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Journal articles on the topic 'Compact object (Astronomy)'

Author: Grafiati

Published: 4 June 2021

Last updated: 12 February 2022

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1

van der Sluys, M. V., C. Röver, A. Stroeer, V. Raymond, I. Mandel, N. Christensen, V. Kalogera, R. Meyer, and A. Vecchio. "Gravitational-Wave Astronomy with Inspiral Signals of Spinning Compact-Object Binaries." Astrophysical Journal 688, no. 2 (October 23, 2008): L61—L64. http://dx.doi.org/10.1086/595279.

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2

Pfeiffer, Harald P. "Numerical simulations of compact object binaries." Classical and Quantum Gravity 29, no. 12 (June 1, 2012): 124004. http://dx.doi.org/10.1088/0264-9381/29/12/124004.

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3

Kalogera, Vassiliki. "Binary compact object inspiral: Detection expectations." Pramana 63, no. 4 (October 2004): 673–83. http://dx.doi.org/10.1007/bf02705191.

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4

Kavic, Michael, Steven L. Liebling, Matthew Lippert, and John H. Simonetti. "Accessing the axion via compact object binaries." Journal of Cosmology and Astroparticle Physics 2020, no. 08 (August 4, 2020): 005. http://dx.doi.org/10.1088/1475-7516/2020/08/005.

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5

Breivik, Katelyn, Sourav Chatterjee, and Jeff J. Andrews. "Constraining Compact Object Formation with 2M0521." Astrophysical Journal 878, no. 1 (June 5, 2019): L4. http://dx.doi.org/10.3847/2041-8213/ab21d3.

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6

Li, Xinyu, Philip Chang, Yuri Levin, Christopher D. Matzner, and Philip J. Armitage. "Simulation of a compact object with outflows moving through a gaseous background." Monthly Notices of the Royal Astronomical Society 494, no. 2 (April 9, 2020): 2327–36. http://dx.doi.org/10.1093/mnras/staa900.

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ABSTRACT A compact object moving relative to surrounding gas accretes material and perturbs the density of gas in its vicinity. In the classical picture of Bondi–Hoyle–Lyttleton accretion, the perturbation takes the form of an overdense wake behind the object, which exerts a dynamical friction drag. We use hydrodynamic simulations to investigate how the accretion rate and strength of dynamical friction are modified by the presence of outflow from the compact object. We show that the destruction of the wake by an outflow reduces dynamical friction, and reverses its sign when the outflow is strong enough, in good quantitative agreement with analytic calculations. For a strong isotropic outflow, the outcome on scales that we have simulated is a negative dynamical friction, i.e. net acceleration. For jet-like outflows driven by reprocessed accretion, both the rate of accretion and the magnitude of dynamical friction drop for more powerful jets. The accretion rate is strongly intermittent when the jet points to the same direction as the motion of the compact object. The dynamical effects of outflows may be important for the evolution of compact objects during the common envelope phase of binary systems, and for accreting compact objects and massive stars encountering active galactic nucleus discs.

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Wiktorowicz, Grzegorz, Matthew Middleton, Norman Khan, Adam Ingram, Poshak Gandhi, and Hugh Dickinson. "Predicting the self-lensing population in optical surveys." Monthly Notices of the Royal Astronomical Society 507, no. 1 (July 29, 2021): 374–84. http://dx.doi.org/10.1093/mnras/stab2135.

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ABSTRACT The vast majority of binaries containing a compact object and a regular star spend most of their time in a quiescent state where no strong interactions occur between components. Detection of these binaries is extremely challenging and only few candidates have been detected through optical spectroscopy. Self-lensing represents a new means of detecting compact objects in binaries, where gravitational lensing of the light from the visible component by the compact object produces periodic optical flares. Here we show that current and planned large-area optical surveys can detect a significant number (∼100–10 000s) of these self-lensing binaries and provide insights into the properties of the compact lenses. We show that many of the predicted population of observable self-lensing binaries will be observed with multiple self-lensing flares; this both improves the chances of detection and also immediately distinguishes them from chance-alignment micro-lensing events. Through self-lensing we can investigate long – but previously hidden – stages of binary evolution and consequently provide new constraints on evolutionary models that impact the number and nature of double compact object mergers.

