脉冲星观测技术与搜寻PPT文档.ppt

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level,Fifth level,*,Fare clic per modificare lo stile del titolo,Fare clic per modificare gli stili del testo dello schema,Secondo livello,Terzo livello,Quarto livello,Quinto livello,*,Large-Scale Surveys Using the Arecibo Telescope,*,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,Click to edit Master title style,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,Click to edit Master title style,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,脉冲星,观测技术和搜寻,1,思考题,/提纲,脉冲星信号发射时的特征是什么？,脉冲星信号传播过程中有那些改变？,脉冲星观测可以用什么样的望远镜？,脉冲星观测和搜寻的关键技术点是什么？,脉冲星搜寻中选择效应,过去脉冲星发现和搜寻结果,脉冲双星系统的搜寻,特殊目标的脉冲星搜寻,将来脉冲星搜寻的主要任务,2,MilkyWay in Sky,0329,中子星,半径仅10公里，,有极强的磁场10,8-14,G，极高的密度10,14,g/cm,3,.,它们旋转，产生脉冲，成为,脉冲星！,3,恒星由气体收缩形成，核合成放出能量，完结后爆炸！,超新星爆炸,中子星,黑 洞,红巨星,超新星爆炸后留下：超新星遗迹，,和,中子星,或,黑洞！,中子星,半径仅10公里，,有极强的磁场10,8-14,G，极高的密度10,14,g/cm,3,.,它们旋转，产生脉冲，成为,脉冲星！,4,电磁波谱,光学波长：几千埃(10,-10,m),电波：=1 m =300 MHz,=1 mm =300 GHz,1054 AD,爆炸，中国史书记录完整，年龄,可靠,.,脉冲星周期33毫秒,.,该脉冲星从射电到光学到高能，全波段辐射,蟹状星云及其,脉冲星,(Abdo et al.2010),6,银河系=恒星+星际介质,+中子星+黑洞+暗物质,Crab,从,射电到光学到,X和,，,全波段辐射,！,讨论几个问题：,1.不同波段周期及变化是否相同？,2.不同波段的脉冲相位一样？,3.不同波段的脉冲现状是否相同？,4.那些波段受星际介质影响？,7,波形随频率变化,:,辐射频率与辐射高度有关,Thorsett 1991,Phillips&Wolsczcan(1992),宽度一般随频率减少,.,低频在高处发出,脉冲宽度,观测频率,8,星际介质的色散：,介质中电磁波传播的,相速度为,v,p,=c/n,;,但群速度为,考虑电磁波 在稀薄气体中传播时，,电子被电磁波电 场加速运动的方程为,n,个电子一起引起的偶极偏振电场：,介电常数为,共振频率为,=0,介质对电磁波的反射系数为,电磁波的传播延时为,注意：与光速的差取决于,2,仅仅低频电磁波收星际介质影响！,9,方法：,将频段分为多个小频带,探测每个小频带的脉冲，然后相加。,射电波段观测：,色散要消除！,10,地球大气窗口,射电窗口,大气吸收率,11,Interstellar medium:,Clouds&large-scale structure?,Chandra,XMM,HST,VLT,观测脉冲星的望远镜,地面：,射电+光学,空间：,红外+光学+紫外+X射线+,射线,12,观测脉冲星的基本要求,因为脉冲星信号微弱，因此望远镜必须足够大，并且积分时间足够长，才能够收集足够多的光子！,因为要观测的是脉冲，必须有足够的时间分辨率采样。观测毫秒脉冲星，要微秒分辨！,因为有各种干扰和辐射背景，观测必须消除它们的影响！,发现一个脉冲星，必须有精确的位置，并与周边的目标明确区别！,13,几种望远镜和脉冲星观测成果举例,射电望远镜,红外、光学、紫外望远镜,X射线望远镜,射线望远镜,14,德国,100,米,美国,104,米,美国,300,米,Arecibo,我国,500,米口径,球面射电望远镜,FAST,：,2007,批准,投资,6,亿。,2009,开建，,5,年完成,澳大利亚,64,米,世界上的大射电望远镜,15,射电望远镜的,组成,框图,射电望远镜,-,引论,天线控制方位俯仰,抛物面天线,副反射面,天线,馈源 和,前端接收机,数字后端,观测监控数据显示,观测者,16,不同形式的抛物面天线基本光路,Prime focus,Cassegrain,Off-axis Cassegrain,Naysmith,Beam waveguide,Offset Cassegrain,=receiver,Parkes,发现了已知2267颗脉冲星的 2/3，包括双脉冲星，RRAT！首次测偏振，确定辐射来自磁极，RVM！