Search

Context. The black holes discovered using Gaia, especially Gaia BH1 and BH2, have low mass companions of solar-like metallicity in wide orbits. For standard isolated binary evolution formation channels including interactions such an extreme mass ratio is unexpected; especially in orbits of hundreds to thousands of days. Aims. Here, we investigate a non-interacting formation path for isolated binaries to explain the formation of Gaia BH1 and BH2. Methods. We use single star models computed with MESA to constrain the main characteristics of possible progenitors of long-period black hole binaries like Gaia BH1 and BH2. Then, we incorporate these model grids into the binary population synthesis code POSYDON, to explore whether the formation of the observed binaries at solar metallicity is indeed possible. Results. We find that winds of massive stars ($\gtrsim 80\,M_\odot$), especially during the Wolf-Rayet phase, tend to cause a plateau in the initial stellar mass to final black hole mass relation (at about $13\,M_\odot$ in our default wind prescription). However, stellar winds at earlier evolutionary phases are also important at high metallicity, as they prevent the most massive stars from expanding ($<100\,R_\odot$) and filling their Roche lobe. Consequently, the strength of the applied winds affects the range of the final black hole masses in non-interacting binaries, making it possible to form systems similar to Gaia BH1 and BH2. Conclusions. We deduce that wide binaries with a black hole and a low mass companion can form at high metallicity without binary interactions. There could be hundreds of such systems in the Milky Way. The mass of the black hole in binaries evolved through the non-interacting channel can potentially provide insights into the wind strength during the progenitors evolution., Comment: 8+4 pages, 6+6 figures, resubmitted to A&A

Knowledge about the internal physical structure of stars is crucial to understanding their evolution. The novel binary population synthesis code POSYDON includes a module for interpolating the stellar and binary properties of any system at the end of binary MESA evolution based on a pre-computed set of models. In this work, we present a new emulation method for predicting stellar profiles, i.e., the internal stellar structure along the radial axis, using machine learning techniques. We use principal component analysis for dimensionality reduction and fully-connected feed-forward neural networks for making predictions. We find accuracy to be comparable to that of nearest neighbor approximation, with a strong advantage in terms of memory and storage efficiency. By delivering more information about the evolution of stellar internal structure, these emulators will enable faster simulations of higher physical fidelity with large-scale simulations of binary star population synthesis possible with POSYDON and other population synthesis codes., Comment: 11 pages, 10 figures. Submitted to Astronomy and Computing

Core-collapse supernovae are explosions of massive stars at the end of their evolution. They are responsible for metal production and for halting star formation, having a significant impact on galaxy evolution. The details of these processes depend on the nature of supernova progenitors, but it is unclear if Type Ic supernovae (without hydrogen or helium lines in their spectra) originate from core-collapses of very massive stars (> 30 Msun) or from less massive stars in binary systems. Here we show that Type II (with hydrogen lines) and Ic supernovae are located in environments with similar molecular gas densities, therefore their progenitors have comparable lifetimes and initial masses. This supports a binary interaction for most Type Ic supernova progenitors, which explains the lack of hydrogen and helium lines. This finding can be implemented in sub-grid prescriptions in numerical cosmological simulations to improve the feedback and chemical mixing., Comment: 9 pages, 3 figures, published in Nature Communications

The three dynamically confirmed wind-fed black hole high-mass X-ray binaries (BH-HMXBs) are suggested to all contain a highly spinning black hole (BH). However, based on the theories of efficient angular momentum transport inside the stars, we expect that the first-born BHs in binary systems should have low spins, which is consistent with gravitational-wave observations. As a result, the origin of the high BH spins measured in wind-fed BH-HMXBs remains a mystery. In this paper, we conduct a binary population synthesis study on wind-fed BH-HMXBs at solar metallicity with the use of the newly developed code POSYDON, considering three scenarios for BH accretion: Eddington-limited, moderately super-Eddington, and fully conservative accretion. Taking into account the conditions for accretion-disk formation, we find that regardless of the accretion model, these systems are more likely to have already experienced a phase of Roche-lobe overflow after the BH formation. To account for the extreme BH spins, highly conservative accretion onto BHs is required, when assuming the accreted material carries the specific angular momentum at the innermost stable orbit. Besides, in our simulations we found that the systems with donor stars within the mass range of $10-20\,M_{\odot}$ are prevalent, posing a challenge in explaining simultaneously all observed properties of the BH-HMXB in our Galaxy, Cygnus X-1, and potentially hinting that the accretion efficiency onto non-degenerate stars, before the formation of the BH, is also more conservative than assumed in our simulations., Comment: Submitted to A&A. Comments are welcome!

