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1、伽玛射线暴 宇宙中最猛烈的爆发,戴 子 高南京大学天文系,能源比较,物质组成：分子原子电子、原子核 核子（质子、中子）夸克化学能：1 eV/原子，效率10-9 20吨汽油=41019尔格=500吨TNT 核能：1 MeV/核子，效率10-3 1公斤235U=21021尔格=2万吨TNT夸克能：100MeV/核子，效率10-1 1公斤物质=21023尔格=200万吨TNT 暴释放能量=1051尔格=1034吨TNT,核弹,A.Einstein:E=mc2 1945，广岛、长崎原子弹爆炸1949，美国成功研制氢弹1951，前苏联成功研制原子弹1964，中国成功研制原子弹1967，美国发射Vela卫
2、星 发现伽玛射线暴1973，Klebesadel,Strong&Olson 发表第一篇文章,花 絮,活跃形势观测概况标准模型物理效应及意义能源机制伽玛暴宇宙学展望,报告内容,一、活跃形势,1997年世界10大科技成就,1999年世界10大科技成就,2003,Science,302,2042-2043,GRB 030329-SN 2003dh;High polarization of GRB 021206;X-ray flashes;Dark bursts;Short bursts in the Swift era.,2003年世界10大科技成就,暴论文的分布 K.Hurley,2001.3,暴
3、论文的逐年 分布。1973-首次发表 1979-Mazets表 1991-GRO卫星 1997-BeppoSAX,暴论文的分布 K.Hurley,2001.3,累计分布暴论文累计已达 到5000篇。,二、观测概况,暴是什么？,暴时间特征,波形复杂、没有规则持续时间 ms-1000 s变化时标 1ms,甚至 0.1ms,恒星层次的事件,T ms Ri cT=300 km(Ri:初始尺度)即使对于黑洞：R=2GM/c2 M 100 M 射线暴:恒星层次天体(且为致密星),暴 能 谱,光子能量：10keV 10GeV非热谱，幂律谱高能未见切断,空间分布,高度各向同性 BATSE,银河系全景图(瑞典吕
4、德天文台),作为对照银河系内天体 脉冲星的空间分布,统计学上支持 宇宙学距离,空间分布：高度各向同性,暴持续时间很短，无法安排后续的观测。暴的发生在空间上是随机的，在时间上也是随机的，无法预先作准备。除短暂的射线（和少量X射线）外，没有其他波段上的对应体，无法借助其他波段上的已知距离的天体加以证认。射线的定位精度极低，在其误差范围内有太多的天体，无法确认哪一个天体与它成协。,1997年之前难点在哪里？,BeppoSAX:暴余辉的发现(1997)宿主星系红移值的测定,距离问题的成功解决,BeppoSAX卫星：导致发现余辉,WFC 226 keV 40o40o 误差范围 3,GRB 监测器 407
5、00 keV,WFC覆盖全天空的 5%,每月约可测1个暴,GRB 970228:a milestone,The Feb.28th burst was caught by BeppoSAX.,On Feb 28,On March 3,Two images:X-ray afterglow of GRB970228,余辉：1997年重大发现,一般特征:多波段,幂律衰减,不少有宿主星系 时标:X-射线:天;光学:月;射电:月 幂律衰减:F t-X=1.1 to 1.6,Optical=1.1 to 2.1 宿主星系:红移可高达3.4，甚至可能达5 确认这些 暴的距离为宇宙学距离,光学余辉,余辉:幂律衰
6、减,射 电 余 辉,早期起伏 空间尺度小 晚期平滑,暴辐射的能量 宇宙中最猛烈的爆发,余辉带来的巨大突破,三、标准模型,火球模型,1.必是黑体2.辐射压大,膨胀火球,(在极高辐射压的作用下，原始火球会快速膨胀到极端相对论的速度，会变成光学薄而导致非热射线辐射.)Ri cT 非热辐射光学厚 解决途径 光学薄极端相论对膨胀Lorentz factor:1,光学厚到光学薄,2,Y.Lithwick,R.Sari,ApJ,555(2001),540,The Standard Internal-External Shock Model,标准模型简化假设,相对论性的运动 各向同性的膨胀 同步辐射 均匀星际
7、介质 典型的质子数密度 1 cm-3 短暂脉冲式的能量注入,统一模型环境效应喷流机制辐射机制能量注入效应 统计关系伽玛暴宇宙学,四、物理效应及意义,极端相对论阶段不长观测可以持续很长时间前人的极端相对论模型不能给出非相对论 和绝热情形的正确极限统一模型的提出,统一模型的提出,动力学演化统一模型,点划线：极端相对论虚线：Sedov极限实线：统一模型,总结性文章 ARA&A(天文与天体物理年鉴)-2000(van Paradijs,Kouveliotou,Wijers),引用Huang,Dai,Lu，1999，MNRAS,309,513,这是统一模型的关键公式,据暴研究其环境的状态据环境状态研究暴
8、的起源,环境效应的研究,非均匀环境,GRB970616 n r-k n r-2(星风环境)(Dai-Lu,MNRAS,1998)支持暴起源于大质量恒星塌缩的观点。(Chevalier-Li,ApJ,2000),GRB990123余辉光变曲线的拐折（Fruchter,et al.,astro-ph/9902236）,环境密度:n 101 106 cm-3.tnr：相对论性火球（或中度喷流）开始转变为非相对 论的时间：tnr（若干天）(n/104 cm-3)-1/3.时间指数:F t-相对论阶段(早期):1=3(p-1)/4 非相对论阶段(晚期):2=(15p-21)/10 1-2=-3(5p-9
9、)/20 1.8)结论:余辉光变曲线在tnr处开始变陡(Wijers et al.1997;Dai&Lu,ApJL,1999).,环境密度效应：余辉光变曲线拐折,致密介质环境,GRB990123的光学余辉光变曲线上的拐折:n104-106 cm-3(相对论到非相对论的过渡 拐折)(Dai-Lu,ApJL,1999)GRB980519的光学到X射线余辉的快速衰减以及其射电余辉(Wang-Dai-Lu,MNRAS,2000),环境效应的意义,环境效应之一：星风效应星风为暴前身星所提供的环境环境效应之二：密度效应 致密环境很可能是分子云暴与恒星形成区成协,两种环境效应的存在均支持“暴起源于大质量恒星
