ApJ, 662, 443, 2007

16 Pages·2007·0.69 MB·English

TheAstrophysicalJournal,662:443Y458,2007June10 A
#2007.TheAmericanAstronomicalSociety.Allrightsreserved.PrintedinU.S.A.
SWIFTAND XMM-NEWTON OBSERVATIONS OF THE EXTRAORDINARY GAMMA-RAY BURST 060729:
MORE THAN 125 DAYS OF X-RAYAFTERGLOW
Dirk Grupe,1 Caryl Gronwall,1 Xiang-Yu Wang,1,2 Peter W. A. Roming,1 Jay Cummings,3 Bing Zhang,4
Peter Me´sza´ros,1,5 Maria Diaz Trigo,6 Paul T. O’Brien,7 Kim L. Page,7 Andy Beardmore,7
Olivier Godet,7 Daniel E. vanden Berk,1 Peter J. Brown,1 Scott Koch,1 David Morris,1
Michael Stroh,1 David N. Burrows,1 John A. Nousek,1 Margaret McMath Chester,1
Stefan Immler,8,9 Vanessa Mangano,10 Patrizia Romano,11 Guido Chincarini,11
Julian Osborne,7 Takanori Sakamoto,3 and Neil Gehrels3
Received2006November7;accepted2007February28
ABSTRACT
WereporttheresultsoftheSwiftandXMM-NewtonobservationsoftheSwift-discoveredGRB060729(T ¼115s).
90
Theafterglowof thisburstwasexceptionallybrightinX-raysaswellasatUV/opticalwavelengths,showingan
unusuallylongslowdecayphase((cid:1) ¼0:14(cid:1)0:02),suggestingalargerenergyinjectionphaseatearlytimesthan
inotherbursts.TheX-raylightcurvedisplaysabreakatabout60ksaftertheburst.TheX-raydecayslopeafterthe
breakis(cid:1) ¼1:29(cid:1)0:03.Upto125daysaftertheburstwedonotdetectajetbreak,suggestingthatthejetopening
angleislargerthan28(cid:2).WefindthattheX-rayspectraoftheearlyphasechangedramaticallyandcanallbefittedby
anabsorbedsingleYpower-lawmodelsoralternativelybyablackbodypluspower-lawmodel.Thepower-lawfits
show that the X-ray spectrum becomes steeper while the absorption column density decreases. In the blackbody
modelthetemperaturedecreasesfromkT ¼0:6to0.1keVbetween85and160saftertheburstintherestframe.The
afterglowwasclearlydetectedupto9daysaftertheburstinallsixUVOTfiltersandinUVW1evenfor31days.A
breakatabout50ksisclearlydetectedinallsixUVOTfiltersfromashallowdecayslopeof about0.3andasteeper
decayslopeof1.3.TheXMM-Newtonobservationsstartedabout12hraftertheburstandshowatypicalafterglow
X-rayspectrumwith(cid:2) ¼1:1andabsorptioncolumndensityof 1;1021 cm(cid:3)2.
X
Subject headinggs: gamma rays: bursts — X-rays: bursts
Online material: color figure
1. INTRODUCTION GRB060729wasdiscoveredbySwifton2006July29(Grupe
et al. 2006) as one of the brightest bursts ever detected by the
Gamma-raybursts(GRBs)arethemostpowerfulexplosionsin
deviceinX-rays(withthebrightestGRBobservedbyXRTsofar
thepresent-dayuniverse.WiththelaunchoftheSwiftGamma-Ray
being GRB061121;Pageetal.2007).BesidesGRB050525A
BurstExplorerMission(Gehrelsetal.2004)in2004November
(Blustinetal.2006),GRB060218(Campanaetal.2006),GRB
anewerainGRBsciencehasstarted.Swiftisabletoobservethe
060614(Manganoetal.2007),andGRB061121(Pageetal.
afterglowofaburstwithitsnarrow-fieldinstruments,theX-Ray
2007),GRB060729istheburstwiththebestUVOTfollow-up
Telescope(XRT;Burrowsetal.2005a)andtheUV/Opticaltele-
evenupto9daysaftertheburstinallsixUVOTfiltersandeven
scope(UVOT;Romingetal.2005),typicallywithin2minutesafter
longer in some of the UV filters. XRT has detected the after-
thedetectionbytheBurstAlertTelescope(BAT;Barthelmyetal.
glow more than 125 days after the burst. This is the longest
2005). Several phenomena were discovered by Swift, such as
follow-upobservationwithadetectionof anaftergloweverper-
theoccurrenceof giantflaresduringthefirst1000saftertheburst
formedbySwift.Similar,butshorter,coveragehasonlybeen
(e.g.,Burrowsetal.2005b;Falconeetal.2006)orthecanonical
performedforGRB050416A,GRB060319,andGRB060614.
lightcurvesofGRBafterglows(Nouseketal.2006;Zhangetal.
Even though the burst was bright in the BAT, it was too faint
2006).
to be detected by Konus-Wind (D. D. Frederiks 2006, private
communication).
1 Departmentof AstronomyandAstrophysics,PennsylvaniaStateUniver- EventhoughtheSunanglewassmallinrightascension(2.2hr),
sity,UniversityPark,PA16802;[email protected]. duetothedeclination(cid:3)62(cid:2),theafterglowwascircumpolarfor
2 DepartmentofAstronomy,NanjingUniversity,Nanjing210093,China. mostsouthernobservatoriesandwasobservedbytheESOVery
3 AstrophysicsScienceDivision,AstroparticlePhysicsLaboratory,NASA
LargeTelescope(VLT)usingFORS2andbyGeminiSouthus-
GoddardSpaceFlightCenter,Greenbelt,MD20771.
4 DepartmentofPhysics,UniversityofNevada,LasVegas,NV89154. ingGMOS(Thoeneetal.2006).Aredshiftof z¼0:54wasde-
5 Departmentof Physics,PennsylvaniaStateUniversity,UniversityPark,PA terminedfromtheopticalspectrabyThoeneetal.(2006).GRB
16802. 060729wasalsoobservedbyROTSEIIIa,locatedattheSiding
6 XMM-Newton Science Operations Centre, European Space Agency, SpringObservatory,Australia,byQuimbyetal.(2006),whore-
VillafrancadelCastillo,28080Madrid,Spain.
portedaninitialupperlimitof 16.6mag64saftertheBATtrig-
7 DepartmentofPhysicsandAstronomy,UniversityofLeicester,Leicester
LE17RH,UK. ger.TheywereabletodetecttheafterglowwithROTSEIIIaup
8 AstrophysicsScienceDivision,X-RayAstrophysicalLaboratory,NASA to175ksaftertheburstwhenitwasstillat19.4mag(Quimby&
GoddardSpaceFlightCenter,Greenbelt,MD20771. Rykoff2006),decayingwithaslope(cid:1) ¼0:23.Cobb&Bailyn
9 UniversitiesSpaceResearchAssociation,Columbia,MD21044.
(2006)measuredadecayslopeintheI bandof (cid:1) ¼1:5based
10 INAFYIstitutodiAstrofisicaSpazialeeFisicaCosmicadiPalermo,I-90146 I
onCTIO1.3mSMARTSobservationsbetween4.6to17.6days
Palermo,Italy.
11 INAFYOsservatorioAstronomicodiBrera,I-23807Merate,Italy. aftertheburst.
443
444 GRUPE ETAL. Vol. 662
Fig.1.—UVW1image(5:70;4:20)ofthefieldofGRB060729withanexposureof550ks.ThecirclesatthesourcepositiondisplaystheXRTpositionasgivenin
x3.1.Thecirclesinthelargeimageshowa800radiusatthesourcejustfordisplaypurposes,andthe800backgroundextractionregion.Thezoom-inimage(8000;6000)inthe
toprightcornershowsthe3:500XRTerrorradius.Notethebrightstarthatisonly10700awayfromthepositionoftheafterglowofGRB060729.[Seetheelectronicedition
oftheJournalforacolorversionofthisfigure.]
