Hard X-ray timing and spectral characteristics of the energetic pulsar PSR J0205+6449 in supernova remnant 3C58

0.4 MB·English

by  L. Kuiper

Astronomy&Astrophysicsmanuscriptno.ms0205-WH˙26˙Jan10 (cid:13)c ESO2010
January27,2010
Hard X-ray timing and spectral characteristics of the energetic
+
pulsar PSRJ0205 6449 in supernova remnant 3C58
An RXTE PCA/HEXTE and XMM-Newton view on the 0.5-250 keV band
L.Kuiper1,W.Hermsen1,2,J.O.Urama3,P.R.denHartog1,4,A.G.Lyne5,andB.W.Stappers5
1 SRON-NetherlandsInstituteforSpaceResearch,Sorbonnelaan2,3584CA,Utrecht,TheNetherlands
e-mail:[email protected]
0 2 AstronomicalInstitute“AntonPannekoek”,UniversityofAmsterdam,POBox94249,1090GE,Amsterdam,TheNetherlands
1 e-mail:[email protected]
0 3 Dept.ofPhysics&Astronomy,UniversityofNigeria,Nsukka
2 e-mail:[email protected]
4 StanfordUniversityHEPL/KIPACPhysics,382ViaPuebloMallStanford,94305,USA
n
e-mail:[email protected]
a 5 JodrellBankCenterforAstrophysics,SchoolofPhysicsandAstronomy,TheUniversityofManchesterManchesterM139PL,UK
J
e-mail:[email protected]; [email protected]

7
2 Received11December2009/Acceptedxxx2010

] ABSTRACT
E
H Aims.PSRJ0205+6449isayoungrotation-poweredpulsarinSNR3C58.Itisoneofonlythreeyoung(<10,000yearold)pulsars
whicharesofardetectedintheradioandtheclassicalX-raybands,aswellasathardX-raysabove20keVandathigh-energy(>100
.
h MeV)γ-rays.TheothertwoyoungpulsarsaretheCrabandPSRB1509-58.Ouraimistoderivethetimingandspectralcharacteristics
p ofPSRJ0205+6449overthebroadX-raybandfrom∼0.5to∼270keV.
- Methods.We used all publicly available RXTE observations of PSRJ0205+6449 to first generate accurate ephemerides over the
o
period September 30, 2000 - March 18, 2006. Next, phase-folding procedures yielded pulse profilesusing data from RXTEPCA
r
t andHEXTE,andXMM-NewtonEPICPN.AllprofileshavebeenphasealignedwitharadioprofilederivedfromtheJodrellBank
s Observatorydata,andthetime-averagedtimingandspectralcharacteristicsofthepulsedX-rayemissionhavebeenderived.
a
Results.Whileourtimingsolutionsareconsistentwithearlierresults,ourworkshowssharperstructuresinthePCAX-rayprofile.
[
TheX-raypulseprofileconsistsoftwosharppulses,separatedinphaseby0.488±0.002,whichcanbedescribedwith2asymmetric
1 Lorentzians,eachwiththerisingwingsteeperthanthetrailingwing,andfull-width-half-maximum1.41±0.05msand2.35±0.22
v ms,respectively.Wefindanindicationforafluxincreasebyafactor∼2,about3.5σabovethetime-averagedvalue,forthesecond,
8 weaker pulse during a two-week interval, while its pulse shape did not change. The spectrum of the pulsed X-ray emission is of
5 non-thermalorigin,exhibitingapower-lawshapewithphotonindexΓ=1.03±0.02overtheenergyband∼0.5to∼270keV.Inthe
9 energybandcoveredwiththePCA(∼3−30keV)thespectraofthetwopulseshavethesamephotonindex,namely,1.04±0.03and
4 1.10±0.08,respectively.ComparisonsofthedetailedtimingandspectralcharacteristicsofPSRJ0205+6449intheradio,hardX-ray
. andgamma-raybandswiththoseoftheCrabpulsar,PSRB1509-58andthemiddle-agedVelapulsardorevealmoredifferencesthan
1
similarities.
0
0 Key words. Stars: neutron – pulsars: individual PSRJ0205+6449, PSR B1509-58, Crab, Vela – X-rays: general – Gamma rays:
1 observations–Radiationmechanisms:non-thermal
:
v
i
X 1. Introduction in doubt the possible association with 3C 58, which coincides
r positionally with the historical 828 yr old supernova SN1191
a PSRJ0205+6449 is a young rotation-poweredpulsar of which (Stephenson&Green, 2002). However,an age of severalthou-
the pulsations were first discovered in X-rays in a 2002 sandyearsfor3C58,closertothecharacteristicageofthepul-
Chandra X-ray Observatory (CXO) observation, reported by sar,canbederivedfromthevelocitiesoftheradioexpansionof
Murrayetal. (2002) together with a confirmation in an the PWN (Bietenholz, 2006) and of optical knots (Fesenetal.,
analysis of archival Rossi X-Ray Timing Explorer (RXTE) 2008).
data. Subsequently, the weak radio signal was detected by
Recently, Livingstoneetal. (2009) presented for
Camiloetal. (2002). PSRJ0205+6449 is a young, 65-ms pul-
PSRJ0205+6449 phase-coherent timing analyses using X-
sarlocatedinthecenterofsupernovaremnant/pulsarwindneb-
raydatafromtheProportionalCounterArray(PCA;2-60keV)
ula(PWN)3C58.Itisoneofthemostenergeticpulsarsinthe
aboardRXTEandradiodatafromtheJodrellBankObservatory
Galaxy with a spin-down luminosity E˙ ∼ 2.7 × 1037erg s−1,
and the Green Bank Telescope (GBT), spanning together 6.4
and characteristic age τ ∼ 5.4 kyr. This characteristic age, es-
yrs. This work revealed timing noise and two spin-up glitches.
timatedwiththevaluesoftheperiodandperiodderivative,puts
Furthermore,theypresenteddetailedcharacteristicsoftheX-ray
profile,which was detectedup to ∼40 keV. TheirX-ray profile
Sendoffprintrequeststo:L.Kuiper template consisted of two Gaussian-shaped pulses, a narrow
2 L.Kuiperetal.:HardX-raycharacteristicsoftheenergeticpulsarPSRJ0205+6449in3C58
(full-width-half-maximum (FWHM) ∼ 1.6 ms), more intense Table1.RXTEPSRJ0205+6449observationsummary
pulse and a broader (FWHM ∼ 3.8 ms) weak pulse separated
0.505 in phase, the single radio pulse leading the main X-ray Obs.id. Datebegin DateEnd MJD Exposurea
pulse by φ = 0.10 ± 0.01. Earlier results from an analysis of (ks)
partoftheRXTEandGBTdatawerereportedbyRansometal.
20259 30-09-1997 30-09-1997 50721-50722 16.96
(2004). These authors also presented spectral fits over the
60130 17-08-2001 19-08-2001 52138-52141 80.35
energy band 3–16 keV for both pulses: the best fit power-law
photon indices were hard, namely Γ = 0.84+0.06 for the main 70089 10-03-2002 23-04-2003 52343-52752 268.95
−0.15
pulseandΓ=1.0+0.4forthesecond(weaker)pulse. 90080 28-02-2004 03-03-2005 53063-53432 243.23
−0.3
Finally, high-energy γ-ray pulsations (≥ 0.1 GeV) from 91063 12-03-2005 18-03-2006 53441-53813 328.74
PSRJ0205+6449 were discovered with the Large Area
Telescope(LAT)aboardtheFermiGamma-raySpaceTelescope aScreened(GTI)exposureforPCAunit-2
(Abdoetal.,2009a),foldingtheγ-rayarrivaltimeswiththera-
diorotationalephemerisfrom,again,theGBTandJodrellBank.
