Nuclear Astrophysics in the new era of multi-messenger Astronomy
LIGO Detects a Neutron Star Merger Astronomy.com
PRL 119, 161101 (2017) Detailed analyses of the gravitational-wave data, together with observations of electromagnetic emissions, are providing new insights into the astrophysics of compact binary systems and γ-ray bursts, dense matter under extreme conditions, the nature of gravitation, and independent tests of cosmology.
National Science Foundation/LIGO/Sonoma State University/A. Simonnet
Two Stars: Pele' and Cassiopeia A
Jorge Piekarewicz Florida State University Outline … Neutron stars as unique cosmic laboratories Heaven and Earth: Laboratory constraints on NS Earth and Heaven: NS constrains on laboratory observables
The BIG questions? The creation of the heavy elements New states of matter at low and high densities The equation of state of neutron-rich matter The Anatomy of a Neutron Star Atmosphere (10 cm): Shapes Thermal Radiation (L=4psR2T4) Envelope (100 m): Huge Temperature Gradient (108K 4106K) Outer Crust (400 m): Coulomb Crystal (Exotic neutron-rich nuclei) Inner Crust (1 km): Coulomb Frustration (“Nuclear Pasta”) Outer Core (10 km): Uniform Neutron-Rich Matter (n,p,e,µ) Inner Core (?): Exotic Matter (Hyperons, condensates, quark matter)
The composition of the outer crust - as well as the r-process - is extremely sensitive to nuclear masses of exotic, neutron-rich nuclei. RIBFs will help — but only to some extent. Theory (e.g., DFT+BNN) is essential to predict the masses of nuclei that will never be measured in the laboratory The unknown EOS of the inner crust (especially in the nuclear pasta phase) is essential to understand the tidal polarizability in BNS mergers The neutron skin of lead has been identified as a proxy for the slope of the symmetry energy (“L”) which in turn largely determines the size of the neutron star — objects that differ by 18 orders of magnitude! Neutron Stars as Nuclear Physics Gold Mines Neutron Stars are the remnants of massive stellar explosions Are bound by gravity NOT by the strong force Satisfy the Tolman-Oppenheimer-Volkoff equation (v /c 1/2) esc ⇠ Only Physics sensitive to: Equation of state of neutron-rich matter EOS mustThe span Holy about Grail:11 orders The ofEquation magnitude ofin baryon density Increase fromState 0.7 of2 MNeutron-Starmust be explained Matter byLETTER NuclearRESEARCH Physics! !
Received 7 July; accepted 1 September 2010. MS0 dM 2 2.5 GR MPA1 ∞ AP3 1. Lattimer, J. M. & Prakash,= M.4 The⇡ physicsr of neutron(r) stars. Science 304, 536–542 < PAL1 P ENG (2004). dr E AP4 MS2 2. Lattimer, J. M. & Prakash, M. Neutron star observations: prognosis for equation of Causality state constraints.dP Phys. Rep. 442, 109–165(r (2007).)M(r) P(r) 2.0 J1614-2230 3. Glendenning, N. K. &= Schaffner-Bielich,G E J. Kaon condensation and1 dynamical+ SQM3 MS1 nucleons in neutron stars. Phys. Rev. Lett. 81, 4564–45672 (1998). J1903+0327 FSU 4. Lackey, B. D.,dr Nayyar, M. & Owen, B. J. Observationalr constraints on hyperons in (r) )
( SQM1 PAL6 GM3 neutron stars. Phys. Rev. D 73, 024021 (2006). E M 1.5 J1909-3744 5. Schulze, H., Polls, A., Ramos, A. & Vidan3 ˜a, I. Maximum mass of neutron stars. Phys. 1 GS1 Double neutron sstar systemssy Rev. C 73, 058801 (2006).4⇡r P(r) 2GM(r)
Mass ( 6. Kurkela, A., Romatschke,1 + P. & Vuorinen, A. Cold quark matter.1 Phys. Rev. D 81, 105021 (2010). 1.0 M(r) r 7. Shapiro, I. I. Fourth test of general relativity. Phys. Rev. Lett. 13, 789–791 (1964). 8. Jacoby, B. A., Hotan, A., Bailes, M., Ord, S. & Kulkarni, S. R. The mass of a millisecond pulsar. Astrophys. J. 629, L113–L116 (2005). 0.5 9. Verbiest,Need J. P. W. et al. Precision an timing EOS: of PSR J0437–4715:P =P an accurate( ) pulsarrelation Rotation distance, a high pulsar mass, and a limit on the variation of Newton’s gravitational constant. Astrophys. J. 679, 675–680 (2008). E 10. Hessels, J. et al. in Binary Radio Pulsars (eds Rasio, F. A. & Stairs, I. H.) 395 (ASP Conf. 0.0 Ser. 328, AstronomicalNuclear Society of the Pacific, Physics 2005). Critical 7 8 9 10 11 12 13 14 15 11. Crawford, F. et al. A survey of 56 midlatitude EGRET error boxes for radio pulsars. Radius (km) Astrophys. J. 652, 1499–1507 (2006). 12. O¨ zel, F., Psaltis, D., Ransom, S., Demorest, P. & Alford, M. The massive pulsar PSR Figure 3 | Neutron star mass–radius diagram. The plot shows non-rotating J161422230: linking quantum chromodynamics, gamma-ray bursts, and mass versus physical radius for several typical EOSs27: blue, nucleons; pink, gravitational wave astronomy. Astrophys. J. (in the press). nucleonsJ. plus Piekarewicz exotic matter; green, (FSU) strange quark matter. The horizontal bands 13.Neutron Hobbs, G. Stars B., Edwards, R. T. & Manchester, R. N. TEMPO2, a newMazurian pulsar-timing Lakes 2015 4 / 15 Many nuclear models packagethat - I. Anaccurately overview. Mon. Not. R. Astron. predict Soc. 369, 655–672 the (2006). show the observational constraint from our J1614-2230 mass measurement of 14. Damour, T. & Deruelle, N. General relativistic celestial mechanics of binary 8,28 (1.97 6 0.04)M[, similar measurementsproperties for two other of millisecond finite pulsars nucleisystems. yield II. The post-Newtonianenormous timing formula. variationsAnn. Inst. Henri Poincare ´inPhys. and the range of observed masses for double neutron star binaries2. Any EOS The´or. 44, 263–292 (1986). line that does not intersectthe the J1614-2230 prediction band is ruled out of by this neutron-star15. Freire, P. C. C. radii & Wex, N. The and orthometric maximum parameterisation of the Shapiromass delay and measurement. In particular, most EOS curves involving exotic matter, such as an improved test of general relativity with binary pulsars. Mon. Not. R. Astron. Soc. kaon condensates or hyperons, tend to predict maximum masses well below (in the press). What 16.is Iben, missing? I. Jr & Tutukov, A. V. On the evolution of close binaries with components of 2.0M[ and are therefore ruled out. Including the effect of neutron star rotation initial mass between 3 solar masses and 12 solar masses. Astrophys. J Suppl. Ser. increases the maximum possible mass for each EOS. For a 3.15-ms spin period, 58, 661–710 (1985). this is a =2% correction29 and does not significantly alter our conclusions. The 17. O¨ zel, F. Soft equations of state for neutron-star matter ruled out by EXO 0748 - grey regions show parameter space that is ruled out by other theoretical or 676. Nature 441, 1115–1117 (2006). observational constraints2. GR, general relativity; P, spin period. 18. Ransom, S. M. et al. Twenty-one millisecond pulsars in Terzan 5 using the Green Bank Telescope. Science 307, 892–896 (2005). 