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Tremblay, S. E., G. B. Taylor, J. F. Helmboldt, C. D. Fassnacht, and T. J. Pearson. "A Shrinking Compact Symmetric Object: J11584+2450?" Astrophysical Journal 684, no. 1 (September 2008): 153–59. http://dx.doi.org/10.1086/590377.

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9

Fryer, Chris L. "Compact object formation and the supernova explosion engine." Classical and Quantum Gravity 30, no. 24 (November 29, 2013): 244002. http://dx.doi.org/10.1088/0264-9381/30/24/244002.

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10

Tanaka, Y. "Observations of Compact X-Ray Sources." International Astronomical Union Colloquium 89 (1986): 198–221. http://dx.doi.org/10.1017/s0252921100086097.

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This paper reviews the present status of observations of compact X-ray sources with emphasis on the aspects related to radiation hydrodynamics, based on the recent observational results, in particular those from the Japanese X-ray astronomy satellite Tenma. The main feature of Tenma is a large-area gas scintillation proportional counters (GSPC) with energy resolution twice that of ordinary proportional counters, which can yield information on energy spectrum superior in quality to previous results. We shall deal here only with those galactic X-ray sources in which the compact object is a neutron star or possibly a black hole, and exclude white dwarf sources.There exist more than one hundred bright X-ray sources in our galaxy in the luminosity range 1036−1038 ergs/sec. They are most probably binaries involving a neutron star or, in some cases, possibly a black hole. The high luminosities of these sources are explained in terms of the large gravitaional energy release by matter accreting from the companion star to the compact object.

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Li, Guang-Xing, and Xun Shi. "Molecular contrails – triggered contraction by passages of massive objects through molecular clouds." Monthly Notices of the Royal Astronomical Society 503, no. 3 (March 13, 2021): 4466–73. http://dx.doi.org/10.1093/mnras/stab735.

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ABSTRACT We study the effects of passages of compact objects such as stars, star clusters, and black holes through molecular clouds, and propose that the gravitational interaction between the compact object and the ambient gas can lead to the formation of thin and collimated features made of dense gas, which we call ‘molecular contrails’. Supercritical contrails can collapse further leading to triggered star formation. The width of a molecular contrail is determined by the mass and velocity of the compact object and the velocity dispersion of the ambient molecular medium. Under typical conditions in the Milky Way, passages of stellar-mass objects lead to the formation of width $d\gtrsim 0.01\,\,\rm {pc}$ contrails, and passages of star clusters lead to the formation of $d\gtrsim 1\,\,\rm {pc}$ contrails. We present a few molecular contrail candidates from both categories identified from ALMA 1.3 mm continuum observations of star-forming regions and the 13CO(1-0) map from the Galactic Ring Survey, respectively. The contrails represent an overlooked channel where stars and gas in the Galactic disc interact to form structures. They also present a potential way of detecting dark compact objects in the Milky Way.

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12

Krezinger, Máté, Sándor Frey, Tao An, Sumit Jaiswal, and Yingkang Zhang. "J1110+4817 – a compact symmetric object candidate revisited." Monthly Notices of the Royal Astronomical Society 496, no. 2 (June 12, 2020): 1811–18. http://dx.doi.org/10.1093/mnras/staa1669.

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ABSTRACT Compact symmetric objects (CSOs) are radio-emitting active galactic nuclei (AGNs) typically with a double-lobed radio structure confined to within 1 kpc. CSOs represent the earliest evolutionary phase of jetted AGNs. Some of them may eventually evolve into large-scale extended double sources, while others stall within the host galaxy and die out, depending on the longevity of nuclear activity, the jet power, and parameters of the surrounding galactic environment. Studying CSOs is a useful tool for understanding the evolution of the galaxies and the interactions between the jets and the medium of the host galaxy. Based on milliarcsec-resolution imaging observations using very long baseline interferometry (VLBI), it is not always straightforward to distinguish between a compact double-lobed or a core–jet structure. The quasar J1110+4817 was considered a CSO candidate in the literature earlier, but because of the lack of clear evidence, it could not be securely classified as a CSO. Here we present a comprehensive analysis of archival multifrequency VLBI observations combined with accurate Gaia optical astrometric information. Lower frequency VLBI images reveal an extended radio feature nearly perpendicular to the main structural axis of the source, apparently emanating from the brighter northern feature, which is rare among the known CSOs. While the presence of a binary AGN system cannot be fully excluded, the most plausible explanation is that J1110+4817 is a CSO.

