Abstract
We construct the first dynamically stable ergostars (equilibrium neutron stars that contain an ergoregion) for a compressible, causal equation of state. We demonstrate their stability by evolving both strict and perturbed equilibrium configurations in full general relativity for over a hundred dynamical timescales (30 rotational periods) and observing their stationary behavior. This stability is in contrast to earlier models which prove radially unstable to collapse. Our solutions are highly differentially rotating hypermassive neutron stars with a corresponding spherical compaction of C=0.3. Such ergostars can provide new insights into the geometry of spacetimes around highly compact, rotating objects and on the equation of state at supranuclear densities. Ergostars may form as remnants of extreme binary neutron star mergers and possibly provide another mechanism for powering short gamma-ray bursts.
| Original language | English (US) |
|---|---|
| Article number | 231103 |
| Journal | Physical review letters |
| Volume | 123 |
| Issue number | 23 |
| DOIs | |
| State | Published - Dec 3 2019 |
ASJC Scopus subject areas
- Physics and Astronomy(all)
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In: Physical review letters, Vol. 123, No. 23, 231103, 03.12.2019.
Research output: Contribution to journal › Article › peer-review
}
TY - JOUR
T1 - Dynamically Stable Ergostars Exist
T2 - General Relativistic Models and Simulations
AU - Tsokaros, Antonios
AU - Ruiz, Milton
AU - Sun, Lunan
AU - Shapiro, Stuart L.
AU - Uryu, Koji
N1 - Funding Information: In this Letter we presented dynamically stable equilibrium rotating NSs that contain ergoregions. The EOS that we employed is causal at the core and ALF2 at the outer layers of the star. We also proved that previously calculated polytropic ergostars are dynamically unstable. The secular evolution of our models will probably be determined by the Friedman instability [7] in the absence of other dissipative mechanisms. Despite that, and given the long timescales involved, the possibility of existence of such equilibria raises a number of questions, the most obvious of them being the fate of ergostars exhibiting internal dissipative mechanisms, such as viscosity or magnetic fields (which may serve as turbulent viscosity). Preliminary calculations of magnetic effects in fixed spacetimes [6] have shown that such systems can launch jets similar to BHs surrounded by magnetized disks. If the merger of two NSs forms an ergostar remnant that can launch a jet, the timescale for jet formation will be earlier than the one for a normal hypermassive NS [37,38] . This feature may have consequences in the theoretical analysis of events like GW170817 and its short gamma-ray burst counterpart GRB 170817A. Such open problems, as well as questions related to the range of EOSs and differential rotating laws that can lead to ergostars, or the possibility of binary ergostar remnants, are under investigation [39] . It is a pleasure to thank R. Haas and V. Paschalidis for useful discussions. We also thank the Illinois Relativity group REU team, G. Liu, K. Nelli, and M. N. T. Nguyen for assistance in creating Figs. 1 and 2 . This work was supported by NSF Grant No. PHY-1662211 and NASA Grant No. 80NSSC17K0070 to the University of Illinois at Urbana-Champaign, as well as by JSPS Grant-in-Aid for Scientific Research (C) 15K05085 and 18K03624 to the University of Ryukyus. This work made use of the Extreme Science and Engineering Discovery Environment (XSEDE), which is supported by National Science Foundation Grant No. TG-MCA99S008. This research is part of the Blue Waters sustained-petascale computing project, which is supported by the National Science Foundation (Grants No. OCI-0725070 and No. ACI-1238993) and the State of Illinois. Blue Waters is a joint effort of the University of Illinois at Urbana-Champaign and its National Center for Supercomputing Applications. Resources supporting this work were also provided by the NASA High-End Computing (HEC) Program through the NASA Advanced Supercomputing (NAS) Division at Ames Research Center. [1] 1a R. Penrose , Riv. Nuovo Cimento 1 , 252 ( 1969 ); RNUCAC 0035-5917 1b R. Penrose Gen. Relativ. Gravit. 