19. Freire, P. C. C. et al. Eight new millisecond pulsars in NGC 6440 and NGC 6441. Astrophys. J. 675, 670–682 (2008). common feature of models that include the appearance of ‘exotic’ 20. Freire, P. C. C., Wolszczan, A., van den Berg, M. & Hessels, J. W. T. A massive neutron 4,5 3 star in the globular cluster M5. Astrophys. J. 679, 1433–1442 (2008). hadronic matter such as hyperons or kaon condensates at densities 21. Alford,M.etal.Astrophysics:quarkmatterincompactstars?Nature445,E7–E8(2007). of a few times the nuclear saturation density (ns), for example models 22. Lattimer, J. M. & Prakash, M. Ultimate energy density of observable cold baryonic GS1 and GM3 in Fig. 3. Almost all such EOSs are ruled out by our matter. Phys. Rev. Lett. 94, 111101 (2005). 23. Podsiadlowski, P., Rappaport, S. & Pfahl, E. D. Evolutionary sequences for low- and results. Our mass measurement does not rule out condensed quark intermediate-mass X-ray binaries. Astrophys. J. 565, 1107–1133 (2002). matter as a component of the neutron star interior6,21, but it strongly 24. Podsiadlowski, P. & Rappaport, S. Cygnus X-2: the descendant of an intermediate- constrains quark matter model parameters12. For the range of allowed mass X-Ray binary. Astrophys. J. 529, 946–951 (2000). 25. Hotan, A. W., van Straten, W. & Manchester, R. N. PSRCHIVE and PSRFITS: an open EOS lines presented in Fig. 3, typical values for the physical parameters approach to radio pulsar data storage and analysis. Publ. Astron. Soc. Aust. 21, of J1614-2230 are a central baryon density of between 2ns and 5ns and a 302–309 (2004). radius of between 11 and 15 km, which is only 2–3 times the 26. Cordes, J. M. & Lazio, T. J. W. NE2001.I. A new model for the Galactic distribution of free electrons and its fluctuations. Preprint at Æhttp://arxiv.org/abs/astro-ph/ Schwarzschild radius for a 1.97M[ star. It has been proposed that 0207156æ (2002). the Tolman VII EOS-independent analytic solution of Einstein’s 27. Lattimer, J. M. & Prakash, M. Neutron star structure and the equation of state. equations marks an upper limit on the ultimate density of observable Astrophys. J. 550, 426–442 (2001). 22 28. Champion, D. J. et al. An eccentric binary millisecond pulsar in the Galactic plane. cold matter . If this argument is correct, it follows that our mass mea- Science 320, 1309–1312 (2008). surement sets an upper limit on this maximum density of 29. Berti, E., White, F., Maniopoulou, A. & Bruni, M. Rotating neutron stars: an invariant (3.74 6 0.15) 3 1015 g cm23, or ,10n . comparison of approximate and numerical space-time models. Mon. Not. R. s Astron. Soc. 358, 923–938 (2005). Evolutionary models resulting in companion masses .0.4M[ gen- erally predict that the neutron star accretes only a few hundredths of a Supplementary Information is linked to the online version of the paper at www.nature.com/nature. solar mass of material, and result in a mildly recycled pulsar23, that is one with a spin period .8 ms. A few models resulting in orbital para- Acknowledgements P.B.D. is a Jansky Fellow of the National Radio Astronomy 23,24 Observatory. J.W.T.H. is a Veni Fellow of The Netherlands Organisation for Scientific meters similar to those of J1614-2230 predict that the neutron star Research. We thank J. Lattimer for providing the EOS data plotted in Fig. 3, and P. Freire, ¨ could accrete up to 0.2M[, which is still significantly less than the F. Ozel and D. Psaltis for discussions. The National Radio Astronomy Observatory is a >0.6M needed to bring a neutron star formed at 1.4M up to the facility of the US National Science Foundation, operated under cooperative agreement [ [ by Associated Universities, Inc. observed mass of J1614-2230. A possible explanation is that some neutron stars are formed massive (,1.9M ). Alternatively, the trans- Author Contributions All authors contributed to collecting data, discussed the results [ and edited the manuscript. In addition, P.B.D. developed the MCMC code, reduced and fer of mass from the companion may be more efficient than current analysed data, and wrote the manuscript. T.P. wrote the observing proposal and models predict. This suggests that systems with shorter initial orbital created Fig. 3. J.W.T.H. originally discovered the pulsar. M.S.E.R. initiated the survey that periods and lower companion masses—those that produce the vast found the pulsar. S.M.R. initiated the high-precision timing proposal. majority of the fully recycled millisecond pulsar population23—may Author Information Reprints and permissions information is available at experience even greater amounts of mass transfer. In either case, our www.nature.com/reprints. The authors declare no competing financial interests. Readers are welcome to comment on the online version of this article at mass measurement for J1614-2230 suggests that many other milli- www.nature.com/nature. Correspondence and requests for materials should be second pulsars may also have masses much greater than 1.4M[. addressed to P.B.D. ([email protected]).
28 OCTOBER 2010 | VOL 467 | NATURE | 1083 ©2010 Macmillan Publishers Limited. All rights reserved An Interesting Challenge A significant tension has emerged! Stunning observations have established the existence of massive (i.e, 2 solar mass) Neutron stars Recent observations has suggested that NS have small radii Extremely difficult to reconcile; evidence of a phase transition?
The Neutron Star Radius
S. Guillot: RNS measurements from NSs in GCs 523 <11 km (99% conf).
+1.3 MS0 model parameterization9.1 1.4 km of the dEoS. It had ini- MS2 2.5 MPA1 (90%conf.) tially been prompted by two precise measure- PAL1 M-R by J. Lattimer ments of massive MNS 2 M NSs (Demorest ) 2.0 ⇠ ⊙ MS1 et al. 2010; Antoniadis et al. 2013), which fa- WFF1=M ( vors proposed dEoS that appear quasi-verticalWiring, Fiks SQM1
NS 1.5 and Fabrocini GS1 GM3 in MNS–RNS space (see Fig. 1). (1988)M In this approach, the simultaneous fitting 1.0 PAL6 of the X-ray spectra of qLMXBs is performed via a Markov-Chain Monte-Carlo (MCMC) 0.5
Contains 6 8 10 12 14 16 method. This allows an e cient sampling of uncertainties from: Distance All spectral R (km) the complicated parameter space (1 R pa- parameters +1.2 NS CalibrationR =10.3 km
Remarkable one-to-one correspondence between MR and EOS TOV equation + EOS MR
“Lindblom’s inversion algorithm” proves the inverse TOV equation + MR EOS
Minimum radius such that: (a) EOS is causal and (b) M
S. Guillot: RNS measurements from NSs in GCs 523 3 MS0 model parameterization of theR8 dEoS. It had ini- MS2 R9 2.5 MPA1 2.5 BHtially been prompted by two preciseR10 measure- PAL1 P Causality R11 & this work L AV14+UVII ments of massive MNS 2 M NSs (Demorest ) FSUGold 2.0 2 ⇠ ⊙ FSUGold2 MS1
et al. 2010; Antoniadis et al. 2013), which fa- M
FSUGarnet ( sun vors proposed dEoS that appearNL3 quasi-vertical SQM1
NS 1.5 GS1 GM3 1.4 in8M 9NS 10–RNS 11space 13 (see Fig. 1). M M/M In this approach, the simultaneous fitting 1.0 1 PAL6 of the X-ray spectra of qLMXBs is performed 0.5 via a Markov-Chain Monte-Carlo (MCMC) 0.5 method. This allows an e cient sampling of 6 8 10 12 14 16 0 R (km) 6 the8 complicated 10 12 parameter 14 16 space18 (1 R 20NS pa- R =10.3+1.2 km
The dawn of a new era: GW Astronomy Initial black hole masses are 36 and 29 solar masses Final black hole mass is 62 solar masses; 3 solar masses radiated in Gravitational Waves!