Mixed-morphology supernova remnants (MMSNRs) are characterized by a shell-like morphology in the radio and centrally-peaked thermal emission in the X-ray band. The nature of this peculiar class of supernova remnants (SNRs) remains a controversial issue. In this work, by pairing the predictions of stellar evolution theory with two-dimensional hydrodynamic simulations we show that the mixed morphology properties of a SNR can arise by the interaction of the SNR with the circumstellar medium shaped by a red supergiant progenitor star, embedded in a dense environment. As a study case, we model the circumstellar medium formation and the subsequent interaction of the SNR with it of a $15~\rm M_{\odot}$ progenitor star. The reflected shock, formed by the collision of the SNR with the density walls of the surrounding circumstellar cavity, accumulates and re-shocks the supernova ejecta at the center of the remnant, increasing its temperature so that the gas becomes X-ray bright. Such a formation mechanism may naturally explain the nature of MMSNRs resulted from Type II supernovae without the demand of additional physical mechanisms and/or ambient medium inhomogeneities. We discuss alternative evolutionary paths that potentially could be ascribed for the MMSNR formation within the framework of the reflected shock model., Comment: 9 pages, 5 figures, accepted to MNRAS

Be X-ray binaries (Be-XRBs) are one of the largest subclasses of high-mass X-ray binaries, comprised of a rapidly rotating Be star and neutron star companion in an eccentric orbit, intermittently accreting material from a decretion disk around the donor. Originating from binary stellar evolution, Be-XRBs are of significant interest to binary population synthesis (BPS) studies, encapsulating the physics of supernovae, common envelope, and mass transfer (MT). Using the state-of-the-art BPS code, POSYDON, which relies on pre-computed grids of detailed binary stellar evolution models, we investigate the Galactic Be-XRB population. POSYDON incorporates stellar rotation self-consistently during MT phases, enabling detailed examination of the rotational distribution of Be stars in multiple phases of evolution. Our fiducial BPS and Be-XRB model align well with the orbital properties of Galactic Be-XRBs, emphasizing the role of rotational constraints. Our modeling reveals a rapidly rotating population ($\omega/\omega_\mathrm{crit} \gtrsim 0.3$) of Be-XRB-like systems with a strong peak at intermediate rotation rates ($\omega/\omega_\mathrm{crit} \simeq 0.6$) in close alignment with observations. All Be-XRBs undergo a MT phase before the first compact object forms, with over half experiencing a second MT phase from a stripped helium companion (Case BB). Computing rotationally-limited MT efficiencies and applying them to our population, we derive a physically motivated MT efficiency distribution, finding that most Be-XRBs have undergone highly non-conservative MT ($\bar{\beta}_\mathrm{rot} \simeq 0.05$). Our study underscores the importance of detailed angular momentum modeling during MT in interpreting Be-XRB populations, emphasizing this population as a key probe for the stability and efficiency of MT in interacting binaries., Comment: 21 pages, 10 figures, Accepted in ApJ; Revised to match published version of manuscript

Current population synthesis modeling suggests that 30-50% of Type II supernovae originate from binary progenitors, however, the identification of a binary progenitor is challenging. One indicator of a binary progenitor is that the surrounding stellar population is too old to contain a massive single star.Measurements of the progenitor mass of SN 2017eaw are starkly divided between observations made temporally close to core-collapse which show a progenitor mass of 13-15 solar masses (final helium core mass of 4.4 to 6.0 solar masses - which is a more informative property than initial mass) and those from the stellar population surrounding the SN which find M<10.8 solar masses (helium core mass <3.4 solar masses). In this paper, we reanalyze the surrounding stellar population with improved astrometry and photometry, finding a median age of 16.8 (+3.2, -1.0) Myr for all stars younger than 50 Myr (helium core mass of 4.7 solar masses) and 85.9 (+3.2, -6.5) Myr for stars younger than 150 Myr. 16.8 Myr is now consistent with the helium core mass range derived from the temporally near explosion observations for single stars. Applying the combined constraints to population synthesis models, we determine that the probability of the progenitor of SN 2017eaw being an initially single-star is 65% compared to 35% for prior binary interaction. 85.9 Myr is inconsistent with any formation scenarios. We demonstrate that combining progenitor age constraints with helium core mass estimates from red supergiant SED modeling, late-time spectra, and indirectly from light curve modeling can help to differentiate single and binary progenitor scenarios and provide a framework for the application of this technique to future observations., Comment: Accepted to AJ

