GRB 080407: an ultra-long burst discovered by the IPN

0.19 MB·English

by  V. Pal'shin

GRB 080407: an ultra-long burst discovered by the
IPN
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1
0
2
∗
V. Pal’shin
n
IoffePhysicalTechnicalInstitute,St. Petersburg,194021,RussianFederation
a
J E-mail:[email protected]

2
2 K. Hurley

U.C.BerkeleySpaceSciencesLaboratory,7GaussWay,Berkeley,CA94720-7450,U.S.A.
]
E E-mail:[email protected]
H
J. Goldsten
.
h AppliedPhysicsLaboratory,JohnsHopkinsUniversity,Laurel,MD20723,U.S.A.
p
E-mail:[email protected]
-
o
r I. G. Mitrofanov
t
s InstituteforSpaceResearch,Profsojuznaja84/32,Moscow117997,RussianFederation
a
E-mail:[email protected]
[

1 W. Boynton
v
UniveristyofArizona,LunarandPlanetaryLaboratory,Tucson,AZ85721,U.S.A.
3
0 E-mail:[email protected]
2
5 A. vonKienlin
. Max-Planck-InstitutfürextraterrestrischePhysik,Giessenbachstrasse,Garching,85748
1
0 Germany
3 E-mail:[email protected]
1
:
v J. Cummings
i
X NASAGoddardSpaceFlightCenter,Code661,Greenbelt,MD20771,U.S.A.
E-mail:[email protected]
r
a
M. Feroci
INAF/IASF-Roma,viaFossodelCavaliere100,00133,Roma,Italy
E-mail:[email protected]
R. Aptekar,D. Frederiks,S. Golenetskii,E.Mazets,D.Svinkin
IoffePhysicalTechnicalInstitute,St. Petersburg,194021,RussianFederation
E-mail:[email protected],[email protected],
[email protected],[email protected],[email protected]
D. Golovin,M.L.Litvak,A.B.Sanin
InstituteforSpaceResearch,Profsojuznaja84/32,Moscow117997,RussianFederation
E-mail:[email protected],[email protected],[email protected]
C. Fellows,K.Harshman
(cid:13)c Copyrightownedbytheauthor(s)underthetermsoftheCreativeCommonsAttribution-NonCommercial-ShareAlikeLicence. http://pos.sissa.it/
UniveristyofArizona,LunarandPlanetaryLaboratory,Tucson,AZ85721,U.S.A.
E-mail:[email protected],[email protected]
R. Starr
PhysicsDepartment,TheCatholicUniversityofAmerica,Washington,DC20064,USA
E-mail:[email protected]
A. Rau,X.Zhang
Max-Planck-InstitutfürextraterrestrischePhysik,Giessenbachstrasse,Garching,85748
Germany
E-mail:[email protected],[email protected]
V. Savchenko
ISDCDataCentreforAstrophysics,Ch. d’Ecogia16,1290,Versoix,Switzerland
E-mail:[email protected]
S. D.Barthelmy,N.Gehrels,H.Krimm, D.Palmer
NASAGoddardSpaceFlightCenter,Code661,Greenbelt,MD20771,U.S.A.
E-mail:[email protected],[email protected],
[email protected],[email protected]
E. DelMonte,M. Marisaldi
INAF/IASF-Roma,viaFossodelCavaliere100,00133,Roma,Italy
E-mail:[email protected],[email protected]
WepresentobservationsoftheextremelylongGRB080704obtainedwiththeinstrumentsofthe
InterplanetaryNetwork(IPN).Theobservationsrevealtwo distinctemissionepisodes,separated
bya∼1500slongperiodofquiescence.Thetotalburstdurationisabout2100s. Wecomparethe
temporalandspectralcharacteristicsofthisburstwiththoseobtainedforotherultra-longGRBs
anddiscussthesecharacteristicsinthecontextofdifferentmodels.
Gamma-RayBursts2012Conference-GRB2012,
May07-11,2012
Munich,Germany
∗
Speaker.
(cid:13)c Copyrightownedbytheauthor(s)underthetermsoftheCreativeCommonsAttribution-NonCommercial-ShareAlikeLicence.
GRB080407:anultra-longburstdiscoveredbytheIPN V.Pal’shin
1. Observations
The first emission episode of GRB 080704 was detected at about 74529 s UT (20:42:09) on
July 4th 2008. It displays a bright initial pulse followed by two weaker pulses – see Fig. 1. The
total duration of the episode is ∼160 s (T = 142.2±1.5 s in the 21–1360 keV band1). The
90
whole episode was observed by Konus-Wind, INTEGRAL-SPI-ACS, and Swift-BAT (outside of
the coded FoV). The initial pulse was also detected by AGILE (SuperAGILE & MCAL), Mars
Odyssey(GRS&HEND),andMESSENGER(GRNS).
Thesecondepisodewasdetectedatabout76000sUT(21:06:40), i.e. ∼1500saftertheonset
oftheburst. Itshowstwobroadpulseswithatotaldurationof∼400sandaweakeremissionbefore
the pulses – see Fig. 1. Both pulses were detected by INTEGRAL-SPI-ACS,Swift-BAT (outside
ofthecodedFoV),andMESSENGER(GRNS).ThefirstpulseisalsodetectedintheHENDdata,
however, the time interval of the second pulse is strongly affected by noise spikes. Unfortunately
this episode was seen by Konus-Wind only in the housekeeping data (80–360 keV range, 3.68 s
resolution) duetodatareadoutafterthetriggerontheinitialpulse,sonospectraldataareavailable
forthisepisode.