,17,不同形式的抛物面天线基本光路,Prime focus,Cassegrain,Off-axis Cassegrain,Naysmith,Beam waveguide,Offset Cassegrain,=receiver,18,Cassegrain,和,Gregorian,光学系统,19,Cassegrain(,卡塞格林,),和,Gregorian,(,格里高利,),望远镜,优势：照明溢出少、照明效率高、馈源仓空间得到拓展；,劣势：较窄的照明角度导致馈源尺寸大、长度长。,德国,Effelsberg100,米射电望远镜,20,不同形式的抛物面天线基本光路,Prime focus,Cassegrain,Off-axis Cassegrain,Naysmith,Beam waveguide,Offset Cassegrain,=receiver,发现质量最大的脉冲星！,发现周期最短的脉冲星！,21,天线装配方式和指向与跟踪,赤道式：无盲区、波束不旋转、跟踪精度高；重力形变大、造价高,地平式：造价低、重力形变小；天顶盲区、波束旋转,英国Jodrell Bank76米射电望远镜,长期Timing了大量脉冲星。首次发现球状星团脉冲星。,22,美国,Arecibo 300,米,发现第一颗脉冲双星-诺贝尔奖！,发现第一颗毫秒脉冲星！,23,Arecibo,光路,24,国际新低频望远镜,LOFAR,的天线,LOw Frequency Array,荷兰主导,LBA,：,10MHz80MHz,HBA,：,120MHz240MHz,无可匹敌的脉冲星,低频观测能力！,美国LWA项目,25,荷兰Westerbork Synthesis Radio Telescope（WSRT),14 面 25m 天线,(4 个可移动),东西向排列,最长基线,2.7km,300 MHz 9 GHz,26,印度G,iant,M,etrewave,R,adio,T,elescope,150 1420 MHz,3045,米,等效,246,米,over 25 km,！,27,光学、红外、紫外观测脉冲星,目前仅仅几颗年轻脉冲星,Crab脉冲星光脉冲探测和定位,Crab脉冲星光脉冲偏振,HST的脉冲图像,HST测脉冲星自行和激波！,2012年拍伴星光谱定最大质量脉冲星！,HST,连续高速摄影是必须的！,28,光学、红外、紫外观测脉冲星,仅仅几颗年轻脉冲星,Crab脉冲星光脉冲探测和定位,Crab脉冲星光脉冲偏振,HST的脉冲图像,HST测脉冲星自行和激波！,2012年拍伴星光谱定最大质量脉冲星！,HST,29,X射线望远镜的脉冲星观测,/导航？,XMM-Newton,Chandra,25 Pulsars,X-ray,Binary,12 Magnetars,RXTE,SWIFT,0.1-10 keV,7 CCOs in SNRs,注意：,1.每秒钟每平方厘米有几个X射线光子？,=请查找答案！,2.每个光子的到达时间要改正,卫星绕地球,和,地球绕太阳,的几何轨道效应！,30,射线望远镜,见教材 31页射线望远镜列表 表3.2,HESS 2,MAGIC,地面,Cerenkov望远镜,VERITAS:Next-Generation TeV Observatory,31,之前感觉美国能够Compton,卫星天文台的EGRET很牛！测到7颗脉冲星,32,射线望远镜Fermi-预想不到的牛,33,技术关键点,卫星记录的每个光子到达时间折算到太阳系质心，必须扣除所有运动项！,难的是几年内把每个光子时间精度弄到亚微秒量级,34,脉冲星周期：,2.5ms,轨道周期：,93分钟,总观测时间：,1437天！,搜寻办法：,盲搜！,35,以射电为例！,脉冲星搜寻的基本问题,36,射电望远镜的,组成,框图,射电望远镜,-,引论,天线控制方位俯仰,抛物面天线,副反射面,天线,馈源 和,前端接收机,数字后端,观测监控数据显示,观测者,37,低噪声,放大器,滤波器,本地,振荡器,可调,滤波器,1570 MHz,1420 MHz,可调本地,振荡器,150 MHz,模数转换器,ADC,计算机,+,+,150 MHz,射电望远镜：超外差接收,天线馈源,天体信号,1420MHz,混频器,1 MHz,混频器,中频信号,滤波器,滤波器,38,脉冲星的真实数据记录,39,傅里叶变换，分析周期,脉冲比较窄，谐波能量要联合检测,40,脉冲信号波包因为星际介质而色散,脉冲星在各个频率上同时辐射信号，但星际介质电离气体使低频信号延迟一些到达地球,.,脉冲星,信号的特点,消色散技术（也是排除干扰的方法）,脉冲星信号的周期和轮廓非常稳定,单个脉冲变化但平均脉冲非常稳定，周期特别精确,.,用,FFT,找周期,!,41,方法：,将频段分为多个小频带,探测每个小频带的脉冲，然后相加。,色散要消除！,42,低噪声,放大器,滤波器,本地,振荡器,可调,滤波器,1570 MHz,1420 MHz,可调本地,振荡器,15,1,MHz,计算机,+,+,150 MHz,射电望远镜：超外差接收,天线馈源,天体信号,1420MHz,混频器,中频信号,滤波器,模数转换器,ADC,混频器,1 MHz,滤波器,模数转换器,ADC,混频器,1 MHz,滤波器,模数转换器,ADC,混频器,1 MHz,滤波器,150 MHz,1,49,MHz,43,标准的脉冲星搜寻方法,from Lorimer&Kramer,44,以射电为例！