Thepaperisorganizedasfollows.Inx2wedescribetheobser- correctedforpileup.Inordertocorrectforpileupinthelight
vations and the data reduction. In x 3 we present the data anal- curveandforthespectralanalysisandthedeterminationofthe
ysis.Thediscussionofourresultsisgiveninx4.Throughoutthe hardness ratio12 we excluded the central regions of the PSF at
paper decay and energy spectral indices (cid:1) and (cid:2) are defined thesourceposition,dependingonthecountrateasdescribedin
byF (t; (cid:3))/(t(cid:3)t )(cid:3)(cid:1)(cid:3)(cid:3)(cid:2),witht thetriggertimeoftheburst. Romanoetal.(2006).ForthePCmodedatathesourcephotons
(cid:3) 0 0
Luminosities are calculated assuming a (cid:1)CDM cosmology wereselectedinacircularregionwitharadiusof r¼5900 and
with (cid:2) ¼0:27, (cid:2) ¼0:73, and a Hubble constant of H ¼ thebackgroundphotonsinacircularregionclosebywithara-
M (cid:1) 0
71 km s(cid:3)1 Mpc(cid:3)1 using the luminosity distances D given by dius r¼17600 in the first segments. For the later data the radii
L
Hogg (1999), resulting in D ¼3120 Mpc. All errors are 1 (cid:4) werereducedto4700and2400forthesourceand13700and9600for
L
unlessstatedotherwise. thebackground.Forthespectraldataonlyeventswithgrades
0Y2 and 0Y12 were selected with XSELECT for the WTand
2.OBSERVATIONS AND DATA REDUCTION PC mode data, respectively. Note that the source photons for
thespectralanalysisofthePCmodedataofthefirstorbitwere
TheSwiftBATtriggeredontheprecursorof GRB060729at
selectedinaringwithaninnerradiusof 16:500andanouterra-
19:12:29UTon2006July29(Grupeetal.2006;Grupe2006).
diusof71:000inordertoavoidtheeffectsofpile-up(e.g.,Pagani
Swift’sXRTbeganobservingtheafterglow124safterthetrigger.
etal.2006;Vaughanetal.2006).Thespectraldatawererebinned
TheUVOTstartedtheobservations135saftertheBATtrigger.
byusinggrpphaversion3.0.0,with20photonsbin(cid:3)1.Thespec-
TheSwiftXRTobservedGRB060729inthewindowedtim-
trawereanalyzedwithXSPECversion12.3.0(Arnaud1996).
ing(WT)andphotoncounting(PC)observingmodes(Hilletal.
The auxiliary response files were created by xrtmkarf and
2004). The XRT data were reduced by the xrtpipeline task
correctedusingtheexposuremaps,andthestandardresponse
version0.10.4.TheWTmodedataatthebeginningof theXRT
matricesswxwt0to2_20010101v008.rmfandswxpc0to12_
observationhadtobetreatedwithspecialcare.Duringthefirst
20safterthestart(130Y150saftertheBATtrigger)of theWT 20010101v008.rmfwereusedfortheWTandPCmodedata,
respectively. All spectral fits were performed in the observed
XRTobservationthesatellitewasstillsettling,causingthetarget
0.3Y10.0keVenergyband.Fortheerrorsofthespectralfitparam-
tomoveontheXRTCCDtowardthedeadcolumnsatDETX¼
319Y321(Abbey2006).Inordertocorrectforthephotonlosses etersweusedthestandard(cid:3)(cid:5)2 ¼2:7inXSPEC,whichisequiv-
alenttoa90%confidenceregionforasingleparameter.
duetothesedeadcolumnswemeasuredtheoffsetof thesource
Background-subtracted X-ray flux light curves in the 0.3Y
ateachsecondandcalculatedacorrectionfactoraccordingtothe
10.0keVenergyrangeoftheSwiftobservationswereconstructed
lossesoftheWTmodepoint-spreadfunction(PSF).After150s
afterthetriggerallWTmodedatawerecorrectedbythesamefac-
tor.SourceandbackgroundphotonswereselectedbyXSELECT
12 ThehardnessratioisdefinedbyHR¼(hard(cid:3)soft)/(hardþsoft)where
version2.4inboxeswithalengthof 40pixels.Forcountrates ‘‘soft’’isthecountsinthe0.3-1.0keVbandand‘‘hard’’isthecountsinthe1.0Y
>150countss(cid:3)1,however,intheWTmodethedatahadtobe 10.0keVband,respectively.
No. 1, 2007 SWIFTAND XMM OBSERVATIONS OF GRB 060729 445
Fig.2.—SwiftBATlightcurvesinthe(toptobottom)15Y25,25Y50,50Y100,and15Y100keVband.Theverticaldashedlineinthe15Y100keVplotmarksthetime
forwhichT wascalculatedandthedotted-dashedlinethebeginningoftheXRTobservationsat124saftertheburst.
90
usingtheESOMunichImageDataAnalysisSoftware(MIDAS withtheUVOTsoftwaretooluvotsource.DuetothebrightF3
vers.04Sep)andbyanIDLprogramthatcorrectsforPSFlosses, VstarHD45187(9.4maginB,107:500awayfromGRB060729)
inparticularwhenthesourceislocated onone of the deadcol- extra caution had to be taken for the source extraction and the
umnsontheXRTCCDdetector.Thelightcurvewasbinnedas backgroundsubtraction.Wechoseaselectionradiusof400forthe
follows:theWTmodedatawith1000photonsbin(cid:3)1,andthepc sourceand800forthebackgroundinallfiltersplacedataposition
modedatawith200countsbin(cid:3)1inthefirstdaysaftertheburst nearbyontherimofthebrightstar’shalo,asdisplayedinFigure1.
and20or10attheendoftheobservations.Thecountrateswere Inordertocorrectforlossesduetothissmallsourceextraction
convertedintounabsorbedfluxunitsusingenergyconversionfac- radius,wedidanaperturecorrectionwithV ¼0:03,B¼0:05,
tors (ECF) that were determined by calculating the count rates U ¼0:05, UVW1¼0:17, UVM2(k ¼2170 8)¼0:15, and
c
andtheunabsorbedfluxesinthe0.3Y10.0keVenergybandusing UVW2¼0:15 mag. All values plotted and listed in this paper
XSPECasdescribedinNouseketal.(2006).TheXRTdataatthe take these corrections into account. The data, however, arenot
beginningoftheobservationshowdramaticspectralchangesand corrected for Galactic reddening, which is E ¼0:050 mag
B(cid:3)V
requirespecificECFsforeachtimebin.Thelaterdata,however,do (Schlegeletal.1998)inthedirectionof theburst.
agreewithatypicalafterglowspectrum,andthecountrateswere GRB060729wasalsoobservedbyXMM-Newton(Jansenetal.