1.3x105 2500
counts / s11..12xx110055 INTEGRAL-SPI-ACS (0.1 - 10 MeV) 112050000000 A C B G1 (21-83 keV)
1.1x105
counts / s 246800000000 Konus-Wind 80-360 keV counts / s 1125050000000000 G2 (83-360 keV)
counts / s 678000000000 Swift-BAT 25 - 350 keV 246000000 G3 (360-1360 keV)
5000 0
counts / s 122505000 ME SSENGER (GRNS) 40 - 200 keV G2/G1 0112....5050

100 0.0
counts / s 200 Mars Odyssey (HEND) 5 0 keV - 3 MeV (rebinned to 10 s) G3/G2 000...123

150 0.0
0 500 1000 1500 2000 2500 0 20 40 60 80 100 120 140 160 180 200
T-T0 (s) T - T0 (s)
Figure 1: GRB 080407light curve. Left: fulllight curve as observedby differentIPN instruments. T =
0
∗
T (KW)=74529.471sUT(20:42:09.471)(*–correctedforthepropagationtimedelaytoEarth;T (KW)
0 0
–theKonus-Windtriggertime). NumerousnoisespikeshavebeenremovedfromtheHENDlc. Right: first
emissionepisodeinthreeenergybandsandhardnessratiosasobservedbyKonus-Wind.
2. IPN localization
We have triangulated the first episode to the rather small 3 sigma error box shown in Fig. 2
(leftpanel). Theerrorboxareais582sq. arcmin,anditsmaximumdimensionis2.67deg. Forthe
second episode we have derived the rather large 3 sigma error box shown in Fig. 2 (right panel).
The error box area is 17.1 sq. deg. This box contains the small box for the first episode. The
coordinates oftheboxesaregiveninTable1.
1asobservedbyKonus-Wind
2
GRB080407:anultra-longburstdiscoveredbytheIPN V.Pal’shin
RA(J2000) (deg)
RA(J2000) (deg)
190 185 180 175
182.5 182.0 181.5 181.0 180.5 180.0 15o 15
-2o 30’ -2.5 Swift-MESSENGER GRB 080407
GRB 080407
-3o 00’ Wind (Konus) - Mars Odyssey (GRS) -3.0 10o 10
-3o 30’ -3.5
-4o 00’ -4.0 5o 5
Dec (J2000)---455ooo 303000’’’ Wind (Konus) - MESSENGER (GRNS) ---554...505 Dec (J2000) (deg) Dec (J2000) -50oo INTEGRAL - Mars Odyssey IPN box for the fisrt episode -05 Dec (J2000) (deg)
-6o 00’ -6.0
-10o -10
-6o 30’ -6.5
-7o 00’ -7.0 -15o -15
12h10m 12h08m 12h06m 12h04m 12h02m 12h00m 12h40m 12h20m 12h00m 11h40m
RA (J2000) RA (J2000)
Figure2: IPNerrorboxesforGRB080407. Left: forthefirstepisode. Right:forthesecondepisode.
Table1: IPNlocalizationofGRB080407
firstepisode secondepisode
RA(2000),deg Dec(2000),deg RA(2000),deg Dec(2000),deg
Center 181.151(12h04m36s) -5.110(-5d06’34")
Corner1 180.589(12h02m21s) -6.136(-6d08’11") 187.413(12h29m39s) +12.295(+12d17’42")
Corner2 180.851(12h03m24s) -5.789(-5d47’22") 185.204(12h20m49s) +7.311(+7d18’39")
Corner3 181.852(12h07m24s) -3.787(-3d47’13") 178.760(11h55m02s) -6.199(-6d11’56")
Corner4 181.499(12h06m00s) -4.327(-4d19’38") 176.185(11h44m44s) -11.005(-11d00’17")
To estimate the probability of chance coincidence we can multiply the relative area of the
large error box (that is W /4p sr = 17.1 sq. deg/ 41252 sq. deg = 4.1×10−4) by the probability
to have two bursts in t .1500 s (that is, for the 2008 IPN detection rate, R, of ∼250 GRBs/year,
p=1−exp(−Rt)≃0.012) to get ∼5×10−6. Multiplying this number by the total number of