,脉冲星搜寻的基本问题,1.灵敏度：,望远镜增益和接收机噪声、,天空背景,2.时间分辨率：,记录数据的快慢：采样率,3.色散,-射电波段,：,不可忽略的星际介质效应,实际上还有散射效应的麻烦,4.干扰,硬盘要能够存储！,数据总线速度匹配才行！,目前还是受限！,45,射电望远镜的灵敏度,用最小可探测的射电源流量来表示。,最小可检流量S,min,由系统噪声温度T,sys决定：,这里，T,sys,是整个射电望远镜系统的噪声温度，要折算到接收机之前。A是望远镜的孔径面积，,A,是天线效率，T是观测时间，B是信号接收带宽，n,P,是偏振通道数。,问题：如何提高望远镜的灵敏度？（即降低,F,min,）,提高灵敏度方法：,1.,提高天线效率；,2.,增大反射面口径；,3.,降低系统噪声；,4.,增加观测时间；,5.,增大接收机带宽；,6.,双偏振通道观测,G=,4,p,A,0,/,l,2,=,4,p,/,W,A,46,脉冲星探测的信噪比,(04-24),脉冲周期为,P,，但仅在,w,的时间内有信号，脉冲的信噪比为：,47,LAMBDA/Haslam et al.(1982)/ATA/CGPS/Fomalont/Junkes/Hughes/Duncan,Radio Sky at 408 MHz,The GBT350 Survey,已知脉冲星在银河系内的分布,49,Radio Sky at 1.4 GHz,by W.Reich,50,脉冲星探测的灵敏度曲线,对脉冲星周期敏感！,对脉冲宽度敏感 假设,5%,！,每一通带,DM,导致的脉冲致宽敏感,双偏振接收！,Tsys,尽量小,G,尽量大,t,尽量长,采样时间：,pc,52,0.43 1.18 1.48 2.4 GHz,Mitra&Ramachandran(2001,):,星际介质散射和脉冲轮廓变宽,Bhat et al.2004,注意与,-4,有关！,53,脉冲星搜寻中选择效应,大,DM,的脉冲星受限,Channel,内,DM,延迟没有清除,短周期的脉冲星受限,(t,samp,),长周期脉冲星受限！,散射使大,DM,脉冲星轮廓延展,(t v,-4,),宽的脉冲星不容易探测,大望远镜：,beam,小,=,天区范围限制！,双星轨道使脉冲周期变化，不能探测！,Parkes Multibeam,巡天灵敏度曲线,54,真实数据的,FFT,FFT,结果含有明显的因为系统限制而出现的红化噪声，必须归一化！,55,干扰问题,干扰不可避免！,如何消除影响？,56,Eatough et al.(2009,MN),57,干扰清除后的效果,58,59,脉冲星数据搜寻输出图,:,实例,-1,60,脉冲星数据搜寻输出图,:,实例,-2,61,强的单个脉冲,和RRAT,搜寻,主要是,DM,考虑,可以用于找,RRAT,可以用于找河外单个脉冲,Lorimer et al.(2007,Scien.),62,思考题,/提纲,脉冲星信号发射时的特征是什么？,脉冲星信号传播过程中有那些改变？,脉冲星观测可以用什么样的望远镜？,脉冲星观测和搜寻的关键技术点是什么？,脉冲星搜寻中选择效应,过去脉冲星发现和搜寻结果,脉冲双星系统的搜寻,特殊目标的脉冲星搜寻,将来脉冲星搜寻的主要任务,63,脉冲星的发现,完全偶然，细心的女学生！,Faster Reaction!,64,过去的一些脉冲星巡天和结果,Manchester,主持的巡天,65,课本44页,66,Parkes Multibeam Pulsar Survey,Principal papers:,A,long Galactic plane,:,-100,o,l 50,o,|b|800,pulsars discovered,High-latitude surveys,:,100,new,pulsars,(,12,MPS),I:Manchester et al.,MNRAS,328,17(2001),System and survey description,100 pulsars,II:Morris et al.,MNRAS,335,275(2002),120 pulsars,preliminary population statistics,III:Kramer et al.,MNRAS,342,1299(2003),200 pulsars,young pulsars and,-ray sources,IV:Hobbs et al.,MNRAS,352,1439(2004),180 pulsars,281 previously known pulsars,V:Faulkner et al.,MNRAS,355,147(2004),Reprocessing methods,17 binary/MSPs,VI:Lorimer et al.,MNRAS,372,777(2006),142 pulsars,Galactic population and evolution,67,脉冲星发现的数目与年代,2000,2010,68,Parkes,巡天的天区覆盖,Parkes