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Banerjee, D., J. R. Bhatt, A. C. Das, and A. R. Prasanna. "Axisymmetric Magnetohydrodynamic Equilibrium around a Magnetized Compact Object." Astrophysical Journal 474, no. 1 (January 1997): 389–96. http://dx.doi.org/10.1086/303430.

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14

Karas, Vladimír, and Rastislav Mucha. "Accretion onto a rotating compact object in general relativity." American Journal of Physics 61, no. 9 (September 1993): 825–28. http://dx.doi.org/10.1119/1.17433.

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15

Arbañil, José D. V., and Manuel Malheiro. "Radial pulsation of a compact object in d dimensions." Journal of Physics: Conference Series 1558 (May 2020): 012003. http://dx.doi.org/10.1088/1742-6596/1558/1/012003.

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16

Andersson, Nils. "A Gravitational-Wave Perspective on Neutron-Star Seismology." Universe 7, no. 4 (April 11, 2021): 97. http://dx.doi.org/10.3390/universe7040097.

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We provide a bird’s-eye view of neutron-star seismology, which aims to probe the extreme physics associated with these objects, in the context of gravitational-wave astronomy. Focussing on the fundamental mode of oscillation, which is an efficient gravitational-wave emitter, we consider the seismology aspects of a number of astrophysically relevant scenarios, ranging from transients (like pulsar glitches and magnetar flares), to the dynamics of tides in inspiralling compact binaries and the eventual merged object and instabilities acting in isolated, rapidly rotating, neutron stars. The aim is not to provide a thorough review, but rather to introduce (some of) the key ideas and highlight issues that need further attention.

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17

Neslušan, L. "The second rise of general relativity in astrophysics." Modern Physics Letters A 34, no. 30 (September 28, 2019): 1950244. http://dx.doi.org/10.1142/s0217732319502444.

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The field equations, which are the mathematical basis of the theory of general relativity, provide us with a much larger variety of solutions to model the neutron stars and other compact objects than are used in the current astrophysics. We point out some important consequences of the new kind of solutions of the field equations, which can be obtained if the astrophysical usage of general relativity is not constrained, and outline an impact of these solutions on the models of internal structure of compact objects. If general relativity is not constrained, it enables to construct the stable object, with the outer surface above the event horizon, of whatever large mass. A new concept of relativistic compact object is a consequence of newly discovered property of gravity, yielded by the field equations in a spherically symmetric configuration of matter: in comparison with the Newtonian case, a particle is more effectively attracted by a nearer than a more distant matter.

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18

Barrett, Jim W., Ilya Mandel, Coenraad J. Neijssel, Simon Stevenson, and Alejandro Vigna-Gómez. "Exploring the Parameter Space of Compact Binary Population Synthesis." Proceedings of the International Astronomical Union 12, S325 (October 2016): 46–50. http://dx.doi.org/10.1017/s1743921317000059.

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AbstractAs we enter the era of gravitational wave astronomy, we are beginning to collect observations which will enable us to explore aspects of astrophysics of massive stellar binaries which were previously beyond reach. In this paper we describe COMPAS (Compact Object Mergers: Population Astrophysics and Statistics), a new platform to allow us to deepen our understanding of isolated binary evolution and the formation of gravitational-wave sources. We describe the computational challenges associated with their exploration, and present preliminary results on overcoming them using Gaussian process regression as a simulation emulation technique.

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19

Veneroni, L. S. M., A. Braz, and M. F. A. da Silva. "Compact object with a local dark energy shell." International Journal of Modern Physics D 30, no. 06 (April 6, 2021): 2150039. http://dx.doi.org/10.1142/s0218271821500395.

