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G round-based W ide A ngle C ameras

This report highlights the scientific requirements and capabilities of ground-based wide-angle cameras (GWAC) for the detection and study of gamma-ray bursts (GRBs), including high-z and sub-luminous GRBs. The report discusses the fast and accurate GRB positions, broadband spectral shape measurement, and temporal properties of prompt emission. It also emphasizes the importance of quickly identifying and providing positions and redshift indicators for detected afterglows.

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G round-based W ide A ngle C ameras

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  1. Ground-based WideAngleCameras WEI Jianyan@SVOM Team NAOC, Beijing Les Chouches Physics School, April 11, 2016

  2. Scientific requirements on SVOM Permit the detection of all know types of GRBs (>200), with a special care on high-z GRBs and low-z sub-luminous GRBs Provide fast, reliable and accurate GRB positions Measure the broadband spectral shape of the prompt emission (from visible to MeV) Measure the temporal properties of the prompt emission Quickly identify the afterglows of detected GRBs, including those which are highly redshifted(z>6) Quickly provide (sub-) arcsec positions of detected afterglows Quickly provide redshift indicators of detected GRBs

  3. 1022 Space GRM 1020 ECLAIRs MXT Frequency (Hz) 1018 1016 VT Slew 1014 Ground 1015 GWAC C-GFT Frequency (Hz) F-GFT 1014 -5 0 1 10 102 103 104 105 Time (s) Log. scale Time (m) Lin. scale Multi-wavelength capabilities of SVOM

  4. SVOM strategy: GRB optical emission detection Wang et al 2013 GWAC GFTs T-T0=30 sec VT

  5. GWAC: an instrument for short time–scale optical transients Wozniak et al. 2009 The key point: trigger by its self !

  6. Scientific objectives of GWAC • Optical emission of GRBs • Optical prompt emission ； • Early optical afterglow • Prior burst optical emission (if existing)； • Other short time-scale Optical Transients(OT) • Gravitational wave burst events • Early light curve of SNs • Tidal events of supermassive black holes • Micro-lensing • Neutrino bursts • Near earth objects (NEO) • Flare stars ……

  7. GWAC System: Parameters • Instruments: • GWAC:36 wide angle cameras with diameter of 18cm • Mini-GWAC:12 cameras with diameter of 7cm • Follow-up telescopes: • 2 dedicated 60cm telescopes • Several dedicated 30cm telescopes

  8. Parameters of GWAC • Cameras： 36 • Diameter： 180mm • Focal Length： 220mm • Wavelength： 500－800nm • Total FoV： ~5000Sq.deg • Limiting Mag： 16.0V（5，10sec） • Self Trigger: ~13*5sec Prompt optical emission detection down to MV ~ 16.0 (10 s exposure)

  9. Status: GFT for GWAC • 2014-2015: two 60cm, from GuangXi Uni. • 2015： one 30cm, from Huaibai Normal Uni.

  10. Status: Mini-GWAC • Having capability to trigger OT: • Oct. 2015: in operation， • ~10 flare stars detected, … • Mini-GWAC at Xinglong Obs.: • 12 CANON EF 85/f1.2 • 12U9000X CCDcameras • FoV: ~5000 Sq.Deg • Limiting Mag: ~12.5mag 2015.12.18：a Flare star，Time scale~700秒 2013.05.28 Light curve

  11. Light curves of GRBs （Wang et al. 2013） A light curve of a flare star （Mini-GWAC 2015） ------------------------------------- -------------------------- -------------------------- Mini-GWAC -------------------------- GWAC 700sec T-T0=30 sec T0

  12. GRB prompt detection efficiency Sites for GFTs and GWAC C-GFT GWAC F-GFT GWAC

  13. GWAC Follow-up Observation Strategy S P E C T R A 2M Telescops ~10Min T R I G G E R Follow-up M U L T B A N D ~1min ~1day P O T O M E T R Y S W I F T ? 1M NetWorks ~1hr + GWAC 60/30CM

