可視・ x 線・ γ 線同時観測で探る γ 線バースト (exploring grbs through optical,...

GRB_Fermi-WAM-Kanata_2008Nov.ppt

Tsunefumi Mizuno 1

可視・可視・ XX 線・線・ γγ 線同時観測で探る線同時観測で探る γγ 線バー線バーストスト (Exploring GRBs through Optical, (Exploring GRBs through Optical,

X-ray and Gamma-ray Observations)X-ray and Gamma-ray Observations)November 27, 2008

Tsunefumi Mizuno (Hiroshima Univ.)[email protected]

Yasushi Fukazawa, Koji Kawabata, Hideaki Katagiri , Yoshitaka Hanabata (Hiroshima Univ.), Goro Sato, Masanori Ohno (ISAS/JAXA) Hiroyasu Tajima

(SLAC) on behalf of the Fermi GBM/LAT Collaboration

Contribution to the Conference “Deciphering the Ancient Universe with Gamma-Ray Bursts” at Mitaka, Tokyo, Japan (Nov 27-29, 2008)


Tsunefumi Mizuno 2

IntroductionIntroduction

•Multiwavelength Observation to explorer GRB phenomenaFermi LAT and GBM

7 decades of energy coverage (8 keV-300 GeV)High sensitivity imaging in GeV band (>100 MeV)Spectral cutoff (-factor), GeV excess (hadronic origin?), etc.

Suzaku WAMLargest Aeff in 300-5000 keV, large FOV (~2)“best friend” to Fermi LAT/GBM; better constrain of the spectral parameter, spectral-lag analysis, time-resolved spectroscoy.

Kanata Optical Telescope1.5 m diameter & very fast driving speed (5deg/sec)HOWPol is about to readyPolarimetry of optical afterglow to constrain the magnetic field structure.


Tsunefumi Mizuno 3

The Fermi ObservatoryThe Fermi Observatory

Large Area Telescope (LAT)• Large Field of View (>2.4 sr)• views entire sky every 3 hrs in wide energy range (20 MeV - 300 GeV)

Gamma-ray Burst Monitor (GBM) • Views entire unocculted sky• 12 NaI detectors:

8 keV - 1 MeV• 2 BGO detectors:

150 keV - 30 MeV

LAT+GBM=>more than 7 energy decades!

(For detail, see talk by K. Asano’s in this afternoon)

~200 GRBs/year expected by the GBM


Tsunefumi Mizuno 4

Fermi Launch !!Fermi Launch !!

(photo taken by M. Ohno)

•Launch from Cape Canaveral Air Station 11 June 2008 at 12:05 PM EDT•Circular orbit, 565 km altitude (96 min period), 25.6 deg inclination.

Operation•Onboard processing (GBM): alerts and updates to GCN with localization.•LAT ground processing (5-12 hours): updates location and the spectrum/flux.

•Scientists serve as “Burst Advocator” (for GBM and LAT individually)

LAT BAs cover 24hrs/day and 7days/week by an international collaboration. They continuously check the GCN Notice and perform the analysis of LAT data.In Japan, ISAS/JAXA, Tokyo Institute of Technology and Hiroshima Univ. are involved in BA. See talk by R. Sato for detail.


Tsunefumi Mizuno 5

GRBs Detected by FermiGRBs Detected by Fermi•Sep. 18, 2008 “Fermi/GBM Data Now Available” (http://heasarc.gsfc.nasa.gov/cgi-bin//W3Browse/w3table.pl?Action=Detailed%20Mission&Observatory=fermi)

32 GRBs from Sep. 12th to Nov. 19th (~0.5/day, as expected before the launch)11 GRBs are also detected by Suzaku WAM

•3 LAT GRBsGRB080825C (<35sec, 14 photons in 100MeV-1GeV)GRB080916C (<100sec, 14 photons above GeV) see K. Asano’s talkGRB081024B (short GRB, up to 3 GeV. GCN Circular #8407)


Tsunefumi Mizuno 6

GRB081024B by FermiGRB081024B by Fermi

Nicola Omodei On behalf of the Fermi LAT Collaboration

•The Fermi LAT telescope detected an increased count rate at 2008/10/24 (21:22:41), associated with a GRB detected also by the Fermi GBM (Trigger number:246576161). The location of the GRB reported by Fermi LAT data ground analysis is: Ra=322.9, Dec=21.204 which corresponds to Ra (J2000) = 21:31:36.00 Dec (J200) = 21:12:14.4 within a statistical uncertainty of 0.16 degrees (68% containment radius). The emission from this point source was seen up to 3 GeV, in the first 5 seconds after the trigger. The Fermi LAT point of contact for this burst is Nicola Omodei ([email protected]). The Fermi LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden. This message can be cited.

LAT GCN Circular #8407

•13 LAT photos above 100 MeV•The first short GRB with emission above GeV (possible exception of GRB930131; Sommer et al. 1994).

Joint analysis of GBM/LAT data is important and is underway by Fermi GBM/LAT team.