convertedbyoneECF¼5;10(cid:3)11ergss(cid:3)1cm(cid:3)2(countss(cid:3)1)(cid:3)1. 2001)foratotalof 61ks(Schartel2006;Campana&DeLuca
TheSwiftUVOTobservationsofGRB060729beganwiththe 2006). XMM-Newton started observing the afterglow of GRB
automatedGRBsequence,whichprovidedfindingchartimages 060729on2006July3007:41(44.9ksafterthetrigger)andcon-
inwhite(100s)andV (400s),andthenbegancyclingthrough tinuedobservationsuntil2006July3101:04UT(107.5ksafter
allsixUVandopticalfiltersstarting739safterthetrigger.The thetrigger).IntheEuropeanPhotonImagingCamera(EPIC)pn
source data of these early white and V images were extracted (Stru¨deretal.2001)thetotalobservingtimewas59.6ksusing
from a circle with a radius of 600. GRB 060729 remained de- themediumlightblockingfilter.However,duetohighparticle
tectableinallsixfiltersformorethan9daysafterthetrigger,then background during partof the observation only 42.3 ks were
for12daysafterthetriggerinUVW2(kc ¼19308)andfor31days used.TheobservationsintheEPICMOS(Turneretal.2001)
afterthetriggerinUVW1(k ¼25108).Duringthefirstdaysafter wereforatotalobservingtimeof 61.2ks.TheMOS1wasusing
c
thebursteachobservationineachsingleorbitwasanalyzed.Forthe themediumfilter,whiletheMOS2observationswereperformed
laterdatatheimageswereco-addedwithuvotimsuminorderto withthethinfilter.Thetotalobservingtimeinthereflectiongrat-
improvethesignal-to-noiseratio(S/N).Thedatawereanalyzed ingspectrometers(RGSs;denHerderetal.2001)was61.5ks.In
446 GRUPE ETAL. Vol. 662
3.2.BAT Data
Figure2displaystheBATlightcurvesinthe15Y25,25Y50
50Y100,and15Y100keVbands(toptobottom)withT ¼2006
0
July 29 19:12:29 UT (spacecraft clock 175893150.592). GRB
060729hadT ¼115s(Parsonsetal.2006).PartlytheT isso
90 90
longbecausethetriggerwasontheprecursor.Aftertheinitialfirst
peak(precursor),whichwasdetectedbytheBATandwhichtrig-
gered the observation, the burst drops back down to the back-
groundlevel.However,twogiantpeaksareobservedatabout60s
afterthetrigger,ofwhichthefirstisharderthanthesecond.There
isathirdpeakabout120safterthetrigger.Thisisthepeakof which
weseetheendof thedecayintheXRTobservation(Fig.3).Forthe
spectralanalysistheBATdataweredividedintofivebinsaslistedin
Table1.ThefirstpeakistheinitialpeaktheBATtriggeredonGRB
060729.AsshowninTable1,thefollowingtwopeaks,whichoccur
between70and124saftertheburst,areafactorof3strongerthan
theinitial peak. The two last peaks (124Y190 safter the burst;
XRTflare1and2inTable1),arealsoobservedsimultaneously
Fig.3.—CombinedSwiftBATandXRTWTlightcurves.Thefigureclearly
intheXRT.ThesedataarediscussedintheXRTsection.
showsthattheXRTwasstartingobservingGRB060729duringthefourthpeak
Table1liststheresultsofthespectralanalysisofthefivepeaks.
seenintheBAT.
AllspectrawerefittedbyasingleYpower-lawmodel.Theinitial
theopticalmonitor(OM;Masonetal.2001)theafterglowwas peakhasahardspectrumwitha15Y150keVenergyspectraindex
observedfor8.3ksinU,5;4ksinUVW1,3;4ksinUVM2, (cid:2)15Y150keV ¼1:05þ(cid:3)00::4322.Thetwostrongpeaksbetween70Y124s
and2;4kswiththeopticalgrism.NotethattheOMUVW1and aftertheburstshowinterestingspectralbehavior.Whilethefirst
UVM2filtersareslightlydifferentcomparedwiththeUVOTUV of thesepeaks(70Y88saftertheburst)hasaratherhardspectral
filters.TheXMM-NewtondatawerereducedwiththelatestSAS slope,with(cid:2)15Y150keV ¼0:59(cid:1)0:11,thesecondof thesepeaks
versionxmmsas_20060628_1801-7.0.0. (88Y124s)wassofter,with(cid:2)15Y150keV ¼0:90(cid:1)0:11.Thetotal
fluenceintheobserved15Y150keVbandis2:7;10(cid:3)6ergscm(cid:3)2
3. DATA ANALYSIS (Parsonsetal.2006)and7:2;10(cid:3)6and1:7;10(cid:3)5ergscm(cid:3)2in
3.1.Position of the Afterglow therest-frame1keVY1MeVand1keVY10MeVbands,respec-
tively,adding all BATspectra together (Table 1)and assuming
The position of the afterglow measured from the UVOT thesamepower-lawspectrumasinthe15Y150keVbandwithout
UVW1 co-added image is R:A: (J2000:0)¼06h21m31:86s,
anybreak.Witharedshiftof z¼0:54thisconvertsintoaniso-
decl: (J2000:0)¼(cid:3)62(cid:2)22012:500witha100error.Thisposition tropicenergyintherest-frame1keVY1MeVand1keVY10MeV
isconsistentwiththeinitialanalysisofthewhiteandV filteranal- bandofE ¼6:7;1051andE ¼1:6;1052ergs,respectively.
ysis(Immler2006).TheUVW1positionis1:100 awayfromthe iso iso
Becausewelackobservationsof thebreakenergyE andthe
X-raypositionR:A: (J2000:0)¼06h21m31:75s,decl: (J2000:0)¼ break
gamma-ray spectrum at higher energies by Konus-Wind, the
(cid:3)62(cid:2)22013:300 (with a 3:500 90% confidence error), which was 1 keVY10 MeV band E value is an upper limit of the true
measuredfortheXRTPCmodedataof segment001usingthe iso
isotropicenergy.
newteldeffileswx20060402v001.teldefasdescribedin
Burrowsetal.(2006).Thispositiondeviatesby3:200fromthere- 3.3.X-Ray Data
finedpositiongiveninGrupe(2006).Themostlikelyreasonfor
3.3.1.TemporalAnalysis
thisdifferenceisthatfortheX-raypositiongiveninGrupe(2006)
onlythePCmodedataof thefirstorbitwereused.Thisisdueto Figure3showsthecombinedBATandXRTlightcurve.The
the burst during the first orbit being placed on one of the bad lightcurveclearlyshowsthatXRTbeganobservingtheGRBat
columnsontheXRTCCD,whichmakesthedeterminationof a thebeginningofthefourthpeakseenintheBAT.Thecombined
positiondifficult.Figure1displaystheUVW1imageofthefield BAT+XRTlightcurvewasconstructedasdescribedinO’Brien
of GRB060729.Thecircleinthetoprightinsertedimageisthe etal.(2006).Duetothedramaticspectralchangewithinthe3min-
3:500 XRTerrorradiusof theX-raypositiongivenabove. utesoftheWTobservation,weappliedanECFforeachindividual
TABLE1
SpectralFitstotheBATData
Fluxa Fluenceb
Spectrum TafterTrigger (cid:2)15Y150keV (cid:5)2/(cid:3) 15Y150keV 1keVY1MeVc 1keVY10MeVc 15Y150keV 1keVY1MeVc 1keVY10MeVc
Firstpeak.......... 0Y10 1.05þ0:42 57/56 3.2 ; 10(cid:3)8 1.0 ; 10(cid:3)7 1.3 ; 10(cid:3)7 3.2 ; 10(cid:3)7 1.0 ; 10(cid:3)6 1.3 ; 10(cid:3)6
(cid:3)0:37
Secondpeak...... 70Y88 0.59þ0:11 59/56 5.8 ; 10(cid:3)8 1.6 ; 10(cid:3)7 4.5 ; 10(cid:3)7 1.0 ; 10(cid:3)6 2.8 ; 10(cid:3)6 8.1 ;10(cid:3)6
(cid:3)0:11
Thirdpeak......... 88Y124 0.90þ0:11 50/56 2.8 ; 10(cid:3)8 7.7 ; 10(cid:3)8 1.2 ; 10(cid:3)7 1.0 ; 10(cid:3)6 2.8 ; 10(cid:3)6 4.3 ; 10(cid:3)6
(cid:3)0:11
XRTflare1....... 124Y160 1.26þ1:58 49/56 2.6 ; 10(cid:3)9 1.1 ;10(cid:3)8 1.3 ; 10(cid:3)8 9.4 ; 10(cid:3)8 4.0 ; 10(cid:3)7 4.7 ; 10(cid:3)7
(cid:3)0:86
XRTflare2....... 180Y190 1.59þ5:23 53/56 1.8 ; 10(cid:3)9 1.5 ; 10(cid:3)8 1.5 ; 10(cid:3)8 1.8 ; 10(cid:3)8 1.5 ; 10(cid:3)7 1.5 ; 10(cid:3)7
(cid:3)1:67
Note.—TheBATdatahavebeendividedintofivesegmentsaslistedinthefirstcolumn.
a The15Y150keVfluxisinunitsofergss(cid:3)1cm(cid:3)2.
b Fluenceinunitsofergscm(cid:3)2.
c Rest-frame1keVY1MeV(0.65Y650keVobserved)and1keVY10MeV(0.65keV-6.5MeVobserved).
