Pulsar'Science'with'a'phased'ALMA'

Transcription

1 Pulsar'Science'with'a'phased'ALMA' ExploringtheUniversewiththe world slargestradiotelescope MichaelKramer JodrellBankCentreforAstrophysics U.Manchester 22January2015

2 Why'should'you'observe'pulsars'with'ALMA?' YoumaythinkthatthisisadaNidea Indeed,thereareseveralverygoodreasonsnottodoit: -Pulsarsgenerallyhavesteepfluxdensityspectra -Weknowmostaboutpulsarsfromfrequencies<2GHznote:inpast<700MHz!) -Theuseofpulsarsasclocksscalesinverselywiththesignal-to-noisera3o. Hence,usingmm-wavelengthsisnotideal FundamentalPhysicsinRadioAstronomy

3 But,'there'are'also'very'good'reasons'...' Pulsarshavebeendetectedatmm-wavelengths,e.g.: 9mm 7mm 3mm B D. Morris et al.: Pulsar detection at 87 GHz B Flux density mjy) F Longitude [deg] Fig. 2. Pulse spectra for PSRs B0 The measurements made at 87 G and as an upper limit at a 5σ lev densities at lower frequencies se ] top ] bottom Fig. 1. Observed pulse profiles of PSR B at several radio frequencies between 1.4 GHz and 87 GHz. Flux density on an arbitrary scale, and different for each frequency,has been plotted vertically. The time resolution is 153µs for frequencies between 1.4 and 14.6 GHz, 458µs for GHz and 763µs for the 43 GHz observations.the 87 GHz profile represents the Pico Veleta measurement smoothed to a time resolution of 4 ms. Krameretal.1996) Krameretal.1997) Morrisetal.1997) FundamentalPhysicsinRadioAstronomy Effelsberg radiotelescope of the MPIfR unpublished data and data presented by Kramer et al. 1997b). The 87 GHz profile has been smoothed by applying a 4 ms running mean to the data, and yields a 5σ detection. The profiles presented have been aligned in time, referring to time of arrival at the solar system barycen- this corresponds to a pulse w w 10 = 11 ±7 where the quo the undetected trailing compo at lower frequencies. In the case of PSR B2021 of 10 hours integration. In acc work e.g. Kramer et al. 199 of 0.78 mjy for the flux dens observed at 43 GHz Kramer The resulting spectra of

4 But,'there'are'also'very'good'reasons...' Pulsarshavebeendetectedatmm-wavelengths Sofar, Table 1. Results of observations at 32 GHz. PSR Pulses Time Flux density No. of total min) mjy) measurements New detections: B ± B ± < K95) B ± Re-detections: B ± ± 0.2 6K95) B ± ± K95) B ± ± K95) B ± ± K95) B ± ± K95) B ± ± K95) Upper flux limits: B <0.06 B <0.09 B <0.3 B <0.17 B <0.13 B <0.3 B <0.13 B <0.9 B <0.08 B <0.3 B <0.6 B <0.4 The designation K95) refers to earlier observations reported by Kramer 1995). Löhmeretal.2008) Un3lrecently: 9sources@32GHz 4sources@43GHz 2sources@87GHz 1source@144GHz Note: - need more sensitivity - 72% of all pulsars δ < 0 deg - no appropriate telescope in the South so far! FundamentalPhysicsinRadioAstronomy

5 Pulsars'may'even'become'stronger' Somepulsarsobservedat9mmand7mmseemtoshowapeculiarspectralchange: Flux Dens FluxdenistymJy) Frequency GHz) B B Frequency GHz) ] ] ] ] Thisdoesnotcometotallyunexpected,e.g.weknowfromtheCrabthatitsinfrared fluxdensityismuchhigherthanthehigh-frequencyradiofluxdensity Similarobserva3onsalsoforVela Unknownemissionradioiscoherent,butthere shouldbealsoincoherentcomponent Findingthetransi3onfrequency betweenthecoherentandincoherent partwouldgivesustheimportant unknownintrinsiccoherencelength!coherentprocess!?! Intensity +1/3 coherent N bunch Krameretal.1997) cf.michel1978) +1/3 incoherent log Frequency

