Prompt GRB Optical Follow-up Experiments

Transcription

1 Prompt GRB Optical Follow-up Experiments Lawrence Livermore National Laboratory Livermore, CA USA

2 Upper Limits on the Prompt Optical Emission From G. G. William s PhD thesis (2000)

3 Experimental Goal & Method Gamma Ray Bursts are flashes of g-ray radiation above 0.1 MeV emanating from point sources, isotropically but inhomogenously distributed in the universe and lasting 1~1000 seconds The BATSE detectors on the CGRO satellite detect ~1 GRB everyday Most Powerful Explosion Since the Big Bang!! NASA press release May 6, 1998 Dedicated and automated system Rapid response utilizing GCN Wide field-of-view system to cover error box of early time notice LOTIS at LLNL LOTIS GRB satellites GCN LOTIS attempts to detect optical radiation simultaneously with the γ -ray bursts to understand γ -ray burst production mechanism

4 LOTIS GRB Counterpart Search Experiments x 17.6 deg Total FOV - Canon Telephoto f/1.8 lenses (200 mm focal length, 11 cm aperture) - 4 of 2048 x 2048 CCD cameras - Rapidly slewing mount - Weather-proof clam shell housing - Weather station - Limiting mv ~ 15 - GRB response time: < 5 sec - Simultaneous g to optical flux ratios - Site: LLNL s test site in California - Operation: Oct 96 ~ current - 100% automated system

5 Simultaneous GRB Counterpart Searches with LOTIS GRB GRB Gamma ray intensity (c/sec) Time since trigger (sec) GRB971006

6 Prompt optical signal and afterglows There are only 2 events that attempted to see prompt optical signal along with other follow-ups during CGRO/BeppoSAX/IPN era GRB by LOTIS no optical flash (Williams et al., ApJ 519, L25) GRB by ROTSE optical flash (Akerlof et al. 1999, Nature, 398, 400)

7 GRB971227: LOTIS obtained 500 images of the X-ray afterglow area from 10 sec to 6 hours; Quasi-simultaneous (10 sec after the burst) limit ~ mv=12.3 (GCNC #19) GRB Cala Alto 2.2 m telescope image; 24 hrs later; J-Band LOTIS Image; 10 sec after mv=10.1 mv=12.3 BeppoSAX 1.5 arcmin error circle

8 GRB LOTIS Result mag = 12.3 at 10 sec after the burst mag = 14.2 at 20 min after the burst Williams et al., ApJ 519, L25 LOTIS g-ray (Band fit) Castro-Tirado R-band X-ray (SAX NFI)

9 GRB990123: Prompt optical flash observed by ROTSE ROTSE Observation (Jan 23, 1999) R-Band Light Curve Gamma-ray fluxes not correlated with the simultaneous optical GRB Prompt Spectrum Akerlof et al. 1999, Nature, 398, 400 Gamma-ray spectra can t be extrapolated Galama et al. 1999, Nature, 398,394; Briggs, Band et al. 1999, astro-ph/ P01322-hsp-u-011

10 Prompt counterparts of Gamma-Ray Bursts: Current understandings and outstanding scientific questions Bright optical flash signal: Is GRB an unique event? Is Prompt broadband spectrum produced by the external reverse shock? (Sari & Piran ApJ 520, 641) No optical flashing events: ~30 events do not have prompt optical signals (Williams ApJ 519 L25, Akerlof ApJ 532 L25) Can prompt signal tell story about progenitors? Is prompt signal obscured by GRB birth-site environment? Is prompt signal dimmer than mag~15? Why early and later time light curves are different? When does afterglow start? 20 sec? 20 min? 2 hours? More prompt measurements are needed

11 Prompt Optical Flash - may be explained by reverse shock (Sari, Soderberg, Ramirez-Ruiz) Great energy ( ergs) released in a small volume -> Relativistic outflow Progenitor unknown Gamma-Ray Burst Inhomogeneities within the outflow result in internal shock Optical, radio, x-ray Afterglows External shock forms where the outflow plows into the surrounding medium Prompt Optical Reverse shock propagates back into the relativistic medium (Sari & Piran ApJ, 520, 641) Synchrotron spectra from reverse shock model: E 52 =5.0; t A =10.0; e e =e B =0.5; S=2.33x10-7 ergcm -2 A: n 1 =0.02, G=200 B: n 1 =0.02; G=400 C: n 1 =0.1; G=400 D: n 1 =0.1; G=400