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We investigate some models of compact objects in the general relativity theory with cosmological constant [Formula: see text], based on two density profiles, one of them attributed to Stewart and the other one to Durgapal and Bannerji, proposed in the literature to model “neutron stars”. For them, a nonlocal equation of state with cosmological constant is obtained as a consequence of the chosen metric. In another direction, we obtain a solution for configurations with null radial pressure. The first model (based on Stewart’s density profile) turned out to be the most interesting, since surprisingly it admits the presence of dark energy in the interior of the star, in the outermost layers, for a certain range of mass–radius ratio [Formula: see text]. This dark energy is independent of the cosmological constant, since it is a consequence of the tangential pressure of the fluid be sufficiently negative. Still in this case, for other values of [Formula: see text], all the energy conditions are satisfied. Another advantage of this model, as well as that based on the density profile of Durgapal and Bannerji, is the existence of intervals of [Formula: see text] compatible with physically acceptable models for [Formula: see text], [Formula: see text] and [Formula: see text], which also allowed us to analyze the influence of [Formula: see text] on the behavior of the fluid with respect to the energy conditions. The other configuration studied here, [Formula: see text], only allows solutions for [Formula: see text], in order to ensure a positive mass for the object and to satisfy all the energy conditions in a specific range of [Formula: see text].

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20

Menzies, Dylan, and Grant J. Mathews. "An axisymmetric object-based search for a flat compact dimension." Journal of Cosmology and Astroparticle Physics 2005, no. 10 (October 18, 2005): 008. http://dx.doi.org/10.1088/1475-7516/2005/10/008.

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21

Di Stefano, R. "Mass from a third star: transformations of close compact-object binaries within hierarchical triples." Monthly Notices of the Royal Astronomical Society 493, no. 2 (February 6, 2020): 1855–73. http://dx.doi.org/10.1093/mnras/staa220.

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ABSTRACT Close-orbit binaries consisting of two compact objects are a centre of attention because of the detection of gravitational-radiation-induced mergers. The creation of close, compact-object binaries involves physical processes that are not yet well understood; there are open questions about the manner in which two compact objects come to be close enough to merge within a Hubble time. Here, we explore an important, and likely common physical process: mass transfer from a third star in a wider, hierarchical orbit. Mass added to the close binary’s components can reduce the time to merger and can even change the nature of an accretor, transforming a white dwarf to a neutron star and/or a neutron star to a black hole. Some accreting WDs in close binaries may even explode as Type Ia supernovae. Given the ubiquity of higher order multiples, the evolutionary channels we lay out may be important pathways to gravitational mergers, including Type Ia supernovae. Fortunately, these pathways also lead to testable predictions.

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22

Deme, Barnabás, Yohai Meiron, and Bence Kocsis. "Intermediate-mass Black Holes’ Effects on Compact Object Binaries." Astrophysical Journal 892, no. 2 (April 6, 2020): 130. http://dx.doi.org/10.3847/1538-4357/ab7921.

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23

Belczynski, Krzysztof, Vassiliki Kalogera, Frederic A. Rasio, Ronald E. Taam, Andreas Zezas, Tomasz Bulik, Thomas J. Maccarone, and Natalia Ivanova. "Compact Object Modeling with the StarTrack Population Synthesis Code." Astrophysical Journal Supplement Series 174, no. 1 (January 2008): 223–60. http://dx.doi.org/10.1086/521026.

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24

Kupi, G., P. Amaro-Seoane, and R. Spurzem. "Dynamics of compact object clusters: a post-Newtonian study." Monthly Notices of the Royal Astronomical Society: Letters 371, no. 1 (September 1, 2006): L45—L49. http://dx.doi.org/10.1111/j.1745-3933.2006.00205.x.

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25

Otani, Jun, Rohta Takahashi, and Yoshiharu Eriguchi. "Equilibrium states of magnetized toroid-central compact object systems." Monthly Notices of the Royal Astronomical Society 396, no. 4 (July 11, 2009): 2152–66. http://dx.doi.org/10.1111/j.1365-2966.2009.14842.x.

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26

Hernández, Jaime Mendoza, Juan Ignacio Musmarra, and Mauricio Bellini. "Waves of space–time from a collapsing compact object." Physics of the Dark Universe 27 (January 2020): 100424. http://dx.doi.org/10.1016/j.dark.2019.100424.

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27

Kovalev, Y. Y., A. P. Lobanov, A. B. Pushkarev, and J. A. Zensus. "Opacity in compact extragalactic radio sources and its effect on radio-optical reference frame alignment." Proceedings of the International Astronomical Union 3, S248 (October 2007): 348–51. http://dx.doi.org/10.1017/s1743921308019546.