6 Use'ALMA'to'understanding'Gravity' Kramer&et&al.&2015) Generalrela3vityconceptuallydifferentthandescrip3onofotherforces ButGRhasbeentestedprecisely,e.g.insolarsystem Classicaltests: -Mercuryperihelionadvance -Light-deflec3onatSun -Gravita3onalredshiN Moderntestsinsolarsystem, -LunarLaserRangingLLR) -Radarreflec3onatplanets,CassinispacecraNsignal -LAGEOS&GravityProbeB -BinaryPulsarsHulse-TaylorPulsar,DoublePulsar) But,isthereaproblem..? Seeprecisioncosmology:Infla3on?DarkMaoer?DarkEnergy? Ques3on:WillEinsteinhavethelastwordonmacroscopic)gravity doesgrfailfarbelowtheplanckenergy?alterna3ves? Weneedtotestgravityinstrong,non-linearcondi3ons,i.e.NS,BH Whataretheproper3esofblackholesandalsogravita3onalwaves? Periastron shift s) Year LR/ITP) Newtonian Gravity Prediction of GR for gravitational quadrupole emission

7 Can'we'probe'Sgr'A*'with'pulsars' 'are'there'any?' Wehaveevidenceforpastforma3onofmassivestarsintheGalac3cCentre, i.e.massivestarsandtheremnantsarebeingobserved Itisaregionofhighstellardensity,soexchangeinterac3oncanproduceall typesofbinarycompanions,wecanexpectallkindsofextremebinarysystems e.g.faucher-giguere&loeb2011)predicthighlyecc.stellarbh-mspsystems Wecanevenexpect>1000pulsars,incl.millisecondpulsarsWhartonetal.2013) Wecanprobe: -starforma3onhistoryfromchar.ages) -localgravita3onalpoten3alfromaccel.) -distribu3onandproper3esofcentralism -proper3es&strengthofcentralb-fieldrm) Observed Derived Lorimeretal.2006)

8 Can'we'probe'Sgr'A*'with'pulsars' 'are'there'any?' Wehaveevidenceforpastforma3onofmassivestarsintheGalac3cCentre, i.e.massivestarsandtheremnantsarebeingobserved Itisaregionofhighstellardensity,soexchangeinterac3oncanproduceall typesofbinarycompanions,wecanexpectallkindsofextremebinarysystems e.g.faucher-giguere&loeb2011)predicthighlyecc.stellarbh-mspsystems Wecanevenexpect>1000pulsars,incl.millisecondpulsarsWhartonetal.2013) Effelsberg10.5GHz Seiradakisetal.1989) Observed Derived Lorimeretal.2006)

9 Can'we'probe'Sgr'A*'with'pulsars' 'are'there'any?' Wehaveevidenceforpastforma3onofmassivestarsintheGalac3cCentre, i.e.massivestarsandtheremnantsarebeingobserved Itisaregionofhighstellardensity,soexchangeinterac3oncanproduceall typesofbinarycompanions,wecanexpectallkindsofextremebinarysystems e.g.faucher-giguere&loeb2011)predicthighlyecc.stellarbh-mspsystems Wecanevenexpect>1000pulsars,incl.millisecondpulsarsWhartonetal.2013) Effelsberg10.5GHz Seiradakisetal.1989) Macquartetal.2010)

10 WehaveonlyprobedtheouterlayeroftheGalac3ccentrepopula3on: usinganominaldistanceof8.33kpcgillessenetal. 09),theclosestweusedtoget wasabout20pc! SearchingforpulsarsintheGalac3cCentre Current state of art: Parkes/Effelsberg Johnstonetal.2006 &unpublisheddata) PSR J % * Dedicatedsurveyssofarinclude: -Effelsberg4.9GHz,Kleinetal GHz,Eatoughetal.)) -GBT1.8GHz,Denevaetal. 09; 14.8GHz,Macquartetal GHz,ongoing) -Parkes2.3/8.5GHz,Johnstonetal. 06) Macquartetal.2010) Background: Seiradakisetal.1989) % Deneva et al. 2009)

11 SelecEon'effects' 'Why'is'it'so'hard? TheinhomogeneousionizedISMssmearsandscaoersthepulsesNB:dispersioniseasy ): Expectedscaoering3meisenormous: Bhatetal.2004) Cordes&Lazio1997) !Inpar3cularatthecentre: At normal searchfrequenciespulsesshouldbeundetectable!