The γ-ray light curve for energies ≥ 0.1 GeV shows also two
peakswithintensitiesdifferingbyafactor∼2,alignedwiththe offivecollimatedXenonproportionalcounterunits(PCUs)with
X-raypeaks,However,themainX-raypulsecoincidesinphase atotaleffectiveareaof∼6500cm2overa∼1◦(FWHM)fieldof
withthe weakestγ-raypulsewhichhasthesoftestspectrumof view.EachPCUhasafrontPropaneanti-coincidencelayerand
the two athigh-energyγ-rays. Thetotal pulsedγ-ray spectrum three Xenonlayerswhichprovidethe basic scientific data, and
exhibitsasimplepower-lawshapewithindexΓ∼2.1andexpo- issensitivetophotonswithenergiesintherange2-60keV.The
nentialcutoffat∼3.0GeV. energy resolution is about 18% at 6 keV. All data used in this
PSRJ0205+6449isnowoneofonlythreeyoung(<10,000 work have been collected from observations in GoodXenon or
yearold)pulsarswhicharedetectedintheclassicalX-rayband GoodXenonwithPropane mode allowing high-time-resolution
andathardX-raysabove20keV,aswellasathigh-energy(>0.1 (0.9µs)studiesin256spectralchannels.
GeV)γ-rayenergies,theothersbeingtheCrabpulsarandPSR TheHEXTEinstrument(Rothschildetal.,1998)consistsof
B1509-58(PSRJ1513-5908).TheCrabpulsarhasbeenstudied twoindependentdetectorclustersAandB,eachcontainingfour
overthetotalhigh-energybandalreadyingreatdetail(seefora Na(Tl)/ CsI(Na) scintillation detectors. The HEXTE detectors
coherenthigh-energypicturefromsoftX-raysuptohigh-energy aremechanicallycollimatedtoa∼1◦(FWHM)fieldofviewand
γ-rays Kuiperetal., 2001), with even a detection of pulsed γ- coverthe15-250keVenergyrangewithanenergyresolutionof
raysabove25GeV(Aliuetal.,2008). ∼15%at60keV.Thecollectingareais1400cm2takingintoac-
Thedetectionofpulsedemissionabove100MeVfromPSR countthelossofthespectralcapabilitiesofoneofthedetectors.
B1509-58hadtowaitforthenewgenerationofcurrentlyoper- Thebesttimeresolutionofthetaggedeventsis7.6µs.Initsde-
ationalγ-raytelescopes(Pellizzonietal.,2009).However,these faultoperationmodethefieldofviewofeachclusterisswitched
threeyoungpulsarshaveverydifferenttimingandspectralchar- onandoffsourcetoprovideinstantaneousbackgroundmeasure-
acteristics.Thismakesitparticularlyinterestingtodeterminethe ments. Due to the co-alignmentof HEXTE and the PCA, both
timingandspectralcharacteristicsofPSRJ0205+6449inmore instrumentssimultaneouslyobservethesamefieldofview.
detail over the high-energyband of the electro-magnetic spec-
RXTEobservedPSRJ0205+6449 forthefirsttimeonSept.
trum in order to compare these with those of Crab and PSR
30,1997(MJD50721)forabout17ks.Datafromthisobserva-
B1509-58andforconfrontationwiththeoreticalpredictions.In
tionwereusedbyMurrayetal.(2002)toconfirmthepulsation
this work our aim is to extend the coverage in the hard X-ray
discoveredwithChandra.Adedicatedmuchdeeperobservation
bandtohigherenergies,exploitingthedataoftheHighEnergy
wasperformedin theperiodAugust17-19,2001(MJD52138-
X-rayTimingExperiment(HEXTE;15-250keV)aboardRXTE,
52141),yieldingabout80ksgoodexposuretime.Next,amoni-
andtoextendtheenergywindowtolowerenergiesbyanalysing
toringcampaignstartedonMarch10,2003(MJD52343)which
data from XMM-Newton.We will presentthe results from our
endedon April23, 2003(MJD 52752).The total (good)expo-
timing study exploiting only the multi-year PCA/RXTE moni-
suretimeforthisperiodwasabout269ks.Asecondmonitoring
toringdata,whichweperformedinparalleltotheworkreported
round commenced on Feb. 28, 2004 and continued till March
byLivingstoneetal.(2009).Ourtimingsolutionsareconsistent
18, 2006 (MJD 53063-53813)yielding a total (good)exposure
with those of the latter authors, but our work revealed sharper
time ofabout572ks. A summaryof allRXTE observationsof
structuresin the PCA X-raypulseprofile.Furthermore,we de-
PSRJ0205+6449isgiveninTable1.Thetotalgood-timeexpo-
rivethespectralcharacteristicsoverthetotalX-rayband.Inthe
sure(afterscreening;seeSect.3.1)amounts938.23ks.
discussion we compare our findings with the characteristics of
PSRJ0205+6449reportedintheradiobandandathigh-energy
γ-rays,aswellaswiththetimingandspectralcharacteristicsof 2.2.XMM-Newton
theCrabpulsar,PSRB1509-58andthemiddle-agedVelapulsar.
WesearchedtheXMM-Newtonobservationdatabaseforobser-
vationsofthefieldaroundPSRJ0205+6449inwhichtheEPIC-
2. Instrumentsandobservations PN camera (Stru¨deretal., 2001) operated in Small-Window
(SW) mode. This mode (4.′4 × 4.′4 field of view) offers suffi-
2.1.RXTE
cient time resolution (∼ 5.67 ms) to sample the pulse-profile
In this study extensive use is made of data from monitoring of PSRJ0205+6449 over the ∼ 0.3-12 keV range. We found
observationsofPSRJ0205+6449withthetwo non-imagingX- two observations (observation ids. 0004010101/0004010201)
ray instrumentsaboard RXTE, the ProportionalCounter Array both performed on February 22, 2001 at 1.′2 offset from
(PCA;2-60keV)andtheHighEnergyX-rayTimingExperiment PSRJ0205+6449 with durations of about 9.2 and 23.6 ks, re-
(HEXTE;15-250keV).ThePCA (Jahodaetal.,1996)consists spectively.
L.Kuiperetal.:HardX-raycharacteristicsoftheenergeticpulsarPSRJ0205+6449in3C58 3
Table2.Phase-coherentephemeridesforPSRJ0205+6449asderivedfromRXTEPCA(monitoring)data.
Entry Start End t ,Epoch ν ν˙ ν¨ Φ3 Validityrange
0 0
# [MJD] [MJD] [MJD,TDB] [Hz] ×10−11Hz/s ×10−21Hz/s2 (days)
0 50721 50722 50721.0 15.230153381(92) -4.489(fixed) 0.0(fixed) 0.2931 2
1 52138 52141 52138.0 15.224659060(16) -4.489(16) 0.0(fixed) 0.5389 4
2 52343 52433 52343.0 15.223863557(3) -4.49605(13) +1.96(38) 0.6540 91
3 52433 52515 52433.0 15.223514035(4) -4.49086(20) -7.98(62) 0.7751 83
41 52639 52752 52639.0 15.2227187742(4) -4.51063(1) 0.0(fixed) 0.4147 114
5 53063 53173 53063.0 15.2211188258(7) -4.56381(2) 0.0(fixed) 0.4814 111
6 53173 53312 53173.0 15.2206851395(13) -4.55932(4) +5.80(8) 0.3170 140
7 53312 53401 53312.0 15.2201380229(35) -4.54739(19) +1.36(49) 0.3458 90
8 53401 53469 53401.0 15.2197884405(37) -4.54444(25) +12.0(9) 0.3273 69
9 53469 53546 53469.0 15.2195216777(26) -4.53041(15) +7.18(47) 0.1970 78
10 53546 53637 53546.0 15.2192204400(23) -4.52131(12) +1.85(32) 0.6030 92
11 53637 53726 53637.0 15.2188650817(24) -4.51951(12) +28.5(3) 0.1413 90
12 53726 53813 53726.0 15.2185183927(26) -4.50300(14) +16.8(4) 0.2436 88
132 53726 53764 53745.0 15.2184445054(20) -4.49904(15) -10.3(61) 0.1147 39
142 53750 53814 53782.0 15.2183007045(13) -4.49502(8) +29.1(16) 0.6055 65
1AglitchoccuredbetweenMJD52515and52571(seeLivingstoneetal.,2009,formoreinformation).Thisentrydescribes
thelastpartoftheglitchrecoveryperiod.ItsvalidityisquestionablegiventhelownumberofTOA’s,namely4,translating
to1degreeoffreedomintheTOAfitprocedure.