Ultra-luminous X-ray sources (ULXs) are sources observed to exceed the Eddington limit of a stellar-mass black hole (BH). A fraction of ULX sources show X-ray pulses which are evidence for accreting neutron stars (NSs). Theoretical studies have suggested that NSs dominate the compact objects of intrinsic ULXs, even though the majority of observed sample is non-pulsating, implying that X-ray pulses from many NS ULXs are unobservable. We use POSYDON to generate and study X-ray binary populations spanning starburst ages 5 to 1000Myr. Following theoretical predictions for the alignment of the NS spin axis with the accretion disc, we estimate the required accreted mass in ULXs so that the alignment suppresses observable X-ray pulses. While the properties of ULXs are sensitive to model assumptions, there are certain trends that the populations follow. Young and old stellar populations are dominated by BH and NS accretors, respectively. The donors go from massive H-rich main-sequence (MS) stars in young populations (<100Myr) to low-mass post-MS H-rich stars in older populations (>100Myr), with stripped He-rich giant stars dominating the populations at around 100Myr. In addition, we find that NS ULXs exhibit stronger geometrical beaming than BH ULXs, leading to an under-representation of NS accretors in observed populations. Coupled with our finding that X-ray pulses are suppressed in at least 60% of the NS ULXs, we suggest that the observed fraction of ULXs with detectable X-ray pulses is very small, in agreement with observations. This study investigates the effects of age on ULXs as well as the effects of different model assumptions on ULX demographics. We show that geometrical beaming and the mass-accretion phase are critical aspects of understanding ULX observations. Our results suggest that even though most ULXs have accreting NSs, those with observable X-ray pulses would be very few., Comment: 22 pages, 12 figures, Accepted by A&A. Fixed typos and updated references. Referee's comments were addressed

Neutron star $-$ black hole (NSBH) merger events bring us new opportunities to constrain theories of stellar and binary evolution, and understand the nature of compact objects. In this work, we investigate the formation of merging NSBH binaries at solar metallicity by performing a binary population synthesis study of merging NSBH binaries with the newly developed code POSYDON. The latter incorporates extensive grids of detailed single and binary evolution models, covering the entire evolution of a double compact object progenitor. We explore the evolution of NSBHs originating from different formation channels, which in some cases differ from earlier studies performed with rapid binary population synthesis codes. Then, we present the population properties of merging NSBH systems and their progenitors such as component masses, orbital features, and BH spins, and investigate the model uncertainties in our treatment of common envelope (CE) evolution and core-collapse process. We find that at solar metallicity, under the default model assumptions, most of the merging NSBHs have BH masses in a range of $3-11\,M{_\odot}$ and chirp masses within $1.5-4\,M{_\odot}$. Independently of our model variations, the BH always forms first with dimensionless spin parameter $\lesssim 0.2$, which is correlated to the initial binary orbital period. Some BHs can subsequently spin up moderately ($\chi_{\rm BH} \lesssim 0.4$) due to mass transfer, which we assume to be Eddington limited. Binaries that experienced CE evolution rarely demonstrate large tilt angles. Conversely, approximately $40\%$ of the binaries that undergo only stable mass transfer without CE evolution contain an anti-aligned BH. Finally, accounting for uncertainties in both the population modeling and the NS equation of state, we find that $0-18.6\%$ of NSBH mergers may be accompanied by an electromagnetic counterpart., Comment: 18 pages, 10 figures, submitted to A&A, comments are welcome

We assemble the most complete and clean red supergiant (RSG) sample (2,121 targets) so far in the Small Magellanic Cloud (SMC) with 53 different bands of data to study the MLR of RSGs. In order to match the observed spectral energy distributions (SEDs), a theoretical grid of 17,820 Oxygen-rich models (``normal'' and ``dusty'' grids are half-and-half) is created by the radiatively-driven wind model of the DUSTY code, covering a wide range of dust parameters. We select the best model for each target by calculating the minimal modified chi-square and visual inspection. The resulting MLRs from DUSTY are converted to real MLRs based on the scaling relation, for which a total MLR of $6.16\times10^{-3}$ $M_\odot$ yr$^{-1}$ is measured (corresponding to a dust-production rate of $\sim6\times10^{-6}$ $M_\odot$ yr$^{-1}$), with a typical MLR of $\sim10^{-6}$ $M_\odot$ yr$^{-1}$ for the general population of the RSGs. The complexity of mass-loss estimation based on the SED is fully discussed for the first time, indicating large uncertainties based on the photometric data (potentially up to one order of magnitude or more). The Hertzsprung-Russell and luminosity versus median absolute deviation diagrams of the sample indicate the positive relation between luminosity and MLR. Meanwhile, the luminosity versus MLR diagrams show a ``knee-like'' shape with enhanced mass-loss occurring above $\log_{10}(L/L_\odot)\approx4.6$, which may be due to the degeneracy of luminosity, pulsation, low surface gravity, convection, and other factors. We derive our MLR relation by using a third-order polynomial to fit the sample and compare our result with previous empirical MLR prescriptions. Given that our MLR prescription is based on a much larger sample than previous determinations, it provides a more accurate relation at the cool and luminous region of the H-R diagram at low-metallicity compared to previous studies., Comment: 16 pages, 19 figures, accepted by A&A