12 'RelaEvisEc'effects'for'a'pulsar'orbit'around'Sgr'A*' Pulsarina0.3yreccentric e=0.5)orbitaroundsgra* Semi-majoraxis: 72AU=860R S Pericenterdistance: 36AU=430R S Pericentervelocity: 0.042c~20 DoublePulsar) Pericenteradvance: 1pN: 2.8deg/yr, ΔL~1.8AU/yr 2pN: 0.014deg/yr, ΔL~1,400,000km/yr Einsteindelay: 1pN: 15min 2pN: 1.6s Propaga3ondelayi=0 /i=80 ): Shapiro1pN: 46.4s/246.9s Shapiro2pN: 0.2s/8.0s Framedragging: 0.1s /6.5s BendingdelayP=1s):0.2ms/4.2ms Lense-Thirringprecession: OrbitalplaneΩLT: 0.052deg/yr,ΔL~10 7 km/yr Similarcontribu3onto FundamentalPhysicsinRadioAstronomy Geod.precession1.4deg/yr

13 'Mass'of'Sgr'A*,'a'first'GR'test'&'the'GC'distance' M BH >>m PSR onlyonerela3vis3ceffectneededtomeasuremassofsgra* Simula3ons:5yrof3ming,one100µsTOAperweek:Massprecision~1M "! Liu2012);Liu&et&al.&2012) AfirstGRtest: M S? = M E Note:massmeasurementnot affectedbytheuncertaintyinr 0! Combiningwith 10μasastrometry frome.g.gravity R 0 with~1pcuncertainty FundamentalPhysicsinRadioAstronomy

14 Determining'magnitude'&'projecEon'of'the'spin'of'Sgr'A*' Tes3ngCosmicCensorshipConjecture: c G S M 2 apple 1 S pericenter plane of the sky λ Φ Ψ i θ ω Liuetal.2012) [Wex&Kopeikin1999,Liuetal.2012] PulsarorbitP b =0.3yr,e=0.5 WeeklyTOA:100μs FundamentalPhysicsinRadioAstronomy

15 Determining'magnitude'&'projecEon'of'the'spin'of'Sgr'A*' Tes3ngCosmicCensorshipConjecture: c G S M 2 apple 1 IncaseofanakedKerr-singularity: 1.. ω 0.5 χλ = χ cosλ) x. ω ẋ. Liuetal.2012) χ θ = χ cosθ) Liuetal.2012) [Wex&Kopeikin1999,Liuetal.2012] PulsarorbitP b =0.3yr,e=0.5 WeeklyTOA:100μs FundamentalPhysicsinRadioAstronomy

16 Pulsarina0.1yrorbitaroundSgrA*: TesEng'the'noNhair'theorem' No-hairtheorem Q=-S 2 /M&&unitswherec=G=1) -Secular&precessioncausedbyquadrupoleis2ordersofmagnitudebelow framedragging,andisnotseparablefromframe-dragging -Fortunately,quadrupoleleadstocharacteris9c&periodic&residuals [Liuetal.2012,Wex&et&al.&in&prep] Χ=1 Χ=0.2 NoAhair&theorem&testable&&to&~1%& Liu&et&al.&2012) Incaseofpertuba3ons, seelater... FundamentalPhysicsinRadioAstronomy

17 The'first'pulsar'in'the'GalacEc'Centre' Eatough et al. 2013) GHz Effelsberg, 2.4 h, 0.24 mjy) FirstdiscoveredwithSWIFTKenneaetal. 13) andnustarmorietal.13) 14.6 GHz Effelsberg, 1.0 h, 0.24 mjy) Pulsa3onsat3.76s DiscoverybyEffelsbergandlaterNancayand Normalized flux density 8.67 GHz VLA, 3.5 h, 0.8 mjy) 8.35 GHz Effelsberg, 3.6 h, 0.22 mjy) 4.85 GHz Effelsberg, 3.7 h, 0.16 mjy) JodrellatradiofrequenciesEatoughetal. 13) Observeddispersionandrota3onmeasures placeitfirmlyinsidethegalac3ccentre Es3mateddistanceabout0.1pc Itisaradio-loudmagnetar=veryrareNS! 2.5 GHz Nançay, 4.2 h, 0.20 mjy) 1.5 GHz Jodrell Bank, 7.0 h, 0.09 mjy) Pulse phase Proofthatpulsarsexistin Galac3cCentreregion!! FundamentalPhysicsinRadioAstronomy

18 Not'normal:'The'interesEng'properEes'of'PSR'J1745N2900! ' Poweroutputfromspin-downnotenough toexplainx-rayluminosity;likelya magnetarmorietal.2013). Couldbeascloseas0.1pcsameasSstars).Orbitalperiod>500yr Proper mo3onpossiblewithvlbi. Singlepulsesmeasured ProbeofGalac3c Centrescaoering. DM1778±3cm -3 pc HighestDMknown ~100%linearlypolarized. Rota3onMeasure-66960±50radm -2 LargestRMmeasuredintheGalaxywith excep3onofsgra*). LetsusprobetheGalac3cmagne3cfieldat theboundaryofthebondiaccre3onzone ofsgra* PSRJ detec3onwiththeVLBAandJVLA. Boweretal.2014,2015) We discovered very rare pulsar! There must be more! FundamentalPhysicsinRadioAstronomy

