ORCID Profile
0000-0002-6134-8946
Current Organisation
Monash University
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Astronomical and Space Sciences | General Relativity and Gravitational Waves | Cosmology and Extragalactic Astronomy | Statistics not elsewhere classified | Astronomical sciences | Space instrumentation | Astronomical and Space Sciences not elsewhere classified | Stellar Astronomy and Planetary Systems | Lasers and Quantum Electronics | Cosmology and extragalactic astronomy | Lasers and quantum electronics | Galactic Astronomy | General relativity and gravitational waves | Astronomical and Space Instrumentation |
ANZSRC Socio-Economic Objective (SEO)
Expanding Knowledge in the Physical Sciences | Expanding Knowledge in the Information and Computing Sciences | Expanding Knowledge in Technology |
Related Links
Publications
The astrophysical science case for a decihertz gravitational-wave detector
Publisher: IOP Publishing
Date: 02-02-2018
Double Neutron Star Populations and Formation Channels
Publisher: American Astronomical Society
Date: 18-07-2019
GRB jet structure and the jet break
Publisher: Oxford University Press (OUP)
Date: 20-07-2021
Abstract: We investigate the shape of the jet break in within-beam gamma-ray burst (GRB) optical afterglows for various lateral jet structure profiles. We consider cases with and without lateral spreading and a range of inclinations within the jet core half-opening angle, θc. We fit model and observed afterglow light curves with a smoothly-broken power-law function with a free-parameter κ that describes the sharpness of the break. We find that the jet break is sharper (κ is greater) when lateral spreading is included than in the absence of lateral spreading. For profiles with a sharp-edged core, the sharpness parameter has a broad range of 0.1 ≲ κ ≲ 4.6, whereas profiles with a smooth-edged core have a narrower range of 0.1 ≲ κ ≲ 2.2 when models both with and without lateral spreading are included. For sharp-edged jets, the jet break sharpness depends strongly on the inclination of the system within θc, whereas for smooth-edged jets, κ is more strongly dependent on the size of θc. Using a s le of 20 GRBs, we find 9 candidate smooth-edged jet structures and 8 candidate sharp-edged jet structures, while the remaining 3 are consistent with either. The shape of the jet break, as measured by the sharpness parameter κ, can be used as an initial check for the presence of lateral structure in within-beam GRBs where the afterglow is well-s led at and around the jet-break time.
An outflow powers the optical rise of the nearby, fast-evolving tidal disruption event AT2019qiz
Publisher: Oxford University Press (OUP)
Date: 12-10-2020
Abstract: At 66 Mpc, AT2019qiz is the closest optical tidal disruption event (TDE) to date, with a luminosity intermediate between the bulk of the population and the faint-and-fast event iPTF16fnl. Its proximity allowed a very early detection and triggering of multiwavelength and spectroscopic follow-up well before maximum light. The velocity dispersion of the host galaxy and fits to the TDE light curve indicate a black hole mass ≈106 M⊙, disrupting a star of ≈1 M⊙. By analysing our comprehensive UV, optical, and X-ray data, we show that the early optical emission is dominated by an outflow, with a luminosity evolution L ∝ t2, consistent with a photosphere expanding at constant velocity (≳2000 km s−1), and a line-forming region producing initially blueshifted H and He ii profiles with v = 3000–10 000 km s−1. The fastest optical ejecta approach the velocity inferred from radio detections (modelled in a forthcoming companion paper from K. D. Alexander et al.), thus the same outflow may be responsible for both the fast optical rise and the radio emission – the first time this connection has been observed in a TDE. The light-curve rise begins 29 ± 2 d before maximum light, peaking when the photosphere reaches the radius where optical photons can escape. The photosphere then undergoes a sudden transition, first cooling at constant radius then contracting at constant temperature. At the same time, the blueshifts disappear from the spectrum and Bowen fluorescence lines (N iii) become prominent, implying a source of far-UV photons, while the X-ray light curve peaks at ≈1041 erg s−1. Assuming that these X-rays are from prompt accretion, the size and mass of the outflow are consistent with the reprocessing layer needed to explain the large optical to X-ray ratio in this and other optical TDEs, possibly favouring accretion-powered over collision-powered outflow models.
Merging stellar-mass binary black holes
Publisher: Elsevier BV
Date: 04-2022
A SEARCH FOR AN OPTICAL COUNTERPART TO THE GRAVITATIONAL-WAVE EVENT GW151226
Publisher: American Astronomical Society
Date: 19-08-2016
Astrophysical science metrics for next-generation gravitational-wave detectors
Publisher: IOP Publishing
Date: 14-11-2019
PARAMETER ESTIMATION FOR BINARY NEUTRON-STAR COALESCENCES WITH REALISTIC NOISE DURING THE ADVANCED LIGO ERA
Publisher: American Astronomical Society
Date: 11-05-2015
Massive Stellar Mergers as Precursors of Hydrogen-rich Pulsational Pair Instability Supernovae
Publisher: American Astronomical Society
Date: 09-05-2019
Detectability of Gravitational Waves from High-Redshift Binaries
Publisher: American Physical Society (APS)
Date: 10-03-2016
Binary population synthesis with probabilistic remnant mass and kick prescriptions
Publisher: Oxford University Press (OUP)
Date: 31-10-2020
Abstract: We report on the impact of a probabilistic prescription for compact remnant masses and kicks on massive binary population synthesis. We find that this prescription populates the putative mass gap between neutron stars and black holes with low-mass black holes. However, evolutionary effects reduce the number of X-ray binary candidates with low-mass black holes, consistent with the dearth of such systems in the observed s le. We further find that this prescription is consistent with the formation of heavier binary neutron stars such as GW190425, but overpredicts the masses of Galactic double neutron stars. The revised natal kicks, particularly increased ultra-stripped supernova kicks, do not directly explain the observed Galactic double neutron star orbital period–eccentricity distribution. Finally, this prescription allows for the formation of systems similar to the recently discovered extreme mass ratio binary GW190814, but only if we allow for the survival of binaries in which the common envelope is initiated by a donor crossing the Hertzsprung gap, contrary to our standard model.