2EphemerisfromJodrellBankradiodata
3Φ isthephaseoffsettobeappliedtoobtainconsistentradio-alignment(seeEquation1inSect.3.4)
0
3. Timing The pulse frequency and its first two time derivatives (ν,ν˙,ν¨)
were determined from PCA X-ray data solely1, demanding a
3.1.RXTEPCAtiminganalysis maximumRMSvalueofonly0.01periodinthetime-of-arrival
(TOA)analysis.Thisrequirementresultedin13timingmodels
The first step in the RXTE PCA data analysis was the screen-
with validity intervals of typically 100 days. The ephemerides
ingofthedata.Wegeneratedgood-timeintervals(GTI)foreach
arelistedinTable2.IntheTOAanalysiswefollowedthesteps
PCUseparately,becausethenumberofactivePCU’satanyin-
outlinedinSection4ofKuiper&Hermsen(2009),inthiscase,
stant was changing.Good time intervals have been determined
however,we madea high-statisticscorrelationtemplate(show-
foreachPCU byincludingonlytimeperiodswhenthePCU in
ing clearly the two X-ray pulses) from the 80 ks observation
questionison,andduringwhichthepointingdirectioniswithin
duringrun60130.Ourmodelsarefullyconsistentwiththosede-
0◦.05 fromthe target,the elevationangle aboveEarth’s horizon
rivedbyLivingstoneetal.(2009),whousedacombinationofX-
isgreaterthan5◦,atimedelayof30minutessincethepeakofa
ray(RXTEPCA)andradio(GBTandJBO)data.Also,wefound
South-Atlantic-Anomalypassage holds, and a low background
evidence for the presence of two timing glitches using solely
level due to contaminating electrons is observed. These good
X-ray data, one occuringsomewhere between MJD 52515 and
time intervals have subsequently been applied in the screening
52571andamuchstrongeroneoccuringintheRXTEmonitor-
processtothedatastreamsfromeachofthePCUs(e.g.seeTable
inggapbetweenMJD52752and53063(seeLivingstoneetal.,
1fortheresultingscreenedexposureofPCU-2perobservation
2009,formoredetailsontheseglitcheswhichtheyreporttohave
run).
fractionalmagnitudes∆ν/ν∼3.4×10−7and∆ν/ν∼3.8×10−6,
Next, we selected event data from all three Xenon lay-
respectively). The frequency evolution history over the RXTE
ers of each PCU allowing us to better characterize the hard
observationtimestretchMJD52138-53813isshowninFig.1.
(> 10 keV) X-ray properties of PSRJ0205+6449. The TT
(Terrestial Time) arrival times of the selected events (for each Themaindifferencebetweenourworkandthatperformedby
sub-observation and for each PCU unit) have been converted Livingstoneetal.(2009)isthatwechoseforanaccurate(RMS
to arrival times at the solar system barycenter (in TDB time <0.01)descriptionoftherotationbehaviourofthepulsarwithat
scale)using1)theJPLDE200solarsystemephemeris,2)thein- most3timingparametersoveralimitedtimestretchinsteadof
stantaneousspacecraftpositionand3)thesub-arcsecondceles- usingmanymoretimingparametersoveramuchwidertimein-
tialpositionofPSRJ0205+6449.Thepositionusedis:(α,δ) = terval.Inthelatterapproachtheneedforthe(unphysical)higher
(02h05m37s.92,+64◦49′42′.′8) for epoch J2000 (Slaneetal., ordertimingparametersreflectsthepresenceof(strong)timing
2002), which corresponds to (l,b)=(130.71931,3.08456) in noise.
Galacticcoordinates.
3.2.Timingsolutions:ephemerides 1 X-ray timing data are not hampered by time-variable dispersion
measure (DM) variations as is the case for the radio data, and there-
We generated pulsar timing models (ephemerides) specifying foretheremainingscatterintheobtainedtimingsolutionsisless.This
the rotationbehaviourof the pulsar overa certain time stretch. hasbeenverifiedfortheCrabpulsar.
4 L.Kuiperetal.:HardX-raycharacteristicsoftheenergeticpulsarPSRJ0205+6449in3C58
Fig.1. Evolution of the spin-frequency of PSRJ0205+6449 as Fig.2. High-statistics radio-aligned PCA pulse phase distribu-
derived from RXTE PCA data over the period MJD 52138- tion in 180 bins for PHA range 5-44 (∼2-20 keV) combining
53813withrespecttothelineartrendofthephasecoherenttim- allavailableradio-alignedpulsephasedistributionsfromdiffer-
ing model of period MJD 52433-52515 (entry #3 of Table 2). entdatasegments.Errorbarsrepresent1σuncertainties.The
As solid lines the entries #1-12 of Table 2 are plotted, while best fit (χ2 = 199.47for 171 degreesof freedom)modelcom-
for the period 52571-52752 also the linear fit to the incoher- posedoftwoasymmetricLorentziansplusbackgroundissuper-
ent frequencymeasurementsis shown as solid line. Incoherent posed as dashed red line. The rising wings of the pulses are
frequencymeasurementsovertheperiodMJD52544-52752are steeperthanthetrailingwings.
shownasdatapoints.Notethepresenceof(atleast)twotiming
glitches:oneintheperiod52515to52571andasecondstronger
asshowninTable2.ProperX-ray/radiophasealignment,Φ(t),
onebetween52752and53063(seetext).
isobtainedbysubtractingΦ asshowninthefollowingformula:
0
1 1
Φ(t)=ν·(t−t )+ ν˙·(t−t )2+ ν¨·(t−t )3−Φ (1)
0 0 0 0
2 6
Combining the radio-aligned phase information for all PCA-
3.3.X-ray/radiopulseprofilephasealignment data coveredwith a proper ephemeris (see Table 2) yielded an
event matrix N(Φ,E) of (180×256) elements. For this purpose
TheJodrellBankobservatory(JBO)madeobservationsatara- webinnedthepulse-phaseinterval[0,1]into180phasebinsfor
diofrequencyof1.4GHzfromMJD53725to54666,andthere- all 256 PCA PHA channels. From this matrix a high-statistics
foreoverlapsforabout89dayswiththesecondRXTEmonitor- pulse-phasedistributionwasextractedforthePHAchannels5-
ingcycleintheperiodMJD53725to53813.Fortwotimeseg- 44(∼2-20keV).ThisdistributionisshowninFig.2.
mentsinthisinterval,MJD53726-53764(numberofTOAs,28)
and MJD 53750-53814(numberof TOAs, 29), accurate (RMS
< 0.01) timing models are constructed with 3 timing parame- 3.5.X-raypulseprofilecharacterization
ters (see also Table 2). The 1.4 GHz single-pulse radio profile
Initially, we fitted, analogous to Livingstoneetal. (2009), our
(in 400 bins) is shown in Fig. 3a with a fiducial point (defin-
high-statistics RXTE PCA pulse profile shown in Fig. 2 with
ing radio-phase 0.0) corresponding to the centre of gravity of
a modelconsisting of 2 Gaussians, each with free scale, width
the single pulse (just before the pulse maximum). Folding the
andposition,plusbackground.However,thismodelrendereda
barycenteredX-raytimetagsfromperiodMJD53726to53813
poor/unacceptablefit (χ2 = 265.48for180- 7 degreesof free-
uponthese radio-ephemeridesputthemainX-raypulse(pulse-
dom).Next,wetriedadoublesymmetricLorentzianmodelplus
1)atphase0.089±0.001(statisticalerroronly),consistentwith
background in order to give more weight to the wings of the
the value quoted for the JBO-PCA offset in Livingstoneetal.
pulses.Thismodelprovidedabetterdescriptionofthemeasured
(2009),namely0.085±0.010.Next,wedeterminethroughcor-
pulse-phase distribution (χ2 = 239.13 for 180 - 7 degrees of
relationanalysisthephaseshiftstobeappliedtotheX-raypulse
freedom), but is still poor. Finally, we abandoned the descrip-
profilesfromthedataperiodsofentries0-12ofTable2toalign
tionintermsofsymmetricfunctionsandusedacombinationof
these to the radio-aligned X-ray profile of period MJD 53726-
2asymmetricLorentziansplusbackground.Thismodel(9free
53813.Theseshifts(Φ )aregiveninTable2.