No. 1, 2007 SWIFTAND XMM OBSERVATIONS OF GRB 060729 447
TABLE2
SpectralAnalysisofthe21BinsoftheSwiftWTModeData
PowerLawwith
SinglePowerLaw Blackbody+PowerLaw ExponentialCutoff
BinNo. Time T CRa HRb N c (cid:2) (cid:5)2/(cid:3) kTd bb-Fluxe R f (cid:5)2/(cid:3) E g (cid:5)2/(cid:3)
obs H X bb cutoff
1................ 131 1.2 919(cid:1)30 0.55(cid:1)0.06 ... ... ... ... ... ... ... ... ...
2................ 132 1.2 841(cid:1)28 0.60(cid:1)0.06 4.06þ1:39 1.51þ0:35 21/23 0.56þ0:05 7.46 2.49 16/23 0.82þ0:44 15/23
(cid:3)1:15 (cid:3)0:31 (cid:3)0:04 (cid:3)0:08
3................ 133 1.4 807(cid:1)27 0.51(cid:1)0.05 ... ... ... ... ... ... ... ... ...
4................ 135 1.6 737(cid:1)25 0.43(cid:1)0.05 4.51þ0:88 2.10þ0:29 39/32 0.45þ0:04 6.13 3.46 51/32 0.78þ0:36 48/32
(cid:3)0:77 (cid:3)0:25 (cid:3)0:03 (cid:3)0:02
5................ 136 1.6 712(cid:1)24 0.47(cid:1)0.05 ... ... ... ... ... ... ... ... ...
6................ 138 1.8 635(cid:1)22 0.42(cid:1)0.05 5.22þ0:98 2.40þ0:33 36/31 0.43þ0:02 6.23 3.91 34/31 0.51þ0:59 33/31
(cid:3)0:85 (cid:3)0:30 (cid:3)0:02 (cid:3)0:39
7................ 140 2.1 579(cid:1)19 0.33(cid:1)0.04 ... ... ... ... ... ... ... ... ...
8................ 142 2.6 520(cid:1)18 0.29(cid:1)0.04 4.35þ0:58 2.47þ0:24 39/46 0.38þ0:02 5.72 4.69 45/46 0.59þ0:46 45/46
(cid:3)0:53 (cid:3)0:21 (cid:3)0:02 (cid:3)0:25
9................ 145 3.1 498(cid:1)16 0.25(cid:1)0.04 ... ... ... ... ... ... ... ... ...
10.............. 149 4.4 380(cid:1)12 0.12(cid:1)0.04 4.70þ0:65 2.99þ0:32 75/50 0.31þ0:02 3.60 5.48 96/50 0.50þ0:3 107/50
(cid:3)0:58 (cid:3)0:28 (cid:3)0:02 (cid:3)0:2
11.............. 154 5.7 289(cid:1)10 (cid:3)0.00(cid:1)0.04 3.00þ0:62 2.64þ0:34 29/34 0.25þ0:02 2.81 7.35 30/34 0.67þ0:47 33/34
(cid:3)0:56 (cid:3)0:30 (cid:3)0:02 (cid:3)0:09
12.............. 161 7.3 227(cid:1)7 (cid:3)0.07(cid:1)0.04 3.07þ0:71 2.73þ0:41 43/32 0.29þ0:02 1.98 4.84 32/32 0.64þ0:47 34/32
(cid:3)0:63 (cid:3)0:36 (cid:3)0:02 (cid:3)0:15
13.............. 167 6.4 258(cid:1)9 0.10(cid:1)0.04 2.29þ0:60 2.04þ0:33 38/32 0.27þ0:03 1.45 4.77 43/32 1.15þ0:64 48/32
(cid:3)0:54 (cid:3)0:29 (cid:3)0:03 (cid:3)0:34
14.............. 173 5.2 320(cid:1)10 0.21(cid:1)0.04 3.60þ0:62 2.46þ0:27 40/33 0.34þ0:03 3.54 4.68 39/33 0.72þ0:37 37/33
(cid:3)0:56 (cid:3)0:24 (cid:3)0:02 (cid:3)0:05
15.............. 179 5.4 310(cid:1)10 0.15(cid:1)0.04 2.43þ0:59 2.01þ0:30 39/35 0.32þ0:03 2.90 4.61 37/35 0.78þ0:40 35/35
(cid:3)0:53 (cid:3)0:28 (cid:3)0:02 (cid:3)0:03
16.............. 184 5.5 301(cid:1)10 0.02(cid:1)0.04 2.97þ0:67 2.57þ0:38 35/34 0.26þ0:02 3.28 7.52 32/34 0.58þ0:56 36/34
(cid:3)0:60 (cid:3)0:34 (cid:3)0:02 (cid:3)0:23
17.............. 190 7.4 227(cid:1)7 -0.09(cid:1)0.03 3.46þ0:85 3.07þ0:51 55/35 0.24þ0:01 3.24 8.76 40/35 0.51þ0:18 45/35
(cid:3)0:76 (cid:3)0:46 (cid:3)0:01 (cid:3)0:13
18.............. 199 9.4 178(cid:1)5 -0.26(cid:1)0.03 2.48þ0:62 2.98þ0:41 62/39 0.19þ0:01 3.44 14.84 58/39 0.55þ0:62 60/39
(cid:3)0:55 (cid:3)0:36 (cid:3)0:01 (cid:3)0:29
19.............. 210 14.0 127(cid:1)4 -0.31(cid:1)0.03 2.34þ0:63 3.07þ0:42 59/38 0.18þ0:01 2.84 15.40 33/38 0.51þ0:69 60/38
(cid:3)0:54 (cid:3)0:36 (cid:3)0:01 (cid:3)0:31
20.............. 229 23.4 72(cid:1)2 -0.50(cid:1)0.03 1.83þ0:53 3.28þ0:41 72/36 0.15þ0:01 2.15 18.19 38/36 0.51þ0:6 76/36
(cid:3)0:44 (cid:3)0:35 (cid:3)0:01 (cid:3)0:5
21.............. 296 112.0 14.8(cid:1)0.4 -0.56(cid:1)0.03 0.84þ0:35 2.83þ0:36 64/37 0.11þ0:01 0.50 15.65 52/37 ... ...
(cid:3)0:30 (cid:3)0:32 (cid:3)0:01
Note.—Fortheblackbodypluspower-lawandthepower-lawwithexponentialcutoffmodelthepower-lawslopewasfixedto(cid:2)X¼1:0.Fortheblackbodypluspower-
lawmodeltheabsorptionparameterwasfixedtotheGalacticvalue(4:82;1020cm(cid:3)2;Dickey&Lockman1990).
a Countrateinunitsofcountss(cid:3)1.
b ThehardnessratioisdefinedasHR¼(hard(cid:3)soft)/(hardþsoft),where‘‘soft’’and‘‘hard’’arethephotonsinthe0.3Y1.0and1.0Y10.0keVband,respectively.
c ThecolumndensityN isgiveninunitsof1021cm(cid:3)2.