PHYSICAL REVIEW LETTERS week ending PRL 116, 061102 (2016) 12 FEBRUARY 2016 Selected for a Viewpoint in Physics properties of space-time in the strong-field, high-velocity the coincident signal GW150914 shownweek in Fig. ending1. The initial PRLregime116, 061102 and confirm (2016) predictions ofPHYSICAL general relativity REVIEW for the detection LETTERS was made by low-latency12 FEBRUARY searches for 2016 generic nonlinear dynamics of highly disturbed black holes. gravitational-wave transients [41] and was reported within three minutes of data acquisition [43]. Subsequently, Observation of Gravitational Waves frommatched-filter a Binary Black analyses Hole that use Merger relativistic models of com- II. OBSERVATION B. P. Abbott et al.pact* binary waveforms [44] recovered GW150914 as the On September 14, 2015 at 09:50:45 UTC, the LIGO most significant event from each detector for the observa- (LIGO Scientific Collaboration and Virgo Collaboration) Hanford, WA, and Livingston,(Received LA, observatories 21 January 2016; detected publishedtions 11 February reported 2016) here. Occurring within the 10-ms intersite On September 14, 2015 at 09:50:45 UTC the two detectors of the Laser Interferometer Gravitational-Wave Observatory simultaneously observed a transient gravitational-wave signal. The signal sweeps upwards in frequency from 35 to 250 Hz with a peak gravitational-wave strain of 1.0 × 10−21. It matches the waveform predicted by general relativity for the inspiral and merger of a pair of black holes and the ringdown of the resulting single black hole. The signal was observed with a matched-filter signal-to-noise ratio of 24 and a false alarm rate estimated to be less than 1 event per 203 000 years, equivalent to a significance greater 160 0.03 than 5.1σ. The source lies at a luminosity distance of 410−þ180 Mpc corresponding to a redshift z 0.09−þ0.04 . 5 4 ¼ In the source frame, the initial black hole masses are 36−þ4 M and 29−þ4 M , and the final black hole mass is 4 0.5 2 ⊙ ⊙ 62−þ4 M , with 3.0−þ0.5 M c radiated in gravitational waves. All uncertainties define 90% credible intervals. These observations⊙ demonstrate⊙ the existence of binary stellar-mass black hole systems. This is the first direct detection of gravitational waves and the first observation of a binary black hole merger.
DOI: 10.1103/PhysRevLett.116.061102
I. INTRODUCTION The discovery of the binary pulsar system PSR B1913 16 þ In 1916, the year after the final formulation of the field by Hulse and Taylor [20] and subsequent observations of equations of general relativity, Albert Einstein predicted its energy loss by Taylor and Weisberg [21] demonstrated the existence of gravitational waves. He found that the existence of gravitational waves. This discovery, the linearized weak-field equations had wave solutions: along with emerging astrophysical understanding [22], transverse waves of spatial strain that travel at the speed of led to the recognition that direct observations of the light, generated by time variations of the mass quadrupole amplitude and phase of gravitational waves would enable moment of the source [1,2].Einsteinunderstoodthat studies of additional relativistic systems and provide new gravitational-wave amplitudes would be remarkably tests of general relativity, especially in the dynamic small; moreover, until the Chapel Hill conference in strong-field regime. 1957 there was significant debate about the physical Experiments to detect gravitational waves began with reality of gravitational waves [3]. Weber and his resonant mass detectors in the 1960s [23], Also in 1916, Schwarzschild published a solution for the followed by an international network of cryogenic reso- field equations [4] that was later understood to describe a nant detectors [24]. Interferometric detectors were first black hole [5,6], and in 1963 Kerr generalized the solution suggested in the early 1960s [25] and the 1970s [26].A to rotating black holes [7]. Starting in the 1970s theoretical study of the noise and performance of such detectors [27], work led to the understanding of black hole quasinormal and further concepts to improve them [28],ledto proposals for long-baseline broadband laser interferome- modes [8–10], and in the 1990s higher-order post- Newtonian calculations [11] preceded extensive analytical ters with the potential for significantly increased sensi- studies of relativistic two-body dynamics [12,13]. These tivity [29–32]. By the early 2000s, a set of initial detectors advances,FIG. 1. together The gravitational-wave with numerical event relativity GW150914 breakthroughs observed bywas the LIGO completed, Hanford including (H1, left TAMAcolumn panels)300 in andJapan, Livingston GEO 600 (L1, right in Germany, the Laser Interferometer Gravitational-Wave in thecolumn past panels) decade detectors.[14–16] Times, have are enabledshown relative modeling to September of 14, 2015 at 09:50:45 UTC. For visualization, all time series are filtered binarywith black a 35–350 hole Hz mergers bandpass and filter accurate to suppress predictions large fluctuations of Observatory outside the detectors (LIGO)’ most in the sensitive United frequency States, band,and Virgo and band-reject in theirfilters gravitational to remove waveforms. the strong instrumental While numerous spectral black lines hole seen in theItaly. Fig. Combinations3 spectra. Top of row, these left: detectorsH1 strain. madeTop row, joint right: obser-L1 strain. GW150914 arrived first at L1 and 6.9 0.5 ms later at H1; for a visualvations comparison, from 2002 the through H1 data 2011, are also setting shown, upper shifted limits in timeon a by this candidates have now been identified through−þ0.4 electromag- amount and inverted (to account for the detectors’ relative orientations).variety ofSecond gravitational-wave row: Gravitational-wave sources while strain evolving projected into onto each netic observations [17–19], black hole mergers have not detector in the 35–350 Hz band. Solid lines show a numerical relativity waveform for a system with parameters consistent with those previously been observed. a global network. In 2015, Advanced LIGO became the recovered from GW150914 [37,38] confirmed to 99.9% by an independentfirst of a significantly calculation based more on sensitive[15]. Shaded network areas of show advanced 90% credible regions for two independent waveform reconstructions. One (darkdetectors gray) models to begin the signal observations using binary[33 black–36]. hole template waveforms *Full[39] author. The list other given (light at the gray) end does of the not article. use an astrophysical model,A but century instead after calculates the fundamental the strain signal predictions as a linear of Einstein combination of sine-Gaussian wavelets [40,41]. These reconstructions have a 94%and overlap, Schwarzschild, as shown in we[39] report. Third the row: firstResiduals direct detection after subtracting of the Published by the American Physical Society under the terms of filtered numerical relativity waveform from the filtered detectorgravitational time series. Bottom waves row: andA the time-frequency first direct representationobservation of[42] a of the the strainCreative data, Commons showing Attribution the signal 3.0frequency License increasing. Further distri- over time. bution of this work must maintain attribution to the author(s) and binary black hole system merging to form a single black the published article’s title, journal citation, and DOI. hole. Our observations provide unique access to the 061102-2 0031-9007=16=116(6)=061102(16) 061102-1 Published by the American Physical Society 2017 BREAKTRHOUGH December 22, 2017- Print Pages of the YEAR!12/22/17, 17'19
http://www.sciencemagazinedigital.org/sciencemagazine/22_decembe…ntMode=false&start=1&end=186&prettyPrint=false&lm=1513880307000 Page 1 of 186 Selected for a Viewpoint in Physics week ending PRL 119, 161101 (2017) PHYSICAL REVIEW LETTERS 20 OCTOBER 2017
Historical first detection GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral B. P. Abbott et al.* (LIGO Scientific Collaboration and Virgo Collaboration) of gravitational waves (Received 26 September 2017; revised manuscript received 2 October 2017; published 16 October 2017) On August 17, 2017 at 12 41:04 UTC the Advanced LIGO and Advanced Virgo gravitational-wave detectors made their first observation∶ of a binary neutron star inspiral. The signal, GW170817, was detected with a combined signal-to-noise ratio of 32.4 and a false-alarm-rate estimate of less than one per 8.0 × 104 years. We infer the component masses of the binary to be between 0.86 and 2.26 M , in from a binary neutron- agreement with masses of known neutron stars. Restricting the component spins to the range inferred⊙ in binary neutron stars, we find the component masses to be in the range 1.17–1.60 M , with the total mass of 0.04 2⊙ the system 2.74−þ0.01 M . The source was localized within a sky region of 28 deg (90% probability) and ⊙ 8 had a luminosity distance of 40−þ14 Mpc, the closest and most precisely localized gravitational-wave signal star merger yet. The association with the γ-ray burst GRB 170817A, detected by Fermi-GBM 1.7 s after the coalescence, corroborates the hypothesis of a neutron star merger and provides the first direct evidence of a link between these mergers and short γ-ray bursts. Subsequent identification of transient counterparts across the electromagnetic spectrum in the same location further supports the interpretation of this event as a neutron star merger. This unprecedented joint gravitational and electromagnetic observation provides insight into astrophysics, dense matter, gravitation, and cosmology.