0 parameters)isspecifiedbelow:
3.4.CombinedX-rayeventmatrixfromPCAobservations N(φ;B,p ,p )= B+N (φ;p )+N (φ;p ) (2)
1 2 1 1 2 2
BarycenteredPCAX-rayeventtimesarefinallyfoldeduponan In this formula p represents the 4 model parameters,
1
appropriatetiming modelcomposedof ν,ν˙,ν¨ and the epocht , (N ,φ ,Γ ,Γ ), of the first asymmetric Lorentzian, p the
0 1 1 1l 1r 2
L.Kuiperetal.:HardX-raycharacteristicsoftheenergeticpulsarPSRJ0205+6449in3C58 5
Table 3. X-ray pulse profile characterization of
PSRJ0205+6449 from a fit involving two asymmetric
Lorentziansplusbackground
Parameter Value 1σ-error
Pulse-1
Φa 0.0831 ± 0.0004
1
Γ 0.0175 ± 0.0009
1l
Γ 0.0252 ± 0.0011
1r
Pulse-2
Φ 0.5709 ± 0.0015
2
Γ 0.0214 ± 0.0036
2l
Γ 0.0502 ± 0.0056
2r
Derivedquantities
Φ −Φ 0.488 ± 0.002
2 1
N /N 3.72 ± 0.23
1 2
Ib 0.688 ± 0.011
1
I 0.312 ± 0.014
2
R=I /I 2.2 ± 0.1
1 2
Γ =(Γ +Γ )/2 0.0214 ± 0.0007
1 1l 1r
1.41 ± 0.05ms
Γ =(Γ +Γ )/2 0.0358 ± 0.0034
2 2l 2r
2.35 ± 0.22ms
aStatisticalerroronly,thesystematicerrorisofthe
orderof0.01(seeLivingstoneetal.,2009)
bRelativecontributionoftheintegratedfluxinpulse-1
tothetotalpulsedflux
equivalent parameters, (N ,φ ,Γ ,Γ ), describing the second
2 2 2l 2r
asymmetric Lorentzian and B is the value of the background Fig.3. A comparison in absolute phase of the JBO radio (1.4
level. The first asymmetric Lorentzian is described by the fol- GHz), RXTE-PCA (∼2-20keV) and FermiLAT (> 100MeV)
lowingexpression: pulseprofiles.NotethechangeintherelativecontributionsofP1
andP2intheX-rayandγ-raywindows.
 N1 φ≤φ
N1(φ;p1)= ((((φφ−−φφ11))//((NΓΓ111lr//22))))22++11 φ>φ11 (3) (L02.i40v90in±9ga0s).t0ou1ns±ien0egt.0Fa1el.2rmm(2ie0aL0sA9u)Tr,ebd>uat1t0ch0oignMhs-iesetVneenrdtgawytaγi.t-hTrahtyhesecbosyempApabaradritosiooenntaoolff.
In this description N is the maximum value of pulse-1 the shapes and absolute phases of the JBO radio, our RXTE-
1
reached at φ , the location of the maximum of pulse-1, Γ /2 PCAX-rayandtheFermi-LATprofilesisshowninFig.3.The
1 1l
is the width of the left wing of the pulse-1, and finally Γ /2 main X-ray pulse (P1) appears to be the sharpest pulse in this
1r
is the width of the rightwing of the pulse-1.A similar expres- comparison.
sion and equivalentdefinitionshold for the second asymmetric
Lorentzian.
Thiscompositemodelprovidedanexcellentfit,χ2 =199.47 3.6.X-raypulseprofilevariability
for 171 degrees of freedom, with best-fit parameters and their WeinvestigatedthestabilityoftheX-raypulse-shapeasafunc-
1σerrorestimateslisted in Table 3 (see also the best-fitmodel tion of time. Therefore, we fitted the measured X-ray pulse-
superposedonthedatainFig.2).Adescriptionintermsoftwo phase distribution (PHA range [4,27] ∼ 2-11 keV) for 15 time
asymmetric Lorentzians plus background provides a 7.7σ im- periods in terms of a constant background and the shapes of
provementoverthetwo-Gaussians-plus-backgroundmodeland pulse-1 and pulse-2, separately. The times of these data points
a 6σ improvement over the two-Lorentzians-plus-background correspondtothoseoftheX-raytimingmodelsshowninTable
model,takingintoaccountthetwo(=9-7)additionaldegreesof 2 (entries 0 to 11; 12 points), augmented with two measure-
freedominbothcases.Therefore,ouranalysisdoesnotsupport ments during the last RXTE monitoring period, MJD 53726-
theassumptionmadebyLivingstoneetal.(2009)ofanunderly- 53813,coveringentry #12 and finally, with a data point cover-
ingdoubleGaussianshapefortheX-rayprofile.WefindtheX- ingthepost-glitch-1periodMJD52544-52607,yieldingeventu-
raypulsestobesharper,especiallyforpulse-2.Forbothpulses ally15independentmeasurements.ThesplittingofperiodMJD
therisingwingsaresignificantlysteeperthanthetrailingwings.
The X-ray peak separation φ2 − φ1 derived in this work 2 Thefirsterrorspecifiesthestatisticalerrorandthesecondthesys-
is 0.488(2), significantly smaller than the value estimated by tematicalerror(seeAbdoetal.,2009a,formoredetails)
6 L.Kuiperetal.:HardX-raycharacteristicsoftheenergeticpulsarPSRJ0205+6449in3C58
Fig.4. The ratio of the integrated flux in pulse-1 over pulse-2
asafunctionoftimeforthePCAenergyband∼2-11keV.One
datapointattimeintervalMJD53736-53749(i.e.the“anomaly”
period) deviates ∼ 3.5σ (single trial) from the time-averaged
valueof2.2±0.1.
Fig.5.ThepulseprofileofPSRJ0205+6449(60bins)inthe∼2-
11keVbandduringthe“anomaly”interval(MJD53736-53749;
53726-53813intotheintervalsMJD53736-53749(2RXTEsub- 2 RXTE sub-observations). Strongly enhanced P2 emission is
observations)and MJD 53760-53813(5 sub-observations)was detected.Thebestfitmodel,composedofabackgroundplustwo
drivenbythedetectionofa“timinganomaly”intheformerin- asymmetricLorentziansofthesameshapesasshowninFig.2,
tervalduringthephase-coherenttiminganalysis.Atalaterstage issuperposedasdashedline.
ofthisworkitturnedoutthatthis“anomaly”wascausedbyin-
correctRXTE clock correctionsjust after the introductionof a
leapsecondon2006,January1.