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AbstractAccurate alignment of the radio and optical celestial reference frames requires detailed understanding of physical factors that may cause offsets between the positions of the same object measured in different spectral bands. Opacity in compact extragalactic jets (due to synchrotron self-absorption and external free-free absorption) is one of the key physical phenomena producing such an offset, and this effect is well-known in radio astronomy (“core shift”). We have measured the core shifts in a sample of 29 bright compact extragalactic radio sources observed by Very Long Baseline Interferometry (VLBI) at 2.3 and 8.6 GHz. We report the results of these measurements and estimate that the average shift between radio and optical positions of distant quasars could be of the order of 0.1--0.2 mas. This shift exceeds the expected positional accuracy of Gaia and SIM. We suggest two possible approaches to carefully investigate and correct for this effect in order to align accurately the radio and optical positions. Both approaches involve determining a Primary Reference Sample of objects to be used for tying the radio and optical reference frames together.

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28

Seo, K. A., C. Y. Hui, R. H. H. Huang, L. Trepl, T. N. Lu, A. K. H. Kong, and F. M. Walter. "X-ray properties of G308.3-1.4 and its central compact object." Proceedings of the International Astronomical Union 8, S291 (August 2012): 489–91. http://dx.doi.org/10.1017/s1743921312024611.

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AbstractWe present a short Chandra observation that confirms a previous unidentified extended X-ray source, G308.3-1.4, as a new supernova remnant (SNR) in the Milky Way. Apart from identifying its SNR nature, a bright X-ray point source has also been discovered at the geometrical center. Its X-ray spectral properties are similar to those of a particular class of neutron star known as central compact objects (CCOs). On the other hand, the optical properties of this counterpart suggests it to be a late-type star. Together with the interesting ~ 1.4 hours X-ray periodicity found by Chandra, this system can possibly provide the first direct evidence of a compact binary survived in a supernova explosion.

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29

Cirilo-Lombardo, D. J., and F. O. Minotti. "Beyond general relativity models, magnetosphere structure and dark matter stars." International Journal of Geometric Methods in Modern Physics 16, no. 04 (April 2019): 1950064. http://dx.doi.org/10.1142/s0219887819500646.

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The magnetosphere structure of compact objects is considered in the context of a theory of gravity with dynamical torsion field beyond standard General Relativity (GR). To this end, a new spherically symmetric solution is obtained in this theoretical framework, physically representing a compact object of pseudoscalar fields (for example, axion field). The axially symmetric version of the Grad–Shafranov equation (GSE) is also derived in this context, and used to describe the magnetosphere dynamics of the obtained “axion star”. The interplay between high-energy processes and the seed magnetic field with respect to the global structure of the magnetosphere is briefly discussed.

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30

Fujioka, Shinsuke, Hideaki Takabe, Norimasa Yamamoto, David Salzmann, Feilu Wang, Hiroaki Nishimura, Yutong Li, et al. "X-ray astronomy in the laboratory with a miniature compact object produced by laser-driven implosion." Nature Physics 5, no. 11 (October 18, 2009): 821–25. http://dx.doi.org/10.1038/nphys1402.

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31

Kunert-Bajraszewska, M., K. Katarzyński, A. Janiuk, and M. Cegłowski. "Jet-linked X-ray emission in radio-loud broad absorption line (BAL) quasars." Proceedings of the International Astronomical Union 8, S290 (August 2012): 243–44. http://dx.doi.org/10.1017/s1743921312019825.

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AbstractWe have applied theoretical models to explain spectral energy distribution (SED) of three radio-loud broad absorption line (BAL) quasars: an extended hybrid object PG 1004+130 and two compact sources 1045+352 and 3C270.1. We calculate the emission from the very inner part of the sources which accounts for more than 90% of the observed X-ray radiation. In our analysis we consider a scenario in which the observed X-ray emission comes from the inverse-Compton (IC) scattering inside a jet and from the accretion disk corona. The compact objects 1045+352 and 3C270.1 are high-redshift quasars (z = 1.604 and 1.532 respectively), with strong radio cores. We argue that in the case of these two sources a non-thermal, inverse-Compton emission from the innermost parts of the jet can explain a large fraction of the observed X-ray emission. The large scale object PG 1004+130 with a peculiar radio morphology is a low-redshift (z = 0.24), lobe-dominated BAL quasar with a weak radio core. In this case simulated inverse-Compton X-ray emission of the jet is relatively low. However, the corona emission appears strong enough to explain the observed X-ray spectrum of this object.