DOI: 10.1103/PhysRevLett.119.161101
I. INTRODUCTION will observe between one BNS merger every few years to hundreds per year [14 21]. This detector network currently On August 17, 2017, the LIGO-Virgo detector network – GW170817: A play in three acts includes three Fabry-Perot-Michelson interferometers that observed a gravitational-wave signal from the inspiral of measure spacetime strain induced by passing gravitational two low-mass compact objects consistent with a binary waves as a varying phase difference between laser light neutron star (BNS) merger. This discovery comes four propagating in perpendicular arms: the two Advanced decades after Hulse and Taylor discovered the first neutron LIGO detectors (Hanford, WA and Livingston, LA) [22] star binary, PSR B1913+16 [1]. Observations of PSR and the Advanced Virgo detector (Cascina, Italy) [23]. B1913+16 found that its orbit was losing energy due to Advanced LIGO’s first observing run (O1), from Act 1: LIGO detects GW from BNS mergerthe emission of gravitational waves, providing the first September 12, 2015, to January 19, 2016, obtained indirect evidence of their existence [2]. As the orbit of a 49 days of simultaneous observation time in two detectors. BNS system shrinks, the gravitational-wave luminosity Extraction of “tidal polarizability” While two confirmed binary black hole (BBH) mergers increases, accelerating the inspiral. This process has long were discovered [24 26], no detections or significant been predicted to produce a gravitational-wave signal – candidates had component masses lower than 5M , placing Stringent limits on the EOS of dense matterobservable by ground-based detectors [3 6] in the final – ⊙ a 90% credible upper limit of 12 600 Gpc−3 yr−1 on the rate minutes before the stars collide [7]. of BNS mergers [27] (credible intervals throughout this Since the Hulse-Taylor discovery, radio pulsar surveys Letter contain 90% of the posterior probability unless noted have found several more BNS systems in our galaxy [8]. otherwise). This measurement did not impinge on the range Understanding the orbital dynamics of these systems Act 2: Fermi/Integral detect short -ray burst of astrophysical predictions, which allow rates as high as g inspired detailed theoretical predictions for gravitational- 10 000 Gpc−3 yr−1 [19]. wave signals from compact binaries [9–13]. Models of the ∼ detected ~2 seconds after GW signal population of compact binaries, informed by the known The second observing run (O2) of Advanced LIGO, from binary pulsars, predicted that the network of advanced November 30, 2016 to August 25, 2017, collected 117 days gravitational-wave detectors operating at design sensitivity of simultaneous LIGO-detector observing time. Advanced Confirms long-held belief of the association between Virgo joined the O2 run on August 1, 2017. At the time of this publication, two BBH detections have been announced BNS merger and -ray bursts *Full author list given at the end of the Letter. [28,29] from the O2 run, and analysis is still in progress. g Toward the end of the O2 run a BNS signal, GW170817, Published by the American Physical Society under the terms of was identified by matched filtering [7,30–33] the data the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to against post-Newtonian waveform models [34–37]. This the author(s) and the published article’s title, journal citation, gravitational-wave signal is the loudest yet observed, with a Act 3: ~70 telescopes tracked the “kilonova”and DOI. combined signal-to-noise ratio (SNR) of 32.4 [38]. After Afterglow of the explosive merger ~11 hours later 0031-9007=17=119(16)=161101(18)Neutron-star 161101-1 Published mergers by the American Physical Society Powered by the radioactive decay of “r-process” create gravitational elements waves, light, and gold! BNS mergers as a critical site for the r-process! (see the Introduction by Smith). Coulter et al. describe how the One-Meter Two-Hemispheres (1M2H) collaboration was the Vrst to locate the electromagnetic source. Drout et al. present the 1M2H measurements of its optical and infrared brightness, and Shappee et al. report their spectroscopy of the event, which is unlike previously detected astronomical transient sources. Kilpatrick et al. show how these observations can be explained by an explosion known as a kilonova, which produces large quantities of heavy elements in nuclear reactions. TheScience ,New this issue p. Periodic1556, p. 1570, p. 1574 Table, p. 1583; see alsoof p. the1554 Elements
Abstract MR Drout et al., Science - Dec, 2017 On 17 August 2017, gravitational waves (GWs) were detected from a binary neutron star merger, GW170817, along with a coincident short gamma-ray burst, GRB 170817A. An optical transient source, Swope Supernova Survey 17a (SSS17a), was subsequently identiVed as the counterpart of this event. We present ultraviolet, optical, and infrared light curves of SSS17a extending from 10.9 hours to 18 days postmerger. We constrain the radioactively powered transient resulting from the ejection of neutron-rich material. The fast rise of the light curves, subsequent decay, and rapid color evolution are consistent with multiple ejecta components of differing lanthanide abundance. The late-time light curve indicates that SSS17a produced at least ~0.05 solar masses of heavy elements, demonstrating that neutron star mergers play a role in rapid neutron capture (r-process) nucleosynthesis in the universe.
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Email week ending PRL 108, 011101 (2012) PHYSICAL REVIEW LETTERS 6 JANUARY 2012
TABLE I. Used EoSs. Mmax and Rmax are mass and radius of pressure contributions. Continuous loss of angular momen- the maximum-mass TOV configuration, fpeak is the peak fre- tum by GWs and redistribution to the outer merger remnant quency of the postmerger GW emission with the FWHM (a cross will finally lead to a ‘‘delayed collapse’’ on time scales of indicates prompt collapse of the remnant). fh~ f is the zð peakÞ typically several 10–100 ms depending on the mass and the effective peak amplitude of the GW signal at a polar distance EoS. For EoSs with a sufficiently high M stable or very of 20 Mpc. The tables of the first five and next seven EoSs are max long-lived rigidly rotating NSs are the final product. taken from [25,26], respectively. A prompt collapse occurs for three EoSs of our sample ~ Mmax Rmax fpeak, FWHM fhz fpeak (marked by x in Table I and Fig. 1). One observes this ð 21 Þ EoS with references [M ] [km] [kHz] [10À ] scenario only for EoSs with small Rmax. In the simulations