10、的坍缩”,暴与大质量恒星的关联,证据1:暴的位置在恒星形成区内。证据2:暴发生率正比于恒星形成率。证据3:宿主星系是星暴星系。证据4:GRB980425与SN1998bw成协。证据5:余辉光变曲线上出现超新星成分。证据6:X射线余辉谱中出现铁发射线。证据7:X射线余辉显示柱密度很高。证据8:软X射线的吸收,Evidence 2:Wijers et al.(1998):The flux distribution of gamma-ray bursts is consistent with the model that the GRB rate tracks the star-formation
11、rate.,Evidence 4:The supernova(SN1998bw,z=0.0085)associated with GRB980425 is type-Ic(Galama et al.1998).,Hjorth,J.et al.,Nature,423,(2003)847-850,GRB030329/SN2003dh,tSN-tGRB=2days.,Evidence 6:The iron emission line implies a pre-burst supernova explosion(Antonelli et al.2001).,GRB000214:Valentines
12、Day Burst,Evidence 7:Column densities from X-ray observations:1022-1023 cm-2.Only giant molecular clouds have such high column densities(Galama&Wijers 2001).,五、能源机制,能 源 模 型对撞:NS-NS,NS-BH:引力辐射时标:108 yr 大质量恒星塌缩:与恒星形成区成协 与超新星成协NSSS相变(Cheng-Dai,PRL,1996;Dai-Lu,PRL,1998)避免重子污染的自然途径:奇异星 快速旋转的 黑洞+盘 最大可用能量
13、29%MBHc2 42%Mdiskc2(通过 Blandford-Znajek 机制)自转能 结合能,能源：大质量恒星的塌缩,NS SS(避免重子污染的一种自然途径),能量:相变 20 MeV/重子 转动能 51051 ergs I4442 重子只存在于薄壳层内 10-5 M 多次子暴-较差自转 产生率(LMXB内经吸积:NS to SS)10-6/yr 每星系(Cheng Dai&Lu,PRL,1998),中子星结构,不同物态的两种情形,奇异星结构,奇异核表面密度是突变的，锐降为零的。电子因只有电磁作用，没有强作用，分布可延伸更远。吸积正常原子核可形成壳层。,六、伽玛暴宇宙学,GRB Cos
14、mology,High-z(even first-)star-formation rateHigh-z intergalactic medium(reionization)Cosmic expansion and dark energy,Studies on cosmic structure,evolution,and dark energy with gamma-ray bursts,WMAP observations on the CMB anisotropy:4%ordinary matter,23%dark matter,and 73%dark energy.This is becau
15、se the“sound”of the early universethe relative abundances and sizes of the hot and cold spots in the CMBdepend on the composition of the universe and its shape.,2003,Science,302,2042-2043,GRB 030329-SN 2003dh;High polarization of GRB 021206;X-ray flashes;Dark bursts;Short bursts in the Swift era.,Co
16、uld gamma-ray bursts be used to measure cosmology?,Einstein equations Friedmann equations,However,these equations cannot explain an assumed static,closed universe(Einstein 1917)!,Einstein equations with Friedmann equations,These equations can explain an assumed static universe,but this is in an unst
17、able equilibrium.Eddington(1932)thought the observed Hubble expansion might well be just the first-order view of a universe accelerating from rest because of.,Krauss,L.M.1999,Scientific American,deceleration,acceleration,(From Li Zong-Wei),Type-Ia Supernovae,When the mass of an accreting white dwarf
18、 increases to the Chandrasekhar limit,this star explodes as an SN Ia.,Hamuy et al.(1993,1995),Observed luminosity distance of a standard candle DL(z)=Lp/(4F)1/2,Supernova Cosmology,More standardized candles from low-z SNe Ia:A tight correlation:Lp m15(Phillips 1993)Multi-color light curve shape(Ries