The maximum mass of black holes formed in isolated binaries is determined by stellar winds and the interactions between the binary components. We consider for the first time fully self-consistent detailed stellar structure and binary evolution calculations in population-synthesis models and a new, qualitatively different picture emerges for the formation of black-hole binaries, compared to studies employing rapid population synthesis models. We find merging binary black holes can form with a non-negligible rate ($\sim 4\times10^{-7}\,M_\odot^{-1}$) at solar metallicity. Their progenitor stars with initial masses $\gtrsim 50\,M_\odot$ do not expand to supergiant radii, mostly avoiding significant dust-driven or luminous blue variable winds. Overall, the progenitor stars lose less mass in stellar winds, resulting in black holes as massive as $\sim 30\,M_\odot$, and, approximately half of them avoid a mass-transfer episode before forming the first-born black hole. Finally, binaries with initial periods of a few days, some of which may undergo episodes of Roche-lobe overflow mass transfer, result in mildly spinning first-born black holes, $\chi_\mathrm{BH1} \lesssim 0.2$, assuming efficient angular-momentum transport., Comment: 14 pages, 6 figures, manuscript submitted for publication

When a compact object is formed in a binary, any mass lost during core collapse will impart a kick on the binary's center of mass. Asymmetries in this mass loss or neutrino emission would impart an additional natal kick on the remnant black hole or neutron star, whether it was formed in a binary or in isolation. While it is well established that neutron stars receive natal kicks upon formation, it is unclear whether black holes do as well. Here, we consider the low-mass X-ray binary MAXI J1305-704, which has been reported to have a space velocity $\gtrsim$ 200 km/s. In addition to integrating its trajectory to infer its velocity upon formation of its black hole, we account for recent estimates of its period, black hole mass, mass ratio, and donor effective temperature from photometric and spectroscopic observations. We find that if MAXI J1305-704 formed via isolated binary evolution in the thick Galactic disk, then the supernova that formed its black hole imparted a natal kick of at least 70 km/s while ejecting less than $\simeq 1$ M$_\odot$ with 95% confidence assuming uninformative priors on mass loss and natal kick velocity., Comment: Accepted Astrophysical Journal Letters; 9 pages, 5 figures

Mass measurements from low-mass black hole X-ray binaries (LMXBs) and radio pulsars have been used to identify a gap between the most massive neutron stars (NSs) and the least massive black holes (BHs). BH mass measurements in LMXBs are typically only possible for transient systems: outburst periods enable detection via all-sky X-ray monitors, while quiescent periods enable radial-velocity measurements of the low-mass donor. We quantitatively study selection biases due to the requirement of transient behavior for BH mass measurements. Using rapid population synthesis simulations (COSMIC), detailed binary stellar-evolution models (MESA), and the disk instability model of transient behavior, we demonstrate that transient-LMXB selection effects introduce observational biases, and can suppress mass-gap BHs in the observed sample. However, we find a population of transient LMXBs with mass-gap BHs form through accretion-induced collapse of a NS during the LMXB phase, which is inconsistent with observations. These results are robust against variations of binary evolution prescriptions. The significance of this accretion-induced collapse population depends upon the maximum NS birth mass $M_\mathrm{ NS, birth-max}$. To reflect the observed dearth of low-mass BHs, COSMIC and MESA models favor $M_\mathrm{ NS, birth-max} \lesssim2M_{\odot}$. In the absence of further observational biases against LMXBs with mass-gap BHs, our results indicate the need for additional physics connected to the modeling of LMXB formation and evolution., Comment: 21 pages, accepted to ApJ

The ever-expanding observational sample of X-ray binaries (XRBs) makes them excellent laboratories for constraining binary evolution theory. Such constraints can be obtained by studying the effects of various physical assumptions on synthetic X-ray luminosity functions (XLFs) and comparing to observed XLFs. In this work, we focus on high-mass XRBs (HMXBs) and study the effects on the XLF of various, poorly-constrained assumptions regarding physical processes such as the common-envelope phase, the core-collapse, and wind-fed accretion. We use the new binary population synthesis code POSYDON, which employs extensive pre-computed grids of detailed stellar structure and binary evolution models, to simulate the evolution of binaries. We generate 96 synthetic XRB populations corresponding to different combinations of model assumptions. The generated HMXB XLFs are feature-rich, deviating from the commonly assumed single-power law. We find a break in our synthetic XLF at luminosity $\sim 10^{38}$ erg s$^{-1}$, similar to observed XLFs. However, we find also a general overabundance of XRBs (up to a factor of $\sim$10 for certain model parameter combinations) driven primarily by XRBs with black hole accretors. Assumptions about the transient behavior of Be-XRBs, asymmetric supernova kicks, and common-envelope physics can significantly affect the shape and normalization of our synthetic XLFs. We find that less well-studied assumptions regarding the circularization of the orbit at the onset of Roche-lobe overflow and criteria for the formation of an X-ray emitting accretion disk around wind-accreting black holes can also impact our synthetic XLFs. Our study reveals the importance of large-scale parameter studies, highlighting the power of XRBs in constraining binary evolution theory., Comment: 31 pages, 32 figures, Accepted by A&A. Fixed typos and updated references. Referee's comments were addressed