I ♥ ‘Heart’ Pluto
Publisher: Informa UK Limited
Date: 02-07-2020
Impact of massive binary star and cosmic evolution on gravitational wave observations I: black hole–neutron star mergers
Publisher: Oxford University Press (OUP)
Date: 23-09-2021
Abstract: Mergers of black hole–neutron star (BHNS) binaries have now been observed by gravitational wave (GW) detectors with the recent announcement of GW200105 and GW200115. Such observations not only provide confirmation that these systems exist but will also give unique insights into the death of massive stars, the evolution of binary systems and their possible association with gamma-ray bursts, r-process enrichment, and kilonovae. Here, we perform binary population synthesis of isolated BHNS systems in order to present their merger rate and characteristics for ground-based GW observatories. We present the results for 420 different model permutations that explore key uncertainties in our assumptions about massive binary star evolution (e.g. mass transfer, common-envelope evolution, supernovae), and the metallicity-specific star formation rate density, and characterize their relative impacts on our predictions. We find intrinsic local BHNS merger rates spanning $\\mathcal {R}_{\\rm {m}}^0 \\approx$ 4–830 $\\, \\rm {Gpc}^{-3}$$\\, \\rm {yr}^{-1}$ for our full range of assumptions. This encompasses the rate inferred from recent BHNS GW detections and would yield detection rates of $\\mathcal {R}_{\\rm {det}} \\approx 1$–180$\\, \\rm {yr}^{-1}$ for a GW network consisting of LIGO, Virgo, and KAGRA at design sensitivity. We find that the binary evolution and metallicity-specific star formation rate density each impacts the predicted merger rates by order $\\mathcal {O}(10)$. We also present predictions for the GW-detected BHNS merger properties and find that all 420 model variations predict that $\\lesssim 5{{\\ \\rm per\\ cent}}$ of the BHNS mergers have BH masses $m_{\\rm {BH}} \\gtrsim 18\\, \\rm {M}_{\\odot }$, total masses $m_{\\rm {tot}} \\gtrsim 20\\, \\rm {M}_{\\odot }$, chirp masses ${\\mathcal {M}}_{\\rm {c}} \\gtrsim 5.5\\, \\rm {M}_{\\odot }$, and mass ratios qf ≳ 12 or qf ≲ 2. Moreover, we find that massive NSs with $m_{\\rm {NS}} \\gt 2\\, \\rm {M}_{\\odot }$ are expected to be commonly detected in BHNS mergers in almost all our model variations. Finally, a wide range of $\\sim 0{{\\ \\rm per\\ cent}}$ to $70{{\\ \\rm per\\ cent}}$ of the BHNS mergers are predicted to eject mass during the merger. Our results highlight the importance of considering variations in binary evolution and cosmological models when predicting, and eventually evaluating, populations of BHNS mergers.
Constraining the masses of microlensing black holes and the mass gap with Gaia DR2
Publisher: EDP Sciences
Date: 04-2020
DOI: 10.1051/0004-6361/201935842
Abstract: Context. Gravitational microlensing is sensitive to compact-object lenses in the Milky Way, including white dwarfs, neutron stars, or black holes, and could potentially probe a wide range of stellar-remnant masses. However, the mass of the lens can be determined only in very limited cases, due to missing information on both source and lens distances and their proper motions. Aims. Our aim is to improve the mass estimates in the annual parallax microlensing events found in the eight years of OGLE-III observations towards the Galactic Bulge with the use of Gaia Data Release 2 (DR2). Methods. We use Gaia DR2 data on distances and proper motions of non-blended sources and recompute the masses of lenses in parallax events. We also identify new events in that s le which are likely to have dark lenses the total number of such events is now 18. Results. The derived distribution of masses of dark lenses is consistent with a continuous distribution of stellar-remnant masses. A mass gap between neutron star and black hole masses in the range between 2 and 5 solar masses is not favoured by our data, unless black holes receive natal kicks above 20−80 km s −1 . We present eight candidates for objects with masses within the putative mass gap, including a spectacular multi-peak parallax event with mass of 2.4 −1.3 +1.9 M ⊙ located just at 600 pc. The absence of an observational mass gap between neutron stars and black holes, or conversely the evidence of black hole natal kicks if a mass gap is assumed, can inform future supernova modelling efforts.
Candidate Type II Be X-Ray Binary Outbursts in NGC 6744
Publisher: American Astronomical Society
Date: 14-09-2021
Abstract: We present the discovery of two new X-ray transients in the galaxy NGC 6744. The properties of these transients are consistent with those of Type II outbursts of Be X-ray binaries, but further data will be required to confirm their nature.
Common Envelope Wind Tunnel: The Effects of Binary Mass Ratio and Implications for the Accretion-driven Growth of LIGO Binary Black Holes
Publisher: American Astronomical Society
Date: 10-07-2020
An observationally derived kick distribution for neutron stars in binary systems
Publisher: Oxford University Press (OUP)
Date: 06-03-2023
Abstract: Understanding the natal kicks received by neutron stars (NSs) during formation is a critical component of modelling the evolution of massive binaries. Natal kicks are an integral input parameter for population synthesis codes, and have implications for the formation of double NS systems and their subsequent merger rates. However, many of the standard observational kick distributions that are used are obtained from s les created only from isolated NSs. Kick distributions derived in this way overestimate the intrinsic NS kick distribution. For NSs in binaries, we can only directly estimate the effect of the natal kick on the binary system, instead of the natal kick received by the NS itself. Here, for the first time, we present a binary kick distribution for NSs with low-mass companions. We compile a catalogue of 145 NSs in low-mass binaries with the best available constraints on proper motion, distance, and systemic radial velocity. For each binary, we use a three-dimensional approach to estimate its binary kick. We discuss the implications of these kicks on system formation, and provide a parametric model for the overall binary kick distribution, for use in future theoretical modelling work. We compare our results with other work on isolated NSs and NSs in binaries, finding that the NS kick distributions fit using only isolated pulsars underestimate the fraction of NSs that receive low kicks. We discuss the implications of our results on modelling double NS systems, and provide suggestions on how to use our results in future theoretical works.
GOING THE DISTANCE: MAPPING HOST GALAXIES OF LIGO AND VIRGO SOURCES IN THREE DIMENSIONS USING LOCAL COSMOGRAPHY AND TARGETED FOLLOW-UP
Publisher: American Astronomical Society
Date: 22-09-2016
Chemically homogeneous evolution: a rapid population synthesis approach
Publisher: Oxford University Press (OUP)
Date: 11-05-2021
Abstract: We explore chemically homogeneous evolution (CHE) as a formation channel for massive merging binary black holes (BBHs). We develop methods to include CHE in a rapid binary population synthesis code, Compact Object Mergers: Population Astrophysics and Statistics (compas), which combines realistic models of binary evolution with cosmological models of the star formation history of the Universe. For the first time, we simultaneously explore conventional isolated binary star evolution under the same set of assumptions. This approach allows us to constrain population properties and make simultaneous predictions about the gravitational-wave detection rates of BBH mergers for the CHE and conventional formation channels. The overall mass distribution of detectable BBHs is consistent with existing gravitational-wave observations. We find that the CHE channel may yield up to ${\\sim} 70{{\\ \\rm per\\ cent}}$ of all gravitational-wave detections of BBH mergers coming from isolated binary evolution.
Simple recipes for compact remnant masses and natal kicks
Publisher: Oxford University Press (OUP)
Date: 02-10-2020
Abstract: Based on recent results from three-dimensional supernova simulations and semi-analytical parametrized models, we develop analytical prescriptions for the dependence of the mass of neutron stars and black holes and the natal kicks, if any, on the pre-supernova carbon–oxygen core and helium shell masses. Our recipes are probabilistic rather than deterministic in order to account for the intrinsic stochasticity of stellar evolution and supernovae. We anticipate that these recipes will be particularly useful for rapid population synthesis, and we illustrate their application to distributions of remnant masses and kicks for a population of single stars.
The Orbit of GW170817 Was Inclined by Less Than 28° to the Line of Sight
Publisher: American Astronomical Society
Date: 23-01-2018
The Impact of Spin-kick Alignment on the Inferred Velocity Distribution of Isolated Pulsars
Publisher: American Astronomical Society
Date: 02-2023
Abstract: The speeds of young isolated pulsars are generally inferred from their observed 2D velocities on the plane of the sky under the assumption that the unobserved radial velocity is not special, i.e., that the measured 2D velocity is an isotropic projection of the full 3D velocity. However, if pulsar spins are preferentially aligned with kicks, then the observer’s viewing angle relative to the pulsar velocity vector is in fact special because the direction of the spin impacts the detectability of the pulsar. This means that the measured 2D velocity of observable pulsars is not an isotropic projection, which affects inference on 3D velocities. We estimate this effect and conclude that it could lead to a ∼15% systematic overestimate of neutron-star natal kicks if young pulsars have high obliquity angles and narrow beams, but the exact correction factor depends on the distribution of beam-spin and spin-kick misalignment angles and beam widths.