Sly4 [27] À 2.05 10.01 3.32, 0.20 2.33 with the remaining EoSs DROs are formed. The evolution þ th APR [28] À 2.19 9.90 3.46, 0.18 2.45 of these mergers is qualitatively similar. The dynamics are þ th FPS [29] À 1.80 9.30 xxdescribed in [21,22]. þ th BBB2 [30] À 1.92 9.55 3.73, 0.22 1.33 For all models that produce a DRO the GW signal is þ th analyzed by a post-Newtonian quadrupole formula [21]. Glendnh3 [31] Àth 1.96 11.48 2.33, 0.13What 1.27 Will We Learn from þ The inset of Fig. 2 shows the GW amplitude of the plus eosAU [32] Àth 2.14 9.45 xx þ polarization at a polar distance of 20 Mpc for NSs de- eosC [33] Àth 1.87 9.89 3.33, 0.22 1.27 þ scribed by the Shen EoS. Clearly visible is the inspiral eosL [34] Àth 2.76 14.30 1.84, 0.10 1.38 þ Neutron-Starphase with an increasing amplitude andMergers frequency (until eosO [35] À 2.39 11.56 2.66, 0.11 2.30 þ th eosUU [32] À 2.21 9.84 3.50, 0.17 2.64 5 ms), followed by the merging and the ringdown of the þ th eosWS [32] À 1.85 9.58 xxpostmerger remnant (from 6 ms). All DROs are stable þ th SKA [36] À 2.21 11.17 2.64, 0.13 1.96 against collapse well beyond the complete damping of þ th Shen [37] 2.24 12.63 2.19, 0.15 1.43 the postmerger oscillations. In Fig. 2 we plot the spectra of the angle-averaged effective amplitude, h 0:4fh~ f LS180 [36] 1.83 10.04 3.26, 0.25 1.19 av ¼ zð Þ LS220 [36] 2.04 10.61 2.89, 0.21 1.63 (see, e.g., [16]), at a distance of 20 Mpc for the Shen LS375 [36] 2.71 12.34 2.40, 0.13 1.82 EoS (solid black) and the eosUU (dash-dotted) together GS1 [38] 2.75 13.27 2.10, 0.12 1.46 with the anticipated sensitivity for Advanced LIGO [17] GS2 [39] 2.09 11.78 2.53, 0.12 2.15 and the planned Einstein Telescope (ET) [41]. Here ~ ~ 2 ~ 2 hz f h h =2 is given by the Fourier trans- ð Þ¼~ ðj þ j þ j  j Þ observations and population synthesis studies suggest forms, hqffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi= , of the waveforms for both polarizations þ  these systems to be most abundant [40]. After energy and observed along the pole. As a characteristic feature of the angular momentum losses by GWs have driven the inspiral spectra a pronounced peak at f 2:19 kHz for the peak ¼ of the NSs for several 100 Myrs, there are two different Shen EoS and 3.50 kHz for eosUU is found, which is 5 outcomes of the coalescence. Either the twoTidal stars directly polarizabilityknown to be connected to the GW scales emission of the merger as R … form a black holeGravitational (BH) shortly after they fusewaves (‘‘prompt – remnantEoS [7survey]. Recently, this peak has been identified as the RECONSTRUCTING THE NEUTRON-STAR EQUATION OF … PHYSICAL REVIEW D 91, 043002 (2015) collapse’’), or the merging leads to the formation of a L d~ ; θ~ ; H; I dθ~ p θ~ H; I p d~ θ~ ; H; I : ð i in;i Þ¼ ex;i ð ex;ij Þ ð ij i Þ differentially rotating object (DRO) that is stabilized −21 Z all 1.35-1.35 simulations x 10 25 against the gravitational collapse by rotation and thermal 1 ð Þ ~ Because Λi is a deterministic function of m 1i, m 2i and the M /M known from EOS parameters, 1 2 0 3 inspiral at 20 Mpc ~ ~ ~ ~ ~ + p Λi m 1i;m 2i; E; H; I δ Λi − Λ m 1i;m 2i; E : 26 h ð j Þ¼ ð ð ÞÞ ð Þ 2.5 −1 −21 0 5 10 15 20 The marginalized PDF finally becomes 10 t [ms]
] 2 f ~ 1 sun peak p E D; H; I dm 11dm 21…dm 1ndm 2n
1.5 (20 Mpc) ð j Þ¼p D H; I −22 Z av ð j Þ n
h 10 M [M ~ ~ 1 × p E H; I p m 1i;m 2i E; H; I ð j Þ i 1 ½ð j Þ Y¼ ~ ~ 0.5 × L di; θin;i; H; I ~ ~ ~ : 27 characterize−23 EoS by radius of Λi Λ m 1i;m 2i;E 10 ð Þj ¼ ð Þ ð Þ 012345 0 nonrotating NS with 1.35 Msun The problem has now been reduced to computing the 8 10 12 14 16 18 f [kHz] quasilikelihood [Eq. (25)] for each BNS event and then R [km] computing Eq. (27). FIG. 2 (color online). Orientation-averaged spectra of the GW FIG. 1 (color online). NS M-R relations for all considered signal for the Shen (solid) and the eosUU (black dash-dotted) B. Likelihood and signal-to-noise ratio Pure TOV property => Radius measurement via fpeak The final ingredient we need to evaluate the marginalized EoSs. Red curvesNS (gray radius in print version) correspondmay to EoSsbe constrainedEoSs and the Advanced LIGO [red by dashed future (gray in print ver- ~ ~ PDF is an expression for the likelihood p di θi; H; I for that include→ Empirical thermal effects relation consistently, between black GW lines frequency indicate andsion)] radius and ET (blackof non-rotating dashed) unity NS SNR sensitivities. The inset each GW event.4 In this paper we assume thatð j each detectorÞ EoSs supplemented with a thermal ideal gas. The horizontal shows the GW amplitude with polarization at a polar distance FIG. 2 (color online). Radius and tidal deformability of in the network has stationary, Gaussian noise and that the BNS mergers to better than 1km!þ tabulated EOS models (solid line) and the least-squares piece- noise between detectors is uncorrelated. This means that line correspondsImportant: to theSimulations1:97M NS [for3]. the same binary mass,of 20 just Mpc with for thevaried Shen EoS.EoS a a wise-polytrope fits (dashed line) to those tabulated models given the power spectral density (PSD) Sn f of the noise n t in Table I. The 20 vertical lines represent the most likely NS in detector a is ð Þ ð Þ Triangles: strange quark matter; red: temperature dependent EoS; others: ideal-gas for thermal effects masses of the ten known BNS systems [38]. Some of these masses, however, have significant uncertainties. The overlapping 011101-2 a a 1 a n~ f n~ à f0 δ f − f0 S f ; 28 vertical bands represent the 1σ uncertainty in the masses of the h ð Þ ð Þi ¼ 2 ð Þ nð Þ ð Þ pulsars J1614-2230 (1.97 0.04M ) [1] and J0348 0432 Æ ⊙ þ (2.01 0.04M ) [2], both in neutron-star–white-dwarf binaries. where n~ a f is the Fourier transform of the noise of Æ ⊙ detector að andÞ · represents an ensemble average. For a GW event withh truei parameters θˆ, resulting in the GW ~ ~ ~ ~ ~ a ˆ p di θi; E; H; I p di θi; H; I . (The waveform signal signal h t; θ , the data stream of detector a will be ð j ~ Þ¼ ð j ~ Þ ð Þ depends on E only through Λi which is already included as a waveform parameter.) da t na t ha t; θˆ : 29 ð Þ¼ ð Þþ ð Þ ð Þ The marginalized PDF [Eq. (20)] is now For stationary, Gaussian noise, it is well known that the probability of obtaining the noise time series n t is ~ 1 ~ ~ ð Þ p E D; H; I dθin;1…dθin;n ð j Þ¼p D H; I − n;n =2 Z pn n t ∝ e ð Þ ; 30 ð j Þ n ½ð Þ ð Þ ~ ~ × p E H; I p m 1i;m 2i E; H; I where a; b is the usual inner product between two time ð j Þ i 1½ð j Þ ð Þ ¼ series a t and b t weighted by the PSD Y ð Þ ð Þ × p Λ~ m ;m ; E;~ H; I L d~ ; θ~ ; H; I ; ð ij 1i 2i Þ ð i in;i Þ ∞ a~ f b~ à f 24 a; b 4Re ð Þ ð Þ df: 31 ð Þ ð Þ¼ S f ð Þ Z0 nð Þ
where we have defined the quasilikelihood for the intrinsic 4In the following subsections, when we discuss the likelihood parameters as for individual GW events, we omit the event index i for brevity.