Understanding the origin of merging binary black holes is currently one of the most pressing quests in astrophysics. We show that if isolated binary evolution dominates the formation mechanism of merging binary black holes, one should expect a correlation between the effective spin parameter, $\chi_\mathrm{eff}$, and the redshift of the merger, $z$, of binary black holes. This correlation comes from tidal spin-up systems preferentially forming and merging at higher redshifts due to the combination of weaker orbital expansion from low metallicity stars given their reduced wind mass loss rate, delayed expansion and have smaller maximal radii during the supergiant phase compared to stars at higher metallicity. As a result, these tightly bound systems merge with short inspiral times. Given our fiducial model of isolated binary evolution, we show that the origin of a $\chi_\mathrm{eff}-z$ correlation in the detectable LIGO--Virgo binary black hole population is different from the intrinsic population, which will become accessible only in the future by third-generation gravitational-wave detectors such as Einstein Telescope and Cosmic Explorer. Finally, we compare our model predictions with population predictions based on the current catalog of binary black hole mergers and find that current data favor a positive correlation of $\chi_\mathrm{eff}-z$ as predicted by our model of isolated binary evolution., Comment: 14 pages, 11 figures, accepted for publication in A&A

Binary stars undergo a variety of interactions and evolutionary phases, critical for predicting and explaining observed properties. Binary population synthesis with full stellar-structure and evolution simulations are computationally expensive requiring a large number of mass-transfer sequences. The recently developed binary population synthesis code POSYDON incorporates grids of MESA binary star simulations which are then interpolated to model large-scale populations of massive binaries. The traditional method of computing a high-density rectilinear grid of simulations is not scalable for higher-dimension grids, accounting for a range of metallicities, rotation, and eccentricity. We present a new active learning algorithm, psy-cris, which uses machine learning in the data-gathering process to adaptively and iteratively select targeted simulations to run, resulting in a custom, high-performance training set. We test psy-cris on a toy problem and find the resulting training sets require fewer simulations for accurate classification and regression than either regular or randomly sampled grids. We further apply psy-cris to the target problem of building a dynamic grid of MESA simulations, and we demonstrate that, even without fine tuning, a simulation set of only $\sim 1/4$ the size of a rectilinear grid is sufficient to achieve the same classification accuracy. We anticipate further gains when algorithmic parameters are optimized for the targeted application. We find that optimizing for classification only may lead to performance losses in regression, and vice versa. Lowering the computational cost of producing grids will enable future versions of POSYDON to cover more input parameters while preserving interpolation accuracies., Comment: 21 pages, 10 figures, ApJ in press

This Letter presents the detection of a source at the position of the Type Ib/c supernova (SN) 2013ge more than four years after the radioactive component is expected to have faded. This source could mark the first post-SN direct detection of a surviving companion to a stripped-envelope Type Ib/c explosion. We test this hypothesis and find the shape of the source's spectral energy distribution is most consistent with that of a B5 I supergiant. While binary models tend to predict OB-type stars for stripped-envelope companions, the location of the source on a color-magnitude diagram (CMD) places it redward of its more likely position on the main sequence (MS). The source may be temporarily out of thermal equilibrium, or a cool and inflated non-MS companion, which is similar to the suggested companion of Type Ib SN 2019yvr that was constrained from pre-SN imaging. We also consider other possible physical scenarios for the source, including a fading SN, circumstellar shock interaction, line of site coincidence, and an unresolved host star cluster, all of which will require future observations to more definitively rule out. Ultimately, the fraction of surviving companions ("binary fraction") will provide necessary constraints on binary evolution models and the underlying physics., Comment: Accepted to ApJL. 9 pages, 4 figures, 1 table

Most massive stars are members of a binary or a higher-order stellar systems, where the presence of a binary companion can decisively alter their evolution via binary interactions. Interacting binaries are also important astrophysical laboratories for the study of compact objects. Binary population synthesis studies have been used extensively over the last two decades to interpret observations of compact-object binaries and to decipher the physical processes that lead to their formation. Here, we present POSYDON, a novel, binary population synthesis code that incorporates full stellar-structure and binary-evolution modeling, using the MESA code, throughout the whole evolution of the binaries. The use of POSYDON enables the self-consistent treatment of physical processes in stellar and binary evolution, including: realistic mass-transfer calculations and assessment of stability, internal angular-momentum transport and tides, stellar core sizes, mass-transfer rates and orbital periods. This paper describes the detailed methodology and implementation of POSYDON, including the assumed physics of stellar- and binary-evolution, the extensive grids of detailed single- and binary-star models, the post-processing, classification and interpolation methods we developed for use with the grids, and the treatment of evolutionary phases that are not based on pre-calculated grids. The first version of POSYDON targets binaries with massive primary stars (potential progenitors of neutron stars or black holes) at solar metallicity., Comment: 60 pages, 33 figures, 8 tables, referee's comments addressed. The code and the accompanying documentations and data products are available at https:\\posydon.org