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32

Downing, J. M. B., and R. Spurzem. "A Post-Newtonian Treatment of Relativistic Compact Object Binaries in Star Clusters." Proceedings of the International Astronomical Union 3, S246 (September 2007): 265–66. http://dx.doi.org/10.1017/s1743921308015731.

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AbstractStellar mass compact object binaries are promising sources of gravitational radiation for the current generation of ground-based detectors, VIRGO and LIGO. Accurate templates for gravitational waveforms are needed in order to extract an event from the VIRGO/LIGO data stream. In the case of relativistic, compact object binaries accurate orbital parameters are necessary in order to produce such templates. Binary systems are affected by their stellar environment and thus the parameters of the binary population of a dense star cluster will be different from those of the field population. We propose to investigate the parameters of relativistic binary populations in dense star clusters using direct N-body simulations with a Post-Newtonian treatment of general relativity for the close binaries.

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33

D’Orazio, Daniel J., and Rosanne Di Stefano. "Detecting gravitational self-lensing from stellar-mass binaries composed of black holes or neutron stars." Monthly Notices of the Royal Astronomical Society 491, no. 1 (November 4, 2019): 1506–17. http://dx.doi.org/10.1093/mnras/stz3086.

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ABSTRACT We explore a unique electromagnetic signature of stellar-mass compact-object binaries long before they are detectable in gravitational waves. We show that gravitational lensing of light emitting components of a compact-object binary, by the other binary component, could be detectable in the nearby Universe. This periodic lensing signature could be detected from present and future X-ray observations, identifying the progenitors of binaries that merge in the LIGO band, and also unveiling populations that do not merge, thus providing a tracer of the compact-object binary population in an enigmatic portion of its life. We argue that periodically repeating lensing flares could be observed for ≲100 ks orbital-period binaries with the future Lynx X-ray mission, possibly concurrent with gravitational wave emission in the LISA band. Binaries with longer orbital periods could be more common and be detectable as single lensing flares, though with reliance on a model for the flare that can be tested by observations of succeeding flares. Non-detection of such events, even with existing X-ray observations, will help to constrain the population of EM bright compact-object binaries.

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34

Tagawa, Hiromichi, Zoltán Haiman, and Bence Kocsis. "Formation and Evolution of Compact-object Binaries in AGN Disks." Astrophysical Journal 898, no. 1 (July 20, 2020): 25. http://dx.doi.org/10.3847/1538-4357/ab9b8c.

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35

Gabuzda, D. C. "VSOP observations of the compact BL Lacertae object 1803+784." New Astronomy Reviews 43, no. 8-10 (November 1999): 691–94. http://dx.doi.org/10.1016/s1387-6473(99)00079-2.

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36

Doroshenko, Victor, Gerd Pühlhofer, Patrick Kavanagh, Andrea Santangelo, Valery Suleimanov, and Dmitry Klochkov. "Evidence for a binary origin of a central compact object." Monthly Notices of the Royal Astronomical Society 458, no. 3 (March 7, 2016): 2565–72. http://dx.doi.org/10.1093/mnras/stw499.

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37

Maness, H. L., G. B. Taylor, R. T. Zavala, A. B. Peck, and L. K. Pollack. "Breaking All the Rules: The Compact Symmetric Object 0402+379." Astrophysical Journal 602, no. 1 (February 10, 2004): 123–34. http://dx.doi.org/10.1086/380919.

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38

Seward, F. D., P. O. Slane, R. K. Smith, and M. Sun. "A Compact Central Object in the Supernova Remnant Kesteven 79." Astrophysical Journal 584, no. 1 (February 10, 2003): 414–17. http://dx.doi.org/10.1086/345600.

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Rutledge, R. E., D. B. Fox, and A. H. Shevchuk. "Discovery of an Isolated Compact Object at High Galactic Latitude." Astrophysical Journal 672, no. 2 (January 10, 2008): 1137–43. http://dx.doi.org/10.1086/522667.

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40

O'Shaughnessy, R., V. Kalogera, and Krzysztof Belczynski. "BINARY COMPACT OBJECT COALESCENCE RATES: THE ROLE OF ELLIPTICAL GALAXIES." Astrophysical Journal 716, no. 1 (May 20, 2010): 615–33. http://dx.doi.org/10.1088/0004-637x/716/1/615.

