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Chandra Observations of Neutron Stars -- An Overview

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arXiv:astro-ph/0209017v1 2 Sep 2002Proceedingsofthe270.WE-HeraeusSeminaron:“NeutronStars,PulsarsandSupernovaRemnants”

PhysikzentrumBadHonnef,Germany,Jan.21-25,2002,eds.W.Becker,H.Lesch&J.Tr¨umper,MPEReport278,pp.58-63

ChandraObservationsofNeutronStars—AnOverview

M.C.Weisskopf

NASAMarshallSpaceFlightCenter,MSFC/SD50,Huntsville,AL35812,USA

Abstract.WepresentabriefreviewofChandraobser-

vationsofneutronstars,withaconcentrationonneutron

starsinsupernovaremnants.TheearlyChandraresults

clearlydemonstratehowcriticaltheangularresolutionhas

beeninordertoseparatetheneutronstaremissionfrom

thesurroundingnebulosity.2M.C.Weisskopf:ChandraObservationsofNeutronStars—AnOverview

Fig.2.ChandraLETG–HRC-Szeroth-orderimageofthe

CrabNebulaandPulsar.Thenearlyverticallineisthedis-

persedspectrumofthepulsar.Thenearlyhorizontalline

isthecross-dispersedspectrumproducedbytheLETG

finesupportbars.

Fig.3.LETG–HRC-Szeroth-orderimagesoftheCrab

Pulsarandinnernebula(ObsID758)atpulsemaximum

(left)andatpulseminimum(right).TheX-raypulsaris

clearlydiscernibleatallpulsephases.

non-thermalemissionatpulseminimum.Second,thesim-

ilarityoftherelativeamplitudesoftheX-rayandvisible

pulsedemissionservedasanotherreason—inparticu-

lar,theratiosoffluxatpulseminimumtothatatpulse

maximumaresimilarinbothbands.Theabsenceofapro-nouncedfloorintheX-raypulseprofileshowninFig.4is

another,qualitativeconsideration.

Subsequently,we(Weisskopfetal.2002,inprepara-

tion)analyzedthedisperseddata(ObsID759),studying

thespectralevolutionasafunctionofpulsephase.Our

analysisshowsavariationofpower-lawspectralindexwith

pulsephase(Fig.5)thatisinsemi-quantitativeagree-

mentwithpreviousmeasurements(e.g.,Pravdo,Angelini,

&Harding1997;Massaroetal.2000)atvariousdifferent

energies.TheChandraresultsextendthephasecoverage

throughpulseminimum,inthatpriorobservationshadFig.4.ThelightcurveoftheCrabpulsationsfromTen-

nantetal.(2001).

totreatthedataatpulseminimumasbackground–a

necessary,butincorrect,assumption.Theseanalysisshow

thatthereisnoreasontoinvokeathermalcomponent,

andresultinanindependentupperlimitsimilartothat

basedonlyontheimagingdata.Unfortunately,neither

limitchallengescurrenttheoriesofneutronstarcooling.

Nevertheless,analysisofthesedatasuggestanewexper-

iment,whichweareproposingforChandraCycle-4,that

canefficientlyaccomplishthisobjective.

Aspartofthespectralanalysis,ourcolleagueFrits

Paerelsemphasizedthatthatscatteringofpoint-sourcera-

diationbyinterstellardustgrainsproducesawavelength-

dependent(bothinintensityandwidth)scatteringhalo

(Mauche&Gorenstein1986,andreferencestherein)and

thatthisscatteringalsorequiresanaperturecorrection

totheeffective-areacurve.Fig.6comparestheenergy

dependenceofinterstellarabsorptionwiththatofdust

scattering.Thecharacteristicscatteringangleisoforder

10arcminandscalesapproximatelyas(1keV)/E.Thus,

weeffectivelymeasureonlytheunscatteredfluxfromthe

pointsourceinournarrowaperture,sothatdustscat-

teringproducesanenergy-dependentmodulationofthe

point-sourcecontinuum.Failuretoaccountfordustscat-

teringinthespectralfittingoverestimatesthehydrogen

column,inthiscasebyabout20%.M.C.Weisskopf:ChandraObservationsofNeutronStars—AnOverview3

Fig.5.SpectralindexoftheCrabPulsarversuspulsephase.