SN 2019yvr is the second Type Ib supernova (SN) with a possible direct detection of its progenitor (system); however, the spectral energy distribution (SED) of the pre-explosion source appears much cooler and overluminous than an expected helium-star progenitor. Using Hubble Space Telescope (HST) images and MUSE integral-field-unit (IFU) spectroscopy, we find the SN environment contains three episodes of star formation; the low ejecta mass suggests the SN progenitor is most likely from the oldest population, corresponding to an initial mass of 10.4$^{+1.5}_{-1.3}$ $M_\odot$. The pre-explosion SED can be reproduced by two components, one for the hot and compact SN progenitor and one for a cool and inflated yellow hypergiant (YHG) companion that dominates the brightness. Thus, SN 2019yvr could possibly be the first Type Ib/c SN for which the progenitor's binary companion is directly detected on pre-explosion images. Both the low progenitor mass and the YHG companion suggest significant binary interaction during their evolution. Similar to SN 2014C, SN 2019yvr exhibits a metamorphosis from Type Ib to Type IIn, showing signatures of interaction with hydrogen-rich circumstellar material (CSM) at >150 days; our result supports enhanced pre-SN mass loss as an important process for hydrogen-poor stars at the low mass end of core-collapse SN progenitors., Comment: 15 pages, 9 figures, accepted for publication in MNRAS

Long-duration gamma-ray bursts are thought to be associated with the core-collapse of massive, rapidly spinning stars and the formation of black holes. However, efficient angular momentum transport in stellar interiors, currently supported by asteroseismic and gravitational-wave constraints, leads to predominantly slowly-spinning stellar cores. Here, we report on binary stellar evolution and population synthesis calculations, showing that tidal interactions in close binaries not only can explain the observed sub-population of spinning, merging binary black holes but also lead to long gamma-ray bursts at the time of black-hole formation. Given our model calibration against the distribution of isotropic-equivalent energies of luminous long gamma-ray bursts, we find that ~10% of the GWTC-2 reported binary black holes had a luminous long gamma-ray burst associated with their formation, with GW190517 and GW190719 having a probability of ~85% and ~60%, respectively, being among them. Moreover, given an assumption about their average beaming fraction, our model predicts the rate density of long gamma-ray bursts, as a function of redshift, originating from this channel. For a constant beaming fraction $f_\mathrm{B}\sim 0.05$ our model predicts a rate density comparable to the observed one, throughout the redshift range, while, at redshift $z \in [0,2.5]$, a tentative comparison with the metallicity distribution of observed LGRB host galaxies implies that between 20% to 85% of the observed long gamma-ray bursts may originate from progenitors of merging binary black holes. The proposed link between a potentially significant fraction of observed, luminous long gamma-ray bursts and the progenitors of spinning binary black-hole mergers allows us to probe the latter well outside the horizon of current-generation gravitational wave observatories, and out to cosmological distances., Comment: Accepted for publication in A&A Letters, 12 pages, 6 figures, 1 table

Recent detailed 1D core-collapse simulations have brought new insights on the final fate of massive stars, which are in contrast to commonly used parametric prescriptions. In this work, we explore the implications of these results to the formation of coalescing black-hole (BH) - neutron-star (NS) binaries, such as the candidate event GW190426_152155 reported in GWTC-2. Furthermore, we investigate the effects of natal kicks and the NS's radius on the synthesis of such systems and potential electromagnetic counterparts linked to them. Synthetic models based on detailed core-collapse simulations result in an increased merger detection rate of BH-NS systems ($\sim 2.3$ yr$^{-1}$), 5 to 10 times larger than the predictions of "standard" parametric prescriptions. This is primarily due to the formation of low-mass BH via direct collapse, and hence no natal kicks, favored by the detailed simulations. The fraction of observed systems that will produce an electromagnetic counterpart, with the detailed supernova engine, ranges from $2$-$25$%, depending on uncertainties in the NS equation of state. Notably, in most merging systems with electromagnetic counterparts, the NS is the first-born compact object, as long as the NS's radius is $\lesssim 12\,\mathrm{km}$. Furthermore, core-collapse models that predict the formation of low-mass BHs with negligible natal kicks increase the detection rate of GW190426_152155-like events to $\sim 0.6 \, $yr$^{-1}$; with an associated probability of electromagnetic counterpart $\leq 10$% for all supernova engines. However, increasing the production of direct-collapse low-mass BHs also increases the synthesis of binary BHs, over-predicting their measured local merger density rate. In all cases, models based on detailed core-collapse simulation predict a ratio of BH-NSs to binary BHs merger rate density that is at least twice as high as other prescriptions., Comment: 13 pages, 5 figures, 3 tables