Age dissection of the Milky Way discs: Red giants in theKeplerfield
Publisher: EDP Sciences
Date: 2021
DOI: 10.1051/0004-6361/202038307
Abstract: Ensemble studies of red-giant stars with exquisite asteroseismic ( Kepler ), spectroscopic (APOGEE), and astrometric ( Gaia ) constraints offer a novel opportunity to recast and address long-standing questions concerning the evolution of stars and of the Galaxy. Here, we infer masses and ages for nearly 5400 giants with available Kepler light curves and APOGEE spectra using the code PARAM , and discuss some of the systematics that may affect the accuracy of the inferred stellar properties. We then present patterns in mass, evolutionary state, age, chemical abundance, and orbital parameters that we deem robust against the systematic uncertainties explored. First, we look at age-chemical-abundances ([Fe/H] and [ α /Fe]) relations. We find a dearth of young, metal-rich ([Fe/H] 0.2) stars, and the existence of a significant population of old (8−9 Gyr), low-[ α /Fe], super-solar metallicity stars, reminiscent of the age and metallicity of the well-studied open cluster NGC 6791. The age-chemo-kinematic properties of these stars indicate that efficient radial migration happens in the thin disc. We find that ages and masses of the nearly 400 α -element-rich red-giant-branch (RGB) stars in our s le are compatible with those of an old (∼11 Gyr), nearly coeval, chemical-thick disc population. Using a statistical model, we show that the width of the observed age distribution is dominated by the random uncertainties on age, and that the spread of the inferred intrinsic age distribution is such that 95% of the population was born within ∼1.5 Gyr. Moreover, we find a difference in the vertical velocity dispersion between low- and high-[α/Fe] populations. This discontinuity, together with the chemical one in the [α/Fe] versus [Fe/H] diagram, and with the inferred age distributions, not only confirms the different chemo-dynamical histories of the chemical-thick and thin discs, but it is also suggestive of a halt in the star formation (quenching) after the formation of the chemical-thick disc. We then exploit the almost coeval α -rich population to gain insight into processes that may have altered the mass of a star along its evolution, which are key to improving the mapping of the current, observed, stellar mass to the initial mass and thus to the age. Comparing the mass distribution of stars on the lower RGB ( R 11 R ⊙ ) with those in the red clump (RC), we find evidence for a mean integrated RGB mass loss ⟨Δ M ⟩ = 0.10 ± 0.02 M ⊙ . Finally, we find that the occurrence of massive ( M ≳ 1.1 M ⊙ ) α -rich stars is of the order of 5% on the RGB, and significantly higher in the RC, supporting the scenario in which most of these stars had undergone an interaction with a companion.
A Precise Distance to the Host Galaxy of the Binary Neutron Star Merger GW170817 Using Surface Brightness Fluctuations
Publisher: American Astronomical Society
Date: 23-02-2018
Constraints on Weak Supernova Kicks from Observed Pulsar Velocities
Publisher: American Astronomical Society
Date: 10-2021
Accelerating gravitational wave parameter estimation with multi-band template interpolation
Publisher: IOP Publishing
Date: 18-05-2017
Cygnus X-1 contains a 21–solar mass black hole—Implications for massive star winds
Publisher: American Association for the Advancement of Science (AAAS)
Date: 05-03-2021
Abstract: If a black hole interacts with a binary companion star, the system emits x-rays and can form a radio jet. The masses of black holes in these x-ray binaries are all lower than those detected using gravitational waves, challenging models of black hole formation from massive stars. Miller-Jones et al. used radio astrometry to refine the distance to Cygnus X-1, a well-studied x-ray binary. They found a larger distance than previous estimates, raising the mass of the black hole in the system to 21 solar masses. The results challenge the wind mass loss rates implemented in stellar evolution models. Science , this issue p. 1046
Distinguishing types of compact-object binaries using the gravitational-wave signatures of their mergers
Publisher: Oxford University Press (OUP)
Date: 05-2015
Wind Mass-loss Rates of Stripped Stars Inferred from Cygnus X-1
Publisher: American Astronomical Society
Date: 02-2021
Abstract: Recent observations of the high-mass X-ray binary Cygnus X-1 have shown that both the companion star (41 solar masses) and the black hole (21 solar masses) are more massive than previously estimated. Furthermore, the black hole appears to be nearly maximally spinning. Here, we present a possible formation channel for the Cygnus X-1 system that matches the observed system properties. In this formation channel, we find that the orbital parameters of Cygnus X-1, combined with the observed metallicity of the companion, imply a significant reduction in mass loss through winds relative to commonly used prescriptions for stripped stars.
A long-duration gamma-ray burst of dynamical origin from the nucleus of an ancient galaxy
Publisher: Research Square Platform LLC
Date: 22-11-2022
DOI: 10.21203/RS.3.RS-2298504/V1
Abstract: The majority of long-duration ( s) gamma-ray bursts (GRBs) are believed to arise from the collapse of massive stars (Hjorth et al. 2003) with a small proportion created from the merger of compact objects (Rastinejad et al. 2022, Yang et al. 2022, Troja et al. 2022). Most of these systems are likely formed via standard stellar evolution pathways. However, it has long been thought that a fraction of GRBs may instead be an outcome of dynamical interactions in dense environments (Grindlay et al. 2006, Fragione et al. 2019, McKernan et al. 2020), channels which could also contribute significantly to the s les of compact object mergers detected as gravitational wave sources (O’Leary et al. 2016). Here we report the case of GRB 191019A, a long GRB (T_90 = 64.4 +/- 4.5 s) which we pinpoint close ( 100 pc projected) to the nucleus of an ancient ( Gyr old) host galaxy at z=0.248. The lack of evidence for star formation and deep limits on any supernova emission makes a massive star origin difficult to reconcile with observations, while the timescales of the emission rule out direct interaction with the supermassive black hole in the nucleus of the galaxy, We suggest that the most likely route for progenitor formation is via dynamical interactions in the dense nucleus of the host, consistent with the centres of such galaxies exhibiting interaction rates up to two orders of magnitude larger than typical field galaxies (French et al. 2014, Stone et al. 2016). The burst properties could naturally be explained via compact object mergers involving white dwarfs (WD), neutron stars (NS), or black holes (BH). These may form dynamically in dense stellar clusters, or originate in a gaseous disc around the supermassive black hole (Perna et al. 2021, Lazzati et al. 2022). Future electromagnetic and gravitational-wave observations in tandem thus offer a route to probe the dynamical fraction and the details of dynamical interactions in galactic nuclei and other high-density stellar systems.
The Impact of Pair-instability Mass Loss on the Binary Black Hole Mass Distribution
Publisher: American Astronomical Society
Date: 10-09-2019
PARAMETER ESTIMATION ON GRAVITATIONAL WAVES FROM NEUTRON-STAR BINARIES WITH SPINNING COMPONENTS
Publisher: American Astronomical Society
Date: 11-07-2016
Rapid Stellar and Binary Population Synthesis with COMPAS
Publisher: American Astronomical Society
Date: 02-2022
Abstract: Compact Object Mergers: Population Astrophysics and Statistics (COMPAS compas.science ) is a public rapid binary population synthesis code. COMPAS generates populations of isolated stellar binaries under a set of parameterized assumptions in order to allow comparisons against observational data sets, such as those coming from gravitational-wave observations of merging compact remnants. It includes a number of tools for population processing in addition to the core binary evolution components. COMPAS is publicly available via the GitHub repository github.com/TeamCOMPAS/COMPAS/ , and is designed to allow for flexible modifications as evolutionary models improve. This paper describes the methodology and implementation of COMPAS. It is a living document that will be updated as new features are added to COMPAS the current document describes COMPAS v02.21.00.