12 LOTIS upper-limits vs. GRB LOTIS upper limits are inconsistent with predicted magnitude by extrapolating grb flux or peak flux Similar results by ROTSE (Akerlof ApJ 532, L25)

13 Predicted magnitude of the Prompt Optical Flashes LOTIS upper limits favor small n 1 and large g 0 as well as large e e and small e B. Parameters: γ o = Lorentz factor n 1 = circumburster material density ε e = fraction of equipartition electron energy ε B = magnetic field Colors = LOTIS detection probability Fixed Variables: E 52 = 5.0 t A = 10.0 s gamma-ray fluence = 5.0 x 10-7 ε e =0.005 ε e =0.05 ε e =0.5 ε B =0.5 ε B =0.05 ε B =0.005

14 Super-LOTIS for HETE era Kitt Peak, Arizona (USA) Solar Observatory WYN S-LOTIS Space Watch Super-LOTIS - Follow-up observations for HETE2, Swift, Integral missions meter aperture: Boller-Chivens telescope -< 30 sec response time : light curve measurement from 30 sec to 4 hours x 2048 CCD on prime focus x 0.8 deg FOV (1.5 arcsec/pixel) - Sensitivity: mv= 17 ~ 20 - V,R,I,Clear filter wheel - Moved to Kitt Peak in April 2000

15 Super-LOTIS Image Gallery Sombrero (M104) The Whirlpool Galaxy (M51) 51 FOV M88 M31

16 Super-LOTIS Afterglow Detections: GRB Super-LOTIS detected GRB afterglow 23.6 hours after the burst. 13 summed image revealed the afterglow at R=20.0.

17 Super-LOTIS for HETE era Kitt Peak, Arizona (USA) Solar Observatory WYN S-LOTIS Space Watch Super-LOTIS - Follow-up observations for HETE2, Swift, Integral missions meter aperture: Boller-Chivens telescope -< 30 sec response time : light curve measurement from 30 sec to 4 hours x 2048 CCD on prime focus x 0.8 deg FOV (1.5 arcsec/pixel) - Sensitivity: mv= 17 ~ 20 - V,R,I,Clear filter wheel - Moved to Kitt Peak in April 2000

18 Super-LOTIS Image Gallery Sombrero (M104) The Whirlpool Galaxy (M51) 51 FOV M88 M31

19 Super-LOTIS Afterglow Detections: GRB Super-LOTIS detected GRB afterglow 23.6 hours after the burst. 13 summed image revealed the afterglow at R=20.0.

20 Super-LOTIS Image Gallery Sombrero (M104) The Whirlpool Galaxy (M51) 51 FOV M88 M31

21 Super-LOTIS Afterglow Detections: GRB Super-LOTIS detected GRB afterglow 23.6 hours after the burst. 13 summed image revealed the afterglow at R=20.0.

22 Super-LOTIS Afterglow Detections: GRB Super-LOTIS detected GRB afterglow 23.6 hours after the burst. 13 summed image revealed the afterglow at R=20.0.

23 GRB010921: HETE/IPN localization LOTIS observation 52 min after the burst LOTIS Clear Filter LOTIS V Filter DSS Image 20 V=13.0 E N 20 Afterglow reported in this area (GCNC 1107) LOTIS observed the GRB optical afterglow area reported in GCNC #1107 on 09/21/2001 at 06:08:31 (52 min after the burst) during a routine sky patrol. We searched for an optical counterpart in the region of GRB and we found no source. The 10 sigma limits are: clear filter = /- 0.15; V filter = /

24 GRB Super-LOTIS afterglow observation Super-LOTIS: T hr Super-LOTIS: T hr Super-LOTIS: T hr E N Super-LOTIS: T hr DSS Image DPOSS R Image Super-LOTIS detected GRB afterglow 21.8 hours after the burst. The measured afterglow intensities are: V=19.4 ±

25 GRB light curve H. S. Park et al, ApjL, will be published on June 1, LOTIS data shows that the power-law decay curve for the afterglow cannot be extended to the early time.

