10 years of grbs observations from the joint Russian-American konus-wind experiment: results and perspectives

10 years of GRBs observations from the joint Russian-American KONUS-WIND experiment: results and perspectives

• E.P.Mazets, R.L.Aptekar, D.D.Frederiks, S.V.Golenetskii, V.N.Il’inskii, V.D.Pal’shin, M.V.Ulanov

• A.F.Ioffe Physico-Technical Institute, St.Petersburg, Russia

• T.L.Cline, P.S.Butterworth

• NASA Goddard Space Flight Center, Greenbelt, Maryland, USA

Main results of the KONUS experiments on the “Venera 11-14” missions (1979-83)

• A number of types of GRBs with different time history and duration distribution were studied.

• Short GRBs were indicated as a separate class.

• Sources of soft repeating bursts were discovered.

• The energy spectra of GRBs were investigated. A rapid spectral variability was found.

• Localization of 160 sources of GRBs revealed their isotropic distribution on the celestial sphere.

GRBs bimodal distribution

• GRBs duration distribution. Data of Konus experiments on Venera 11-14 (1979 – 1983)

GRBs celestial distribution

• Konus GRBs distribution

Wind Instruments

Wind trajectory

• Wind trajectory during extended mission

• phase 10:

• Low-inclination phasing orbit

• July 2002 to November 2002

• XY (ecliptic plane) projection

Scientific objectives of Konus-Wind experiment

• study of GRBs including a determination of their occurence rate above a sensitivity threshold of ~ 10-7 erg cm-2, detailed measuring of the time histories of bursts with high time resolution of 2 – 64 milliseconds, detailed spectral measurements in the broad energy range of 10 keV – 10 MeV, investigations of a fast spectral variability on a time bin scale of a few milliseconds;

• precise localization of GRBs by means of an arrival time triangulation method together with other Interplanetary Network (IPN) spacecraft using the Wind s/c as a constant and effective vertex of the IPN;

• comprehensive study of the Soft Gamma Repeater (SGR) – very rare astrophysical objects in our Galaxy thought to be neutron stars with a huge magnetic field of 1014 - 1015 G – including a monitoring of a long-term variations of their activity and waiting for exceptional rare giant flares in SGR’s with energy release up to 1044 erg;

• detection and study much more slower gamma-ray transients especially those which are coming from objects believed to contain a black hole.

Konus-Wind Gamma-Ray Burst Experiment on US GGS-Wind spacecraft

• Two detectors S1 and S2:

• NaI(Tl) 13 cm diameter, 7.5 cm height, 12.5 cm Be window.

• Located on opposite faces of spacecraft, observing correspondingly the southern and northern celestial hemispheres

• Burst mode:

• Time history analyzer: resolution 2ms – 256 ms, total duration 230s

• 12 – 50 keV 4096 ch

• 50 – 200 keV 4096 ch

• 200 – 770 keV 4096 ch

Instrument description (continue)

• Pulse Height analyzer: accumulation time 64ms – 8.192 s, duration 79 – 492 s

• PHA1 12 – 770 keV 63 ch quasilog scale

• PHA2 0.2 – 10 MeV 63 ch quasilog scale

• Background mode: accumulation time 1.47 – 2.94 s

• Count rate:

• 12 – 50 keV

• 50 – 200 keV

• 200 – 770 keV

• > 10 MeV

Konus-Wind Summary

• Joint Russian-American experiment on US GGS-WIND spacecraft

• Launch: November 1, 1994

• Konus-Wind instrument switched on:

• November 11, 1994

• Orbit: beyond the magnetosphere of the Earth

• Observations:

• November 11, 1994 –December 18, 2004 ( 3689 days)

• Gamma ray bursts total 2524

• Burst mode 1419

• Background mode 1105

• Solar flares 729

Konus-Wind GRBs

• GRB 980706a – an example of short hard GRB.

• Ep = 1.6 MeV.

Konus-Wind GRBs

• GRB 041211 – a recent example of long multipeak hard GRB.

Duration distribution of Konus-Wind trigger GRBs

Fast spectral variability of GRB 991208

• KONUS-WIND GRB 991208 T0= 16613.263s UT

• Two pulses with clear spectral evolution

Fast spectral evolution of GRB 991208

• Pulse 1

Fast spectral variability of GRB 970828

Konus-Wind-Ulysses-Konus-A localization for GRB 970228

• GRB 970228 was localized by BeppoSAX WFC (IAUC 6572)

• Independent IPN Ulysses/Wind triangulation (IAUC 6593)

• X-ray and optical transient was found

• z = 0.695 ± 0.002

Localization of GRB 010109

Konus-Wind observations of Soft Gamma Repeaters

• Konus-Wind detected more than 150 trigger SGR bursts from 4 SGRs: 1900+14, 1806-20, 1627-41, 1801-23.

• Numerous SGR bursts were detected in the background mode

• Giant outbursts were detected from SGR 1900+14 and SGR 1627-41

• Series of bursts were detected from SGR 1900+14 and recently from SGR 1806-20 (GCN 2769)

• Now Konus-Wind continue to register bursts from SGR 1806-20, which stay in active state

SGR 0526-66

• Burst 790306 detected from SGR 0526-66 by Konus on Venera 11

Konus-Wind observations of SGR 1900+14

• Burst 790324 - the first burst detected from SGR 1900+14 by Konus on Venera-11

• Burst 980902b – a typical burst from SGR 1900+14 detected by Konus-Wind

SGR 1806-20

• Burst 040828 – the most intense burst (both in peak flux and fluence) detected by Konus-Wind from this SGR.