19 The'magneEc'field'of'Sgr'A*' LETTER doi: /nature12499 Eatoughetal.2013) A strong magnetic field around the supermassive black hole at the centre of the Galaxy R. P. Eatough 1, H. Falcke 1,2,3, R. Karuppusamy 1, K. J. Lee 1, D. J. Champion 1, E. F. Keane 4, G. Desvignes 1, D. H. F. M. Schnitzeler 1, L. G. Spitler 1, M. Kramer 1,4, B. Klein 1,5, C. Bassa 4, G. C. Bower 6, A. Brunthaler 1, I. Cognard 7,8, A. T. Deller 3, P. B. Demorest 9, P. C. C. Freire 1, A. Kraus 1,A.G.Lyne 4, A. Noutsos 1, B. Stappers 4 & N. Wex 1 Direction Earth 2 1 Q 0 Amplitude Wavelength U f GHz) f GHz) FundamentalPhysicsinRadioAstronomy

20 Record'observaEons'of'the'GC'Magnetar' Torneetal.tobesubmioed) Detec3onupto154GHz,perhaps even225ghz! Singlepulsesupto154GHz! Simultaneousobserva3onswithPico VeletaandEffelsberg:5-154GHz

21 Also'normal'pulsars'detectable!' PSR'B ' Newrecord! Detec3onalsoat102&134GHz Changeofspectrum? WecandetectpulsarsatALMA frequencies! Torneetal.tobesubmioed)

22 Where'are'the'pulsars?' 'Sca\ering'revisited' BasedonourmeasurementsofthescaoeringforthemagnetarSpioleretal.2013) lotsofpeoplehaveclaimedthattherearenotanypulsars,sincescaoeringsolow However,mediumisveryturbulentandthereisalotof"weather" newresult: 8000 Spioleretal.inprep.) Scattering 1 GHz ms) Epoch MJD)!Scaoeringmaterialisclosetosource,consistentwithRMchange!! Wemaynotseepulsarsallthe3me!

23 ParEal'visibility'&'External'perturbaEons' InWexetal.inprep.)wedevelopfulldynamictreatmentofpulsar3mingaboutSGRA* WegobeyondbeyondWex&Kopeikin1999)andLiuetal.2012)tostudyresiduals Onlymeasuringpartoforbitaroundpericentresufficienttodeterminespin Wexpriv.comm.) Wexpriv.comm.) par3alorbits FundamentalPhysicsinRadioAstronomy

24 ParEal'visibility'&'External'perturbaEons' InWexetal.inprep.)wedevelopfulldynamictreatmentofpulsar3mingaboutSGRA* WegobeyondbeyondWex&Kopeikin1999)andLiuetal.2012)tostudyresiduals Onlymeasuringpartoforbitaroundpericentresufficienttodeterminespin Wexpriv.comm.) Wexpriv.comm.) par3alorbitswithpertuba3ons worstcase) Evenincaseofperturba3ons whichwillactawayfrompericentre wecanuse par3alorbitobserva3onstomeasurespin! FundamentalPhysicsinRadioAstronomy

25 3DNdirecEon'of'BH'spin'from'pulsar'orbit' InWexetal.inprep.)weshowthattherela3vemo3onofSGRA*toSSBaffects observedpulsarorbitinadrama3cwaythatallowsustodeterminefullbhspin notonlyprojec3ons!): P b =1yr,e=0.8,i=60 o,ω=45 o ) S K0 λ r φ Υ Ω=0 o,ω=90 o Wexpriv.comm.) Wecancomparetheseprecisionmeasurement toehtresults... FundamentalPhysicsinRadioAstronomy

26 Combining'the'image'and'pulsars' Asinglepulsarcangiveyouprecisespin&direc3on poten3allyverycleanly! A: face-on GR Models with two orientations of spin axis B: edge-on pulsar orbit Thepulsarprobesthefar-field. Theimageprobesthenear-field. Theybothmustfit,i.e.predictimage frompulsarobserva3onsandcompare. Combiningthetwoinforma3onisa uniquetestoftheoriesofgravity =attheheartofercblackholecam seealsowex,psal3s&kramer,inprep.) Spin axis B Spin axis A FundamentalPhysicsinRadioAstronomy