Rates of compact object coalescences
Publisher: Springer Science and Business Media LLC
Date: 17-02-2022
DOI: 10.1007/S41114-021-00034-3
Abstract: Gravitational-wave detections are enabling measurements of the rate of coalescences of binaries composed of two compact objects—neutron stars and/or black holes. The coalescence rate of binaries containing neutron stars is further constrained by electromagnetic observations, including Galactic radio binary pulsars and short gamma-ray bursts. Meanwhile, increasingly sophisticated models of compact objects merging through a variety of evolutionary channels produce a range of theoretically predicted rates. Rapid improvements in instrument sensitivity, along with plans for new and improved surveys, make this an opportune time to summarise the existing observational and theoretical knowledge of compact-binary coalescence rates.
The Redshift Evolution of the Binary Black Hole Merger Rate: A Weighty Matter
Publisher: American Astronomical Society
Date: 05-2022
Abstract: Gravitational-wave detectors are starting to reveal the redshift evolution of the binary black hole (BBH) merger rate, R BBH ( z ). We make predictions for R BBH ( z ) as a function of black hole mass for systems originating from isolated binaries. To this end, we investigate correlations between the delay time and black hole mass by means of the suite of binary population synthesis simulations, COMPAS . We distinguish two channels: the common envelope (CE), and the stable Roche-lobe overflow (RLOF) channel, characterized by whether the system has experienced a common envelope or not. We find that the CE channel preferentially produces BHs with masses below about 30 M ⊙ and short delay times ( t delay ≲ 1 Gyr), while the stable RLOF channel primarily forms systems with BH masses above 30 M ⊙ and long delay times ( t delay ≳ 1 Gyr). We provide a new fit for the metallicity-dependent specific star formation rate density based on the Illustris TNG simulations, and use this to convert the delay time distributions into a prediction of R BBH ( z ). This leads to a distinct redshift evolution of R BBH ( z ) for high and low primary BH masses. We furthermore find that, at high redshift, R BBH ( z ) is dominated by the CE channel, while at low redshift, it contains a large contribution (∼40%) from the stable RLOF channel. Our results predict that, for increasing redshifts, BBHs with component masses above 30 M ⊙ will become increasingly scarce relative to less massive BBH systems. Evidence of this distinct evolution of R BBH ( z ) for different BH masses can be tested with future detectors.
The Optical Afterglow of GW170817 at One Year Post-merger
Publisher: American Astronomical Society
Date: 09-01-2019
An Alternative Interpretation of GW190412 as a Binary Black Hole Merger with a Rapidly Spinning Secondary
Publisher: American Astronomical Society
Date: 27-05-2020
Comment on “An excess of massive stars in the local 30 Doradus starburst”
Publisher: American Association for the Advancement of Science (AAAS)
Date: 27-07-2018
Abstract: Schneider et al . (Reports, 5 January 2018, p. 69) used an ad hoc statistical method in their calculation of the stellar initial mass function. Adopting an improved approach, we reanalyze their data and determine a power-law exponent of 2.05 − 0.13 + 0.14 . Alternative assumptions regarding dataset completeness and the star formation history model can shift the inferred exponent to 2.11 − 0.17 + 0.19 and 2.15 − 0.13 + 0.13 , respectively.
Constraining the rotation profile in a low-luminosity subgiant with a surface rotation measurement
Publisher: Oxford University Press (OUP)
Date: 17-03-2023
Abstract: Rotationally induced mode splitting frequencies of low-luminosity subgiants suggest that angular momentum transport mechanisms are 1–2 orders of magnitude more efficient in these stars than predicted by theory. Constraints on the rotation profile of low-luminosity subgiants could be used to identify the dominant mechanism for angular momentum transport. We develop a forward model for the rotation profile given observed rotational splittings, assuming a step-like rotation profile. We identify a consistent degeneracy between the position of the profile discontinuity and the surface rotation rate. We perform mock experiments that show the discontinuity position can be better constrained with a prior on the surface rotation rate, which is informed by star spot modulations. We finally apply this approach to KIC 12508433, a well-studied low-luminosity subgiant, as an ex le case. With the observed surface rotation prior, we obtain a factor of 2 increase in precision of the position of strong rotation gradient. We recover the literature values of the core and surface rotation rates and find the highest support for a discontinuity in the radiative zone. Auxiliary measurements of surface rotation could substantially improve inferences on the rotation profile of low-luminosity subgiants with already available data.
Global calibration of novel 3-hydroxy fatty acid based temperature and pH proxies
Publisher: Elsevier BV
Date: 06-2021
Can Neutron Star Mergers Alone Explain the r-process Enrichment of the Milky Way?
Publisher: American Astronomical Society
Date: 30-01-2023
Abstract: Comparing Galactic chemical evolution models to the observed elemental abundances in the Milky Way, we show that neutron star mergers can be a leading r-process site only if at low metallicities such mergers have very short delay times and significant ejecta masses that are facilitated by the masses of the compact objects. Namely, black hole–neutron star mergers, depending on the black hole spins, can play an important role in the early chemical enrichment of the Milky Way. We also show that none of the binary population synthesis models used in this Letter, i.e., COMPAS, StarTrack, Brussels, ComBinE, and BPASS, can currently reproduce the elemental abundance observations. The predictions are problematic not only for neutron star mergers, but also for Type Ia supernovae, which may point to shortcomings in binary evolution models.
Common envelopes in massive stars: towards the role of radiation pressure and recombination energy in ejecting red supergiant envelopes
Publisher: Oxford University Press (OUP)
Date: 10-01-2022
Abstract: We perform 3D hydrodynamical simulations of a common-envelope event involving a 12$\\, \\rm {M}_{\\odot }$ red supergiant donor. Massive stars are expected to be qualitatively different from low-mass stars as their envelopes have significant support from radiation pressure, which increases both the final separation and amount of mass ejected through the common-envelope interaction. We perform adiabatic simulations that include radiation energy through the equation of state, which results in ejecting 60 per cent more mass (up to two thirds of the total envelope mass becoming unbound, or more) and yield a 10 per cent larger final separation compared to simulations that assume an ideal gas. When also including recombination energy, we find that at least three quarters of the envelope, and possibly the entire envelope, may be unbound. The final separation further increases by almost 20 per cent. The additional amount of ejected material is mainly due to energy injected from helium recombination. Hydrogen recombination plays a comparatively small role, as it mainly occurs in gas that has already become unbound. We conclude that the internal energy of the envelope can be a significant energy source for ejecting the common envelope, but ultimately radiation transport and convection need to be included.