H
d Blackbodytemperatureinunitsof keV.
e Thefluxesaregiveninunitsof10(cid:3)9ergss(cid:3)1cm(cid:3)2.
f BlackbodyradiusR giveninunitsof1012cm.
bb
g ThebreakenergyisgiveninunitsofkeV.
binassumingapower-lawmodelcorrectedforabsorptionwiththe (T (cid:3)T ¼130Y150 s). The WT mode data were divided into
0
parameterslistedinTable2.However,fortheBATdataweapplied 21binswith1000sourcephotonsineachbin.Becauseofthehigh
onlyoneECF,whichreflectsthemainspectrum. countrateatthebeginningof theobservationsweappliedthe
Figure4displaysthe SwiftXRTlightcurve,withWTmode methodasdescribedinRomanoetal.(2006)toavoidtheeffects
dataastrianglesandPCmodedataascrosses.Theverticaldashed of pileup. However, this procedure reduced significantly the
linesinthefiguremarkthestartandendtimesoftheXMM-Newton numberofsourcephotonsineachsinglespectrum.Wetherefore
observations.Thegeneralbehaviorof thelightcurvecanbede-
scribedasfollows:aftertheinitialsteepdecaywithadecayslope
(cid:1) ¼5:11(cid:1)0:22thelightcurveflattensatT ¼530(cid:1)25s,
1 break;1
withadecayslope(cid:1) ¼0:14(cid:1)0:02.AtT ¼56:8(cid:1)10ks
2 break;2
thelightcurveof theafterglowbreaksagainandcontinuesde-
cayingwithadecayslope(cid:1) ¼1:29(cid:1)0:03.Thedefinitionsof
3
thedecayslopesfollowthedescriptionsgiveninNouseketal.
(2006)andZhangetal.(2006).Wedonotdetectajetbreakeven
125daysaftertheburst.Thelast3(cid:4)detectionof theX-rayaf-
terglowwasobtainedbetween2006November21toDecember1,
withatotalexposuretimeof 69.9ks.Theafterglowcontinuedto
beobservedbySwiftuntilDecember27,foratotalof63.5ks.How-
ever,theseobservationswereinterruptedbyseveralnewbursts,and
attheendonlya3(cid:4)upperlimitof2:1;10(cid:3)14ergss(cid:3)1cm(cid:3)2could
beobtained.ItwasdroppedfromtheSwiftscheduleafter2006
December 27 because it was not detectable anymore with the
XRTwithinareasonableamountof observingtime.
3.3.2.Spectral Analysis Fig.4.—SwiftXRTlightcurveoftheWT(triangles)andPC(crosses)mode.
Thedownwardarrowmarksthe3(cid:4)upperlimitattheendoftheSwiftobserva-
Dramatic spectral change at the beginning.—In order to ex-
tions.Thisupperlimitcontainsatotalexposuretimeof63.5ksobtainedbetween
aminethespectralbehaviorinmoredetail,sourceandbackground
2006December8andDecember27.Thedottedverticallinesmarkthestartand
spectra were created for each bin, except for the first 10 bins endtimesoftheXMM-Newtonobservation.
448 GRUPE ETAL. Vol. 662
Fig.5.—SwiftXRTWTmodelightcurve.Thepanelsdisplay(toptobottom)theXRTcountrate(inunitsofcountss(cid:3)1),thehardnessratio(seetextfordefinition),the
X-rayspectralslope(cid:2) ofasingleYpower-lawfit,thefree-fitcolumndensityN inunitsof1021cm(cid:3)2,theblackbodytemperaturekT,theblackbodyradiusR (inunitsof
X H bb
1012cm),andthecutoffenergyE ofapowerlawwithexponentialcutoff.AllthesefitparametersarelistedinTable2.Thenumbersinthetoppanelmarkthebinsthat
break
wereusedforthespectrashowninFig.6.
combined two bins into one for bins 1+2, 3+4, 5+6, 7+8, and (cid:2) from an absorbed singleYpower-law fit with a free-fit ab-
X
9+10toincreasetheS/N. sorptioncolumndensityN ,blackbodytemperaturekT(inkeV)
H
Each of the 16 spectra were fitted by an absorbed singleY fromtheblackbodypluspower-lawfit,blackbodyradius13R ,
bb
power-law,blackbodypluspower-law,andapower-lawwithex- and the break energy E of a power-law with exponential
break
ponentialcutoffmodel.Theresultsofthesespectralfitsarelisted
inTable2.Figure5showsplotsoftheWTmodedataasfollows: 13 The blackbody radii were derived for each bin from the relation L¼
(top to bottom) count rate, hardness ratio, X-ray spectral slope 4(cid:6)R2 (cid:4)T4,where(cid:4)istheStefan-Boltzmannconstant.
bb
No. 1, 2007 SWIFTAND XMM OBSERVATIONS OF GRB 060729 449
from2:5;1012to16;1012cm.Fittingthedatawithanabsorbed
blackbodypluspower-lawmodelwiththeabsorptioncolumn
density at z¼0 set to the Galactic value and at z¼ 0:54 to
1;1021 cm(cid:3)2(seethediscussionabouttheXMM-Newtonspec-
tralanalysis)resultsinsimilarvaluesforthetemperature.The
onlydifferencesarethatthetemperaturestendtobelowerby
40eVandthenormalizationsarehigher.
Thepromptemissionof GRBsisoftenfittedbyaBandfunc-
tion (Bandetal.1993). Wealsotriedapower-lawmodel with
exponentialcutoff,asurrogatefor theBandmodelthathasthe
advantage of using fewer parameters than the Band model. In
ordertoobtainbetterconstraintswefixedtheabsorptioncolumn
totheGalacticvalue.AslistedinTable2,typicallythepower-law
modelwithexponentialcutoffdoesnotshowimprovementover
thesingleYpower-lawortheblackbodypluspower-lawmodels.
ThechangeintheX-rayspectraisalsodisplayedinFigure6,
whichshowsthespectraof bins 1,12,14,and21.Bin12isthe
Fig.6.—SwiftXRTWTspectraofbins1+2(blackfilledcircles),12(redopen binbeforethesmallflareat170saftertheburst,andbin14isthe
squares),14(greenopencircles),and21(bluefilledsquares)fittedbyabsorbed peakof thatflare.
singlepowerlawsasgiveninTable2.Thenumbersrefertothebinsasshownin
Later PC mode data.—All PC mode data can be fitted by a
Fig.5.
power-lawmodelwithaenergyspectralslope(cid:2) ¼1:2andan
X
absorptioncolumndensityofabout1:5;1021cm(cid:3)2.Thisabsorp-
cutoffmodel.ThehardnessratiochangesfromHR¼0:6atthe tioncolumndensityissignificantlyabovetheGalacticvalue.
beginningoftheobservationtoHR¼(cid:3)0:56attheend,indicat- Theintrinsicabsorptioncolumndensityattheredshiftz¼0:54
ingadramaticevolutionintheX-rayspectrumwithin2minutes is1:9(cid:1)0:4;1021cm(cid:3)2.Table3liststheXRTPCmodeobser-
of observingtime,whichtranslatesinto1.3minutesintherest vationsat20Y40ksaftertheburstandat200ksaftertheburst,so
frame. beforeandaftertheXMMobservation.Thefitstothesedatasug-
Whilethespectraduringthefirst20sof theWTmodeobser- gestnosignificantspectralvariabilitybeforeorafterthebreakin
vationarewellfittedbyasingleYpower-lawmodel,afterabout theX-raylightcurvearound60ksaftertheburst.
150 s after the burst the data are better fit by a blackbody plus The XMM-Newton observations.—The combined spectra of
power-lawspectrum.Fortheabsorbedpower-lawfits,allparam- the XMM-Newton EPIC pn and MOS and Swift XRT data are
eterswereleftfree.Wefoundthatwhilethespectraatthebe- showninFigure7.TheXRTdatawereselectedbetween44,900
ginningoftheobservationwereratherhard,with(cid:2) ¼1:5and and 107,500 s after the burst.The details of the spectral fitsto
X
N ¼4;1021cm(cid:3)2,thespectrabecameverysoft,with(cid:2) (cid:4)3:0 thesedataaresummarizedinTable3.Attheselatetimes,the
H X
andN ¼1;1021cm(cid:3)2.Notethattheabsorptioncolumndensity X-rayspectrawerewellfittedbyabsorbedsingleYpower-law
H
N decreases, while the energy spectral index (cid:2) becomes models.However,asacheckthespectrawerefittedalsobya
H X
steeper—theoppositeofwhatisexpectedifthespectralslopeand blackbody plus power-law model,although atthese latetimes
the absorption column density were just linked in the fitting the power-law component dominates the spectra. Therefore,
program.However,notethatespeciallyduringthelaterbins,the weonlydiscusstheabsorbedpower-lawmodelfitsaslistedin
spectraarenotwellfitbyasinglepowerlawanddorequiremore Table3.
