stellar wind)
Courtesy of David Coward, UWA

13. first possible association between long GRB 980425 and the supernova SN 1998bw
Galama et al，1998, Nature

14. possible association between long GRBs and Type Ic supernovae (indirect / late rebrightening or bump)
Bloom J. S. et al.,1999, Nature, 401, 453

15. first confirmed association between long GRB and the supernova SN 2003dh (direct / spectroscopy)
one of the breakthroughs of the year 2003, Science magazine
Hjorth et al., 2003, Nature, 423, 847

16. GRB-SNe associations：Sample A
strong spectroscopic evidence, spectroscopic SNe
association redshift
980425/1998bw
030329/2003dh
031203/2003lw
060218/2006aj
091127/2009nz
100316D/2010bh
120422A/2012bz
120714B/2012eb
130215A/2013ez
130427A/2013cq
130702A/2013dx
130831A/2013fu
redshift distribution：0.0085～0. 597，mean z = ；
SN 2008D / XRF not listed, because this association is under debate，(Hjorth & Bloom 2012)
Credit: Shanqin Wang

17. GRB-SNe associations：Sample B
a clear lightcurve bump as well as some spectroscopic evidence resembling a GRB-SN.
association redshift
011121/2001ke
021211/2002lt
050525A/2005nc
081007/2008hw
101219B/2010ma
111211A
120714B/2012eb
redshift distribution：0.251 ～1.006 ，mean z = 0.55
Credit: Shanqin Wang

18. GRB-SNe associations：Sample C
a clear bump consistent with other GRB-SNe putting at the spectroscopic redshift of the GRB.
association redshift
080319B
120729A
redshift distribution：0.433 ～0.938 ，mean z = 0.709
Credit: Shanqin Wang

19. GRB-SNe associations：Sample D
a bump，but the inferred SN properties are not fully consistent with other GRB-SNe, or the bump was not well sampled, or there is no spectroscopic redshift for the GRB.
association redshift caveat
red bump
discovered via bump
red bump，X-ray excess
050416A poor sampling
070419A poor sampling
100418A
101225A
redshift distribution：0.654～ 0.971，mean z = 0.774
Credit: Shanqin Wang

20. GRB-SNe associations：Sample E
a bump，either of low significance or inconsistent with other GRB-SNe.
association redshift caveat
low significance
low significance
not fitted by GRB-SNe
low significance
afterglow dominated
111209A
redshift distribution：0.543～1.058，mean z = 0.762
Credit: Shanqin Wang

21. GRB-SNe associations: why most long GRBs are not detected with Ic SNe?
External reasons:
(1) Pre-Swift era, lack of quick precise positioning pretend the follow-up of large optical facilities;
(2) Some GRBs are close to Sun or full moon;
(3) Dust extinction;
(4) SN brightness decreases with increase redshift, especially for z>0.5. For z>1.2, it is extremely
difficult to identify the SN component from GRB afterglow;
(5) Host galaxy contamination (host can be as bright as SN, i.e., M=-19).
Internal reasons:
(1) Associated SN is intrinsically dim;
(2) Some GRB late afterglows are relatively bright.

22. jet signature in GRB afterglows
Greiner et al., 2003, ApJ, 599, 1223

23. Origin of Long GRBs Long Bursts: collapsars Young (few million yrs)
Star-forming regions

24. GRB 050509B: first discovered X-ray afterglow from short GRBs
one of the breakthroughs of the year 2005, Science magazine
BAT
error circle
XRT
error circle
possibility of the chance superposition
of GRB B with the elliptical galaxy:
P<0.2% (Pedersen et al., 2005, ApJ 634, L17)
Gehrels et al., Nature 437, 851

25. GRB 050509B: optical up limits
Hjorth et al., 2005, ApJ 630, L117

26. GRB 050709: host galaxy host galaxy: z=0.160
GRB located in the outskirt of the host
galaxy with irregular morphology
host galaxy: z=0.160
Fox et al., Nature 437, 845

27. Properties of short GRBs compared with long GRBs
1. usually happened at low redshifts (z<1)；
2. typical isotropic energy of1048 – 1050 erg, smaller than that of long GRBs by 2-3 orders of magnitude；
3. unassociated with supernovae;
4. diversity of host galaxies, from early ellipticals to irregulars; usually take place at the ourskirt of the host galaxy
 support the NS-NS/NS-BH merger model !