DOUBLE TIDAL DISRUPTIONS IN GALACTIC NUCLEI
Publisher: American Astronomical Society
Date: 14-05-2015
Surrogate Forward Models for Population Inference on Compact Binary Mergers
Publisher: American Astronomical Society
Date: 06-2023
Abstract: Rapidly growing catalogs of compact binary mergers from advanced gravitational wave detectors allow us to explore the astrophysics of massive stellar binaries. Merger observations can constrain the uncertain parameters that describe the underlying processes in the evolution of stars and binary systems in population models. In this paper, we demonstrate that binary black hole populations—in particular, their detection rates, chirp masses, and redshifts—can be used to measure cosmological parameters describing the redshift-dependent star formation rate and metallicity distribution. We present a method that uses artificial neural networks to emulate binary population synthesis computer models, and construct a fast, flexible, parallelizable surrogate model that we use for inference.
GW200115: A Nonspinning Black Hole–Neutron Star Merger
Publisher: American Astronomical Society
Date: 11-2021
Abstract: GW200115 was the second merger of a black hole and a neutron star confidently detected through gravitational waves. Inference on the signal allows for a large black hole spin misaligned with the orbital angular momentum, but shows little support for aligned spin values. We show that this is a natural consequence of measuring the parameters of a black hole–neutron star binary with nonspinning components while assuming the priors used in the LIGO–Virgo–KAGRA analysis. We suggest that, a priori, a nonspinning binary is more consistent with current astrophysical understanding.
SN2018kzr: A Rapidly Declining Transient from the Destruction of a White Dwarf
Publisher: American Astronomical Society
Date: 31-10-2019
Geometry of a naked singularity created by standing waves near a Schwarzschild horizon, and its application to the binary black hole problem
Publisher: American Physical Society (APS)
Date: 25-10-2005
On the Maximum Stellar Rotation to form a Black Hole without an Accompanying Luminous Transient
Publisher: American Astronomical Society
Date: 25-09-2020
Abstract: The collapse of a massive star with low angular momentum content is commonly thought to result in the formation of a black hole without an accompanying bright transient. Our goal in this Letter is to understand the flow in and around a newly formed black hole, involving accretion and rotation, via general relativistic hydrodynamics simulations aimed at studying the conditions under which infalling material can accrete without forming a centrifugally supported structure and, as a result, generate no effective feedback. On the other hand, if the feedback from the black hole is significant, the collapse would be halted and we suggest that the event is likely to be followed by a bright transient. We find that feedback is only efficient if the specific angular momentum of the infalling material at the innermost stable circular orbit exceeds that of geodesic circular flow at that radius by at least ≈20%. We use the results of our simulations to constrain the maximal stellar rotation rates of the disappearing massive progenitors PHL293B-LBV and N6946-BH1, and to provide an estimate of the overall rate of disappearing massive stars. We find that about a few percent of single O-type stars with measured rotational velocities are expected to spin below the critical value before collapse and are thus predicted to vanish without a trace.
Stellar response after stripping as a model for common-envelope outcomes
Publisher: Oxford University Press (OUP)
Date: 29-01-2022
Abstract: Binary neutron stars have been observed as millisecond pulsars, gravitational-wave sources, and as the progenitors of short gamma-ray bursts and kilonovae. Massive stellar binaries that evolve into merging double neutron stars are believed to experience a common-envelope episode. During this episode, the envelope of a giant star engulfs the whole binary. The energy transferred from the orbit to the envelope by drag forces or from other energy sources can eject the envelope from the binary system, leading to a stripped short-period binary. In this paper, we use one-dimensional single stellar evolution to explore the final stages of the common-envelope phase in progenitors of neutron star binaries. We consider an instantaneously stripped donor star as a proxy for the common-envelope phase and study the star’s subsequent radial evolution. We determine a range of stripping boundaries that allow the star to avoid significant rapid re-expansion and that thus represent plausible boundaries for the termination of the common-envelope episode. We find that these boundaries lie above the maximum compression point, a commonly used location of the core/envelope boundary. We conclude that stars may retain fractions of a solar mass of hydrogen-rich material even after the common-envelope episode. If we consider orbital energy as the only energy source available, all of our models would overfill their Roche lobe after ejecting the envelope, whose binding energy includes gravitational, thermal, radiation, and recombination energy terms.
Common envelopes in massive stars II: The distinct roles of hydrogen and helium recombination
Publisher: Oxford University Press (OUP)
Date: 03-09-2022
Abstract: The role of recombination during a common-envelope event has been long debated. Many studies have argued that much of hydrogen recombination energy, which is radiated in relatively cool and optically thin layers, might not thermalize in the envelope. On the other hand, helium recombination contains ≈30 per cent of the total recombination energy, and occurs much deeper in the stellar envelope. We investigate the distinct roles played by hydrogen and helium recombination in a common-envelope interaction experienced by a 12 $\\, \\rm {M}_{\\odot }$ red supergiant donor. We perform adiabatic, 3D hydrodynamical simulations that (i) include hydrogen, helium, and H2 recombination, (ii) include hydrogen and helium recombination, (iii) include only helium recombination, and (iv) do not include recombination energy. By comparing these simulations, we find that the addition of helium recombination energy alone ejects 30 per cent more envelope mass, and leads to a 16 per cent larger post-plunge-in separation. Under the adiabatic assumption, adding hydrogen recombination energy increases the amount of ejected mass by a further 40 per cent, possibly unbinding the entire envelope, but does not affect the post-plunge separation. Most of the ejecta becomes unbound at relatively high (& per cent) degrees of hydrogen ionisation, where the hydrogen recombination energy is likely to expand the envelope instead of being radiated away.
The optical afterglow of the short gamma-ray burst associated with GW170817
Publisher: Springer Science and Business Media LLC
Date: 02-07-2018
Measuring Intermediate-Mass Black-Hole Binaries with Advanced Gravitational Wave Detectors
Publisher: American Physical Society (APS)
Date: 29-09-2015
Limits of Astrophysics with Gravitational-Wave Backgrounds
Publisher: American Physical Society (APS)
Date: 04-08-2016
Rapid population synthesis of black hole high-mass X-ray binaries: implications for binary stellar evolution
Publisher: Oxford University Press (OUP)
Date: 15-06-2023
Abstract: We conduct binary population synthesis to investigate the formation of wind-fed high-mass X-ray binaries containing black holes (BH-HMXBs). We evolve multiple populations of high-mass binary stars and consider BH-HMXB formation rates, masses, spins, and separations. We find that systems similar to Cygnus X-1 likely form after stable Case A mass transfer (MT) from the main-sequence progenitors of BHs, provided such MT is characterized by low accretion efficiency, β ≲ 0.1, with modest orbital angular momentum losses from the non-accreted material. Additionally, efficient BH-HMXB formation relies on a new simple treatment for Case A MT that allows donors to retain larger core masses compared to traditional rapid population-synthesis assumptions. At solar metallicity, our Preferred model yields $\\mathcal {O}(1)$ observable BH-HMXBs in the Galaxy today, consistent with observations. In this simulation, 8 per cent of BH-HMXBs go on to merge as binary black holes or neutron star-black hole binaries within a Hubble time however, none of the merging binaries have BH-HMXB progenitors with properties similar to Cygnus X-1. With our preferred settings for core mass growth, mass transfer efficiency, and angular momentum loss, accounting for an evolving metallicity, and integrating over the metallicity-specific star formation history of the Universe, we find that BH-HMXBs may have contributed ≈2–5 BBH merger signals to detections reported in the third gravitational-wave transient catalogue of the LIGO–Virgo–KAGRA Collaboration. We also suggest MT efficiency should be higher during stable Case B MT than during Case A MT.