043002-7 Tidal Polarizability, Neutron-Star Radii, and the Equation of State
Electric Polarizability: Electric field induced a polarization of charge A time dependent electric dipole emits PHYSICAL REVIEW LETTERS week ending PRL 119, 161101 (2017) electromagnetic waves: 20P OCTOBERi = 2017Ei low-spin priors. As a comparison, we show predictions coming from a set of candidate equations of state for neutron-star matter [156–160], generated using fits from Tidal[161]. Polarizability: All EOS support masses of 2.01 0.04M . TidalAssuming field that bothinduces components a are polarization neutron starsÆ described⊙ of mass by the same equation of state, a single function Λ m is 2 5 A computedtime dependent from the static l 2massperturbation quadrupole of a Tolman-ð Þ emits c R R 5 Oppenheimer-Volkoff solution¼ [103]. The shaded regions in ⇤ gravitationalFig. 5 represent the values waves: of the tidal Q deformabilitiesij = ⇤Λ1 andij ⇡ 2GM ' Rs Λ2 generated using an equation of state from the 90% mostE ✓ ◆ probable fraction of the values of m1 and m2, consistent with ⇣ the posterior shown in Fig. 4. We find that our constraints on Λ1 and Λ2 disfavor equations of state that predict less compact stars, since the mass range we recover generates PHYSICAL REVIEW LETTERS week ending PRL 119, 161101 (2017) Λ values outside20 OCTOBER the 90% 2017 probability region. This is con- The tidal polarizability sistent with radius constraints from x-ray observations of neutron stars [162–166]. Analysis methods, in development, measures the “fluffiness” that a priori assume the sameEquations EOS governs bothof state stars should with improve our constraints [167]. FIG. 4. Two-dimensional posterior distribution for the compo- To leading order in anda very, the stiff gravitational-wave symmetry (or stiffness) nent masses m and m in the rest frame of the source for the low- Λ1 Λ2 1 2 phase is determined by theenergy parameter (and very larger spin scenario ( χ < 0.05, blue) and the high-spin scenario of a neutron star against ( χ < 0.89, red).j j The colored contours enclose 90% of the neutron star radii ) j j 4 4 probability from the joint posterior probability density function ~ 16 m1 12m2 m1Λ1 m2 12m1 m2Λ2 Λ ð þ Þ þðare5þ ruledÞ out! 1 deformation for m1 and m2. The shape of the two dimensional posterior is ¼ 13 m1 m2 ð Þ determined by a line of constant M and its width is determined ð þ Þ by the uncertainty in M. The widths of the marginal distributions [101,117]. Assuming a uniform prior on Λ~ , we place a 90% (shown on axes, dashed lines enclose 90% probability away from FIG. 5. Probability density for the tidal deformability parameters of the high and lowupper mass components limit ofinferred~ from≤ 800 the detectedin the low-spin case and ~ ≤ 700 in equal mass of 1.36signalsM using) is the strongly post-Newtonian affected model. Contours by the enclosing choice 90% andof 50% spin of the probability density are overlaidΛ (dashed lines). The Λ diagonal⊙ dashed line indicates the Λ1 Λ2 boundary. The Λ1 and Λ2 parameters characterize the size of the tidally induced mass ¼ the high-spin case. We can also constrain the function Λ m priors. The result usingdeformations the of low-spin each star and are prior proportional (blue) to k isR=m consistent5. Constraints with are shown for the high-spin scenario χ ≤ 0.89 (left panel) and 2ð Þ j j ð Þ for the low-spin χ ≤ 0.05 (right panel). As a comparison, we plot predictions for tidalmore deformability directly given by a set by of representative expanding m linearly about m the masses of all known binaryj j neutron star systems. Λ equations of state [156–160] (shaded filled regions), with labels following [161], all of which support stars of 2.01M . Under the ð Þ ¼ assumption that both components are neutron stars, we apply the function Λ m prescribed1.4M by that equation(as in of state[112,115] to the⊙ 90% most), which gives Λ 1.4M ≤ 1400 probable region of the component mass posterior distributions shown in Fig. ð4. EOSÞ that produce⊙ less compact stars, such as MS1 and ð ⊙Þ MS1b, predict Λ values outside our 90% contour. for the high-spin prior and Λ 1.4M ≤ 800 for the low- From M and q, we obtain a measure of the component spin prior. A 95% upper boundð inferred⊙Þ with the low-spin masses m 1low-spin.36; 2 case.26 andM (1.0, 0.7)and in them high-spin0 case..86 Further; 1.36 consistentM , with the rate inferred from observations of 1 ∈ analysis is required to establish the2 uncertainties∈ of these galactic BNS systemsprior,[19,20,155,180]Λ 1.4M. ≤ 970, begins to compete with the 95% ð Þ ⊙ ð Þ ⊙ ð ⊙Þ shown in Fig. 4tighter. As bounds, discussed and a detailed in study Sec. of systematicsI, these is a subject valuesFrom are this inferredupper rate, bound the stochastic of background 1000 ofderived from x-ray observations of ongoing work. gravitational wave s produced by unresolved BNS mergers within the range ofPreliminary known comparisons neutron-star with waveform masses models under and belowthroughout thein history[168] of the. Universe should be compa- development [171,173–177] also suggest the post- rable in magnitude to the stochastic background produced those of knownNewtonian black holes. model used In will combination systematically overestimate with electro-by BBH mergers [181,182]Since. the As the energy advanced emitted detector in gravitational waves depends magnetic observations,the value of the we tidal regard deformabilities. this Therefore, as evidence based on ofnetwork the improvescritically in sensitivity on in the the coming EOS years, of the neutron-star matter, with a wide our current understanding of the physics of neutron stars, total stochastic background from BNS and BBH mergers BNS nature of GW170817.we consider the post-Newtonian results presented in this should be detectablerange[183] consistent. with constraints above, we are only able to The fastest-spinningLetter to be known conservative neutron upper limits star on has tidal a deform- dimension- place a lower bound on the energy emitted before the onset ability. Refinements should be possible as our knowledge B. Remnant and models improve. 2 less spin 0.4 [153], and the possible BNS J1807-2500BBinary has neutronof star strong mergers may tidal result effects in a short- at or long-fGW ∼600Hz as Erad > 0.025M c. ≲ lived neutron star remnant that could emit gravitational ⊙ spin 0.2 [154], after allowing for a broad range of equations This is consistent with Erad obtained from numerical ≲ V. IMPLICATIONS waves following the merger [184–190]. The ringdown of of state. However, amongA. BNS Astrophysical that rate will merge withina black a hole formedsimulations after the coalescence and could fits also produce for BNS systems consistent with gravitational waves, at frequencies around 6 kHz, but the Hubble time, PSROur J0737-3039A analyses identified[155] GW170817has as the only most BNS- extremereduced interferometerGW170817 response at high[114,169 frequencies– makes171]. spin, less than mass0. signal04 after detected spin-downin O2 with a false is alarm extrapolated rate below their to observation unfeasible.We estimate Consequently, systematic searches have errors from waveform modeling 1∼=100 yr. Using a method derived from [27,178,179], and been made for short (tens of ms) and intermediate duration merger. If we restrictassuming the that the spin mass magnitude distribution of the in components our analysis of (≤ 500 tos) gravitational-waveby comparing signals from the a neutron post-Newtonian star results with parameters BNS systems is flat between 1 and 2 M and their remnant at frequencies up to 4 kHz [75,191,192]. For the ⊙ χ ≤ 0.05, consistentdimensionless with spins theare below observed 0.4, we are population,able to infer latter, we the data examinedrecovered start at the using time of the an coalescence effective-one-body model [124] aug- j j the local coalescence rate density R of BNS systems. and extend to the end of the observing run on August 25, 3 1 mented with tidal effects extracted from numerical relativity recover the massIncorporating ratio q ∈ the upper0.7; limit1.0 of 12600andGpc component− yr− from O1 masses2017. With the time scales and methods considered so far 3200 −3 −1 as a prior, R ð1540þ GpcÞ yr . Our findings are [193], there is no evidence of a postmerger signal of m1 ∈ 1.36;1.60 M and¼m2 ∈−12201.17; 1.36 M (see Fig. 4). with hydrodynamics [172]. This does not change the We alsoð recover Þχ ⊙ 0.01; 0ð.02 , whereÞ the⊙ upper limit 90% credible intervals for component masses and effective eff ∈ − 161101-7 is consistent with the low-spinð prior.Þ spin under low-spin priors, but in the case of high-spin priors, Our first analysis allows the tidal deformabilities of the we obtain the more restrictive m1 ∈ 1.36; 1.93 M , m2 ∈ ð Þ ⊙ high-mass and low-mass component, Λ1 and Λ2, to vary 0.99; 1.36 M , and χeff ∈ 0.0; 0.09 . Recovered tidal ð Þ ⊙ ð Þ independently. Figure 5 shows the resulting 90% and deformabilities indicate shifts in the posterior distributions 50% contours on the posterior distribution with the towards smaller values, with upper bounds for Λ~ and post-Newtonian waveform model for the high-spin and Λ 1.4M reduced by a factor of roughly (0.8, 0.8) in the ð ⊙Þ