timeshavesubsequentlybeenbarycenteredandfoldeduponthe
The profile fitting procedureyields the flux ratio R = I /I
1 2 ephemerideslisted inTable 2takingintoaccountproperradio-
(seeforthedefinitionTable3)foreachtimeinterval.Theresults,
phase referencing. Thus, we obtained time-averaged HEXTE
R(t) vs. t, are shown in Fig. 4 with superposed as long-dashed
pulsephasedistributionsin256spectralchannels(15-250keV)
line the P1/P2-flux ratio from the time-averaged high-statistics
for the combinationofobservationslisted in Table 1. The total
profile(R=2.2±0.1;seeTable3)alongwithits1-σerrorregion
dead-timecorrectedexposuretime collected forclusters A and
(shadedarea). One data point, correspondingto the “anomaly”
B amounts, 400.6 ks and 426.3 ks, respectively. Pulse profiles
period, deviates ∼ 3.5σ from the time-averaged value. Taking forthebands3,14.7-28and33.1-132.6keV,areshowninpanels
into account the number of trials (15) its significance reduces
canddofFig.6.Fittingamodel,comprisingthe(asymmetric)
to 2.7σ, still indicating an interesting hint for variability. The
Lorentziansshapesof Pulses 1 and 2 and a flat background,to
pulse-phase distribution during the “anomaly” period is shown
thesephasedistributionsyieldeddetectionsignificancesof7.8σ
inFig.5.Inthisfigurewealsosuperposedasdottedlinethebest
and3.8σforthe14.7-28and33.1-132.6keVbands,respectively
fitmodelinwhichtheshapes(twoasymmetricLorentzians)for
(2.9σfortheband,64.1-132.6keV).Therefore,pulsedemission
eachofthetwopulsesareidenticaltothosederivedforthetime- of PSRJ0205+6449 has been detected up to ∼ 132 keV, well
averagedprofileinFig.2anddetailedinTable3.
abovethesensitivitybandofthePCA.
Compared to the other measurements, where P2 is some-
timeshardlyvisible,weseestronglyenhancedP2emissiondur-
ing this period. From spectral analysis of the P1 and P2 emis- 3.8.XMM-Newtontiminganalysis
sions during the “anomaly” period it turns out that the P1 flux
TheXMM EPIC-PN data were screenedforsolar(softproton)
iscomparabletoitstime-averagedvaluecontrarytotheP2flux,
flares by creating a light curve for events with energies in ex-
whichshowsaclearenhancementbyalmostafactor2.
cess of 10 keV. From the resulting count rate distribution, as-
Thisleadstotheconclusionthatweseeaninterestingindi-
sumed to be Gaussian in absence of any flares, we could iden-
cation for flux variability for P2 without a change of its pulse
tify periods during which the rate exceeds its mean value plus
shape.Finally,wecheckedtheJBOradioprofileassembleddur-
three times the width of the distribution. These periods are ig-
ingthe“anomaly”periodforpossiblemorphologychangese.g.
nored in subsequent analysis. Next, we selected events from a
theappearanceofanewfeature,butwefoundnone.
sufficiently large circular region centered on PSRJ0205+6449
witharadiusof60′′toensurethatallpulsarcountsareincluded
3.7.RXTEHEXTEtiminganalysis and barycentered the event times of these events. Because the
XMM-Newtonobservationshavebeenperformedbeforethe80
HEXTEoperatedinitsdefaultrockingmodeduringtheobserva- ksRXTEobservation(60130)novalidephemeriswasavailable
tionslistedinTable1,allowingthecollectionofreal-timeback- fortheXMMdataperiod.Therefore,weperformedalimitedpe-
grounddatafromtwoindependentpositions±1◦.5toeitherside riodicitysearch aroundthe predictedfrequencyvalue based on
of the on-source position. For the timing analysis we selected
only the on-source data from both clusters. Good-time inter- 3 Weignoredspectraldatafromtheband28-33.1keVbecauseofthe
valshavebeendeterminedusingsimilarscreeningfiltersasused presenceofahuge background lineoriginatingfromtheactivationof
in the case of the PCA. The selected on-source HEXTE event Iodine.
L.Kuiperetal.:HardX-raycharacteristicsoftheenergeticpulsarPSRJ0205+6449in3C58 7
ous to our X-ray pulse profile variability study shown in Sect.
3.6)tothemeasuredpulse-phasedistribution,N(Φ),invarious
user-selectedenergybands:
N(Φ)=b+c ×T (Φ)+c ×T (Φ) (4)
1 1 2 2
Inthisformulabrepresentsthe(constant)unpulsed/DClevel,c
1
andc thescalesofthetwoasymmetricLorentziantemplates,T
2 1
andT (bothnormalizedto1),respectively(seeSect.3.5).This
2
model provided statistically good fits to all PCA and HEXTE
profiles. Good fits could be derived for the EPIC-PN profiles
after convolvingthe Lorentziantemplateswith the poorertime
resolution.
Foreachinstrumentthepulsedexcesscountsinthevarious
energy bands for the first (P1) and the second pulse (P2) and
the sum (=total pulsed, TP) can be translated to photon fluxes
providedthatproperenergyresponsematricesareused.
In the case of the PCA we constructed time-averaged en-
ergyresponsematricesforeachPCU separatelytakingintoac-
count the different (screened) exposure times of the involved
PCU’s during the time period of interest. For this purpose we
usedtheftoolsversion6.4programspcarspandaddrmf.Tocon-
vert PHA channels to measured energy values, E , for PCU
PHA
combined/stackedproductswealsogeneratedaweightedPCU-
combinedenergyresponsematrix.
ForHEXTEweemployedclusterAandBenergy-response
matrices separately, taking into account the different screened
on-sourceexposuretimesandthereductioninefficiencyincase
ofoff-axisobservations.Theon-sourceexposuretimesforboth
clustershavebeencorrectedforconsiderabledead-timeeffects.
Finally,wecreatedenergyresponsefiles(effectivearea(arf)
andenergyredistributionmatrix(rmf))fortheEPICPNoperat-
inginsmallwindowmodetakingintoaccountthereductionin
effective area given the 15′′ source extraction radius used. For
thispurposewe employedthe XMM SAS(vrs.7.1.0)software
Fig.6. XMM-Newton EPIC-PN pulse profiles (30 bins) of
PSRJ0205+6449 for the 0.5-3 and 3-12 keV energy bands toolsarfgen1.73.3andrmfgen1.55.1.
(panels a,b). Panels c and d show the RXTE HEXTE profiles We assume simple power-law models in the form, Fγ =
(60 bins) for the 14.7-28 and 33.1-132.8 keV energy bands. K · (Eγ/E0)−Γ with Γ the photon-index and K the normaliza-
Significant pulsed emission is detected up to ∼ 130 keV and tion in ph/cm2s keV at the pivot energy E , for the underlying
0
downto∼0.95keV. photon spectra of P1, P2 and its sum TP. We fixed the absorb-
ing interstellar Hydrogen column N to 3.4 × 1021 cm−2 (see
H
the“PL-modelforneutronstar”entryinTable2ofSlaneetal.,
entry-1 of Table 2. We found a ∼ 10σ signal right at the pre-
2004).Thesemodelshavebeenfitted ina forwardfoldingpro-
dictedfrequencyusingonlyeventswithenergiesbetween4and
cedureusingtheappropriateresponsematricestoobtaintheop-
12keV.Thefoldedpulseprofilewascompatiblewiththehigh-
timumspectralparameters,KandΓ,andthereconstructedspec-
statisticsPCAprofile(seeFig.2)takingintoaccounttheblurring
tral flux points from the observed pulsed count rates. We veri-
ofthepulseprofileduetothelimitedtimeresolutionof5.67ms
fied that the measured high-statistics RXTE-PCA spectrum, as
(=0.086inphaseunits).Forsubsequentstudieswe usedanex-
well as the EPIC-PN spectrum and the total spectrum includ-
tractionradiusof15′′ becausethesignal-to-noiseratiopeaksat
ingalsoHEXTEdataarefullyconsistentwiththisnon-thermal
thatvalue.Wecreatedpulse-phasedistributions,combiningboth
simplepower-lawmodel.ThereisinthepulsedX-rayspectrum
adjacent XMM observations, in 30 bins (i.e. oversampledby a
above∼0.5keVnoindicationforathermalblack-bodycompo-
factor of ∼ 3) for 585 energy intervals over the 0.3 to 12 keV
nent, a conclusionalso reached for the total emission from the
range,each0.02keVwide.The(radio-aligned)EPIC-PNpulse
compact source by Slaneetal. (2002) and Slaneetal. (2004),
profilesforthe0.5-3and3-12keVbandsareshowninthepanels
whoreportedapower-lawspectralindexof∼1.7.Wenotethat
aandbofFig.6andhavesignificancesof5.8and9.7σ(adopt-
Kargaltsev&Pavlov (2008) in their Table I erroneously mark
ingZ2-test;Buccherietal.,1983),respectively.Pulsedemission
7 thispulsartohaveablack-bodycomponent.Furthermore,inthis
hasbeendetecteddownto∼0.95keV.
work we only show the unabsorbed spectra i.e. the interstellar
absorptionhasbeenmodeledout.