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Kargaltsev, Oleg, George G. Pavlov, Divas Sanwal, and Gordon P. Garmire. "The Compact Central Object in the Supernova Remnant G266.2−1.2." Astrophysical Journal 580, no. 2 (December 2002): 1060–64. http://dx.doi.org/10.1086/343852.

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42

Cowie, L. L., A. Songaila, E. M. Hu, E. Egami, J. S. Huang, A. J. Pickles, S. E. Ridgway, R. J. Wainscoat, and R. J. Weymann. "Hawaii 167: A compact absorption-line object at Z = 2.35." Astrophysical Journal 432 (September 1994): L83. http://dx.doi.org/10.1086/187517.

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Rossi, Elena M., and Mitchell C. Begelman. "Delayed X-ray emission from fallback in compact-object mergers." Monthly Notices of the Royal Astronomical Society 392, no. 4 (February 1, 2009): 1451–55. http://dx.doi.org/10.1111/j.1365-2966.2008.14139.x.

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Lemos, José P. S., and Oleg B. Zaslavskii. "Compact objects in general relativity: From Buchdahl stars to quasiblack holes." International Journal of Modern Physics D 29, no. 11 (July 30, 2020): 2041019. http://dx.doi.org/10.1142/s0218271820410199.

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A Buchdahl star is a highly compact star for which the boundary radius [Formula: see text] obeys [Formula: see text], where [Formula: see text] is the gravitational radius of the star itself. A quasiblack hole is a maximum compact star, or more generically a maximum compact object, for which the boundary radius [Formula: see text] obeys [Formula: see text]. Quasiblack holes are objects on the verge of becoming black holes. Continued gravitational collapse ends in black holes and has to be handled with the Oppenheimer–Snyder formalism. Quasistatic contraction ends in a quasiblack hole and should be treated with appropriate techniques. Quasiblack holes, not black holes, are the real descendants of Mitchell and Laplace dark stars. Quasiblack holes have many interesting properties. We develop the concept of a quasiblack hole, give several examples of such an object, define what it is, draw its Carter–Penrose diagram, study its pressure properties, obtain its mass formula, derive the entropy of a nonextremal quasiblack hole and through an extremal quasiblack hole give a solution to the puzzling entropy of extremal black holes.

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Mitra, Abhas. "Masses of radiation pressure supported stars in extreme relativistic realm." Proceedings of the International Astronomical Union 2, S238 (August 2006): 409–10. http://dx.doi.org/10.1017/s1743921307005698.

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AbstractWe discuss that in the extreme relativistic limit, i.e., when z ≫ 1, where z is the surface gravitational redshift, there could be radiation pressure supported and dominated stars with arbitrary gravitational mass, high or low. Such objects are called Eternally Collapsing Objects (ECOs). ECOs are practically as compact as Schwarzschild black holes (BH) and, observationally, are likely to be mistaken as BHs. Further since any object undergoing continued collapse must first become an ECO before becoming a true BH state characterized by M = 0, the observed BH Candidates are ECOs.

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Estevez-Delgado, Gabino, and Joaquin Estevez-Delgado. "Compact stars." Modern Physics Letters A 33, no. 15 (May 20, 2018): 1850081. http://dx.doi.org/10.1142/s0217732318500815.

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An analysis and construction is presented for a stellar model characterized by two parameters (w, n) associated with the compactness ratio and anisotropy, respectively. The reliability range for the parameter w [Formula: see text] 1.97981225149 corresponds with a compactness ratio u [Formula: see text] 0.2644959374, the density and pressures are positive, regular and monotonic decrescent functions, the radial and tangential speed of sound are lower than the light speed, moreover, than the plausible stability. The behavior of the speeds of sound are determinate for the anisotropy parameter n, admitting a subinterval where the speeds are monotonic crescent functions and other where we have monotonic decrescent functions for the same speeds, both cases describing a compact object that is also potentially stable. In the bigger value for the observational mass M = 2.05 M[Formula: see text] and radii R = 12.957 Km for the star PSR J0348+0432, the model indicates that the maximum central density [Formula: see text] = 1.283820319 × 10[Formula: see text] Kg/m3 corresponds to the maximum value of the anisotropy parameter and the radial and tangential speed of the sound are monotonic decrescent functions.

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Gruzinov, Andrei, Yuri Levin, and Christopher D. Matzner. "Negative dynamical friction on compact objects moving through dense gas." Monthly Notices of the Royal Astronomical Society 492, no. 2 (January 16, 2020): 2755–61. http://dx.doi.org/10.1093/mnras/staa013.