Heavy element production in a compact object merger observed by JWST
Publisher: Springer Science and Business Media LLC
Date: 25-10-2023
Special Issue on Robot and Human Interactive Communication 2020 (Part II)
Publisher: Informa UK Limited
Date: 13-12-2020
Formation pathway for lonely stripped-envelope supernova progenitors: implications for Cassiopeia A
Publisher: Oxford University Press (OUP)
Date: 23-09-2020
Abstract: We explore a new scenario for producing stripped-envelope supernova progenitors. In our scenario, the stripped-envelope supernova is the second supernova of the binary, in which the envelope of the secondary was removed during its red supergiant phase by the impact of the first supernova. Through 2D hydrodynamical simulations, we find that ∼50–90 ${{\\ \\rm per\\ cent}}$ of the envelope can be unbound as long as the pre-supernova orbital separation is ≲5 times the stellar radius. Recombination energy plays a significant role in the unbinding, especially for relatively high mass systems (≳18 M⊙). We predict that more than half of the unbound mass should be distributed as a one-sided shell at about ∼10–100 pc away from the second supernova site. We discuss possible applications to known supernova remnants such as Cassiopeia A, RX J1713.7−3946, G11.2−0.3, and find promising agreements. The predicted rate is ∼0.35–1${{\\ \\rm per\\ cent}}$ of the core-collapse population. This new scenario could be a major channel for the subclass of stripped-envelope or type IIL supernovae that lack companion detections like Cassiopeia A.
Extreme Eccentricities of Triple Systems: Analytic Results
Publisher: American Astronomical Society
Date: 07-2022
Abstract: Triple stars and compact objects are ubiquitously observed in nature. Their long-term evolution is complex in particular, the von Zeipel–Lidov–Kozai (ZLK) mechanism can potentially lead to highly eccentric encounters of the inner binary. Such encounters can lead to a plethora of interacting binary phenomena, as well as stellar and compact-object mergers. Here we find implicit analytical formulae for the maximal eccentricity, e max , of the inner binary undergoing ZLK oscillations, where both the test-particle limit (parameterized by the inner-to-outer angular momentum ratio η ) and the double-averaging approximation (parameterized by the period ratio, ϵ SA ) are relaxed, for circular outer orbits. We recover known results in both limiting cases (either η or ϵ SA → 0) and verify the validity of our model using numerical simulations. We test our results with two accurate numerical N -body codes, rebound for Newtonian dynamics and tsunami for general-relativistic dynamics, and find excellent correspondence. We discuss the implications of our results for stellar triples and both stellar and supermassive triple black hole mergers.
Explosions Driven by the Coalescence of a Compact Object with the Core of a Massive-star Companion inside a Common Envelope: Circumstellar Properties, Light Curves, and Population Statistics
Publisher: American Astronomical Society
Date: 19-03-2020
Abstract: We model explosions driven by the coalescence of a black hole or neutron star with the core of its massive-star companion. Upon entering a common-envelope phase, a compact object may spiral all the way to the core. The concurrent release of energy is likely to be deposited into the surrounding common envelope, powering a merger-driven explosion. We use hydrodynamic models of binary coalescence to model the common-envelope density distribution at the time of coalescence. We find toroidal profiles of material, concentrated in the binary’s equatorial plane and extending to many times the massive star’s original radius. We use the spherically averaged properties of this circumstellar material (CSM) to estimate the emergent light curves that result from the interaction between the blast wave and the CSM. We find that typical merger-driven explosions are brightened by up to three magnitudes by CSM interaction. From population synthesis models, we discover that the brightest merger-driven explosions, M V ∼ −18 to −20, are those involving black holes because they have the most massive and extended CSM. Black hole coalescence events are also common they represent about 50% of all merger-driven explosions and approximately 0.25% of the core-collapse rate. Merger-driven explosions offer a window into the highly uncertain physics of common-envelope interactions in binary systems by probing the properties of systems that merge rather than eject their envelopes.
The Spectral Evolution of AT 2018dyb and the Presence of Metal Lines in Tidal Disruption Events
Publisher: American Astronomical Society
Date: 20-12-2019
Eclipses of continuous gravitational waves as a probe of stellar structure
Publisher: American Physical Society (APS)
Date: 22-01-2020
Efficient method for measuring the parameters encoded in a gravitational-wave signal
Publisher: IOP Publishing
Date: 12-11-2015
Be X-ray binaries in the SMC as indicators of mass-transfer efficiency
Publisher: Oxford University Press (OUP)
Date: 04-09-2020
Abstract: Be X-ray binaries (BeXRBs) consist of rapidly rotating Be stars with neutron star (NS) companions accreting from the circumstellar emission disc. We compare the observed population of BeXRBs in the Small Magellanic Cloud (SMC) with simulated populations of BeXRB-like systems produced with the compas population synthesis code. We focus on the apparently higher minimal mass of Be stars in BeXRBs than in the Be population at large. Assuming that BeXRBs experienced only dynamically stable mass transfer, their mass distribution suggests that at least $\\sim 30{{\\ \\rm per\\ cent}}$ of the mass donated by the progenitor of the NS is typically accreted by the B-star companion. We expect these results to affect predictions for the population of double compact object mergers. A convolution of the simulated BeXRB population with the star formation history of the SMC shows that the excess of BeXRBs is most likely explained by this galaxy’s burst of star formation ∼20–40 Myr ago.
An efficient interpolation technique for jump proposals in reversible-jump Markov chain Monte Carlo calculations
Publisher: The Royal Society
Date: 06-2015
DOI: 10.1098/RSOS.150030
Abstract: Selection among alternative theoretical models given an observed dataset is an important challenge in many areas of physics and astronomy. Reversible-jump Markov chain Monte Carlo (RJMCMC) is an extremely powerful technique for performing Bayesian model selection, but it suffers from a fundamental difficulty and it requires jumps between model parameter spaces, but cannot efficiently explore both parameter spaces at once. Thus, a naive jump between parameter spaces is unlikely to be accepted in the Markov chain Monte Carlo (MCMC) algorithm and convergence is correspondingly slow. Here, we demonstrate an interpolation technique that uses s les from single-model MCMCs to propose intermodel jumps from an approximation to the single-model posterior of the target parameter space. The interpolation technique, based on a kD-tree data structure, is adaptive and efficient in modest dimensionality. We show that our technique leads to improved convergence over naive jumps in an RJMCMC, and compare it to other proposals in the literature to improve the convergence of RJMCMCs. We also demonstrate the use of the same interpolation technique as a way to construct efficient ‘global’ proposal distributions for single-model MCMCs without prior knowledge of the structure of the posterior distribution, and discuss improvements that permit the method to be used in higher dimensional spaces efficiently.