Core-collapse supernovae (SNe) are the inevitable fate of most massive stars. Since most stars form in groups, SN progenitors can be constrained with information of their environments. It remains challenging to accurately analyse the various components in the environment and to correctly identify their relationships with the SN progenitors. Using a combined dataset of VLT/MUSE spatially-resolved integral-field-unit (IFU) spectroscopy and HST/ACS+WFC3 high-spatial resolution imaging, we present a detailed investigation of the environment of the Type II-P SN 2004dg and Type IIb SN 2012P. The two SNe occurred in a spiral arm of NGC 5806, where a star-forming complex is apparent with a giant H II region. By modelling the ionised gas, a compact star cluster and the resolved stars, we derive the ages and extinctions of stellar populations in the vicinity of the SNe. The various components are consistent with a sequence of triggered star formation as the spiral density wave swept through their positions. For SNe 2004dg and 2012P, we identify their host stellar populations and derive initial masses of $10.0^{+0.3}_{-0.2}~M_\odot$ and $15.2^{+2.0}_{-1.0}~M_\odot$ for their progenitors, respectively. Both results are consistent with those from pre-explosion images or nebular-phase spectroscopy. SN 2012P is spatially coincident but less likely to be coeval with the star-forming complex. As in this case, star formation bursts on small scales may appear correlated if they are controlled by any physical processes on larger scales; this may lead to a high probability of chance alignment between older SN progenitors and younger stellar populations., Comment: 21 pages, 17 figures, accepted for publication in MNRAS

We study the impact of mass-transfer physics on the observable properties of binary black hole populations formed through isolated binary evolution. We investigate the impact of mass-accretion efficiency onto compact objects and common-envelope efficiency on the observed distributions of $\chi_{eff}$, $M_{chirp}$ and $q$. We find that low common envelope efficiency translates to tighter orbits post common envelope and therefore more tidally spun up second-born black holes. However, these systems have short merger timescales and are only marginally detectable by current gravitational-waves detectors as they form and merge at high redshifts ($z\sim 2$), outside current detector horizons. Assuming Eddington-limited accretion efficiency and that the first-born black hole is formed with a negligible spin, we find that all non-zero $\chi_{eff}$ systems in the detectable population can come only from the common envelope channel as the stable mass-transfer channel cannot shrink the orbits enough for efficient tidal spin-up to take place. We find the local rate density ($z\simeq 0.01$) for the common envelope channel is in the range $\sim 17-113~Gpc^{-3}yr^{-1}$ considering a range of $\alpha_{CE} \in [0.2,5.0]$ while for the stable mass transfer channel the rate density is $\sim 25~Gpc^{-3}yr^{-1}$. The latter drops by two orders of magnitude if the mass accretion onto the black hole is not Eddington limited because conservative mass transfer does not shrink the orbit as efficiently as non-conservative mass transfer does. Finally, using GWTC-2 events, we constrain the lower bound of branching fraction from other formation channels in the detected population to be $\sim 0.2$. Assuming all remaining events to be formed through either stable mass transfer or common envelope channels, we find moderate to strong evidence in favour of models with inefficient common envelopes., Comment: 26 pages, 13 figures, accepted for publication in A&A

Massive stars are born predominantly as members of binary (or higher multiplicity) systems, and the presence of a companion can significantly alter their life and final fate. Therefore, any observed sample of massive stars or associated transients is likely to be significantly influenced by the effects of binarity. Here, we focus on the relationship between massive binary evolution and core-collapse supernova events. In the vast majority of the cases, the first core-collapse event happening in a binary system unbinds the two stars. Studying the population of companion stars, either at the supernova site, or as "widowed" stars long after the explosion, can be used to constrain the previous orbital evolution of the binary progenitor, and explosion physics of their former companion. Specifically, the population of "widowed" stars might provide statistical constraints on the typical amplitude of black hole natal kicks without seeing neither the black holes nor the transient possibly associated with their formation. Binarity also has a large impact on the predicted population of supernova sub-types, including hydrogen-rich type II supernovae, with a significant fraction of hydrogen-rich stars at explosions being either merger products or accretors., Comment: proceedings of the conference "Universe of binaries, binaries in the Universe" held in Telc in Sep, 2019