Multibeam Pulsar Survey(completed),Parkes High Latitude Pulsar Survey(completed),Perseus Arm Pulsar Survey (in progress),Parkes Methanol Pulsar Survey (just started),Globular Clusters Pulsars Search(in progress),69,Parkes 64m:,2010-2013 July.30th,I-VII,70,Parkes 64m:,2013 July.30th,71,Effelsberg 100m:,2013 Aug.5th,72,Effelsberg 100m:,2013 Aug.5th,73,Parkes multibeam pulsar surveys,74,脉冲星发现的数目与年代,75,Pulsars:Significant Discoveries,The first radio pulsar,PSR 1919+21 was discovered in 1967(,Nature,217,:709-713,1968).,The first binary pulsar,PSR 1913+16,whose orbit is decaying at the exact rate predicted due to the emission of,gravitational radiation,by,general relativity,The first millisecond pulsar,PSR B1937+21,The first,extrasolar planets,to be discovered orbit the pulsar,PSR B1257+12,The first,double pulsar,binary system,PSR J07373039,T,he most massive pulsars:2M,(PSR J1614-2230&J0348+0432),The magnetar,SGR 1806-20,produced the,largest burst of energy in the Galaxy ever experimentally recorded,on 27 December,2004,PSR B1931+24.appears as a normal pulsar for about a week and then switches off for about one month before emitting pulses again.,PSR J1748-2446ad,at 716 Hz,the pulsar with,the highest rotation speed,.,PSR J0108-1431,the closest pulsar to the Earth at a distance of about 86,parsecs,.,The brightest millisecond pulsar,PSR J0437-4715,The first X-ray pulsar,Cen X-3,The first accreting millisecond X-ray pulsar,SAX J1808.4-3658,76,The GBT350 Survey,已知脉冲星在银河系内的分布,第一颗河外脉冲星？,27 PSRs in LMC&SMC,77,银河与LMC之间 HI 的桥,HI in LMC,Magellanic,Stream,160 kpc across,LMC,78,银河与LMC之间 HI 的桥,HI in LMC,Magellanic,Stream,160 kpc across,LMC,79,80,Arecibo Multibeam Surveys,Pulsars,HI,Galactic RMs,北半球的可观测天区,Arecibo,的天区,Arecibo,的天区,82,银河系=恒星+星际介质,+中子星+黑洞+暗物质,83,Arecibo,的,ALFA,脉冲星巡天,Arecibo telescope+7-beam ALFA receiver,Frequency:1.23-1.53 GHz;BW=300 MHz;1024 Channel,Integration time:67s(precursor),135s/278s(ongoing),2.5 to 5 times further than Parkes MB,Beam size:204”x 232”;outer beam:329”x 384”,Central beam gain:11 K/Jy;outer beam gain:8 K/Jy,Tsys:about 25 K at 1400 MHz,Deep Galactic plane survey:|b|5 deg,32 l 80 deg,Medium latitude surveys:5|b|25 deg,Millisecond