4. PulsedspectrafromRXTEPCA/HEXTEand InTable4thebestfitvaluesarelistedofthespectralparam-
etersforthetotalpulsedemissionTP, andemissionsof P1 and
XMM-Newtondata:Totalpulsed,P1andP2
P2 using PCA data only, and for TP using the EPIC PN, PCA
From the pulse-phasedistributions N(Φ,E), derivedfor RXTE andHEXTEcombinationovertheextendedenergyband0.56to
PCA,HEXTEandXMM-NewtonEPICPN,weextractedpulsed 267.5keV.Allspectrahaveaconsistentshapewithindex∼1.03.
excesscountsbyfittingthefollowingmodelfunction(analogu- Wenoteforcomparison,thatforenergies>100MeVtheFermi
8 L.Kuiperetal.:HardX-raycharacteristicsoftheenergeticpulsarPSRJ0205+6449in3C58
Table 4. Best fit values for the photon flux spectra of the total tematicerrors)reportedforhigh-energyγ-raysabove100MeV
pulsedemission(TP),thefirst(P1)andsecond(P2)pulseemis- (Abdoetal.,2009a).
sions of PSRJ0205+6449assuming a power-law model of the – We find an indication for a flux increase by a factor ∼ 2,
formF = K·(E /E )−Γ. ∼ 3.5σ above the time-averagedvalue, for the second, weaker
γ γ 0
pulseduringatwo-weektimeinterval,whileitspulseshapedid
not change. During this time window, the morphology of the
Parameter TP P1 P2 JBO radioprofile of PSRJ0205+6449did notchange,notably,
therewasnoindicationforasecondpulse.
PCA (2.5-54.0keV) –Wedetectedthepulsedsignalsignificantlyforthefirsttime
K(10−6ph/cm2skeV) 2.93±0.05 2.03±0.03 0.90±0.04 downto∼0.95keVwithXMM-NewtonEPICPN,andupto∼
Γ 1.06±0.03 1.04±0.03 1.10±0.08 130keVbyanalysingRXTEHEXTEdata.Themorphologiesof
E (keV) 8.34 8.34 8.34 theEPICPN(takingintoaccountthecoarsertimingresolution)
0
F (10−13erg/cm2s) 10.67±0.16 7.43±0.11 3.24±0.13 andtheHEXTEprofilesareconsistentwiththatmeasuredwith
2−30
thePCA.
XMM/PCA/HEXTE (0.56-267.5keV)
– The spectrum of the pulsed X-ray emission is of non-
K(10−6ph/cm2skeV) 2.85±0.04
thermalorigin,exhibitingapower-lawshapewithphotonindex
Γ 1.03±0.02
Γ=1.06± 0.03,fittingjustthehigh-statisticsPCA data,andΓ
E (keV) 8.49
0 = 1.03± 0.02,fitting overthe broaderenergybandfrom∼ 0.5
F (10−12erg/cm2s) 5.48±0.28
0.5−150 to ∼ 270keVbyincludingalso the EPIC-PN andHEXTEflux
values.Thereisnoindicationforablack-bodycomponentinthe
softX-rayspectrumabove0.5keV.
–Wedonotseeaspectraldifferencebetweenthespectraof
thetwoX-raypulsesinthePCA data.Bothspectralphotonin-
LATmeasuresforTPamuchsofterspectrumwithspectralindex dicesarefullyconsistentwiththetimeaveragedvaluefortheto-
2.1withcutoffat∼3GeV(Abdoetal.,2009a),andthatP2ex- talpulsedemission(seeTable4).Notethattherelativestrengths
hibitsathigh-energyγ-raysasignificantlyharderspectrumthan of P1 and P2 in the X-ray and high-energyγ-ray windows re-
P1. verse(seeFig.3);thespectrumofP2hastohardensignificantly
The photon spectrum (νF representation) over the 0.56 - with respectto thatof P1 betweena few hundredkeV and100
ν
267.5 keV energy band of the total pulsed emission combin- MeV.
ingXMM-NewtonEPIC-PN,RXTE-PCAandHEXTEdata,as
derived in this work, is shown in Fig. 7 in a much wider en-
6. DiscussionandConclusions
ergy frame (0.1 keV-10 GeV) by including the best fit and its
uncertaintyrange measured by Fermi for energies> 100 MeV In the introduction we noted that PSRJ0205+6449is now one
(Abdoetal., 2009a). The luminosity of the pulsed emission of of onlythree young(< 10,000year old)pulsarswhichare de-
PSRJ0205+6449 apparently reaches a maximum in the MeV tected in the classical X-ray band and at hard X-raysabove20
band.Forcomparisonare also shownthe totalpulsedemission keV, as well as at high-energy (> 100 MeV) γ-rays, the oth-
spectraoftheCrab,PSRB1509-58aswellasthe“middle-aged” ersbeingtheCrabpulsarandPSRB1509-58.Fig.7showsthat
Velapulsar. thesethreeyoungpulsarsreachtheirmaximumluminositiesbe-
low 100 MeV, while the “middle-aged”Vela pulsar (character-
istic age 11.4 kyr) reaches its maximum at GeV energies (for
5. Summary thelatestresultsontheVelapulsarforenergiesabove100MeV,
seetheFermiresultsbyAbdoetal.,2009b).Thelatterspectrum
In thispaperwe derivedforthe youngrotation-poweredpulsar is characteristicfor olderpulsarsreportedto be detected above
PSRJ0205+6449thetimingandspectralcharacteristicsoverthe 100MeV(e.g.seethefirstFermiLargeAreaTelescopecatalog
broadX-raybandfrom∼0.5to∼270keV,usingdatafromthe ofγ-raypulsarsbyAbdoetal.,2009c)
RXTE PCA and HEXTE, and XMM-NewtonEPIC PN. These Comparing in more detail the high-energy spectra of the
X-raycharacteristicscomplementourknowledgeaboutthispul- youngpulsars in Figure 7, we notice large differences. For en-
sarintheradiodomainandthehigh-energyγ-raybandforener- ergiesbelow 10 keV the flux values of PSRJ0205+6449are ∼
giesabove100MeV. 4 orders of magnitude below those of the Crab, while around
– Our phase-coherent ephemerides (see Table 2) are con- 10 MeV the difference is reduced to about a factor of 10.
sistent with those derivedby Livingstoneetal. (2009) with the The X-ray spectrum of PSRJ0205+6449 is, thus, very much
maindifferencethatweusedsolelyX-raydata(fromtheRXTE harder than that of the Crab. The total high-energy spectrum
PCA) and fitted at most three timing parameters (ν,ν˙,ν¨) over of PSRJ0205+6449 appears to reach its maximum luminos-
morelimitedtimeintervals. ity at MeV energies, like is the case for PSR B1509-58/PSR
–TheX-raypulseprofileconsistsoftwosharppulseswhich J1513-5908.Thespectralbreakforthelatterspectrumbetween
canbedescribedwith 2asymmetricLorentzians,eachwiththe 10 MeV and 100 MeV (see flux values in Figure 7) measured
rising wing steeper than the trailing wing, and full-width-half- with COMPTEL and EGRET aboard the Compton Gamma-
maximum 1.41 ± 0.05 ms and 2.35 ± 0.22 ms, respectively. RayObservatorybyKuiperetal.(1999)hasbeenconfirmedby
These profiles are sharper than reported by Livingstoneetal. Pellizzonietal.(2009).TheseauthorsreportforPSRB1509-58
(2009). asofteningofthephotonindexΓfrom∼1.7to∼2.5goingfrom
– The first X-ray pulse lags the single radio pulse in phase tenstohundredsofMeV(butdonotprovidepulsed-fluxvalues).
by 0.089 ± 0.001 (statistical error); the phase separation be- Interestingly, the X-ray spectrum above 2 keV of
tween the two X-ray pulses amounts0.488 ± 0.002,fully con- PSRJ0205+6449resembles that of the slightly older Vela pul-
sistent with the value 0.49 ± 0.01 ± 0.01 (statistical and sys- sar (similar spectral index), but the L /L ratio for the pulsed
X γ
L.Kuiperetal.:HardX-raycharacteristicsoftheenergeticpulsarPSRJ0205+6449in3C58 9
Table5.Characteristicsofthethreeyoung(< 10kyr)X-rayandγ-rayemittingpulsarsincomparisonwiththemiddle-agedVela
pulsar(PSRB0833-045).TheluminositiesofthepulsedemissionLarecalculatedas L = 4πd2Ff withvaluesforthedistanced
Ω
takenfromthetable,andthebeamingfraction f setto1.F representthepulsedflux.
