Discovery of X-ray Pulsations from the HMXB Source AXJ1749.1-2733

We are reporting a discovery of X-ray pulsations from the source AX J1749.1-2733 with the period of ~132 s based on the XMM-Newton data obtained in March 2007. The observed pulse profile has a double-peaked structure with the pulse fraction of about 25-30

Mon.Not.R.Astron.Soc.000,(2007)Printed2February2008

A(MNLTEXstyle lev2.2)

DiscoveryofX-rayPulsationsfromtheHMXBSource

AXJ1749.1-2733

arXiv:0801.3247v1 [astro-ph] 21 Jan 2008

1 11

D.I.Karasev,S.S.Tsygankov,A.A.Lutovinov1

SpaceResearchInstitute,ProfsoyuznayaStr.84/32,Moscow117997,Russia

Accepted....Received....

ABSTRACT

WearereportingadiscoveryofX-raypulsationsfromthesourceAXJ1749.1-2733

withtheperiodof~132sbasedontheXMM-NewtondataobtainedinMarch2007.Theobservedpulsepro lehasadouble-peakedstructurewiththepulsefractionofabout25 30%inthe3-10keVenergyband.WehavealsofoundthataperiodicitywithpracticallythesameperiodhasbeendetectedfromthesourcebytheIBIStelescopeonboardtheINTEGRALobservatoryduringanoutburstonSept.9,2003inthe20-50keVenergyband.Duetothedouble-peakedpulsepro le,thereisanadditionalpeakonbothperiodogramsofnearly~66s,thereforewehavealsoinvestigatedthepossibilitythatthelastvalueisthetruepulseperiod.ThesourcespectrumobtainedbytheXMM-Newtonobservatoryinthesoftenergybandisbeingheavilyabsorbed(NH 2×1023cm 2)duetoastrongintrinsicabsorptioninthebinarysystemthatleadstotheconclusionthatAXJ1749.1-2733isanewtransientX-raypulsarinthehighmassX-raybinarysystem.

Keywords:X-ray:binaries–(stars:)X-raypulsars:individual–AXJ1749.1-2733

1INTRODUCTION

ThesourceAXJ1749.1-2733wasdiscoveredonSept.19,1996bytheASCAspaceobservatory(Sakanoetal.2002).Theobjecthadnotbeendetectedduringpreviousobserva-tionsofthisregionin1995evenwithahigherexposureandwassigni cantlydetectedagainonlyinSeptember1997andMarch1998,whichre ectsitstransientnature.Duetothefaintnessofthesourceemission(1.5 6×10 12ergcm 2s 1inthe0.7 10keVenergyband),itwaspracticallyimpos-sibletoobtaingoodrestrictionstoitsspectralparameters,butsomeevidenceforthestrongabsorptioninthesystemwasmentioned2002).

OnSept.9,2003ashort(withadurationof~1day)outburstfromthesourcewasobservedbytheINTEGRALobservatoryinhardX-rayswiththepeak uxof~40mCrabinthe20-60keVenergyband(GrebenevDetailedin-vestigationsofthesourcebehavioranditscharacteristicsduringtheoutburstallowedGrebenev&Sunyaev(2007)toclassifyAXJ1749.1-2733asafastX-raytransient.Duringtheoutburst,thesourcepositioninhardX-rayswasre-solvedasRA=17h49m07s,Dec=-27 .32′38′′(J2000)withtheuncertaintyof1.8′et2006),thatiscoinci-dentwiththesourcepositionrevealedbytheASCAobserva-

tory–RA=17h49m10s,Dec=-27 .33′14′′(J2000)theuncer-taintyofabout55′′,Sakanoetal.(2002).Subsequentanal-ysisshowedthatthesourcehadbeensigni cantlydetectedbyINTEGRALfromtimetotimein2004-2007,butthetyp-icalvalueofits uxwasabout5 8mCrab.Nevertheless,basedonthesedata,ZuritaHerasetal.(2007)suggestedthepresenceinthesystemofthe~185-dayorbitalperiod.ObservationsofAXJ1749.1-2733performedinsoftX-raysbytheSWIFTobservatoryin2007,allowedKong(2007)toimproveitslocalizationto3.8′′andrevealedastrongabsorp-tion(NH 1.9×1023cm 2)inthesourcespectrum.

Inthiswork,wereanalyzedtheINTEGRALdataob-tainedduringtheoutburstinSeptember2003andanalyzedtheXMM-NewtondataobtainedinMarch2007.Inbothdatasets,strongperiodicmodulationsoftheX-ray uxwiththeperiodof~sThepreliminaryresultswerereportedby(2007).

2OBSERVATIONSANDDATAANALYSIS

E-mail:dkarasev@hea.iki.rssi.ru

ThesourceAXJ1749.1-2733wasobservedwiththeXMM-NewtonobservatoryonMarch31,2007.OuranalysiswasbasedingeneralonthedatafromtheEPIC-PNcamera,butthedatafromtheMOStelescopeswereusedalsoforthetestoftheconsistencyoftheusedspectralmodels.Alldata

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