GRBsdetected bythe3rdIPNsofar(∼6000), wegeta3% probability ofobserving suchaclose
(intimeandonthesky)pairofIPNeventsfortheentire3rdIPNhistory. Actually thisprobability
issignificantly overestimated sincewecountedallIPNbursts, ratherthanjustthosebright enough
tobedetected bytheleastsensitiveinstrument intheIPN,MOHEND.
Thissimpleestimateshowsthattheseepisodes likelybelongtothesameultra-long GRB.
3. Spectral analysisandenergetics
The Konus-Wind spectral data from 20 to 1200 keV for the first episode were fitted by the
GRBM(Band)modelforthreespecifictimeintervalsdenotedonFigure1(rightpanel). Theresults
are given inTable2. Allspectra have ahigh-energy power-law tailwithb ∼−2.3. Thespectrum
of the weaker pulses at ∼T +117 s is significantly softer (in terms of E ) than the spectrum of
0 peak
theinitialbrightpulse.
Using the parameters of the time-integrated spectrum (Int. C), the calculated fluence of this
episode is(1.43±0.04)×10−4 erg cm−2,andthepeakfluxis(7.76±0.38)×10−6 ergcm−2 s−1
asmeasuredfrom10.4sona1stimescale(bothinthe20–1000 keV)2.
Therearenospectraldataforthesecondepisode. Comparisonofthecountsaccumulatedover
several time intervals by different instruments shows that the hardness of the second episode is
2inthe20keV-10MeVbandtheyare(2.01±0.27)×10−4 ergcm−2and(1.08±0.10)×10−5 ergcm−2s−1.
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GRB080407:anultra-longburstdiscoveredbytheIPN V.Pal’shin
Table 2: SpectralparametersofGRB 080407forthreetime intervalsdenotedonFig. 1(rightpanel). All
errorsareat90%CL.
Int Tstart(s) dT(s) a Epeak(keV) b c 2/dof(nullhypothesisprobability)
A 0 43 -1.02±0.06 325+−2295 -2.43−+00..2176 60.8/59(0.41)
B 117 41 -1.49+−00..7367 114+−7474 -2.25(<-2.02) 48.3/59(0.84)
C(total) 0 158 -1.15+−00..1009 287+−4325 -2.35−+00..4200 57.1/59(0.54)
Table3: Ultra-longGRBs
GRB Tstart dT Fluence lcshape z Eiso Refs.
sUT s ergcm−2 erg
840304 ? ∼1200 ∼2.8×10−3 Twobroadpulses(∼200s) - ∼7.6×1054 [6]
+extendedtail(∼1000s) (forz=1)
971208 28092 ∼2500 (2.55±0.11)×10−4 Single smooth FRED-like - ∼6.9×1053 [1,3,10]
(07:48:12) pulse (forz=1)
020410 38380 ∼1600 ∼2.8×10−5 Multi-episode ≃0.5 ∼1.8×1052 [9,7]
(10:39:40)
060814B 37070 ∼2700 (2.35±0.22)×10−4 Single smooth FRED-like - ∼6.4×1053 [10]
(10:17:50) pulse (forz=1)
080407 74529 ∼2100 ∼4.5×10−4 Multi-episode - ∼1.2×1054 thiswork
(20:42:09) (forz=1)
091024 32161 ∼1200 (1.13±0.12)×10−4 Multi-episode 1.09 ∼3.5×1053 [8,4,5]
(08:56:01)
closertothehardnessoftheweakerpulsesofthefirstepisode. Usingaconversion factorof1SPI-
ACScount=(4.1±0.5)×10−10 ergcm−2 (obtained fortheweakerpulsesofthefirstepisode;for
the initial pulse this factor is (2.31±0.04)×10−10 erg cm−2 cnt−1), the estimated fluence of this
episodeis∼3×10−4ergcm−2. SothetotalfluenceofGRB080704isabout4.4×10−4ergcm−2.
4. Comparisonwithother ultra-long GRBs
Table 3 contains a comparison of the parameters of the six classical gamma-ray bursts with