Fig.6.Spectraldependenceofdustscattering(smooth

curve)andofinterstellarphoto-electricabsorption.

2.2.VelaPulsar

Fig.7showsthebeautifulimage(Pavlovetal.2001a,

2001b)oftheVelaPulsarandthecomplexmorphol-

ogy—similartothatoftheCrab,andB1509-58(see

below)—ofitssurroundingnebula.Inthatthissym-

posiumconcentratesontheneutronstarsthemselves,I

shallnotdiscussthefascinatingmorphologyofthepulsar-

winddrivennebulahere.AswiththeCrabPulsar,the

angularresolutionofChandraisessentialtoprobingthe

detailedspectralpropertiesofthepulsarandtoisolate

thesefromthoseofthenebula.Pavlovetal.performed

observationsusingtheLow-EnergyTransmissionGrat-

ingwiththeHigh-ResolutionCamera(LETGS)andusing

theAdvancedCCDImagingSpectrometer(ACIS)back-

illuminatedCCDs,inordertocharacterizethespectral

properties.SeparatefitstoLETGSandACIS-S3datade-Fig.7.SmoothedChandraimageoftheVelaPulsar.

Inthis3.5-arcmin-squareimage,thegreenarrowdenotes

theproper-motiondirection.Theimageiscourtesyof

NASA/PSU/Pavlovetal.(2001a).

terminedthespectralparameters.However,thedatawere

insufficienttodiscriminatefullybetweenvariousspectral

models—blackbodypluspowerlawversusahydrogenat-

mospherepluspowerlaw.Nevertheless,animportantre-

sultwastheevidenceforaharderspectralcomponent—

athermalinterpretationleadingto”animplausiblysmall

size”of10m(stretchingevenaquark-starinterpreta-

tion!!)—thusindicatingspectralsimilaritieswithmiddle-

aged(105−106-y)X-raypulsars.

2.3.B1509-58

Fig.8showstheyoungpulsarB1509-58,within

SNRG230.4-1.2intheconstellationCircinus.Thisisan-

otherexampleofapulsar-driven(plerionic)synchrotron

合集下载

The evolution of stars(恒星的演化)

The evolution of stars(恒星的演化)

The evolution of stars

Stars are the most noticeable objects in the vast universe

except the sun, moon and a few planets. In ancient times,

people were full of curiosity and fantasy about stars, and very

moving myths and legends were popular in China and abroad.

However, it was not until the telescope appeared that people

had the most basic understanding of stars and realized that

stars were not constant in the sky. At the beginning of the

20th century, Einstein published the famous mass-energy

relationship, people gradually realized the huge energy

produced by the nuclear reaction and knew the source of the

star's energy before they gradually realized that the star

itself also had a life cycle, they would be born, grow, and die

just like people. However, the birth of stars was still a

JEM-X background models

JEM-X background models

arXiv:astro-ph/0309287v1 10 Sep 2003Astronomy&Astrophysicsmanuscriptno.INTEGRAL32February2,2008

(DOI:willbeinsertedbyhandlater)

JEM-Xbackgroundmodels⋆

J.Huovelin,1S.Maisala,1J.Schultz,1N.J.Westergaard,2C.A.Oxborrow,2P.Kretschmar,3,4andN.Lund2

1Observatory,P.O.B.14(Kopernikuksentie1),FIN-00014UniversityofHelsinki,Finland2DanishSpaceReasearchInstitute,JulianeMariesVej30,DK2100Copenhagen,Denmark3Max-Planck-Institutf¨urExtraterrestrischePhysik,Giessenbachstrasse,85748Garching,Germany4INTEGRALScienceDataCenter,Chemind’Ecogia16,Versoix,Switzerland