Cosmic rates of black hole mergers and pair-instability supernovae from chemically homogeneous binary evolution
Publisher: Oxford University Press (OUP)
Date: 16-10-2020
Abstract: During the first three observing runs of the Advanced gravitational-wave detector network, the LIGO/Virgo collaboration detected several black hole binary (BHBH) mergers. As the population of detected BHBH mergers grows, it will become possible to constrain different channels for their formation. Here we consider the chemically homogeneous evolution (CHE) channel in close binaries, by performing population synthesis simulations that combine realistic binary models with detailed cosmological calculations of the chemical and star-formation history of the Universe. This allows us to constrain population properties, as well as cosmological and aLIGO/aVirgo detection rates of BHBH mergers formed through this pathway. We predict a BHBH merger rate at redshift zero of $5.8 \\textrm {Gpc}^{-3} \\textrm {yr}^{-1}$ through the CHE channel, to be compared with aLIGO/aVirgo’s measured rate of ${53.2}_{-28.2}^{+55.8} \\text{Gpc}^{-3}\\text{yr}^{-1}$, and find that eventual merger systems have BH masses in the range $17{-}43 \\,\\textrm {M}_{\\odot }$ below the pair-instability supernova (PISN) gap, and ${\\gt}124 \\textrm {M}_{\\odot }$ above the PISN gap. We investigate effects of momentum kicks during black hole formation, and calculate cosmological and magnitude limited PISN rates. We also study the effects of high-redshift deviations in the star formation rate. We find that momentum kicks tend to increase delay times of BHBH systems, and our magnitude limited PISN rate estimates indicate that current deep surveys should be able to detect such events. Lastly, we find that our cosmological merger rate estimates change by at most ${\\sim}8{{\\ \\rm per\\ cent}}$ for mild deviations of the star formation rate in the early Universe, and by up to ${\\sim}40\\,\\text{per cent}$ for extreme deviations.
Impact of massive binary star and cosmic evolution on gravitational wave observations – II. Double compact object rates and properties
Publisher: Oxford University Press (OUP)
Date: 04-07-2022
Abstract: Making the most of the rapidly increasing population of gravitational-wave detections of black hole (BH) and neutron star (NS) mergers requires comparing observations with population synthesis predictions. In this work, we investigate the combined impact from the key uncertainties in population synthesis modelling of the isolated binary evolution channel: the physical processes in massive binary-star evolution and the star formation history as a function of metallicity, Z, and redshift z, $\\mathcal {S}(Z,z)$. Considering these uncertainties, we create 560 different publicly available model realizations and calculate the rate and distribution characteristics of detectable BHBH, BHNS, and NSNS mergers. We find that our stellar evolution and $\\mathcal {S}(Z,z)$ variations can combined impact the predicted intrinsic and detectable merger rates by factors in the range 102–104. We find that BHBH rates are dominantly impacted by $\\mathcal {S}(Z,z)$ variations, NSNS rates by stellar evolution variations and BHNS rates by both. We then consider the combined impact from all uncertainties considered in this work on the detectable mass distribution shapes (chirp mass, in idual masses, and mass ratio). We find that the BHNS mass distributions are predominantly impacted by massive binary-star evolution changes. For BHBH and NSNS, we find that both uncertainties are important. We also find that the shape of the delay time and birth metallicity distributions are typically dominated by the choice of $\\mathcal {S}(Z,z)$ for BHBH, BHNS, and NSNS. We identify several ex les of robust features in the mass distributions predicted by all 560 models, such that we expect more than 95 per cent of BHBH detections to contain a BH $\\gtrsim 8\\, \\rm {M}_{\\odot }$ and have mass ratios ≲ 4. Our work demonstrates that it is essential to consider a wide range of allowed models to study double compact object merger rates and properties. Conversely, larger observed s les could allow us to decipher currently unconstrained stages of stellar and binary evolution.
A long-duration gamma-ray burst of dynamical origin from the nucleus of an ancient galaxy
Publisher: Springer Science and Business Media LLC
Date: 22-06-2023
A Two-stage Formalism for Common-envelope Phases of Massive Stars
Publisher: American Astronomical Society
Date: 10-2022
Abstract: We propose a new simple formalism to predict the orbital separations after common-envelope phases with massive-star donors. We focus on the fact that massive red supergiants tend to have a sizable radiative layer between the dense helium core and the convective envelope. Our formalism treats the common-envelope phase in two stages: dynamical inspiral through the outer convective envelope and thermal timescale mass transfer from the radiative intershell. With fiducial choices of parameters, the new formalism typically predicts much wider separations compared to the classical energy formalism. Moreover, our formalism predicts that final separations strongly depend on the donor evolutionary stage and companion mass. Our formalism provides a physically motivated alternative option for population synthesis studies to treat common-envelope evolution. This treatment will impact predictions for massive-star binaries, including gravitational-wave sources, X-ray binaries, and stripped-envelope supernovae.
Calibration of neutron star natal kick velocities to isolated pulsar observations
Publisher: Oxford University Press (OUP)
Date: 09-01-2023
Abstract: Current prescriptions for supernova natal kicks in rapid binary population synthesis simulations are based on fits of simple functions to single pulsar velocity data. We explore a new parametrization of natal kicks received by neutron stars in isolated and binary systems developed by Mandel & Müller, which is based on 1D models and 3D supernova simulations, and accounts for the physical correlations between progenitor properties, remnant mass, and the kick velocity. We constrain two free parameters in this model using very long baseline interferometry velocity measurements of Galactic single pulsars. We find that the inferred values of natal kick parameters do not differ significantly between single and binary evolution scenarios. The best-fitting values of these parameters are $v$ns = 520 km s−1 for the scaling prefactor for neutron star kicks, and σns = 0.3 for the fractional stochastic scatter in the kick velocities.
Building Better Spin Models for Merging Binary Black Holes: Evidence for Nonspinning and Rapidly Spinning Nearly Aligned Subpopulations
Publisher: American Astronomical Society
Date: 29-10-2021
Abstract: Recent work paints a conflicting portrait of the distribution of black hole spins in merging binaries measured with gravitational waves. Some analyses find that a significant fraction of merging binaries contain at least one black hole with a spin tilt ° with respect to the orbital angular momentum vector, which has been interpreted as a signature for dynamical assembly. Other analyses find that the data are consistent with a bimodal population in which some binaries contain black holes with negligible spin while the rest contain black holes with spin vectors preferentially aligned with the orbital angular momentum vector. In this work, we scrutinize models for the distribution of black hole spins to pinpoint possible failure modes in which the model yields a faulty conclusion. We reanalyze data from the second LIGO–Virgo gravitational-wave transient catalog (GWTC-2) using a revised spin model, which allows for a subpopulation of black holes with negligible spins. In agreement with recent results by Roulet et al., we show that the GWTC-2 detections are consistent with two distinct subpopulations. We estimate that 69%–90% (90% credible interval) of merging binaries contain black holes with negligible spin χ ≈ 0. The remaining binaries are part of a second subpopulation in which the spin vectors are preferentially (but not exactly) aligned to the orbital angular momentum. The black holes in this second subpopulation are characterized by spins of χ ∼ 0.5. We suggest that the inferred spin distribution is consistent with the hypothesis that all merging binaries form via the field formation scenario.
Erratum: “Building Better Spin Models for Merging Binary Black Holes: Evidence for Nonspinning and Rapidly Spinning Nearly Aligned Subpopulations” (2021, ApJL, 921, L15)
Publisher: American Astronomical Society
Date: 09-2022
Delayed appearance and evolution of coronal lines in the TDE AT2019qiz
Publisher: Oxford University Press (OUP)
Date: 26-07-2023
Abstract: Tidal disruption events (TDEs) occur when a star gets torn apart by a supermassive black hole as it crosses its tidal radius. We present late-time optical and X-ray observations of the nuclear transient AT2019qiz, which showed the typical signs of an optical-UV transient class commonly believed to be TDEs. Optical spectra were obtained 428, 481, and 828 rest-frame days after optical light-curve peak, and a UV/X-ray observation coincided with the later spectrum. The optical spectra show strong coronal emission lines, including [Fe vii], [Fe x], [Fe xi], and [Fe xiv]. The Fe lines rise and then fall, except [Fe xiv] that appears late and rises. We observe increasing flux of narrow H α and H β and a decrease in broad H α flux. The coronal lines have full width at half-maximum ranging from ∼150−300 km s−1, suggesting they originate from a region between the broad- and narrow-line emitting gas. Between the optical flare and late-time observation, the X-ray spectrum softens dramatically. The 0.3–1 keV X-ray flux increases by a factor of ∼50, while the hard X-ray flux decreases by a factor of ∼6. Wide-field Infrared Survey Explorer fluxes also rose over the same period, indicating the presence of an infrared echo. With AT2017gge, AT2019qiz is one of two ex les of a spectroscopically confirmed optical-UV TDE showing delayed coronal line emission, supporting speculations that Extreme Coronal Line Emitters in quiescent galaxies can be echos of unobserved past TDEs. We argue that the coronal lines, narrow lines, and infrared emission arise from the illumination of pre-existing material likely related to either a previous TDE or active galactic nucleus activity.
