The HETE-2 Mission D. Q. Lamb (U. Chicago)

Outline of This Talk  HETE-2 Mission Goals and Program  HETE-2 Spacecraft and Instruments  French Gamma Telescope (FREGATE) (6-400 keV)  Wide-Field X-Ray Monitor (WXM) (2-25 keV)  Soft X-Ray Camera (SXC) (2-10 keV)  Spacecraft and Instrument Operations  Summary of First Two Years of HETE-2 Mission  HETE-2 Mission Future

HETE-2 International Science Team Cosmic Radiation Laboratory Institute of Physical and Chemical Research (RIKEN) JAPAN Masaru Matsuoka Nobuyuki Kawai Atsumasa Yoshida Centre D’Etude Spatiale des Rayonnements (CESR) FRANCE Jean-Luc Atteia Michel Boer Gilbert Vedrenne Brazil + India + Italy (Burst Alert Station Scientists) Joao Braga Ravi Manchanda Graziella Pizzichini Los Alamos National Laboratory Los Alamos, NM USA Edward E. Fenimore Mark Galassi Space Science Laboratory University of California at Berkeley, CA USA Kevin Hurley J. Garrett Jernigan Astronomy and Astrophysics Department University of Chicago, IL USA Donald Q. Lamb Jr. Carlo Graziani Tim Donaghy Board of Astronomy and Astrophysics University of California at Santa Cruz, CA USA Stanford E. Woosley Thomas L.Cline (NASA Project Scientist ) Goddard Space Flight Center Greenbelt, MD USA Center for Space Research Massachusetts Institute of Technology Cambridge, MA USA George R. Ricker (PI) Geoffrey B. Crew John P. Doty Alan M. Levine Roland K. Vanderspek Joel Villasenor (Mission Scientist)

High Energy Transient Explorer HETE ~ 1st Dedicated  -Ray Burst Satellite ~ GOALS: Locate GRBs Accurately (~10' - 10" ) Distribute Locations in Near Real-Time (~ s delay) Measure multi-wavelength spectra [ Soft X-ray ~  -ray; 2 keV ~ 400 keV ] PROGRAM: University-managed; NASA +Japan+France University-constructed spacecraft and ground stations Mission of Opportunity 1/3 cost of NASA Small Explorer (SMEX) Mission Goals And Program

HETE During Ground Testing

Science Instrument Package Soft X-ray Cameras (SXC): 2-10 keV; ~40” localizations Wide-Field X-ray Monitor (WXM): 2-25 keV; ~5’-10’ localizations French Gamma-ray Telescope (FREGATE): keV; ~π FOV

HETE-2 Launch qHETE-2 was successfully launched on 9 October 2000 from Kwajalein in the Marshall Islands. qLaunch vehicle was a Pegasus rocket. qHETE-2 is in an equatorial orbit.

HETE-2 Primary and Secondary Ground Stations  Three primary ground stations and 14 secondary ground stations designed, built, and maintained by the HETE-2 science team.  When HETE-2 detects a GRB, burst alert is sent by VHF radio to secondary ground station, then via Internet to MIT and to 700 astronomers and observatories around the world.  Thus HETE-2 pinpoints location of burst and provides it in “real time” to the astronomical community.

HETE-2 Operations qFREGATE is now always on; WXM now on for ~ 55 minutes/orbit qSpacecraft instruments generally point anti-sun (every GRB localized by HETE-2 can be observed by ground-based and space-based optical, radio, and X-ray telescopes) qDuring May-August when Galactic Plane would be in FOV of instruments, HETE-2 “head nods:” q Before dusk terminator and after dawn terminator, HETE-2 slews as much as 40 degrees in order to keep Galactic plane (and esp. Sco X-1) out of FOV of instruments q Head nodding may also be done at other times for calibration purposes (e.g., using the Crab nebula, Sco X-1, and XRB sources) qThe direction that HETE-2 will be pointing during the next 6 orbits is always available (and can be automatically downloaded) from the HETE-2 website:

 Soft Gamma Repeaters (SGRs):  25 SGR events in Summer 2001 (14 triggered + 11 untriggered)  SGR , SGR  2 SGR events in Summer 2002  X-ray Bursts (most XRBs do not trigger; thus, no GCN Burst Alert):  ~670 X-ray bursts detected:  170 in Summer 2001  500+ in June-August 2002  ~20 different XRB sources localized with WXM  ~10 different XRB sources localized with SXC Non-GRB Results from Two Years of HETE-2 Operations

 Classical GRBs:  33 GRB localizations by WXM  9 optical counterparts; 7 redshifts (so far)  1 “short, hard” GRB localized (GRB )  Current HETE-2 localization rate ~ 25 localizations yr - (14 in past 6 months)  ~250 FREGATE GRBs (120 coincident w. other S/C). GRB Results From Two Years of HETE-2 Operations  “X-ray Rich GRBs:”  23 detected and 14 localized with log (S_x/S_gamma) > -0.5  7 are “X-ray flashes” (XRFs: Heise et al. 2002); i.e., log (S_x/S_gamma) > 0  In other respects, they are similar to “classical GRBs”

HETE-2 Mission Future qHETE-2 spacecraft and instruments are working well qMany real-time WXM GRB localizations have been sent out qReal-time SXC localizations will soon be possible q“Gating” (using spacecraft and ground software) now exits that will enable HETE-2 to provide real-time localizations of XRFs (this will be difficult for Swift) qHETE-2 orbit is high enough that operations can continue for > 10 years, if spacecraft and instruments continue to function (HETE-2 is currently funded through FY04 )