complicatedmodels. The obvious difference between the Swift XRT and XMM-
Fortheblackbodypluspower-lawmodel,theabsorptionparam- NewtonpnandMOSdataisthemuchhighervalueoftheabsorp-
eter was fixed at the Galactic value (4:82;1020 cm(cid:3)2; Dickey tioncolumndensity.Fromthefreefitabsorptioncolumndensity
&Lockman1990)andthehardenergyspectralslopea(cid:2) ¼1:0. atz¼0wemeasuredanabsorptioncolumndensityN ¼15:7;
X H
The blackbody temperature changes dramatically from kT ¼ 1020cm(cid:3)2intheSwiftXRTdata.Thisvalueisabouttwiceashigh
0:56keVatthebeginningoftheXRTWTobservationto0.11keV aswhatismeasuredfromtheXMM-NewtonEPICpnandMOS
attheend,accompaniedbyanincreaseof theblackbodyradius spectra.TheEPICpniswellcalibratedtoenergiesbelow0.2keV
TABLE3
SpectralFitstotheSwiftXRTPCModeandXMMEPICpnandMOSData
Detector N a (cid:2) (cid:5)2/(cid:3) N b (cid:2) (cid:5)2/(cid:3)
H X H,intr X
SwiftXRT(20Y40ksafterburst)................. 16.83þ2:30 1.21þ0:10 87/103 21.57þ4:22 1.12(cid:1)0.08 88/103
(cid:3)2:17 (cid:3)0:09 (cid:3)3:92
SwiftXRT(44.9Y107.5ksafterburst)......... 15.72þ2:22 1.19þ0:09 134/120 19.20þ4:00 1.11þ0:08 134/120
(cid:3)2:10 (cid:3)0:09 (cid:3)3:72 (cid:3)0:07
SwiftXRT(200ksafterburst)...................... 14.65þ6:22 1.17þ0:25 33/25 17.46þ11:10 1.10þ0:20 33/25
(cid:3)5:55 (cid:3)0:22 (cid:3)9:65 (cid:3)0:19
XMMEPICpn.............................................. 8.58þ0:20 1.12þ0:01 1159/1149 7.79þ0:39 1.11þ0:01 1124/1149
(cid:3)0:20 (cid:3)0:01 (cid:3)0:38 (cid:3)0:01
XMMMOS1+MOS2..................................... 9.33þ0:33 1.04þ0:02 937/800 8.23þ0:59 1.01þ0:01 929/800
(cid:3)0:32 (cid:3)0:02 (cid:3)0:58 (cid:3)0:01
XMMMOS1+2+SwiftXRT......................... 9.54þ0:32 1.05þ0:02 1106/920 8.61þ0:06 1.02þ0:01 1097/920
(cid:3)0:32 (cid:3)0:02 (cid:3)0:06 (cid:3)0:01
XMMpn+MOS1+2+SwiftXRTb.................. 8.57þ0:17 1.08þ0:01 2599/2071 7.55þ0:03 1.06þ0:01 2508/2071
(cid:3)0:17 (cid:3)0:01 (cid:3)0:03 (cid:3)0:01
Note.—XMMobservedtheafterglowbetween44.9Y107.5ksaftertheburst.
a ThecolumndensityNHatz¼0isgiveninunitsof1020cm(cid:3)2.
b IntrinsiccolumndensityNH;intrattheredshiftoftheburst,z¼0:54,isgiveninunitsof1020cm(cid:3)2.Theabsorptioncolumndensityatz¼0issettothe
Galacticvalue,4:82;1020cm(cid:3)2.
450 GRUPE ETAL.
uncertaintiesinthedecayslopes,thisisallconsistentwithan
achromatic break. Note that due to a rebrightening of the after-
glowatabout20ksseeninX-raysandallsixUVOTfiltersthe
determinationof(cid:1) isratheruncertain.InBtheafterglowdecays
2
the slowest with (cid:1) ¼0:98. The decay slopes at shorter wave-
3
lengthsaresteeperwith(cid:1) (cid:5)¼1:3.Notethattheflatterslopein
3
theBfilteriscausedbyarebrighteningatabout200ksthatisnot
seenintheotherfilters.Bylimitingtheanalysistodataonlyupto
200ksthedecayslopeis(cid:1) ¼1:17(cid:1)0:16,whichisconsistent
3
withthedecayslopesseenintheotherfilters.Therebrighteningin
Batabout200ksaftertheburstseemstobereal.Wecheckedfor
anystrongvariabilityinthebackgroundbutcouldnotdetectany
atthattime.Thedecayslopes(cid:1) and(cid:1) areconsistentwiththe
2 3
decayslopesreportedbyQuimby&Rykoff(2006)andCobb&
Bailyn(2006).
Figure 9 displays the UVOT white and V and XRT light
curvesof thefirstorbit.TheUVOTdataof thisperiodarelisted
Fig. 7.—Absorbed-power-lawmodelfitswithNH¼8:57;1020 cm(cid:3)2and inTable6.Theleftpanelof Figure9displaystheUVOTwhite
(cid:2)X¼1:08,aslistedinTable3,totheXMM-NewtonEPICpn(blackfilledcir- filtereventmodeandXRTWTmodedata.TheUVOTwhitefil-
cles),MOS1(redopensquares),MOS2(greenopencircles),andSwiftXRTPC
terdataweregroupedinto10sbins.ThefirstUVOTwhitepoints
mode(bluefilledsquares)spectra.TheSwiftXRTdatawereselectedbetween
44.9and107.5ksaftertheburst,simultaneouswiththeXMM-Newtonobservation. showadecaysimilartotheXRTWTlightcurve.However,after
thesefewpointstheUVOTwhitelightcurveflattens,whichagrees
withtheflareseenintheXRTdataat170saftertheburst.Atabout
(e.g., Haberl et al. 2003). We also applied the gain fit model
200safterthebursttheafterglowstartstobecomebrighterinthe
withinXSPEC,but itdid notremovethe discrepancy. Thisdis-
UVOTwhite,whileitisstilldecayingintheX-ray.
crepancymaybeduetoproblemswiththeSwiftXRTbiasmaps
Therightpanelof Figure9showstheUVOTV eventmode
duringthetimeperiodbetween2006July21andAugust3.This
dataandtheXRTPCmodedataof thefirstorbit.TheUVOTV
biasmapproblemcausedanoffsetinthegainandthereforecom-
dataweregroupedin25sbinsandtheXRTPCmodedatawith
promisedthespectralanalysisofSwiftXRTPCmodedataduring
25 source photons bin(cid:3)1. The UVOT V light curve shows the
thattime.However,thisgainshiftdoesnotaffecttheearlySwift
afterglowfairlyconstantatabout17.5mag,whiletheXRTPC
XRTWTmodedata.Duetothebetterresponseof theEPICpn
modelightcurvesshowsaninitialdecayuntilabout600sand
at lower energies we consider the absorption column densities
flattensafterthat.
measuredbytheEPICpnthemostreliable.Withtheredshiftof
TheXMM-Newtonopticalmonitorobservationsaresummarized
theburstatz¼0:54wecanalsousetheX-rayspectratodeter-
inTable7.WhiletheU filterresultsagreewellwiththeUVOTU
minetheintrinsicabsorptioncolumndensityatthelocationofthe
dataaslistedinTable4,thereisadiscrepancyintheUVW1and
afterglow.Theintrinsiccolumndensitiesofallfitsareintheorder
UVM2 filters. There may be three explanations for this discrep-
of 1;1021 cm(cid:3)2, except for the Swift XRT data, which again
ancy: (1) the OM and UVOT UV filter sets have different filter
showanabsorptioncolumndensityabouttwiceashigh.Asweshow
transmission;(2)theOMsuffersfromsignificantlyhigherlevelof
laterinx3.5,theabsorptioncolumndensityof 1;1021cm(cid:3)2is
scatteredlightthantheUVOT;and(3)theextractionradiusof the
in good agreement with what can be derived from the spectral
automatedOMsoftwareis1200,whichistoolargeforanaccurate
energydistribution(SED)of theafterglow.
analysisof theUVdataduetothebrightstar(seeUVOTsection).