ReceivedJuly15,2003;accepted

Abstract.BackgroundanddeterminationofitscomponentsfortheJEM-XX-raytelescopeonINTEGRALarediscussed.ApartofthefirstbackgroundobservationsbyJEM-Xareanalysedandresultsarecomparedtopredictions.TheobservationsarebasedonextensiveimagingofbackgroundneartheCrabNebulaonrevolution41ofINTEGRAL.Totalobservingtimeusedfortheanalysiswas216502s,withtheaverageof25cpsofbackgroundforeachofthetwoJEM-Xtelescopes.JEM-X1showedslightlyhigheraveragebackgroundintensitythanJEM-X2.Thedetectorswerestableduringthelongexposures,andweakorbitalphasedependenceinthebackgroundoutsideradiationbeltswasobserved.Theanalysisyieldedanaverageof5cpsforthediffusebackground,and20cpsfortheinstrumentbackground.Theinstrumentbackgroundwasfoundhighlydependentonposition,bothforspectralshapeandintensity.Diffusebackgroundwasenhancedinthecentralareaofadetector,anditdecreasedradiallytowardstheedge,withaclearvignettingeffectforbothJEM-Xunits.TheinstrumentbackgroundwasweakestinthecentralareaofadetectorandshowedasteepincreaseattheveryedgesofbothJEM-Xdetectors,withsignificantdifferenceinspatialsignaturesbetweenJEM-Xunits.Accordingtoourmodelling,instrumentbackgrounddominatesoverdiffusebackgroundinallpositionsandforallenergiesofJEM-X.

Physics Letters B

Physics Letters B

DESY02-096ISSN0418-9833

July2002

SearchforExcitedElectronsatHERA

H1Collaboration

Abstract

Asearchforexcitedelectron(e∗

)productionisdescribedinwhichtheelectroweakdecays

e∗

→eγ,e∗

→eZande∗

→νWareconsidered.Thedatausedcorrespondtoan

integratedluminosityof120pb−1

takenine±

pcollisionsfrom1994to2000withtheH1

detectoratHERAatcentre-of-massenergiesof300and318GeV.Noevidenceforasignal

isfound.Massdependentexclusionlimitsarederivedfortheratioofthecouplingstothe

compositenessscale,f/Λ.Theselimitsextendtheexcludedregiontohighermassesthan

hasbeenpossibleinpreviousdirectsearchesforexcitedelectrons.

Tobesubmittedto

PhysicsLettersBC.Adloff33

,V.Andreev24

,B.Andrieu27

,T.Anthonis4

,A.Astvatsatourov35

,A.Babaev23

,

J.B¨ahr35

,P.Baranov24

,E.Barrelet28

,W.Bartel10

,S.Baumgartner36

,J.Becker37

,

M.Beckingham21

,A.Beglarian34

,O.Behnke13

,A.Belousov24

,Ch.Berger1

A new type of long gamma--ray burst

A new type of long gamma--ray burst

ar

X

i

v:astro-ph/0610452v1 16 Oct 2006Mon.Not.R.Astron.Soc.000,1–3(2006)Printed5February2008(MNLATEXstylefilev2.2)

Anewtypeoflonggamma–rayburst

AndrewKing1⋆,EmmaOlsson1andMelvynB.Davies2

1TheoreticalAstrophysicsGroup,UniversityofLeicester,LeicesterLE17RH,UK.2LundObservatory,Box43,SE–22100,Lund,Sweden.

Accepted;Received;

ABSTRACTWeconsidergamma–rayburstsproducedbythemergerofamassivewhitedwarf

withaneutronstar.Weshowthatthesearelikelytoproducelong–durationGRBs,in

somecasesdefinitelywithoutanaccompanyingsupernova,asobservedrecently.This

classofburstwouldhaveastrongcorrelationwithstarformation,andoccurclose

tothehostgalaxy.Howeverraremembersoftheclassneednotbenearstar–forming

regions,andcouldhaveanytypeofhostgalaxy.Thusalong–durationburstfarfrom

anystar–formingregionwouldalsobeasignatureofthisclass.Estimatesbasedonthe

existenceofaknownprogenitorsuggestthatourproposedclassmaybeanimportant