28. Gehrels, Piro & Leonard 2002, Scientific American

29. Gehrels, Piro & Leonard 2002, Scientific American

30. Gehrels, Piro & Leonard 2002, Scientific American

31. Radio-selected GRB afterglow sample
（ , Chandra & Frail 2012）
Crazy day of 5 bursts in 24 hours
Optical viewing before burst
5.3 visible to naked eye for ~40 s 31

32. Radio-selected GRB afterglow sample
（ , Chandra & Frail 2012）
(216GRBs)
(53GRBs)
(163GRBs)
Crazy day of 5 bursts in 24 hours
Optical viewing before burst
5.3 visible to naked eye for ~40 s 32

33. GRB research with AST3 Regular GRB optical observation
GRB orphan afterglow survey
Merger-nova optical observation

34. regular GRB optical observation
I Prompt phase and early afterglow
optical counterparts of prompt GRBs
early optical afterglows
II Late optical observation
light curve jet breaks
origin of chromatic afterglows
III GRB-SN associations
progenitors and explosion mechanisms
prompt/quick response (minutes to hours)
deep limit magnitude

35. Long GRB optical afterglow lightcurves
MW dust extinction corrected
AST3极限星等？
Kann, et al., 2010, ApJ, 720, 1513

36. Peak Mag vs. Peak Time

37. orphan afterglow survey
I、off-axis GRBs：
jet, radiation is relativistic beamed
on-axis：
prompt GRB
afterglow
off-axis：
jet decelerates
beaming effect decreases
orphan afterglow
true GRB rate !
true GRB energy !
II、failed GRBs：
less energetic (lower Lorentz factor),
less gamma-ray released, even undetectable
on-axis：
orphan afterglow

38. Merger-nova optical observation: EM signals for a BH post-merger (NS-NS) product
SGRB
Multi-band transient
~hours, days, weeks,
or even years
dimmer X-ray counterpart
Li-Paczyński Nova
Li & Paczyński, 1998
Opical flare
~ 1 day
Ejecta-ISM shock
Nakar& Piran, 2011
Radio
~years
Metzger & Berger, 2012

39. Merger-nova optical observation: EM signals for a ms magnetar post-merger (NS-NS) product
SGRB
EP detectable X-ray counterpart!
Jet-ISM shock (Afterglow)
Shocked ISM
Ejecta
SGRB
Radio
Optical
X-ray
Poynting flux
MNS
Late central engine activity
~Plateau & X-ray flare
Magnetic Dissipation
X-ray Afterglow
1000 ~10000 s
Zhang, 2013
Photosphere emission
Optical and soft X-ray transient
~ days, weeks
Yu, Gao &Zhang, 2013
Ejecta-ISM shock with
Energy Injection (EI)
Multi-band transient
~hours, days, weeks,
or even years
Gao, Ding, Wu, Zhang & Dai, 2013
Wu et al. 2014; Wang & Dai, 2013

40. GRB research with optical polarimeter
(e.g., installed in >30cm antarctic telescope )

41. GRB optical polarization
GRB090102: first poln detection of reverse shock emission
F~ t -a, a1~1.50, tb ~ 103 s, a2~0.97
偏振曝光时间: t s to t s
线偏振度: (10.1+/-1.3)%
RINGO: 2-m Liverpool Telescope in La Palma
Steele et al., 2009, Nature, 462, 767

42. GRB optical polarization
GRB060418: first poln observation (upper limit) of the early emission from the forward shock
F~ t -a, a1~-2.7, tb ~ 130s, a2~1.2
偏振曝光时间: t0+203s to t0+233s
线偏振度: <8%
RINGO: 2-m Liverpool Telescope in La Palma
Mundell et al., 2007, Science, 315, 1822

43. GRB optical polarization
GRB091208: first poln detection of the early emission from the forward shock
F~ t -a, a1~0.75；
偏振曝光时间: t0+149s to t0+706s
线偏振度: 10.4+/-2.5 %
Kanata 1.5-m Telescope
Uehara et al., 2012, ApJL, 752, L6

44. GRB optical polarization
GRB120308A: first poln evolution from reverse shock to forward shock emission r’
RINGO: 2-m Liverpool Telescope in La Palma
Mundell et al., 2013, Nature, 504, 119

45. GRB research with infrared CCD

46. Dust Extinction

47. Origin of dark GRBs Dust extinction ? High-redshift GRBs?
Intrinsically dark?

48. high-z or high extinction?
photometric z~9.4，the most distant stellar object ever detected？

49. GRB research with KDUST

50. redshift record
GRBs
Quasars
Galaxies
Zhang, B., 2009, Nature

51. High-z GRBs (Pop II, Pop III stars)
4+1 GRBs with z > 6：
GRB (z=6.3), GRB (z=6.7), GRB (z=8.2)
GRB B (z=9.4?), GRB A (z=6.33)

52. detectability of high-z GRB afterglows at infrared band
1216A*(1+20) = 2.4 micron
Lamb, & Reichart, 2000, ApJ

53. GRBs as probe of cosmic star forming history
Wei, Wu, Melia, Wei, Feng, 2014, MNRAS

54. Thank You!