durations >1000 s. It does not include very long underluminous XRFs like XRF 060218, which
arethoughttobeadifferentphenomenon fromclassical GRBs. Thetablealsodoesnotlistseveral
ultra-long GRB candidates found in the BATSE data [11], since it is difficult to establish reliably
thatthevariousemissionepisodes belongtothesameGRB.
OnlyashortnoteonGRB840304hasbeenpublished, soitisnotquiteclearwhetheritreally
belongs totheclassofultra-long GRBsandhasaverylargefluence.
Incommonthese ultra-long GRBshavelarge fluences (except GRB020410 whichhasrather
moderatefluence)duetotheirverylongdurationsandrather hardspectrawithE ofhundredsof
peak
keV.Buttheyhavequitedifferent morphologies: GRB971208 andGRB060814B showsasingle,
smooth, FRED-like pulse, whereas GRB 020410, GRB 080407, and GRB 091024 show several
emissionepisodes separated bylongperiod(s) ofquiescence.
There is also a difference in the light curves of GRB 080407 and two other multi-episode
bursts: GRB080407showsabright initialpulsefollowedbysubstantially weakerpulses, whereas
GRB 020410 and GRB 091024 do not display a decrease of pulse intensities with time (on the
contrary, the last pulse of GRB 091024 is brighter that the first one). But in all three cases the
initialpulseissignificantly harderthansubsequent ones.
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GRB080407:anultra-longburstdiscoveredbytheIPN V.Pal’shin
5. Summary
Only a few ultra-long GRBs (with durations > 1000 s) have been reported to date. We have
presented observations of GRB 080407, probably the longest multi-episode GRB detected so far.
Themeasuredburstfluenceof ∼4×10−4 ergcm−2 (20–1000 keV)isamongthelargestobserved
in long GRBs. This burst demonstrates similarities with other ultra-long bursts: a long quiescent
time between the episodes (∼1500 s), spectral evolution from hard initial pulse to significantly
softer subsequent pulses, and a large fluence. The duration of the second emission episode of
GRB 080704 (following the quiescent time) is substantially longer that the duration of the first
episode, which is a common feature of long GRBs. The existence of such long quiescent times
mayfavorthedormantinnerenginescenario overwindmodulation models[2].
Withoutknowledgeoftheburstredshiftitisnotpossibletodeterminetherestframeproperties
oftheburst,butitslargefluenceandhighE suggestamoderatezof∼1–2(forz=1E ∼1.2×
peak iso
1054 erg). In such a case, the rest frame burst duration of ∼1000 s and the rest frame quiescence
timeof∼500scanposeaproblemforsomecentralenginemodelsintheframeworkofthecollapsar
scenario. Specifically suchlong durations might behard toexplain inthemagnetarmodel oflong
GRBs.
The Konus-Wind experiment is supported by a Russian Space Agency contract and RFBR
grant12-02-00032a. KHisgratefulforIPNsupportunderthefollowingNASAgrants: NNX07AR71G
(MESSENGER),NNX08AN23G(Swift),andNNX08AC90G(INTEGRAL).
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