34 , 1141 ( 2002 ). GRGVA8 0001-7701 10.1023/A:1016578408204 [2] 2 R. D. Blandford and R. L. Znajek , Mon. Not. R. Astron. Soc. 179 , 433 ( 1977 ). MNRAA4 0035-8711 10.1093/mnras/179.3.433 [3] 3 K. S. 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PRVDAQ 2470-0010 10.1103/PhysRevD.93.044056 [28] 28 K. Uryu , A. Tsokaros , L. Baiotti , F. Galeazzi , K. Taniguchi , and S. Yoshida , Phys. Rev. D 96 , 103011 ( 2017 ). PRVDAQ 2470-0010 10.1103/PhysRevD.96.103011 [29] 29 Z. B. Etienne , Y. T. Liu , and S. L. Shapiro , Phys. Rev. D 82 , 084031 ( 2010 ). PRVDAQ 1550-7998 10.1103/PhysRevD.82.084031 [30] 30 M. Shibata and T. Nakamura , Phys. Rev. D 52 , 5428 ( 1995 ). PRVDAQ 0556-2821 10.1103/PhysRevD.52.5428 [31] 31 T. W. Baumgarte and S. L. Shapiro , Phys. Rev. D 59 , 024007 ( 1998 ). PRVDAQ 0556-2821 10.1103/PhysRevD.59.024007 [32] 32 V. Paschalidis , W. E. East , F. Pretorius , and S. L. Shapiro , Phys. Rev. D 92 , 121502(R) ( 2015 ). PRVDAQ 1550-7998 10.1103/PhysRevD.92.121502 [33] 33 T. W. Baumgarte , S. L. Shapiro , and M. Shibata , Astrophys. J. 528 , L29 ( 2000 ). ASJOAB 0004-637X 10.1086/312425 [34] 34 M. Shibata , T. W. Baumgarte , and S. L. Shapiro , Astrophys. J. 542 , 453 ( 2000 ). ASJOAB 0004-637X 10.1086/309525 [35] 35 See the Supplemental Material at http://link.aps.org/supplemental/10.1103/PhysRevLett.123.231103 for a numerical stability analysis. [36] 36 P. L. Espino , V. Paschalidis , T. W. Baumgarte , and S. L. Shapiro , Phys. Rev. D 100 , 043014 ( 2019 ). PRVDAQ 2470-0010 10.1103/PhysRevD.100.043014 [37] 37 M. Ruiz , R. N. Lang , V. Paschalidis , and S. L. Shapiro , Astrophys. J. 824 , L6 ( 2016 ). ASJOAB 0004-637X 10.3847/2041-8205/824/1/L6 [38] 38 M. Ruiz , S. L. Shapiro , and A. Tsokaros , Phys. Rev. D 98 , 123017 ( 2018 ). PRVDAQ 2470-0010 10.1103/PhysRevD.98.123017 [39] 39 Movies highlighting results of our simulations can be found at http://research.physics.illinois.edu/cta/movies/Ergostar/ . Publisher Copyright: © 2019 American Physical Society.
PY - 2019/12/3
Y1 - 2019/12/3
N2 - We construct the first dynamically stable ergostars (equilibrium neutron stars that contain an ergoregion) for a compressible, causal equation of state. We demonstrate their stability by evolving both strict and perturbed equilibrium configurations in full general relativity for over a hundred dynamical timescales (30 rotational periods) and observing their stationary behavior. This stability is in contrast to earlier models which prove radially unstable to collapse. Our solutions are highly differentially rotating hypermassive neutron stars with a corresponding spherical compaction of C=0.3. Such ergostars can provide new insights into the geometry of spacetimes around highly compact, rotating objects and on the equation of state at supranuclear densities. Ergostars may form as remnants of extreme binary neutron star mergers and possibly provide another mechanism for powering short gamma-ray bursts.
AB - We construct the first dynamically stable ergostars (equilibrium neutron stars that contain an ergoregion) for a compressible, causal equation of state. We demonstrate their stability by evolving both strict and perturbed equilibrium configurations in full general relativity for over a hundred dynamical timescales (30 rotational periods) and observing their stationary behavior. This stability is in contrast to earlier models which prove radially unstable to collapse. Our solutions are highly differentially rotating hypermassive neutron stars with a corresponding spherical compaction of C=0.3. Such ergostars can provide new insights into the geometry of spacetimes around highly compact, rotating objects and on the equation of state at supranuclear densities. Ergostars may form as remnants of extreme binary neutron star mergers and possibly provide another mechanism for powering short gamma-ray bursts.
UR - http://www.scopus.com/inward/record.url?scp=85076561986&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85076561986&partnerID=8YFLogxK
U2 - 10.1103/PhysRevLett.123.231103
DO - 10.1103/PhysRevLett.123.231103
M3 - Article
C2 - 31868499
AN - SCOPUS:85076561986
SN - 0031-9007
VL - 123
JO - Physical Review Letters
JF - Physical Review Letters
IS - 23
M1 - 231103
ER -