The origin of spin in binary black holes
Publisher: EDP Sciences
Date: 03-2020
DOI: 10.1051/0004-6361/201936204
Abstract: Context. After years of scientific progress, the origin of stellar binary black holes is still a great mystery. Several formation channels for merging black holes have been proposed in the literature. As more merger detections are expected with future gravitational-wave observations, population synthesis studies can help to distinguish between them. Aims. We study the formation of coalescing binary black holes via the evolution of isolated field binaries that go through the common envelope phase in order to obtain the combined distributions of observables such as black-hole spins, masses and cosmological redshifts of mergers. Methods. To achieve this aim, we used a hybrid technique that combines the parametric binary population synthesis code COMPAS with detailed binary evolution simulations performed with the MESA code. We then convolved our binary evolution calculations with the redshift- and metallicity-dependent star-formation rate and the selection effects of gravitational-wave detectors to obtain predictions of observable properties. Results. By assuming efficient angular momentum transport, we are able to present a model that is capable of simultaneously predicting the following three main gravitational-wave observables: the effective inspiral spin parameter χ eff , the chirp mass M chirp and the cosmological redshift of merger z merger . We find an excellent agreement between our model and the ten events from the first two advanced detector observing runs. We make predictions for the third observing run O3 and for Advanced LIGO design sensitivity. We expect approximately 80% of events with χ eff 0.1, while the remaining 20% of events with χ eff ≥ 0.1 are split into ∼10% with M chirp 15 M ⊙ and ∼10% with M chirp ≥ 15 M ⊙ . Moreover, we find that M chirp and χ eff distributions are very weakly dependent on the detector sensitivity. Conclusions. The favorable comparison of the existing LIGO/Virgo observations with our model predictions gives support to the idea that the majority, if not all of the observed mergers, originate from the evolution of isolated binaries. The first-born black hole has negligible spin because it lost its envelope after it expanded to become a giant star, while the spin of the second-born black hole is determined by the tidal spin up of its naked helium star progenitor by the first-born black hole companion after the binary finished the common-envelope phase.
N-BODY DYNAMICS OF INTERMEDIATE MASS-RATIO INSPIRALS IN STAR CLUSTERS
Publisher: American Astronomical Society
Date: 12-2016
Supernova explosions in active galactic nuclear discs
Publisher: Oxford University Press (OUP)
Date: 12-07-2021
Abstract: Active galactic nuclei (AGNs) are prominent environments for stellar capture, growth, and formation. These environments may catalyse stellar mergers and explosive transients, such as thermonuclear and core-collapse supernovae (SNe). SN explosions in AGN discs generate strong shocks, leading to unique observable signatures. We develop an analytical model that follows the evolution of the shock propagating in the disc until it eventually breaks out. We derive the peak luminosity, bolometric light curve, and breakout time. The peak luminosities may exceed 1045 erg s−1 and last from hours to days. The brightest explosions occur in regions of reduced density: either off-plane, or in discs around low-mass central black holes (${\\sim} 10^6\\ \\rm {M}_\\odot$), or in starved subluminous AGNs. Explosions in the latter two sites are easier to observe due to a reduced AGN background luminosity. We perform suites of 1D Lagrangian radiative hydrodynamics snec code simulations to validate our results and obtain the luminosity in different bands, and 2D axisymmetric Eulerian hydrodynamics code hormone simulations to study the morphology of the ejecta and its deviation from spherical symmetry. The observed signature is expected to be a bright blue, UV or X-ray flare on top of the AGN luminosity from the initial shock breakout, while the subsequent red part of the light curve will largely be unobservable. We estimate the upper limit for the total event rate to be $\\mathcal {R}\\lesssim 100\\ \\rm yr^{-1}\\ Gpc^{-3}$ for optimal conditions and discuss the large uncertainties in this estimate. Future high-cadence transient searches may reveal these events. Some existing tidal disruption event candidates may originate from AGN SNe.
JWST detection of heavy neutron capture elements in a compact object merger
Publisher: Research Square Platform LLC
Date: 24-07-2023
DOI: 10.21203/RS.3.RS-3135743/V1
Abstract: The mergers of binary compact objects such as neutron stars and black holes are of central interest to several areas of astrophysics, including as the progenitors of gamma-ray bursts (GRBs), sources of high-frequency gravitational waves and likely production sites for heavy element nucleosynthesis via rapid neutron capture (the r-process). These heavy elements include some of great geophysical, biological and cultural importance, such as thorium, iodine, and gold. Here we present observations of the exceptionally bright gamma-ray burst GRB230307A. We show that GRB 230307A belongs to the class of long-duration gamma-ray bursts associated with compact object mergers, and contains a kilonova similar to AT2017gfo, associated with the gravitational-wave merger GW170817. We obtained James Webb Space Telescope mid-infrared (mid-IR) imaging and spectroscopy 29 & 61 days after the burst. The spectroscopy shows an emission line at 2.1 microns which we interpret as tellurium (atomic mass A=130), and a very red source, emitting most of its light in the mid-IR due to the production of lanthanides. These observations demonstrate that nucleosynthesis in GRBs can create r-process elements across a broad atomic mass range and play a central role in heavy element nucleosynthesis across the Universe.
Constraints on the merging binary neutron star mass distribution and equation of state based on the incidence of jets in the population
Publisher: EDP Sciences
Date: 10-2022
DOI: 10.1051/0004-6361/202243260
Abstract: A relativistic jet has been produced in the single well-localised binary neutron star (BNS) merger detected to date in gravitational waves (GWs), and the local rates of BNS mergers and short gamma-ray bursts are of the same order of magnitude. This suggests that jet formation is not a rare outcome for BNS mergers, and we show that this intuition can be turned into a quantitative constraint: at least about one-third of GW-detected BNS mergers and at least about one-fifth of all BNS mergers should produce a successful jet (90% credible level). Whether a jet is launched depends on the properties of the merger remnant and of the surrounding accretion disc, which in turn are a function of the progenitor binary masses and equation of state (EoS). The incidence of jets in the population therefore carries information about the binary component mass distribution and EoS. Under the assumption that a jet can only be produced by a black hole remnant surrounded by a non-negligible accretion disc, we show how the jet incidence can be used to place a joint constraint on the space of BNS component mass distributions and EoS. The result points to a broad mass distribution, with particularly strong support for masses in the 1.3 − 1.6 M ⊙ range. The constraints on the EoS are shallow, but we show how they will tighten as the knowledge on the jet incidence improves. We also discuss how to extend the method to include future BNS mergers, with possibly uncertain jet associations.
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