26 Other prompt optical counterpart search experiments Experiment Location Aper (cm) FOV Pixel Scale (arcsec) Sensitivity (V) Integration (sec) Response Time (sec) Status LOTIS CA x ~5 operating Super- AZ x ~ ~ operating LOTIS TAROT France 25 2 x operating ROTSE-III Austrailia x Raptor outer NM x 19.5 x under construction Raptor x center Bootes Spain x operating TAROT Raptor ROTSE BOOTES-II

27 Current & future space programs to solve GRB mysteries Mission Agency Coordinate Error Notice time delay Event Rate Mission Schedule BATSE/CGRO NASA ~5 sec 300 / year Current, Mission ended on June 3, 2000 SAX Italian-Dutch 10 (WFC) 1~12 hrs 1 / month Mission ended on April 30, 2002 HETE-2 NASA 10 ~ 10 real-time 15 / year Current Launched on Oct. 2, 2000 INTEGRAL International 12 1~10 min 20~40 / year October, 2002 SWIFT NASA <4 15 sec 100 / year 2003 AGILE European <2 1~2/month 2004 GLAST NASA 5 Real-time 100/year 2005 HETE-2 FREGATE: NaI detector : 6 to 400 kev WXM : coded aperture camera : 2 to 25 kev SXM : CCD camera: 0.5 to 10 kev SWIFT BAT: CZT detector : 50 to 300 kev XRT: X-ray telescope: 0.2 to 10 kev UVOT: CCD camera: 170 to 650 nm No infrared measurements!

28 S-LOTIS Prompt NIR and Optical GRB Counterpart Searches mount motor drives Current system filter wheel CCD camera invar spider frame focus stage Planned upgrade system secondary mirror invar spider frame coma corrector IR camera dichroic beam splitter CCD camera focus stage Focal plane upgrade to install a CCD camera AND an NIR camera Candidate NIR FPA array Rockwell HAWAII HgCdTe array;18.5 mm pitch, 77K cooling, 10 e - RO noise I,J,H,K filters Secondary optics to produce f/7 system NIR camera FOV will be 8 x8 (512 x 512 array) Optical CCD FOV will be 22 x 22 (2048 x 2048 array) Utilize already existing Super-LOTIS optics, mount, control system

29 Super-LOTIS upgrade Filters Atmospheric Transmission T V ( λ) T R ( λ) 0.8 T I ( λ) T J ( λ) T H ( λ) 0.6 T K ( λ) T B ( λ) HawaiiQE( λ) LoralQE( λ) tr atm ( λ) R Ι J H Κ HgCdTe QE λ Front illuminated CCD QE µm 3

30 Super-LOTIS NIR camera expected performance SNR J ( mstar, 30 sec, 2) 100 SNR H ( mstar, 30 sec, 2) SNR K ( mstar, 30 sec, 2) mstar 18 Assumptions: G-type star Atmospheric transmission Mirror reflectivity Transmission efficiency through filters HgCdTe array quantum efficiency Constant sky background 30 sec & SNR = 10 J = 16.5 H = 16.2 K = 15.8

31 REM Telescope: prompt NIR counterpart search experiment at la Silla ROSS spectroscophy NIR camera Ritchey-Chretien system 60 cm, f/2.2 primary, f/8 effective Alt-azi mount Dichroic beam splitter One FPA: HgCdTe 512 x 512 array with JHK filters, 18 mm pitch, Stirling cyro pump cooling Other FPA: Optical spectroscophy with a prism and a CCD camera Site: la Silla Observatory Expect to start October 2002 F. M Zerbi et al., astro-ph/

32 Summary Early-time light curves are still mystery Simultaneous optical light curve measurement will provide clues to understand GRB s progenitors and their environment We need many more prompt / simultaneous GRB counterpart detections S-LOTIS and a few other automatic telescopes can measure prompt optical afterglows triggered by HETE 2 Prompt IR follow-ups by upgraded S-LOTIS and REM will be important measurements for Swift LOTIS? SLOTIS