19、s et al.1995)The stretch method(Perlmutter et al.1999)The Bayesian adapted template match(BATM)method(Tonry et al.2003)A tight correlation:Lp C12(B-V colors after the B maximum,Wang et al.2005),Phillips(1993),Integral Method for Theoretical DL,Calculate 2(H0,M,)or 2(H0,M,w),which is model-dependent,
20、and obtain confidence contours from 1 to 3.,or,Accelerating UniverseRiess et al.(1998):50 SNe Ia,Dotted:excluding SN1997ck(z=0.97),Accelerating UniversePerlmutter et al.(1999):42 high-z SNe Ia,The biggest question in physics:What is the invisible stuff blowing the universe apart?A decade ago,the ide
21、a of“dark energy”was a historical footnote,something Einstein concocted to balance his equations and later regretted.Now,thanks to observations of distant supernovae and the faint afterglow of the big bang,dark energy is weighing heavily upon the minds of cosmologists.-Charles Seife,2003(June 20),Sc
22、ience,300,1896,The discovery of cosmic speedup,perhaps one of the most important in all of science over the past 25 years,saved a beautiful theory-inflation-and presented theorists with a wonderful puzzle-“dark energy”,the stuff causing cosmic speedup.-Michael S.Turner,2003(April),Physics Today,Ries
23、s et al.(2004,ApJ,607,665):16 SNe Ia discovered by HST.,Transition from deceleration to acceleration:zT=-q0/(dq/dz)=0.46,The deceleration factor:q(z)=q0+z(dq/dz),Riess et al.(2004):=0.71,q0 0(3),and w=-1.02+0.13-0.19(1),Disadvantages in SN cosmology:Redshift 1.7 Dust extinction,GRBs are believed to
24、be detectable out to very high redshifts up to z25(the first stars:Lamb Bromm&Loeb 2002).SNe Ia are detected only at redshifts of z 1.7.,GRB Cosmology Advantages over SNe Ia,GRBs can occur at higher redshifts up to z25;Gamma rays suffer from no dust extinction.So,GRBs are an attractive probe of the
25、universe.,The afterglow jet model(Rhoads 1999;Sari et al.1999;Dai&Cheng 2001 for 1p2):,Ghirlanda et al.(2004a);Dai,Liang&Xu(2004):a tight correlation with a slope of 1.5 and a reduced 20.53,suggesting a promising and interesting probe of cosmography.,Physical Explanations,Synchrotron radiation+jet m
26、odel(Dai,Liang Zhang&Meszaros 2002)Viewing angle effect+jet model(Levinson&Eichler 2005)Comptonization of the thermal radiation flux that is advected from the base of an outflow(Rees&Meszaros 2005)Propagation of relativistic jets in the envelopes of massive stars an energy limit(compared to the Chan
27、drasekhar limit)(our work,in preparation),Dai,Liang&Xu(2004)assumed a cosmology-independent correlation.,Conclusions and Implications,For a flat universe,M=0.35 0.15(1)w=-0.84+0.57-0.83(1)A larger sample established by Swift and WIMS is expected to provide further constraints.Our work stimulated som
