The HETE-2 Mission and GRBs

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

Why work on GRBs?The first GRBs detected by an Italian instrument, the second error box not fron IPN

Why Optical Observations of GRB Afterglows?See Pedersen et al., Nature, 1984 (It was an SGR in N49, but no one knew that)

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. is currently localizing ~ 25 GRBs yr^-1, many more are detected, but

not localized has localized 41 GRBs so far, delays ranging from < 1 minute for

onboard error boxes to 2 – 3 hours for refined ground locations 14 of these localizations have led to the detection of X-ray, optical,

or radio afterglows 11 of these afterglows have led to redshift determinations

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

Which hardware did we contribute to HETE?

In order to disseminate fast on-board burst alerts and locations, HETE needs to be constantly in contact with a chain of “Secondary Ground Stations” along its equatorial orbit. Our double SGS , funded by ASI and hosted by CRPSM, is located in the San Marco base in Malindi, Kenia. It was set up by Ennio Morelli and Fulvio Gianotti. We constantly monitor it.

Funding: only ASI, residual from 2002, ~ 20000 euro “mesi-uomo” 24 (11 + 9 + 2 + 2)

HETE’s future

HETE’s operations are approved by NASA until July 2004. New “senior review” in 3 months shall decide on further extension HETE is complementary to Swift and INTEGRAL: it observes a

different part of the sky than both of them and it detects and localizes very well also XRFs, while Swift shall detect mostly “classical”, i.e. > 30 keV GRBs.

HETE points in the “anti-sun” direction, its GRB locations are well suited for optical observations.

Note: HETE was built for GRBs, but it detects also many x-ray flashes and SGR events. It has probably discovered a new SGR source.

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

z = 0.1675 probability of detecting a GRB this close by is ~1/3000=> unlikely that HETE-2 or Swift will see another such event

Vanderspek et al. (2003)

GRB030329:Spectrum of SN 2003dh

Stanek et al. (2003)

GRB030329: Implications

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

Science Magazine lists this one and other HETE result as one of the top ten in 2003, actually the only one in Astrophysics, and explicitly mentions HETE’ results and HETE’s key “Team work”

Implications: We must understand Type Ib/Ic core collapse SNe in order to

understand GRBs and GRBs in order to fully understand Type Ib/Ic core collapse SNe

GRBs are a vital laboratory for studying core collapse SNe GRBs occur out to high z , and are therefore a powerful probe of

cosmology and the early universe 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……”

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 .

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

Lamb et al. (2002)

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”

HETE-2 Observations of GRB021211

Crew et al. (2003)

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)

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

Sakamoto et al. (2003)

Conclusions

HETE-2 has confirmed the GRB – SN connection HETE-2 and Chandra follow-up observations of short, hard

GRB 020531 show that its X-ray afterglow is > 100 x fainter than is typical of long GRBs (Swift XRT observations likely crucial)

HETE-2 is solving the mystery of “optically dark” GRBs: HETE-2 and follow-up observations of GRB030115 have provided

the best example so far of a GRB which is “optically dark” because of extinction by dust (Swift XRT should detect all of these)

HETE-2 and follow-up observations of GRB021211 have shown that the afterglows of some GRBs can be much fainter than those observed previously (i.e., they are “optically dim,” rather than “optically dark”); yet these afterglows can be very bright at t < 10 minutes after the burst (Swift UVOT should detect most of these)

Other “optically dark” GRBs are expected to lie at very high redshifts (Lamb and Reichart 2000); we hope HETE-2 will soon detect some – and Swift many!

HETE-2 observations have provided strong new evidence that XRFs, “X-ray-rich” GRBs, and GRBs are the same phenomenon; and that a unified (uniform) jet model can explain them all

Observations of GRB afterglows from Loiano: GRB021004

TOO Observations of GRB optical afterglows made at the 152 cm telescope of the Bologna Observatory in Loiano, in collaboration with C. Bartolini, A, Guarnieri and A. Piccioni of the Department of Astronomy of the University of Bologna, for a short time also with N. Masetti (IASF/CNR, Bologna).We try as much as possible to makemultifilter observations, in order to further confirm the findings of Simon, Hudec, Pizzichini & Masetti, 2001 on the colors of afterglows. THE FUTURE: we expect many more TOO observations also from INTEGRAL and Swift GRBs.

Observations of optical afterglows from Loiano: GRB030226

Observations of optical afterglows from Loiano: GRB030328

Observations of Optical Afterglows from Loiano: GRB030418