  14. 2015.12.18: early spectra from the 2.16M

  15. GRB140629A ：Spectrum from 2.16M@~1hr Z=2.275

  16. The strategy for SVOM to observe GW bursts 2015 2019 2022 Error box: ~600 Sq.Deg ~>10 Sq.Deg. GRM Eclairs MXT VT GWAC

  17. March 2015: MoU between SVOM and LIGO/VIRGO

  18. 2015.12.26：Mini-GWAC first pointed to G211117 LIGO/Virgo G211117: List of near-term future observation regions by Project Mini-GWAC of SVOM • J.Y. Wei (NAOC), C. WU(NAOC), N.Leroy (LAL), L.P. Xin (NAOC), X.H. Han (NAOC), X.M. Meng(NAOC), L. Huang(NAOC), Y. Xu(NAOC), H.B. Cai(NAOC),J. Wang(NAOC), X.M. Lu(NAOC), Y.L. Qiu (NAOC), J.S. Deng(NAOC), L. Cao(NAOC),S. Wang(NAOC), E.W.Liang (GXU), Y.G. Yang (HBNU), B. Cordier(CEA),S.N. Zhang (NAOC),S. Basa (LAM), B.B. Wu(IHEP), Jean-Luc Atteia (IRAP), D. Götz (CEA), Cyril Lachaud (APC) on behalf of the SVOM Gravitational Astronomy group report: • We observed about 3200 square degree (8 sky regions) of the skymap of the advanced LIGO and Virgo trigger G211117, with Mini-GWAC(Mini Ground Wide Angle Camera), at Xinglong Observatory of NAOC equipped with U9000 camera(FOV~400 square degree/camera). Mini-GWAC comprises of 12 wide field angle cameras(aperture=7cm), working with unfiltered band. The observations are operated in time-series mode, taking one exposure in 15 seconds (10s exposure + 5s readout). The limit magnitude is ~12 mag in R band. The coordinates of the 8 regions and observation time are list following: The report to LIGO Mini-GWAC covered the north sky

  19. Current Status and Schedule Budget ~33 + ~30M ￥(10M USD) (~6000Sq.deg) 20M ￥ more? (~9000Sq.deg) • Mini-GWAC • 2011-14: ready for observation • GWAC • 2010-11：dome at Xinglong Obs. • 2010-12：40 CCD chips • 2010-13：engineering models • 2012-14: Pipelines ( V1.0) • 2015-16： 1/2 of GWAC • 2017： 1/2 of GWAC • Follow-up telescopes • 2015: two 60cm. • 2015： one 30cm • 2016-17: more 20cm • Re-set up at Chile • 2018/20： TBD

  20. Summary • GWAC is an dedicated instrument for short time scale optical transcients: • 10~20 GRBs per year will be monitored; • Several bursting SNs per year will be detected; • A promising instrument to detect GW counterparts. • Several years before SVOM launch: excellent chances to train BAs and Science Centers.

  21. Engineering models of GWAC----Camera(FoV + high image quality) + Mount

  22. Camera design and manufacture Optical design 装配图

  23. GWAC：大面阵e2v CCD • Oct. 2010：signed contract with e2v • July 2012: 40 4k4k back-illu. CCDs

  24. 2012.12.18 2013.1.4 • -50C ！ • Vacuum is stable Dowar with cooling system

  25. 目标温度：-71C 冷端：-71C 热端：+32.7C V：8.37V I：5.38A 平稳态 Sept. 24,2014, New Dowar, -70C! 目标温度：-70C 冷端：-66.1C 热端：+47.3C V：13V I：9.6A 全力上升中 目标温度：-50C 冷端：-49.9C 热端：+25.8C V：5.75V I：3.52A 目标温度：-71C 冷端：-71C 热端：+30.0C V：7.64V I：4.91A 当若真空度很好

  26. ？？ Detection prompt emission in visible will extend 3-4 orders to low energy band, to provide new chances to understand GRBs. ？ 10-6 Visible

  27. Comparing with the Existing Instruments GWAC is 2~3 orders more powerful !

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