28、e studies:Ghirlanda et al.(2004),Friedman&Bloom(2004),Firmani et al.(2005),Mortsell&Sollerman(2005),Di Girolamo et al(2005),Liang&Zhang(2005),WIMS:Wide-sky Image Multiband Spectrometry(PI:张双南教授),Swift,Cosmology-dependent correlation,Cosmology-independent correlation,A larger sample including X-ray,o
29、ptical,and radio light curve breaks?Cosmology-dependent correlationDifferent error analysis X,Still,the correlation is so striking that just 15 gamma ray bursts already reveal the mass content of the universe and its expansion nearly as well as type Ia supernovae and other techniques,Ghirlanda says.
30、His team confidently calls gamma ray bursts“new rulers to measure the universe”in the 20 September Astrophysical Journal Letters.A team from Nanjing University in China,led by Zigao Dai,reached a similar conclusion.Swifts cornucopia of bursts should settle the debate,Xu D.,Dai Z.G.&Liang E.W.(2005,A
31、pJ,in press),A recent improvement:astro-ph/0504404,Wang F.Y.&Dai Z.G.(2005):only SN(solid contours),SN+GRB(dashed contours)following LZ05.,Cosmological constraints from 157 SN+15 GRB,Future Observations,Xu,Dai&Liang(2005):red contours based on a simulated 157-GRB sample,Perlmutter(2003):smallest con
32、tours from SNAP,CMB,Clusters,Comparison of Cosmological Probes,吴雪峰、戴子高、梁恩维,2004,ApJ,615,359-365,Phillips(1993),Conclusions,Finding:GRBs appear to provide an attractive,promising probe of the universe and dark energy one of the most enigmatic clouds.Status:The current GRB cosmology is at babyhood bec
33、ause of the small sample and model assumptions.Prospect:In the Swift and WIMS eras,the GRB cosmology would progress from its infancy to childhood,if a large sample(including low-&high-z bursts)and a more standardized candle are found.Experience:“Chance favors(only)the prepared mind”(Trimble V.2003 o
34、n the GRB meeting in Santa Fe).,七、展 望,GRB领域存在的主要问题,暴的中心天体是什么？分类？有多少亚类？暴本身的辐射机制?早期余辉的观测与规律？暴的宇宙学意义?短暴及其余辉？.,长暴与短暴,2秒：短暴（25%）；2秒：长暴（75%）,How to solve problems?,GLAST,Will study the spectra of bursts over large energy bands and with improved detailDesigned to replace the role of the Compton Observatory
35、,Launch in 2007,Swift,A combined gamma-ray,x-ray,ultraviolet,and optical telescopeDesigned to rapidly identify and pinpoint gamma ray burstsExpected to observe over 1000 gamma ray burst events in unprecedented detail,Launch on 20 Nov 2004,Future instruments:Swift,GLAST,SVOM?!,Gamma-ray Coordinates Network(GCN),一个跨世纪的、综合性的研究课题,1997年获得突破，许多重大问题正开始研究多波段、全波段课题空间的、地面的设备高灵敏的、快速反应的设计要求,深层次、多学科研究的焦点,天体物理光学无线电相对论核物理粒子物理等离子体物理,这是一个有可能获Nobel奖的项目Klebesadel,et al.,条件尚不足的是:深刻的理论意义还没有得到澄清,Thank you,