SGR 1627-41

• An intense burst 980625 from SGR 1627-41 which demonstrates strong spectral evolution typical for this SGR.

Giant outburst on 1998 August 27 (SGR 1900+14)

• Time and energy characteristics of the August 27 event.

• Top: Background subtracted light curve of the outburst. Horizontal sections with triangles specify count rates averaged over the period. The sloped dashed line is a plot of exp(-t/) for  = 91.5 s.

• Bottom: Horizontal sections with squares specify kT averaged over the period.

Giant outburst on 1979 March 5 (SGR 0526-66)

• Time and energy characteristics of the March 5 event.

• Top: Background subtracted light curve of the outburst. Horizontal sections with triangles specify count rates averaged over the period. The sloped dashed line is a plot of exp(-t/) relation for =100 s.

• Bottom: Horizontal sections with squares specify kT averaged over the period.

Giant outburst on 1998 June 18 (SGR 1627-41)

• Time and energy characteristics of the June 18 event.

• Top: Background subtracted light curve of the outburst. period. The rise time os about 100 ms.

• Bottom: Spectral evolution during the burst.

New SGR 1801-23

• New SGR was discovered by Wind, Kosmos2326, CGRO, and Ulysses

• Only 2 short bursts from this source were detected up to date

• Burst 970629b T0=23493.221 s UT

Giant outbursts from Gygnus X-1

• the Cyg X-1 outburst on 950325 as observed by Konus-Wind

• The narrow spike at 25,841 s in the beginning of interval B is the GRB that triggered a series of multichannel spectral measurements, covering the entire interval B. The gap after B was caused by the transmission of high-resolution data to the onboard tape recorder.

• Background levels are indicated by the dashed lines.

Giant outbursts from Gygnus X-1 (continue)

• Konus F spectrum of the outburst on 950325. The spectrum was accumulated during the decay stage of the flare over 360 s of interval B with moderate statistics. The solid curve is the result of the spectral fit. The spectral shape is consistent with that of the hard state of Cyg X-1.

Giant outbursts from Gygnus X-1 (continue)

• Konus 15–300 keV photon fluxes (background subtracted) and hardness ratios for the outburst on 020224. The time resolution is 23.552 s.

Konus-Wind observations of GRBs with known redshifts

• Konus-Wind has been successfully operating since November 1994. Of more than 30 GRBs with known redshifts, Konus-Wind has detected 23 GRBs in the trigger mode and 7 in the background mode. It is the largest subset of GRBs with known redshifts collected by one instrument.

Konus-Wind observations of GRBs with known redshifts: GRB 030329 (z=0.1685)

• Konus-Wind light curve of the famous GRB 030329.

• Fluence:

• (1.74±0.01)×10-4 erg cm-2.

• Peak Flux:

• (2.62±0.04)×10-5 erg cm-2 s-1

• 26 high resolution spectra were obtained with Ep varies from 30 to 180 keV.

Konus-Wind observations of GRBs with known redshifts

• Correlation of isotropic equivalent maximal Luminosity with Ep (in the source rest frame) for Konus-Wind GRBs with known redshifts.

Main scientific results of the Konus-Wind experiment

• in the course of Konus-Wind experiment more than 1400 GRBs were detected in a triggered mode with high time and spectral resolution;

• Time histories, energy spectra, a fast spectral variability, and inherent correlations in the bursts have been studied;

• the IPN with Konus-Wind as a basic vertex has precisely localized a large number of GRB sources by triangulation method, producing crucial data for the multiwavelength study of the GRB afterglows with many telescopes, both ground-based and in orbit;

Main scientific results of the Konus-Wind experiment (continue)

• A comprehensive study of SGRs was carried out. Two new sources, SGR1627-41 and SGR1801-23 were discovered in addition to three known SGRs. The Konus-Wind experiment was succeeded in detailed studying of the huge outburst in SGR1900+14 on August 27, 1998. It was the second observed giant flare in SGRs after the famous March 5, 1979 event in SGR0526-66. Third giant flare was observed from the new SGR1627-41.

• About more than 300 more common repeating bursts were observed in SGRs at revealed phases of their burst activity;

• Rare strong and long outbursts from Cygnus X-1 were discovered. Such type of its behavior represents a new feature of gamma-ray emission of binary system contained a black hole.

The Konus-Wind experiment data collection, archiving and dissemination.

• Obtained information are stored on CD ROM’s at GSFC and at Ioffe Institute. To make it available for scientific community several websites were opened.

• Time histories of GRB’s given with the time resolution of 64 ms are available though GCN website at GSFC (http://gcn.gsfc.nasa.gov ) immediately after receiving telemetry data on the ground.

• Two complete sets of an accumulated information, “Konus Catalog of Soft Gamma Repeater Activity: 1978 to 2000” and “Konus Catalog of Short GRBs” are presented on the Ioffe Institute websites at http://www.ioffe.rssi.ru/LEA/SGR/Catalog/ ,and http://www.ioffe.rssi.ru/LEA/shortGRBs/Catalog/ , respectively.

• The complete catalog of all observed GRBs is now in preparation

Perspectives of the Konus-Wind experiment

• The Konus-Wind experiment remains an important source of time resolved GRB’s spectral data in the wide energy range from 15 keV up to 12 MeV. This information is a real contribution in the GRB’s multiwavelength study as a whole and especially for GRBs detected by SWIFT, since the spectral coverage of the SWIFT BAT instrument is extremely limited (about 20 – 150 keV). Recent developments in our understanding of GRBs suggest that broad-band spectral information about prompt GRB emission can provide important constrains on models.