Tsunefumi Mizuno 7

Detailed GBM Light CurveDetailed GBM Light Curve

NaI (30-110 keV)

NaI (110-240 keV)

NaI (240-520 keV)

BGO (520-960 keV)

•Background subtracted light curves, with 0.09375s bin width (to make them match with WAM light curves)

•3 time regions could be specified (colored areas)

•Only below ~100 keV, two pulses are clearly separated.

possible soft lag of the 2nd pulse.

•2nd pulse is shorter in high energy band.

possible spectral evolution

-2 0 2 (s)


Tsunefumi Mizuno 8

GBM Spectra of GRB081024BGBM Spectra of GRB081024B

NaI & BGO fit by a single power-law model:index ~ 1.0 +/- 0.1

Interval1 (0-0.094 s) Interval2 (0.094-0.28 s)

Interval3 (0.28-0.75 s)

•Apparent cutoff not seen up to 1 MeV•Possible spectral evolution

In interval 3, spectrum softens and shows deficit of photons below 30 keV.

•Statistics-limited analysis with preliminary detector responses. Further analysis using more accurate responses is underway.

single PL-fit:Index ~ 0.9 +/- 0.2

single PL-fit:Index~ 1.35 +/- 0.15

Preliminary


Tsunefumi Mizuno 9

Suzaku WAM also Detected the GRBSuzaku WAM also Detected the GRB

WAM TH0(50-110 keV)

WAM TH1(110-240 keV)

WAM TH2(240-520 keV)

WAM TH3(520-5000 keV)

•Barycentric correction not applied yet•counts/significance in 0-0.75s (stat error only)

TH0: 75(3.3)TH1: 178(7.6)TH2: 85(3.2)TH3:139(3.9)

•Above 100 keV, factor of ~2 higher counts and slightly better significance than GBM => WAM/GBM joint analysis could improve the spectral fit.

-2 0 2 (s)


Tsunefumi Mizuno 10

HOWPol on Kanata TelescopeHOWPol on Kanata Telescope (1)(1)(Hiroshima One-shot Wide-field Polarimeter)

CCD dewer

Focus adj. stage

Focal maskexchanger

Collimatorlens Camera lens

Filter exchanger Prism exchanger

Shutter and pupilPolarmetric

unit exchanger

１露出型偏光撮像（広視野 7’×7’ 、狭視野 1’×15’ ）

•2008 年 7 月 28-31 日ファーストライト効率測定： B: 7%, V: 19%, R: 27%, I: 25% ( 大気含む )

•2008 年 11 月 4 日～広視野用偏光プリズム導入定常試験観測開始　器械偏光 ~4% 　（第三鏡による偏光面回転のみで 0.4% 精度での補正が可能、他の依存性調査中）


Tsunefumi Mizuno 11

HOWPol on Kanata Telescope (2)HOWPol on Kanata Telescope (2)

050820A

050922C

101 102 103 104

Time after burst (sec)

10

15

20

Mag

nitu

de (

V o

r R

or

r')

Polarimetry1min limit

Polarimetry10min limit

Photometry10min limit

060607A

990123

021211

030329

050525A

050801

060111B

060117061007

1000 秒

•Akerlof & Heather (2007) Statistics of 108 Swift GRBs

40% で光学残光　うち t=1000 秒換算での等級が 14 等 ,16等 ,18 等より明るいもの 0.9%,4.6%,16.7%

•4 年間観測を続けると1000 秒後でも 16 等より明るいサンプルを１個 /4 年 (100-1000s の間で偏光の変化を追う )200s で 16 等より明るいサンプルを 3-4 個 (10 分露出で偏光測定 )

=> 年 1 個程度の偏光観測を期待

仮定：　発見レート 100 個 / 年　高度係数 0.33 (>20 度）　夜間係数 0.4

　晴天係数 0.4

• 2008 年 12 月～　ＧＲＢアラート対応観測開始• ⇒ バーストから 100 秒以内の偏光観測開始めざす

1 分露出時

10 分露出時

Δp=0.2%

偏光測定限界

200 秒


Tsunefumi Mizuno 12

SummarySummary•Fermi GBM detects ~0.5GRB/day, as expected before the launch. Now the GBM data is publicly available.•Three LAT GRBs above 100 MeV

Two long (GRB080825C, GRB080916C) and one short (GRB081024B).

•GRB081024B is the first short GRB with photons above 1 GeV.LAT detected photons up to 3 GeVIn GBM band, we observed a “hint” of the soft lag below 100 keV and the spectral evolution in the 2nd pulse. (preliminary statement)Detailed analysis is underway by GBM/LAT team.

•Suzaku-WAM has largest Aeff in 300-5000 keV and is the best friend of Fermi GBM/LAT

Simultaneous detection of GRB081024B. Better statistics above 100 keV.

•HOWPol on Kanata Telescope is about to readyStudy the magnetic filed of external shock. ~1GRB/year (<16mag@200s) is expected.

可視・ x 線・ γ 線同時観測で探る γ 線バースト (exploring grbs through optical,...

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