InadditiontotheEPICpnandMOSdatawealsoanalyzedthe
ThebrighteningoftheafterglowinthelastOMUVM2observation
two RGS spectra. We found that the analysis of the RGS con-
at101ksaftertheburstismostlikelyduetoabadsubtractionofthe
tinuum spectra agrees within the errors with the pn and MOS
backgroundwithintheautomaticOMdatareductionsoftware.
data. We did not find any obvious emission or absorption fea-
turesintheRGSspectra. 3.5. Spectral Energy Distribution
Asshowninsection3.4thelong-termlightcurvesinallsix
3.4.UV/Optical Data Analysis
UVOTfiltersandinX-raysdofollowthesamedecayslopewith
The magnitudes resulting from the UVOT data analysis are similar break times at about 50 ks after the burst. In order to
listedinTable4.Figure8showstheresultsoftheUVOTphotom- checkthiswedeterminedSEDsof theafterglowat800s,20,
etryincomparisonwiththeXRT.UVOTwasabletofollowthe 100,and500ks,withexposuretimesintheXRTof 400s,1.8,
afterglowinallsixfiltersupto9daysaftertheburst.InUVW1 3.3,and4.8ks,respectively.Figure10displaysthesefourSEDs.
the afterglow was followed up 31 days after the burst, which ThesetimesarealsomarkedinFigure8.Thesetimeswerepicked
translatesinto20daysintherestframe.Thisisoneof thelon- torepresenttheSEDsoftheearliestandlatesttimepossiblewhen
gestintervalsSwift’sUVOThaseverdetectedanafterglowinthe the afterglow was detected in all six UVOT filters and shortly
optical/UV.OnlyGRBs060218(Campanaetal.2006)and060614 beforeandafterthebreak.AllfluxesinallsixUVOTfiltersand
(Manganoetal.2007)weredetectedatslightlylaterobserved theXRTwerecalculatedaccordingtothelightcurves.Thereseem
timesthanGRB060729. tobenoobviouschangesintheSEDs,besidesthechangesinthe
Inallbands,XRTaswellasinallsixUVOTfilters,asignif- fluxes,overtime.Anothermeasureof anychangesintheSEDs
icantbreakoccursinthelightcurve.Table5liststhedecayslopes overtimeistheoptical/UVtoX-rayspectralslopeorX-ray
(cid:1)2and(cid:1)3beforeandafterthebreaktimeTbreak.Withintheerrors loudness14(cid:2)oX.Fortheafterglowof GRB060729wemeasured
allbreaktimesseemtooccuratabout50ksaftertheburst(33ks
intherestframe),withtheearliestbreakinBatabout30ksand 14 The X-ray loudness is defined by Tananbaum et al. (1979) as (cid:2)oX¼
thelaterbreaksatshorterwavelengths.However,consideringthe Y0:384log(f2keV/f25008).
TABLE4
CentralTimes,ExposureTimes,andAperture-correctedMagnitudesoftheUVOTLightCurves
VFilter BFilter UFilter UVW1Filter UVM2Filter UVW2Filter
BinNo. Timea T b Mag Timea T b Mag Timea T b Mag Timea T b Mag Timea T b Mag Timea T b Mag
exp exp exp exp exp exp
1................... 120 9 17.07(cid:1)0.31 715 10 18.27(cid:1)0.38 696 20 16.48(cid:1)0.12 673 20 16.92(cid:1)0.20 649 18 16.81(cid:1)0.24 749 20 17.54(cid:1)0.25
2................... 440 390 17.37(cid:1)0.06 1451 20 18.03(cid:1)0.23 844 20 16.88(cid:1)0.15 820 20 16.89(cid:1)0.20 796 20 17.57(cid:1)0.33 1489 20 16.95(cid:1)0.19
3................... 773 19 17.36(cid:1)0.26 1609 20 18.10(cid:1)0.26 1427 20 16.85(cid:1)0.16 1403 20 17.47(cid:1)0.26 1379 20 17.12(cid:1)0.26 1647 20 17.39(cid:1)0.23
4................... 1164 393 17.32(cid:1)0.06 1767 20 18.26(cid:1)0.30 1585 20 16.85(cid:1)0.15 1561 20 17.31(cid:1)0.24 1537 20 16.85(cid:1)0.23 1805 19 16.92(cid:1)0.19
5................... 1513 19 17.45(cid:1)0.32 6224 197 18.45(cid:1)0.10 1743 20 16.49(cid:1)0.13 1719 20 17.14(cid:1)0.23 1695 20 16.75(cid:1)0.22 6634 197 17.70(cid:1)0.09
6................... 1671 19 17.16(cid:1)0.24 7657 197 18.45(cid:1)0.11 6020 197 17.52(cid:1)0.07 5815 197 17.55(cid:1)0.09 1850 13 17.63(cid:1)0.45 7998 63 17.86(cid:1)0.17
7................... 1829 19 17.55(cid:1)0.34 12919 134 18.68(cid:1)0.14 7452 197 17.54(cid:1)0.07 7247 197 17.62(cid:1)0.09 7043 197 17.80(cid:1)0.12 11878 751 18.08(cid:1)0.06
8................... 6838 197 18.10(cid:1)0.16 18042 211 17.86(cid:1)0.06 12778 134 17.89(cid:1)0.11 12568 268 18.09(cid:1)0.10 13880 377 17.76(cid:1)0.09 13266 537 18.17(cid:1)0.07
9................... 13613 134 18.38(cid:1)0.25 23824 211 17.84(cid:1)0.06 17822 211 16.91(cid:1)0.05 17495 422 17.11(cid:1)0.05 19550 600 17.07(cid:1)0.05 18585 844 17.36(cid:1)0.04
10................. 19128 211 17.33(cid:1)0.09 29606 211 17.78(cid:1)0.06 23603 211 17.20(cid:1)0.06 23276 422 17.23(cid:1)0.05 25338 599 17.20(cid:1)0.05 24367 845 17.52(cid:1)0.04
11................. 24911 211 17.73(cid:1)0.11 35388 211 18.14(cid:1)0.08 29387 211 17.17(cid:1)0.06 29059 422 17.22(cid:1)0.05 31109 600 17.37(cid:1)0.06 30149 844 17.51(cid:1)0.04
12................. 30692 211 17.53(cid:1)0.10 41205 208 18.12(cid:1)0.08 35167 211 17.20(cid:1)0.06 34840 422 17.35(cid:1)0.05 36892 599 17.40(cid:1)0.06 35931 845 17.64(cid:1)0.04
13................. 36475 211 17.98(cid:1)0.13 47494 147 18.22(cid:1)0.09 40989 207 17.26(cid:1)0.06 40666 415 17.35(cid:1)0.05 42681 587 17.45(cid:1)0.06 41738 829 17.76(cid:1)0.05
14................. 42273 207 17.86(cid:1)0.13 56873 129 18.31(cid:1)0.11 47340 147 17.18(cid:1)0.07 47109 296 17.24(cid:1)0.06 48550 416 17.25(cid:1)0.06 47877 592 17.56(cid:1)0.05
15................. 48259 147 17.47(cid:1)0.11 67943 42 18.94(cid:1)0.33 53746 83 17.32(cid:1)0.10 52836 183 17.36(cid:1)0.08 54427 229 17.63(cid:1)0.10 54050 330 17.78(cid:1)0.08
16................. 54265 83 18.12(cid:1)0.26 75864 211 18.77(cid:1)0.12 62872 69 17.24(cid:1)0.11 58802 385 17.60(cid:1)0.06 63155 177 17.93(cid:1)0.14 62989 277 18.18(cid:1)0.10
17................. 63099 69 18.29(cid:1)0.35 81646 211 18.88(cid:1)0.13 69860 211 17.75(cid:1)0.08 64698 436 17.76(cid:1)0.07 100500 603 18.66(cid:1)0.11 76105 249 18.14(cid:1)0.10