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ABSTRACT An overdense wake is created by a gravitating object moving through a gaseous medium, and this wake pulls back on the object and slows it down. This is conventional dynamical friction in a gaseous medium. We argue that if the object drives a sufficiently powerful outflow, the wake is destroyed and instead an extended underdense region is created behind the object. In this case the overall gravitational force is applied in the direction of the object’s motion, producing a negative dynamical friction (NDF). Black holes in dense gas drive powerful outflows and may experience the NDF, although extensive numerical work is probably needed to demonstrate or refute this conclusively. NDF may be important for stellar-mass black holes and neutron stars inside ‘common envelopes’ in binary systems, for stellar mass black holes inside active galactic nucleus discs, or for massive black holes growing through super-Eddington accretion in early Universe.

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Rosswog, Stephan. "The dynamic ejecta of compact object mergers and eccentric collisions." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 371, no. 1992 (June 13, 2013): 20120272. http://dx.doi.org/10.1098/rsta.2012.0272.

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Compact object mergers eject neutron-rich matter in a number of ways: by the dynamical ejection mediated by gravitational torques, as neutrino-driven winds, and probably also a good fraction of the resulting accretion disc finally becomes unbound by a combination of viscous and nuclear processes. If compact binary mergers indeed produce gamma-ray bursts, there should also be an interaction region where an ultra-relativistic outflow interacts with the neutrino-driven wind and produces moderately relativistic ejecta. Each type of ejecta has different physical properties, and therefore plays a different role for nucleosynthesis and for the electromagnetic (EM) transients that go along with compact object encounters. Here, we focus on the dynamic ejecta and present results for over 30 hydrodynamical simulations of both gravitational wave-driven mergers and parabolic encounters as they may occur in globular clusters. We find that mergers eject approximately 1 per cent of a Solar mass of extremely neutron-rich material. The exact amount, as well as the ejection velocity, depends on the involved masses with asymmetric systems ejecting more material at higher velocities. This material undergoes a robust r-process and both ejecta amount and abundance pattern are consistent with neutron star mergers being a major source of the ‘heavy’ ( A >130) r-process isotopes. Parabolic collisions, especially those between neutron stars and black holes, eject substantially larger amounts of mass, and therefore cannot occur frequently without overproducing gala- ctic r-process matter. We also discuss the EM transients that are powered by radioactive decays within the ejecta (‘macronovae’), and the radio flares that emerge when the ejecta dissipate their large kinetic energies in the ambient medium.

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Bowler, M. G. "SS 433: Two robust determinations fix the mass ratio." Astronomy & Astrophysics 619 (November 2018): L4. http://dx.doi.org/10.1051/0004-6361/201834121.

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Context. The unique Galactic microquasar SS 433 is an X-ray binary with a 13.08 day orbital period. Over some forty years, estimates of the mass of the compact object have spanned the range 1–30 solar masses; from neutron star to massive stellar black hole. Aims. To fix the mass ratio q and hence the mass of the super-Eddington accretor. Methods. We present a new and robust estimate of q derived from data on the circumbinary disk and compare it with a recent determination from the observed constancy of the binary period. Results. These two robust analyses agree to a remarkable extent. They reinforce each other; q is ∼0.7 and the mass of the compact object 15 ± 2 M⊙. Conclusions. The mass is such as to identify the compact object as a massive stellar black hole.

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Shamir, M. Farasat, and Saeeda Zia. "Analysis of charged compact stars in modified gravity." International Journal of Modern Physics D 27, no. 08 (May 30, 2018): 1850082. http://dx.doi.org/10.1142/s0218271818500827.

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Current study highlights the physical characteristics of charged anisotropic compact stars by exploring some exact solutions of modified field equations in [Formula: see text] gravity. A comprehensive analysis is performed from the obtained solutions regarding stability, energy conditions, regularity, sound velocity and compactness. These solutions can be referred to model the compact celestial entities. In particular, a compact star named, [Formula: see text] has been modeled which indicates that current solution fits and is in conformity to the observational data as well. A useful and interesting fact from this model arises that relative difference between two forces of anisotropic pressure and electromagnetic force may occur inside the aforementioned compact star. This is another mechanism which is essential for stability of the compact object and prevent stellar object to annihilate.

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