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How the Swift mission responds to alerts

How the Swift mission responds to alerts

Paul O'Brien
LOFAR TKP Meeting, Amsterdam, June 2011



June 17, 2012


  1. 1! How the Swift mission responds to alerts Paul O’Brien

    University of Leicester
  2. 2! •  Burst Alert Telescope (BAT) (~1/6 sky) –  CdZnTe

    detectors (32768) –  Detect ~100 GRBs per year •  X-Ray Telescope (XRT) (23ʹ FoV) –  Arcsecond positions –  CCD spectroscopy •  UV/Optical Telescope (UVOT) (17ʹ FoV) –  Sub-arcsec imaging –  Grism spectroscopy •  Autonomous operation with very fast slew (~1o second-1) •  Rapid data download via TDRSS, alerts sent out over GCN/VOEvent •  Bulk data download via ground station – processed in ~2hrs •  ALL data are public immediately Spacecraft BAT XRT Spacecraft UVOT BAT UVOT XRT The Swift Gamma Ray Burst Explorer “Catching Gamma Ray Bursts on the Fly”
  3. 3! Communication made simple You

  4. 4! The GCN System (adapted from Scott Barthelmy) •  Three

    basic activities: –  NOTICES: Collect GRB locations from various s/c and distribute them to interested parties. –  CIRCULARS: Collect reports from burst follow-up observers & distribute them to the GRB community. –  REPORTS: Collect full/detailed/final reports from burst follow-up observers & distribute them to the GRB community. •  These activities compliment each other –  Notices for the real-time observation needs. –  Circulars for the humans-in-the-loop after-the-observations. –  Reports provide the final (full analysis) reference. •  GCN also talks VOEvent for those who use it (like LOFAR)
  5. 5! Distribution Methods (adapted from Scott Barthelmy) •  Internet Socket

    (for the robotic instruments) –  4 msec to write to 65 sockets –  0.01-2.0 sec roundtrip travel time (~0.3 sec 98-percentile) –  Each end can break/make the connection at will; there are re-try loops. –  Software provided (socket_demo.c from the web site). •  E-mail (for the humans) –  9 msec to generate the ~250 email commands –  40 sec to execute those commands –  0.1-2 min for delivery •  Pagers & Cell-phones (also for humans) –  Uses e-mail –  Multiple formats for the various service providers: long, short & subject- only. •  Web site (“pull” technology) –  Archive all the Notices & Circulars, LightCurves, Images, Spectra, etc.
  6. 6! Swift real-life operations •  Swift is “up” ~98% of

    the time •  Slews accurate to ~3’ >99% •  Standard day is very complicated –  Several GRBs –  4-5 ToOs –  GI and Fill-in targets •  Typically 70-75 observations per day •  ToOs triggered in 5 ways: –  Highest, 4hrs (wake up the PI!) –  High, 24 hrs –  Medium, days - weeks –  Low, weeks – months –  Observing campaign (GI) http://www.swift.psu.edu/too.html
  7. 7! Cont.

  8. 8! Follow-up observations Swift has a follow-up network of dozens

    of telescopes: •  Fully robotic response (e.g. ROTSE, FT, P60, REM…) •  Rapid trigger but with human in the loop (e.g. VLT, Gemini, XMM-Newton…) •  Later trigger (e.g. HST, Chandra…) These facilities provide vital data: redshifts, light curves (from radio to X-ray) and some non-electromagnetic data (neutrinos, gravity waves) VLT RRM alert
  9. 9! Summary •  Swift is an ideal high-energy complement to

    LOFAR – provides rapid-response gamma-ray, X-ray and optical/UV data •  Swift has “standard” response protocols in place for Fermi, MAXI, LIGO, IceCube etc. (some including tiling patterns) •  Follow-up of LOFAR sources is an accepted Swift “Key Project” (PIs: O’Brien, Brocksopp, Wijands, Jonkers) – exactly how to handle multiple science goals is TBD •  LOFAR will also receive alerts from Swift and could participate in monitoring campaigns (should someone apply for GI time?)