pulsars(z scale height 0.5 kpc),High-velocity pulsars(50%escape)(scale height=?),NS-NS binaries (typical z 5 kpc),NS-BH binaries(typical z few kpc?),Nice et al.,35 pulsars,Simulated 1000 pulsars to be found in ALFA survey,Known Pulsars discovered with Parkes,Arecibo&GBT,Nice et al.,35 pulsars,detect MSPs at DMs 16 times larger than PMB,able to detect sub-millisecond pulsars(if they exist).,better sensitivity to binary pulsars with short orbital periods,no complex and CPU-intensive algorithms are needed to detect fast binary systems,discovery of PSR J1906+0746,：,no curvature is seen.Pulsar is faint.,Arecibo,的,ALFA,脉冲星巡天,Discovery of PSR J1906+0746,PMB data:pulsar was detected only after Arecibo!,Acceleration prevented the earlydetection of this system!,首例双星中的脉冲星,观测与理论预言完全一致！,Russell Hulse Joseph Taylor,1993,2nd Nobel Prize for pulsar!,PSR B1913+16：1975年用 Arecibo发现!,它是一个双星系统,相对论预言，,因为发出引力波（是已知电磁波外的新辐射形式：,Gravitational Wave,），,轨道进动，轨道缩小,(每天1cm！),。最后会并合！,89,双脉冲星的发现,PSR J0737-3039AB,：,Pb=2.4 h e=0.08,Merging in 85Myr!,最强的相对论效应系统！,22.7 ms,1.7 x 10,-18,200 Myr,6 x 10,9,G,1,080 km,5 x 10,3,G,6000 x 10,30,erg/s,301 km s,-1,A,2.77 s,0.88 x 10,-15,50 Myr,1.6 x 10,12,G,132,000 km,0.7 G,1.6 x 10,30,erg/s,323 km s,-1,P,P,age,B,surf,R,LC,B,LC,dE/dt,V,orb,B,.,基本参数,.,观测到,A,星粒子调制,B,星信号,观测到,B,星磁层堰塞,A,信号传播,引力理论有更精确地测时,(Burgay et al.2003,Lyne et al.2004),90,M,A,=1.3381,0.0007 M,sun,M,B,=1.2489,0.0007 M,sun,(Kramer et al.2006 Science,314,97,),爱因斯坦99.95%地准确!,+16 -39,双脉冲星系统,更强的相对论轨道，给与更快更好的引力理论检验,GR value Measured value Improves as,Periast.adv.(deg/yr)-16.8995,0.0007 T,1.5,Grav.Redshift(ms)0.3842 0.386,0.003 T,1.5,P,b,Orbit decay -1.248 x 10,-12,(-1.252,0.017)x 10,-12,T,2.5,r,Shapiro range(,s)6.15 6.2,0.3 T,0.5,s,Shapiro sin,i,0.99987 0.99974 T,0.5,.,.,91,几个双星轨道的比较,2M,92,脉冲星搜寻中选择效应,大,DM,的脉冲星受限,Channel,内,DM,延迟没有清除,短周期的脉冲星受限,(t,samp,),长周期脉冲星受限！,散射使大,DM,脉冲星轮廓延展,(t v,-4,),宽的脉冲星不容易探测,大望远镜：,beam,小,=,天区范围限制！,双星轨道使脉冲周期变化，不能探测！,Parkes Multibeam,巡天灵敏度曲线,93,轨道周期,P,orb,调制在脉冲星,的精确周期上，使脉冲星,FFT,周期搜寻出现麻烦！,分三种情况考虑：,1,）,长轨道周期,：观测数据的时间跨度,TP,orb,-,直接搜寻！暂时不考虑轨道周期,2,）,中等轨道周期,：,T P,orb,-,做,DFT,但要搜寻脉冲星频率的旁瓣,双星系统和加速搜寻,94,轨道频率的调制和脉冲星的搜寻,Ransom et al.(2003,ApJ 589,911),没有轨道调制的,FFT,实际观测数据分析：,8,小时对,47Tuc,的观测