161101-6 Neutron skins and neutron stars in the multi-messenger era
Neutron skins and neutron stars in the multi-messenger era
1, 2, 1, F. J. Fattoyev, ⇤ J. Piekarewicz, † and C. J. Horowitz ‡ 1Center for Exploration of Energy and Matter and Department of Physics, Indiana University, Bloomington, IN 47405, USA 2Department of Physics, Florida State University, Tallahassee, FL 32306, USA (Dated: November 16, 2017) The historical first detection of a binary neutron star merger by the LIGO-Virgo collaboration [B. P. Abbott et208 al. Phys. Rev. Lett. 119, 161101 (2017)] is providing fundamental new insights into the astrophysicalRskin(fm) site for the r-process and on the nature of3 dense matter. A set of realistic models of the equation of state (EOS) that yield an accurate description of the properties of finite .16 .22 .25 .28 .30 .33 NL3 FSUGold2 1400 nuclei, support neutron stars of two solar masses, and provide a Lorentz covariant extrapolation RMF022 to dense nuclear matter are used to confront its predictions against2.5 tidal polarizabilities extracted RMF028 from the gravitational-wave data.PREX Given the sensitivity of the gravitational-waveCausality signal to the RMF032
underlying EOS, limits on the tidal polarizabilities inferred from the observation translateTAMUc into TAMUb TAMUa 1200 stringent constraints on the neutron-star radius. Based on these constraints, modelsFSUGarnet that predict J0348+0432 asti↵ symmetry energy, and thus large stellar radii, can be ruled out. Indeed, under a particular 2 1.6 binary-mass scenario, we deduce an upper limit on the radius of a 1.6 M neutron star of R? < J1614-2230 208 IU-FSU
13.25km. Given the sensitivity of the neutron-skin thickness ofsun Pb to the symmetry energy, albeit 208
1000 Bauswein at a lower density, we infer a corresponding upper limit of Rskin .0.25 fm.1.6 However, if the upcoming M / ★
1.4 PREX-II experiment measures a significantly thicker skin, this1.5 may be evidence of a softening of the GW170817 ★
Λ symmetry energy at high densities—likely indicative of a phase transition in the interior of neutron 90%stars. upper bound 800 800 M et al PACS numbers: 04.40.Dg,r=0.98; 21.60.Jz, 21.65.Ef,α=5.28 24.10.Jv, 26.60.Kp, 97.60.Jd.1 LIGO 600 What are the new states of matter at exceedingly high with the large0.5 opacity typical of the lanthanides (atomic density and temperature? and how were the elements number 57–71) and have revealed that about 0.05 solar from iron to uranium made? are two of the “eleven sci- masses (or about 104 earth masses) of r-process elements 400ence questions for the next century” identified by the were synthesized in this single event [5–7]. The gravi- National12 Academies12.5 Committee13 13.5 on14 the Physics14.5 of15 the tational wave0 detection from the BNS merger, together 1.4 10 12 14 16 18 Universe [1]. In framingR these★ (km) questions, the committee with its associated electromagnetic counterparts, open recognized the deep connections between the very small the new era of multi-messengerRastronomy★(km) and provide and the very large. In one clean sweep, the historical first compelling evidence in favor of the long-held belief that detection of a binary neutron star (BNS) merger by the neutron-star mergers play a critical role in the production LIGO-Virgo collaboration [2] has started to answer these of heavy elements in the cosmos. Exciting possibility:fundamental If questions PREX by confirms providing critical that insights Rskin into isBesides the identificationThe very of thefirst BNS observation merger as a dom- of a BNS large and LIGO-Virgothe nature of dense that matter NS-radius and on the synthesis is small, of the thisinant site for the r-process,merger such an unprecedented already eventprovides heavy elements. imposes significant constraints on the EOS of dense mat- ter. In particular, the tidal polarizability (or deformabil- may be evidenceGravitational of a waves softening (GW) from of the the BNS EOS merger at a treasure trove of insights into the ity) is an intrinsic neutron-star property highly sensitive GW170817 emitted from a distance of about 40 Mpc high densities (phase transition?) to the stellar compactnessnature [8–13] that of describes dense the ten-matter! were detected by the LIGO gravitational-wave observa- dency of a neutron star to develop a mass quadrupole tory [2]. About two seconds later, the Fermi Gamma- as a response to the tidal field induced by its compan- ray Space Telescope (Fermi) [3] and the International ion [14, 15]. The dimensionless tidal polarizability ⇤ is Gamma-Ray Astrophysics Laboratory (INTEGRAL) [4] defined as follows: identified a short duration -ray burst associated with the BNS merger. Within eleven hours of the GW de- 5 5 2 c2R 64 R tection, ground- and spaced-based telescopes operating ⇤ = k = k , (1) 3 2 GM 3 2 R at a variety of wavelengths identified the associated kilo- ✓ ◆ ✓ s ◆ nova—the electromagnetic transient powered by the ra- dioactive decay of the heavy elements synthesized in where k2 is the second Love number [16, 17], M and R are the neutron star mass and radius, respectively, and the rapid neutron-capture process (r-process). Charac- 2 teristic features of the optical spectrum are consistent Rs 2GM/c is the Schwarzschild radius. A great virtue of the⌘ tidal polarizability is its high sensitivity to the stel- lar radius (⇤ R5) a quantity that has been notoriously di cult to constrain⇠ [18–28]. Pictorially, a “flu↵y” neu- tron star having a large radius is much easier to polarize ⇤Electronic address: [email protected] †Electronic address: [email protected] than the corresponding compact star with the same mass ‡Electronic address: [email protected] but a smaller radius. Finally, a derived quantity from the Color Superconductivity in Quark Matter QCD MADE SIMPLE uantum chromodynamics, Quantum chromodynamics is to the presence or motion of Qfamiliarly called QCD, is color charge, very similar to the modern theory of the conceptually simple. Its realization the way photons respond to strong interaction.1 Historic- in nature, however, is usually electric charge. ally its roots are in nuclear physics and the description of very complex. But not always. Quarks and gluons ordinary matter—understand- One class of particles that ing what protons and neu- carry color charge are the trons are and how they inter- Frank Wilczek quarks. We know of six differ- act. Nowadays QCD is used to ent kinds, or “flavors,” of describe most of what goes on at high-energy accelerators. quarks—denoted u, d, s, c, b, and t, for: up, down, Twenty or even fifteen years ago, this activity was strange, charmed, bottom, and top. Of these, only u and d commonly called “testing QCD.” Such is the success of the quarks play a significant role in the structure of ordinary theory, that we now speak instead of “calculating QCD matter. The other, much heavier quarks are all unstable. backgrounds” for the investigation of more speculative Aquark of any one of the six flavors can also carry a unit phenomena. For example, discovery of the heavy W and Z of any of the three color charges. Although the different bosons that mediate the weak interaction, or of the top quark flavors all have different masses, the theory is per- quark, would have been a much more difficult and uncer- fectly symmetrical with respect to the three colors. This tain affair if one did not have a precise, reliable under- color symmetry is described by the Lie group SU(3). standing of the more common processes governed by Quarks are spin-1/2 point particles, very much like QCD. With regard to things still to be found, search electrons. But instead of electric charge, they carry color strategies for the Higgs particle and for manifestations of charge. To be more precise, quarks carry fractional elec- supersymmetry depend on detailed understanding of pro- tric charge (+ 2e/3 for the u, c, and t quarks, and – e/3 for . duction mechanisms and backgrounds calculated by the d, s, and b quarks) in addition to their color charge. means of QCD. For all their similarities, however, there are a few Quantum chromodynamics is a precise and beautiful crucial differences between QCD and QED. First of all, theory. One reflection of this elegance is that the essence the response of gluons to color charge, as measured by the of QCD can be portrayed, without severe distortion, in the QCD coupling constant, is much more vigorous than the few simple pictures at the bottom of the box on the next response of photons to electric charge. Second, as shown page. But first, for comparison, let me remind you that the in the box, in addition to just responding to color charge, essence of quantum electrodynamics (QED), which is a gluons can also change one color charge into another. All generation older than QCD, can be portrayed by the sin- possible changes of this kind are allowed, and yet color gle picture at the top of the box, which represents the charge is conserved. So the gluons themselves must be interaction vertex at which a photon responds to the pres- able to carry unbalanced color charges. For example, if ence or motion of electric charge.2 This is not just a absorption of a gluon changes a blue quark into a red