Ω
Source d P τ L Fa Fb La ηa Lb ηb
sd x γ x x γ γ
[kpc] [ms] [ky] [erg/s] [erg/cm2s] [erg/cm2s] [erg/s] [erg/s]
B0531+21 2.0 29.7 1.3 4.4E+38 (5.68±0.05)E-09 (1.3±0.1)E-09 (2.72±0.02)E+36 6.2E-3 (6.1±0.3)E+35 1.4E-3
B1509-58 5.8 151.5 1.6 1.7E+37 (1.46±0.02)E-10 (5.1±2.5)E-11c (5.88±0.08)E+35 3.5E-2 (2.1±1.0)E+35c 1.2E-2c
J0205+6449 3.2 65.7 5.4 2.7E+37 (0.36±0.02)E-11 (6.7±0.5)E-11 (4.45±0.20)E+33 1.7E-4 (8.2±0.6)E+34 3.0E-3
B0833-045 0.287 89.3 11.4 6.9E+36 (0.88±0.29)E-11 (7.9±0.3)E-09 (8.67±2.85)E+31 1.3E-5 (7.8±0.3)E+34 1.1E-2
aLuminosities,fluxesandefficiencieslabeledwithxareevaluatedforthe2-100keVband.
bLuminosities,fluxesandefficiencieslabeledwithγareevaluatedforthe0.1-10GeVband.
cTheγ-rayenergyfluxofPSRB1509-58inthe0.1-10GeVbandhasbeenderivedfromthe(total)photonfluxvaluesforthe100-300and
300-1000MeVbandsasgiveninKuiperetal.(1999)assumingapower-lawshapewithphotonindexof2.5,andshouldbeconsideredas
anupper-limittothepulsedfluxofPSRB1509-58inthe0.1-10GeVband.
componentdiffersbyafactor∼50;higherforPSRJ0205+6449
(see Table 5, which is introduced below). The L /L ratio of
X γ
PSRJ0205+6449is in between those of Vela and PSR B1509-
58, namely, the L /L ratio for PSRJ0205+6449 is a factor
X γ
∼50 smaller than that for PSR B1509-58. Note, that for the
quoted flux ratios it is assumed that the beaming fractions in
theX-rayandγ-raybandsarethesame.Weknow,however,that
these are in many cases different. More importantly, in the X-
rayspectrabelowe.g.2keVtherearenoindicationsforblack-
body components in the spectra of Crab, PSR B1509-58 and
PSRJ0205+6449. In contrast, the (pulsed) Vela spectrum ex-
hibitsbelow2keVablack-bodypeak(notshowninFig.7;see
e.g.Pavlovetal.,2001),whichischaracteristicformiddle-aged
andolderrotationpoweredpulsars.Therefore,thespectralprop-
erties of PSRJ0205+6449 confirm that we are dealing with a
youngpulsar,andsuggestarealagebetweenthoseofVelaand
PSR B1509-58,favouringits characteristic age of 5.4 kyr over
thatofSN1181(828yr).
Table5listsforthefourpulsarsdiscussedaboveinorderof
characteristic age (τ = P/2P˙) the spin-down luminosities L
sd
and fluxes F and luminosities L in the X-ray 2-100 keV and
gamma-ray0.1-10GeVbands,aswellasthecorrespondingeffi- Fig.7. Broad-band total-pulsed photon spectrum of
cienciestoconvertspin-downenergyintoemissionintheseen- PSRJ0205+6449 (aqua colored) compared with the pulsed
ergy bands. The luminosities are calculated as L = 4πd2Ff , spectra of PSR B0531+21 (Crab; red), PSR B0833-45 (Vela;
Ω
with the valuesforthe distance d takenfromthe table, andthe dark blue) and PSR B1509-58 (purple). The (hard) X-ray
valuefor f ,whichisthebeamingfraction,setto1.Atfirstsight spectrum (0.56-267.5 keV) of PSRJ0205+6449 has been
Ω
onecouldarguethatthereisanevidentanticorrelationbetween derived in this work, and the best-fit power-law model (index
characteristic age and X-ray luminosity, independentfrom dif- ∼ 1.03) has been superposed. The > 100 MeV spectrum of
ferencesinthebeamingfractions,butthisbecomeslessobvious PSRJ0205+6449 is the model fit to the Fermi spectrum from
whenweconsidertheX-rayefficienciesinsteadofluminosities. Abdoetal. (2009a). Also for Crab and Vela the best-model
Inthegamma-raybandthereisnotanyindicationforacorrela- fits to the recently published Fermi spectra for energies > 100
tion. The listed gamma-rayefficiencies differ less than a factor MeVareshown(seeAbdoetal.,2009b,d,respectively).Forall
∼10, ignoring differences in beaming fraction, while the latter spectra the interstellar absorption has been modeled out (only
differencescanbesubstantial. effectivebelow∼5keV).
There are also large differences in the morphologiesof the
pulse profiles of the three young pulsars. Comparing the pulse
profiles detected for Crab and PSRJ0205+6449at X-ray ener- emissionbetweenthepulseshasbeendetectedintheFermipro-
giesandhigh-energyγ-rays,thentherearealsosomesimulari- fileatthe5σlevel.
ties:bothexhibittwopulseswithpeaksseparated∼0.5and∼0.4 Furthermore,the Crab main radiopulse is in generalphase
inpulsephase,respectively,andtheX-rayandγ-raypulsesare coincidencewith thebroadX-ray/γ-raypulse.Thepeakofthis
alignedinphase.However,thepulsesintheCrabprofilearesig- mainradiopulselagsthatofthefirstX-ray/γ-raypulseinphase
nificantlybroaderthanthoseofPSRJ0205+6449 andemission by only ∼ 0.008 or 280 µs; see for consistent estimates from
isalsodetectedbetweenthetwoCrabpulses.Thelatterisnotthe INTEGRAL,RXTEandEGRETKuiperetal.(2003),andfrom
casefortheX-rayprofileofPSRJ0205+6449,but,interestingly, Fermi Abdoetal. (2009d). On the other hand, the Crab radio
10 L.Kuiperetal.:HardX-raycharacteristicsoftheenergeticpulsarPSRJ0205+6449in3C58
precursorpreceedsthefirst,mainX-ray/γ-raypulseinphaseby drawstrongconclusions,butitseemswarantedtostartsearching
∼0.09, or 3.2 ms, being located around the start of the leading for such variabilityin the emission fromthe increasingsample
wingofthehigh-energypulse.InthecaseofPSRJ0205+6449, of rotation-powered pulsars emitting non-thermal high-energy
thesingleradiopulseisalsopreceedingthefirstnarrowX-ray/γ- emission.