18................. 91349 223 18.68(cid:1)0.22 87426 211 18.96(cid:1)0.14 75644 211 17.84(cid:1)0.08 69533 422 17.85(cid:1)0.07 106280 599 18.57(cid:1)0.11 82086 640 18.48(cid:1)0.08
19................. 100080 211 18.45(cid:1)0.22 93208 211 18.72(cid:1)0.11 81426 211 18.07(cid:1)0.10 75315 423 17.93(cid:1)0.07 112060 597 18.58(cid:1)0.11 87970 846 18.54(cid:1)0.07
20................. 105860 211 18.87(cid:1)0.28 98988 211 19.11(cid:1)0.15 87206 211 17.98(cid:1)0.10 81097 423 18.05(cid:1)0.08 117840 600 18.52(cid:1)0.10 93752 846 18.84(cid:1)0.08
21................. 111650 211 18.49(cid:1)0.19 104770 211 19.02(cid:1)0.13 92987 211 18.03(cid:1)0.10 86877 423 18.17(cid:1)0.08 123630 600 18.90(cid:1)0.13 99532 847 18.79(cid:1)0.08
22................. 117430 211 19.03(cid:1)0.32 110560 211 18.84(cid:1)0.13 98767 211 18.40(cid:1)0.12 92658 423 18.35(cid:1)0.09 129410 601 18.81(cid:1)0.12 105320 846 18.68(cid:1)0.07
23................. 123210 211 18.40(cid:1)0.20 116340 211 19.18(cid:1)0.16 104550 211 18.23(cid:1)0.11 98438 423 18.33(cid:1)0.09 135340 294 18.79(cid:1)0.17 111100 846 18.74(cid:1)0.08
24................. 128990 211 18.92(cid:1)0.27 122120 211 19.62(cid:1)0.23 110340 211 18.50(cid:1)0.14 104230 423 18.53(cid:1)0.10 146960 342 18.99(cid:1)0.19 116880 846 18.87(cid:1)0.08
25................. 135120 111 18.77(cid:1)0.38 127900 211 19.32(cid:1)0.17 116120 211 18.33(cid:1)0.12 110010 423 18.52(cid:1)0.10 195280 737 19.62(cid:1)0.20 122660 845 19.05(cid:1)0.09
26................. 158090 156 19.36(cid:1)0.56 140600 225 19.37(cid:1)0.19 121900 211 18.60(cid:1)0.16 115790 423 18.56(cid:1)0.10 204280 189 19.48(cid:1)0.11 128450 845 19.05(cid:1)0.09
27................. 226950 941 19.82(cid:1)0.29 154780 180 19.77(cid:1)0.30 127680 211 18.43(cid:1)0.12 121570 422 18.63(cid:1)0.11 235840 471 19.84(cid:1)0.29 134830 445 19.07(cid:1)0.13
28................. 319820 1374 20.22(cid:1)0.34 168380 211 19.66(cid:1)0.24 134430 110 18.46(cid:1)0.17 127360 423 18.76(cid:1)0.11 288290 1550 19.86(cid:1)0.16 146750 522 18.84(cid:1)0.11
29................. 576790 5531 21.04(cid:1)0.40 174170 209 20.00(cid:1)0.32 146620 178 19.08(cid:1)0.25 137350 412 18.79(cid:1)0.12 331760 2240 20.21(cid:1)0.18 168860 729 19.32(cid:1)0.11
30................. 897975 2368 3(cid:4)ul=20.92 179940 211 20.00(cid:1)0.32 156590 211 18.64(cid:1)0.15 145550 291 18.76(cid:1)0.14 397970 3140 20.33(cid:1)0.16 174710 839 19.20(cid:1)0.10
31................. ... ... ... 194290 275 19.68(cid:1)0.20 168160 211 18.70(cid:1)0.15 150480 423 18.78(cid:1)0.12 487880 2980 20.59(cid:1)0.20 180340 556 19.31(cid:1)0.13
32................. ... ... ... 206460 273 19.29(cid:1)0.15 173950 209 18.84(cid:1)0.16 154560 456 18.94(cid:1)0.12 663250 8830 21.68(cid:1)0.30 194650 1100 19.60(cid:1)0.11
33................. ... ... ... 319120 1374 20.11(cid:1)0.14 179720 211 19.09(cid:1)0.21 162860 261 19.18(cid:1)0.19 926689 3976 3(cid:4)ul=21.96 206810 1092 19.51(cid:1)0.10
34................. ... ... ... 449360 2304 20.38(cid:1)0.13 194150 275 18.82(cid:1)0.13 167830 423 19.04(cid:1)0.13 ... ... ... 218500 8795 19.52(cid:1)0.12
35................. ... ... ... 662500 3619 21.23(cid:1)0.20 206310 273 19.03(cid:1)0.16 173630 420 18.98(cid:1)0.13 ... ... ... 250410 1111 19.84(cid:1)0.13
36................. ... ... ... 897470 2368 21.48(cid:1)0.29 221160 280 19.35(cid:1)0.22 179390 423 19.20(cid:1)0.15 ... ... ... 287670 2200 20.16(cid:1)0.11
37................. ... ... ... ... ... ... 253230 361 19.57(cid:1)0.23 193930 549 19.21(cid:1)0.12 ... ... ... 331140 3288 20.59(cid:1)0.13
38................. ... ... ... ... ... ... 318970 1374 19.75(cid:1)0.13 206100 545 19.37(cid:1)0.14 ... ... ... 397340 4561 20.57(cid:1)0.11
TABLE4—Continued
VFilter BFilter UFilter UVW1Filter UVM2Filter UVW2Filter
BinNo. Timea T b Mag Timea T b Mag Timea T b Mag Timea T b Mag Timea T b Mag Timea T b Mag
exp exp exp exp exp exp
39................. ... ... ... ... ... ... 449220 2304 20.39(cid:1)0.16 220980 559 19.37(cid:1)0.15 ... ... ... 487280 4656 20.99(cid:1)0.14
40................. ... ... ... ... ... ... 662390 3622 21.55(cid:1)0.35 286960 1100 19.77(cid:1)0.14 ... ... ... 662770 13555 21.45(cid:1)0.12
41................. ... ... ... ... ... ... 897363 2368 3(cid:4)ul=21.58 330430 1648 19.93(cid:1)0.13 ... ... ... 897780 9498 22.02(cid:1)0.23
42................. ... ... ... ... ... ... ... ... ... 396620 2276 20.09(cid:1)0.11 ... ... ... 1099600 13675 22.43(cid:1)0.29
43................. ... ... ... ... ... ... ... ... ... 486600 2323 20.29(cid:1)0.13 ... ... ... 1487290 17912 3(cid:4)ul=23.04
44................. ... ... ... ... ... ... ... ... ... 662230 7331 21.20(cid:1)0.15 ... ... ... ... ... ...
45................. ... ... ... ... ... ... ... ... ... 897220 4748 21.20(cid:1)0.18 ... ... ... ... ... ...
46................. ... ... ... ... ... ... ... ... ... 1012900 17014 21.65(cid:1)0.15 ... ... ... ... ... ...
47................. ... ... ... ... ... ... ... ... ... 1614900 12901 21.82(cid:1)0.22 ... ... ... ... ... ...
48................. ... ... ... ... ... ... ... ... ... 1697900 14706 22.46(cid:1)0.32 ... ... ... ... ... ...
49................. ... ... ... ... ... ... ... ... ... 1874500 24764 22.68(cid:1)0.27 ... ... ... ... ... ...
50................. ... ... ... ... ... ... ... ... ... 2091400 20552 22.11(cid:1)0.20 ... ... ... ... ... ...
51................. ... ... ... ... ... ... ... ... ... 2394800 39794 22.63(cid:1)0.38 ... ... ... ... ... ...
52................. ... ... ... ... ... ... ... ... ... 3431882 44673 (cid:4)ul=22.76 ... ... ... ... ... ...
a Thetimesmarkthemiddleofthetimebininsaftertheburst.
b TheexposuretimesT aregiveninseconds.
exp