HETE (High Energy Transient Explorer) and GRBs

HETE first launch (failed): Nov. 4, 1996. HETE second launch (HETE-2) : Oct .9, 2000.

HETE’s energy range

Blue: HETE Red: Swift

GRB030329: HETE “Hits a Home Run”(Don Lamb’s quotation)

z = 0.1675 probability of detecting a GRB this close by is ~1/3000unlikely that HETE-2 or Swift will see another such event.First localization by HETE released after 73 minutes (HETE can do much better), first optical detection after 37 more (Peterson & Price).

Vanderspek et al. (2003)

GRB030329: Implications

HETE-2—localized burst GRB030329/SN 2003dh confirms the GRB – SN connection.

Quotation from Palumbo, Pizzichini & Vespignani, 1974: “If one assumes that the burst is of extragalactic origin, the energy output would call for a supernova explosion……”,

Quotation from S. Colgate, 1959, to the Russian delegation of the conference in Geneva for the cessation of nuclear testing in space: “SNe or something like them might trigger our treaty detectors in orbit, causing us to lob nuclear weapons at each other”.

HETE-2 Observations of GRB021211

Crew et al. (2003) first HETE localization after 33 sec., OT reported by Fox & Price (GCN 1731) after 53’17”.

GRB021211: Afterglow Light Curve Relative to Those of Other GRBs

The optical afterglow of some bursts is much fainter (~ 3 mag) than those previously observed: without HETE’s prompt localization, this GRB would very likely have been listed as “dark”, instead of “dim”. But it proves that at t < 10 min even “dim” afterglows may be bright (m ~ 13). This is very promising for Swift.

Fox et al. (2003)

Are GRB021211 and GRB030329 unusual events?

They fit the Epeak-Erad Amati relationship, also if corrected by the jet opening angle (graph from Ghirlanda, Ghisellini & Lazzati 2004), but 030329 has lower Epeak,Erad

They are both XRR, but with a different duration: T90 = 2.41s for 021211 and 22.86s for 030329

CONCLUSION: we CANNOT TELL from the GRB if it is coincident or not with a SN.

Why did it take so long to find the GRB-SN connection?

Even when GRBs where still not well and promptly localized, we might have found the SN-GRB connection as an excess of coincidences within fixed time intervals: why did not we find them?

We do not detect all SNe and all GRBs.

GRBs are highly directional, thus we detect only a small fraction of them.

We detect SNe at most at redshift 1, while for a large fraction of GRBs the detected redshift is larger:

SN1998bw z=0.0085; SN2003dh z=0.1685, GRB021211 z= 1.006, GRB031203 z= 0.1055

HETE-2 extends “Amati’s relationship” to XRFs and X-ray Rich GRBs: same phenomenon?

Sakamoto et al. (2003)

Long and short GRBs

HETE-2 is Solving Mystery of “Optically Dark” GRBs

Two explanations of “optically dark” GRBs have been widely discussed: Optical afterglows are extinguished by dust in the host

galaxy (see, e.g., Reichart and Price 2001), GRBs lie at very high redshifts (Lamb and Reichart 2000).

Rapid follow-up observations of HETE-2—localized burst GRB030115 show that this burst is best case to date of extinction by dust.

Rapid follow-up observations of HETE-2—localized burst GRB021211 show that this burst is “optically dim” – without rapid follow-up would have been classified as “optically dark”.

FREGATE and WXM

The YB counter of the WXM is not working since 2003 January 11

SXC

Built by MIT/CSR Dimensions: 10 cm x 10 cm x 17.5 cm Effective area 7.4 sqcm per unit Two CCDs per SXC 2048 x 4096 15 micron pixels Energy range: 0.5 to 14 keV Spectral resolution: 46 eV @ 525 eV, 129 eV @ 5.9 keV Detector quantum efficiency: 93% @ 5 keV, >20% (0.5-14 keV) Timing resolution: 1.2 s Field of View: 0.91 sr Focal plane scale: 33” per CCD pixel Burst sensitivity: (4 sigma) ~ 700mcrab t**(-1/2) Localization precision: 15” (5 sigma burst) to 3” (22 sigma burst)

HETE-2 Observations of GRB 020531

GRB 020531 is the first detection of a short, hard GRB that has allowed rapid (t = 2-3 hours) optical and X-ray follow-up observations: none from BeppoSax in 6 years . First HETE error box after 88 minutes.

X-Ray afterglow detected (Butler et al. 2002), no optical detection. Probably need even faster localizations.

Lamb et al. (2002)

HETE-2 RESULTS on GRBs

HETE-2 : Instruments: Fregate 6-400 keV, 3 sr; WXM 2 – 25 keV, 1.6 sr; SXC 0.5

keV, o.91 sr. HETE’s main task: fast (even < 1 minute) and precise (even <3 arcmin)

localization of GRBs: is currently localizing ~ 20 (?)GRBs yr^-1, many more are detected, but not

localized, has localized 55 GRBs so far, delays ranging from < 1 minute for onboard

error boxes to 2 – 3 hours for refined ground locations, 8 of these localizations have led to the detection of X-ray afterglow, 18 to

optical and 5 to radio afterglows, 13 of these afterglows have led to redshift determinations. Including HETE events, 183 GRBs well localized since 1996, detected

afterglows: 54 X-rays, 51 optical, 27 radio (BSAX 57, 30, 19, 12 in 6 years). HETE is a small mission : height 89 cm, width < 47 cm, weight <124 Kg: no

pointing instruments for afterglow observations. Implications of HETE-2 and follow-up observations for:

GRB-SN connection, Short, hard GRBs, “Optically dark” GRBs, X-Ray Flashes (XRFs) and X-ray-rich GRBs, Nature of GRB jets.

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 AtteiaMichel 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. FenimoreMark 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 GrazianiTim 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. VanderspekJoel Villasenor

(Mission Scientist)

IASF/CNR, Bologna:Graziella Pizzichini,Ennio Morelli, Fulvio Gianotti,Patrizia Ferrero

HETE-2 is a very small spacecraft

HETE-2 compared to some X and Gamma-Ray experiments.

Weight: < 124 Kg. Height: 89 cm. Width approx. 47 x 47 cm.

HETE: most data are public immediately

Burst locations, light curves, spectral information and a possible estimate of z for all HETE GRBs are free and available as soon as possible via the public HETE web page. This fit (red line) of the GRB030329 HETE light curve was published on the preprint server astro-ph on April 6, 2003 (Dado, Dar & De Rujula).

Up to now there are 58 papers and preprints on this event, plus 187 GCN messages.

HETE GRB rates