metaphor. Quite definite and precise algorithms for calcu- quark, then the gluon itself must have carried one unit of lating physical processes are attached to the Feynman red charge and minus one unit of blue charge. graphs of QED, constructed by connecting just such inter- All this would seem to require 3 × 3=9 different action vertices. color gluons. But one particular combination of gluons— In the same pictorial language, QCD appears as an the color-SU(3) singlet—which responds equally to all expanded version of QED. Whereas in QED there is just charges, is different from the rest. We must remove it if one kind of charge, QCDFIGURE has three1. THE differentQCD L kindsAGRANGIAN of we are⇒ displayed to have ahere perfectly is, in principle, color-symmetric a complete theory. description Then of the strong interaction. But, in charge, labeled by “color.” Avoiding chauvinism, we might we are left with only 8 physical gluon states (forming a practice, it leads to equations that are notoriously hard to solve. Here mj and qj are the mass and quantum field of the quark of jth choose red, green, and flavor, blue. But,and A of is course, the gluon the field, color withcolor-SU(3) spacetime octet). indices Fortunately, m and n and this color conclusion indices is a,vindicat- b, c. The numerical coefficients f and t guaran- charges of QCD have nothing to do with physical colors.Physicsed by experiment! Today - August, 2000 Rather, they have propertiestee SU(3) analogous color to symmetry. electric charge. Aside from Thethe thirdquark difference masses, the between one coupling QCD and constant QED, which g is theis only free parameter of the theory. In particular, the color charges are conserved in all phys- the most profound, follows from the second. Because glu- ons respond to the presence and motion of color charge ical processes, and there are photon-like massless parti- 6 cles, called color gluons, arethat comparedrespond in appropriatewith their waysmeasuredand values.they carry The unbalanced agreement colordirection. charge, it followsIn about that 90% of these hardron-producing is encouraging. gluons, quite unlike photons, respondevents, directlythere are to just one two jets, emerging in opposite direc- Such calculations clearly demonstrateanother. Photons, that of confine- course, aretions. electrically Occasionally—in neutral. about 9% of the hadronic final FRANKWILCZEK is the J. Robertment Oppenheimer and chiral-symmetry Professor of Physics at breakingTherefore are the consequences laser sword fights of you’vestates—one seen in Starsees Warsthree jets. the Institute for Advanced Study in Princeton, New Jersey. Next month wouldn’t work. But it’s a movie about the future, so maybe he moves to Cambridge, Massachusetts,solving to takethe up equations the Herman Feshbachof QCD. The calculations show us no Compare those multiparticle hadronic events to colli- Chair of Physics at the Massachusetts Institute of Technology. they’re using color gluon lasers. massless gluons, nor any fractionallyWe can charged display particles,QCD even moresions compactly, in which in terms leptons, of say muons, are produced. In that nor the enlarged multiplets that would indicate unbroken case, about 99% of the time one observes simply a muon chiral symmetry. Just the observed particles, with the and an antimuon, emerging in opposite directions. But 22 AUGUST 2000 PHYSICSright properties—neitherTODAY more nor less. © 2000 American Instituteoccasionally—in of Physics, S-0031-9228-0008-010-8 about 1% of the muonic final states—a While these and other massive numerical calcula- photon is emitted as well. tions give impressive and useful results, they are not the If history had happened in a different order, the end of all desire. There are many physically interesting observation of jet-like hadronic final states would surely questions about QCD for which the known numerical have led physicists to propose that they manifest under- techniques become impractical. Also, it is not entirely sat- lying phenomena like those displayed on the right-hand isfying to have our computers acting as oracles, delivering side of figure 3. Their resemblance to leptonic scattering answers without explanations. and QED would be too striking to ignore. ୴ The second approach is to give up on solving QCD Eventually, by studying the details of how energy was itself, and to focus instead on models that are simpler to apportioned among the jets, and the relative probabilities deal with, but still bear some significant resemblance to of different angles between them, the physicists would the real thing. Theorists have studied, for example, QCD- have deduced directly from experimental data that there like models in fewer dimensions, or models incorporating are light spin-1/2 and massless spin-1 objects lurking supersymmetry or different gauge groups, and several beneath the appearances, and how these covert objects other simplified variants. Many edifying insights have couple to one another. By studying the rare 4-jet events, been obtained in this way. By their nature, however, such they could even have learned about the coupling of the modelistic insights are not suited to hard-nosed con- spin-1 particles to each other. So all the basic couplings we frontation with physical reality. know in QCD might have been inferred, more or less ୴ The third approach, which is the subject of the rest of directly, from experiment. But there would still be one big this article, is to consider physical circumstances in which puzzle: Why are there jets, rather than simply particles? the equations somehow become simpler. The answer is profound, and rich in consequences. It is that the strength with which gluons couple depends Extreme virtuality radically on their energy and momentum. “Hard’’ gluons, The most fundamental simplification of QCD is illustrat- which carry a lot of energy and momentum, couple weak- ed in figure 3. There we see, on the left, the jet-like ly; whereas the less energetic “soft’’ gluons, couple strong- appearance of collision events in which strongly interact- ly. Thus, only rarely will a fast-moving colored quark or ing particles (hadrons) are produced in electron–positron gluon emit “radiation” (a gluon) that significantly redi- annihilations at high energy. One finds many particles in rects the flow of energy and momentum. That explains the the final state, but most of them are clearly organized into collimated flows one sees in jets. On the other hand, there a few collimated “jets” of particles that share a common can be a great deal of soft radiation, which explains the
24 AUGUST 2000 PHYSICS TODAY Have We Discovered Quark Stars?
EnhancedHave We vs Discovered Minimal Cooling Quarks of Neutron Stars? Stars: Quark Stars? Core-collapse supernovae generates hot (proto) neutron star T 1012K ' Neutron stars cool promptly by ⌫-emission (URCA) n p + e +¯⌫ ... ! e Direct URCA process cools down the star until T 109K ' Inefficient modified URCA takes over (n)+n (n)+p + e +¯⌫ ... ! e
Threshold Direct Urca Mass 3 FSU-like NL3-like 2.5 NLC-like )
sun 2 Maximum Mass (M Urca ! 1.5 M
Neutrino “enhanced” cooling possible in exotic1 quark matter Experiment/Obervation (assumed!) Unless ... symmetry energy is stiff: large Yp large neutron skin 0.5 0.16, 0.2 0.24 0.28 Rn-Rp (fm) J. Piekarewicz (FSU) Neutron-Rich Nuclei in Heaven and Earth CSM-2008 17 / 23 George Gamow and Assume Rn Rp . 0.18 fm and M(3C58) . 1.3M Then the pulsar in 3C58 may indeed be a quark star URCA cooling
J. Piekarewicz (FSU) Neutron-Rich Nuclei in Heaven and Earth CSM-2008 18 / 23 Gamow, Schenberg, and URCA Cooling?
URCA is not an acronym but rather, the name of a Casino in Rio de Janeiro where George Gamow commented to the Brazilian astrophysicist Mario Schenberg: “The energy disappears in the nucleus of the supernova as quickly as the money disappears at the roulette table”
In Gamow’s Russian dialect, “urca” also means a pickpocket, someone that can steel your money in a matter of seconds!
URCA Casino, Rio de Janeiro Gamow and Schenberg Conclusions: It is all Connected Astrophysics: What is the minimum mass of a black hole? C.Matter Physics: Existence of Coulomb-Frustrated Nuclear Pasta? General Relativity: Can BNS mergers constrain stellar radii? Nuclear Physics: What is the EOS of neutron-rich matter? Particle Physics: What exotic phases inhabit the dense core? Machine Learning: Extrapolation to where no man has gone before? Neutron Stars are the natural meeting place for interdisciplinary, fundamental, and fascinating physics!
Multi-messenger Astronomy with Gravitational Waves
Binary Neutron Star Merger
X-rays/Gamma-rays Gravita.onal Waves
Visible/Infrared Light Neutrinos
Radio Waves A message from Feynman to all the students
May 11, 1918
“That night I calculated all kinds of things with this theory (V-A theory of the weak interactions) The first thing I calculated was the rate of disintegration of the muon and the neutron. I went on and checked some other things, which fit, and new things fit, new things fit, and I was very excited. It was the first time, and the only time, in my career that I knew a law of nature that nobody else knew.” Until we meet again … Muito obrigado Florianópolis!