raypulse in phaseby ∼ 0.083or 5.4ms, andis fullyseparated Inconclusion,weaccuratelymeasuredfortheyoungrotation
in phase, the radio pulse being located just before the onset poweredpulsar PSRJ0205+6449the morphologyof the X-ray
of the first high-energy pulse (see Fig. 3). This strongly sug- lightcurve and the spectrum overthe broadX-rayband ∼0.5 -
gests that the analogue of the radio pulse of PSRJ0205+6449 ∼270 keV. The PSRJ0205+6449X-ray spectrum above 2 keV
is the weak radio precursor of the Crab. Also, that there are has the same power-law shape (Γ ∼ 1.03) as the middle-aged
no counterparts in the radio profile of PSRJ0205+6449 to the Vela pulsar,but the overallhigh-energyspectralshape, consid-
twohigh-energypulsesofPSRJ0205+6449,contrarytothesit- ering also the Fermi γ-ray spectrum,resemblesmore the spec-
uation for the Crab. This means that for this young pulsar ex- trumexpectedforayoungerpulsar,i.e.noevidenceforathermal
hibiting sharp non-thermal high-energy pulses, we do not see black-bodycomponent,andmaximumluminosityatMeVener-
evidence for radio emission originating from the same site in giesandnotatGeVenergies.
themagnetosphere,e.g.inslotgaps(two-polecausticemission, Themorphologyofthedouble-pulsePSRJ0205+6449light
Dyks&Rudak,2003)oroutergaps(outer-magnetosphereemis- curvecanbeexplainedinaconventionalouter-gapscenariofora
sion,seeChengetal.,1986;Romani,1996;Hirotani,2006,from rotatingdipoleinvacuumassuminglow-altituderadioemission,
a region close to the light cylinder). Possibly, this radio com- similartothecaseoftheCrabpulsarwhentakingtheCrabpre-
ponent of PSRJ0205+6449 is just too weak to be detectable, cursorradiopulseasthecounterpartofthesingleradiopulsede-
but might be revealed in a search for giant radio pulses in the tectedforPSRJ0205+6449.Thiscanbe verifiedinthe “Atlas”
phaseintervalsofthehigh-energypulses.Namely,foranumber of model γ-ray light curves simulated by Wattersetal. (2009).
ofyoungandmilli-secondradiopulsarsphasecoincidencesbe- However, see also the alternative Atlas by Bai&Spitkovsky
tween the high-energypulses and giant radio pulses have been (2009a), who point out an inconsistency in the model calcu-
reported.Two examples:the Crab forwhich the distributionof lations by Wattersetal. (2009) and in earlier reports, affecting
giantradiopulsesisremarkablysimilartotheaverageemission particularly profile shapes calculated for the two-pole caustic
profileoftheradiomainandinterpulse(Popovetal.,2006)and model.
milli-second pulsar PSR B1937+21 for which Cusumanoetal. Furthermore, it should be realized that the sharp pulses in
(2003)reportedthephasecoincidenceoftwosharphigh-energy the high-energy profile of this young pulsar PSRJ0205+6449
X-ray pulses with two phase intervals exhibiting giant radio do not have radio counterparts like we see for the Crab, and
pulses, which trail the two normal radio pulses. The latter ex- we encourage a search for giant radio pulses in the phase in-
amplemightberevealedforPSRJ0205+6449. tervals of these high-energy pulses. Recent model calculations
The high-energypulse profile of PSR B1509-58 differs to- byBai&Spitkovsky(2009b)usingaforce-freefieldinsteadof
tally from those of Crab and PSRJ0205+6449.At hardX-rays the vacuumdipolefield show thatalternativescenariossuch as
and soft γ-rays below 10 MeV the profile consists of a single their annular-gap model are required to produce over a wide
structured broad pulse, which can be explained as being com- range of parameterstwo sharp high-energypulses as exhibited
posed of two Gaussian pulse profiles separated ∼0.14 in phase byPSRJ0205+6449.Moreextensive3-Dsimulationsincluding
with different spectra (Kuiperetal., 1999; Cusumanoetal., thephysicsoftheproductionprocessesarerequiredformorede-
2001),thesecondbroaderpulsepeakingat∼0.35,withthemain tailedcomparisonswiththespectralandtimingcharacteristics.
radio pulse at phase 0. Above 10 MeV, the COMPTEL pro-
Acknowledgements. ThisresearchhasmadeuseofdataobtainedfromtheHigh
file between 10 and 30 MeV and the EGRET profile between
EnergyAstrophysicsScienceArchiveResearchCenter(HEASARC),provided
30 and 100 MeV suggest the presence of an additional high-
by NASA’s Goddard Space Flight Center. We have extensively used NASA’s
energy pulse at phase ∼0.85 (Kuiperetal., 1999). The latter Astrophysics Data System (ADS). JOU acknowledges the IAU Travel Grant
seemsnowtobeconfirmedintheAGILEprofileofPSRB1509- that enabled him to visit SRON; and the support and hospitality of SRON
58Pellizzonietal.(2009),whichshowsthemainpulseforener- NetherlandsInsituteforSpaceResearch.
giesabove100MeVatphase∼0.35,andasecondpossiblepulse
at ∼0.85. It is now ambiguous what phase difference between
References
high-energypulsesofPSRB1509-58(∼0.14or∼0.5)shouldbe
consideredforcomparisonwiththemorphologyofpulseprofiles Abdo,A.A,etal.2009a,ApJ,699,L102
Abdo,A.A.etal.2009b,ApJ,696,1084
oftheotheryoungpulsars.
Abdo,A.A.etal.2009c,astro-ph,arXiv:0910.1608
Theaboveciteddifferentmodelsaimingtoexplainthepro- Abdo,A.A.etal.2010,ApJ,708,1254
duction of non-thermal high-energy emission in the magneto- Aliu,E.,Anderhub,H.,Antonelli,L.A.etal.(TheMAGICCollaboration)2008,
spheres of rotation-powered pulsars do not address flux vari- Science,322,1221
Bai,X.-N.&Spitkovsky,A.,2009a,submittedtoApJ,arXiv:0910.5740
ability. Furthermore, there was also no observational evidence
Bai,X.-N.&Spitkovsky,A.,2009b,submittedtoApJ,arXiv:0910.5741
for such variability till the magnetar-like outburst of the high-
Bietenholz,M.F.2006,ApJ,645,1180
field pulsar PSR J1846-0258 (Gavriiletal., 2008), which de- Buccheri,R.,Bennett,K.,Bignami,G.,etal.1983,A&A,128,245
cayedwithan1/e-timeconstantof∼55days.Itwasshownby Camilo,F.,Stairs,I.H.,Lorimer,D.R.,etal.2002,ApJ,571,L41
Kuiper&Hermsen (2009) that the radiative outburst was trig- Cheng,K.S.,Ho,C.,&Ruderman,M.A.,1986,ApJ,300,522
Cusumano,G.,Mineo,T.,Massaro,E.,etal.,2001,A&A,375,379
gered by a major spin-up glitch, and that, most interestingly,
Cusumano,G.,Hermsen,W.,Kramer,M.,etal.,2003,A&A,410,L9
the shape of the X-ray pulse profile did not change during the Dyks,J.,&Rudak,B.,2003,ApJ,598,1201
outburst. For the flux increase by a factor of ∼ 2 of the non- Fesen,R.,Rudie,G.,Hurford,A.,&Soto,A.2008,ApJS,174,379
thermal emission from the second pulse of PSRJ0205+6449 Gavriil,F.P.,Gonzales,M.E.,Gotthelf,E.V.,etal.,2008,Science,319,1802
Hirotani,K.,2006,ApJ,652,1475
during a two-week time period, we did not see a variation in
Jahoda,K.,Swank,J.H.,Giles,A.B.,etal.1996,Proc.SPIE,2808,59
pulseshape,either.However,therewasnoindicationforglitch-
Kargaltsev,O.&Pavlov,G.G.2008,AIPConf.Proc.983,171
ing activity.Thesignificance of the variabilityis insufficientto Kuiper,L.,Hermsen,W.,Krijger,J.M.etal.1999,A&A,351,119