Ultra-luminous X-ray sources (ULXs) are those X-ray sources located away from the centre of their host galaxy with luminosities exceeding the Eddington limit of a stellar-mass black hole ($L_X>10^{39}\;{\rm erg\,s}^{-1}$). The discovery of X-ray pulsations in some of these objects (e.g. M82~X-2) suggests that a certain fraction of the ULX population may have a neutron star accretor. We present systematic modelling of low- and intermediate-mass X-ray binaries (LMXBs and IMXBs; donor-star mass range $0.92$--$8.0$~M$_{\odot}$ and neutron-star accretors) to explain the formation of this sub-population of ULXs. Using MESA, we explored the allowed initial parameter space of binary systems consisting of a neutron star and a low- or intermediate-mass donor star that could explain the observed properties of ULXs. Our simulations take into account beaming effects, stellar rotation, general angular momentum losses, and a detailed and self-consistent calculation of the mass-transfer rate. We study the conditions that lead to dynamical stability of these systems, which depends strongly on the response of the donor star to mass loss. Using two values for the initial neutron star mass ($1.3$~M$_{\odot}$ and $2.0$~M$_{\odot}$), we present two sets of mass-transfer calculation grids. We find that LMXBs/IMXBs can produce NS-ULXs with typical time-averaged isotropic-equivalent X-ray luminosities of $10^{39}$--$10^{41}\;{\rm erg\,s}^{-1}$ on a timescale up to $\sim\!1.0\;{\rm Myr}$ for the lower luminosities. We also estimate their likelihood of detection, the types of white-dwarf remnants left behind by the donors, and the total amount of mass accreted by the neutron stars. We also compare our results to the observed pulsating ULXs. Our results suggest that a large subset of the observed pulsating ULX population can be explained by LMXBs/IMXBs undergoing a super-Eddington mass-transfer phase., Comment: 19 pages, 13 figures, Accepted by A&A. Parameter space was increased to include low-mass XRBs and corresponding changes made to the text (including the title) and figures 4, 6-11. Changed axes for figures 1 and 2. Fixed typos and updated references. Added arguments about why spin period is not an accurate reflection of mass accretion rate in the introduction

The majority of massive stars, the progenitors of core-collapse supernovae (SNe), are found in close binary systems. Zapartas et al. (2019) modeled the fraction of hydrogen-rich, Type II SN progenitors which have their evolution affected by mass exchange with their companion, finding this to be between 1/3 and 1/2 for most assumptions. Here we study in more depth the impact of this binary history of Type II SN progenitors on their final pre-SN core mass distribution, using population synthesis simulations. We find that binary star progenitors of Type II SNe typically end their life with a larger core mass than they would have had if they had lived in isolation, because they gained mass or merged with a companion before explosion. The combination of the diverse binary evolutionary paths typically lead to a marginally shallower final core mass distribution. Discussing our results in the context of the red supergiant problem, i.e., the reported lack of detected high luminosity progenitors, we conclude that binary evolution does not seem to significantly affect the issue. This conclusion is quite robust against our variations in the assumptions of binary physics. We also predict that inferring the initial masses of Type II SN progenitors from "age-dating" its surrounding environment systematically yields lower masses compared to methods that probe the pre-SN core mass or luminosity. A robust discrepancy between the inferred initial masses of a SN progenitor from those different techniques could indicate an evolutionary history of binary mass accretion or merging., Comment: Published in Astronomy & Astrophysics, Volume 645

Context: White dwarfs (WDs) are important and abundant tools to study the structure and evolution of the Galactic environment. However, the multiplicity of WD progenitors is generally neglected. Specifically, a merger in a binary system can lead to a single WD, which could result in wrongly inferred quantities if only single stellar evolution (SSE) is considered. These mergers are linked to transients such as luminous red novae and Type Ia supernovae. Aims: We investigate the impact of binary evolution (BE) upon observable single WDs, and compare their properties to WDs formed through SSE. We assess the evolutionary channels and the age and mass distributions of the resulting single Wds. Methods: We employed \texttt{SeBa} to model the evolution of single star and binary populations. We synthesised the observable single WD population within $100$ pc, including cooling and observational selection effects. Additionally, we constructed models with different evolution and primordial population properties to study the effects on the properties of the resulting single WDs. Results: White dwarfs from binary mergers make up about $10-30\%$ of all observable single WDs and $30-50\%$ of massive WDs. On average, individual WDs take $3.1-5$ times longer to form through BE than SE, and so appear ${\sim} 1$ Gyr younger than they are if BE is ignored. In all models, the effect of mergers on the age distribution is clearly noticeable. The median age typically increases by $85-430$ Myr and $200-390$ Myr for massive WDs. Although abundant, we do not find evidence that WDs from mergers significantly alter the shape of the WD mass distribution. Conclusions: Assuming SSE for inferring properties of single WDs gives rise to intrinsic errors as single WDs can also be formed following a binary merger. Strategies for mitigating the effect of mergers on the WD age distributions are discussed., Comment: 16 pages, 14 figures. Published in A&A

Hydrogen-rich supernovae, known as Type II (SNe II), are the most common class of explosions observed following the collapse of the core of massive stars. We use analytical estimates and population synthesis simulations to assess the fraction of SNe II progenitors that are expected to have exchanged mass with a companion prior to explosion. We estimate that 1/3 to 1/2 of SN II progenitors have a history of mass exchange with a binary companion before exploding. The dominant binary channels leading to SN II progenitors involve the merger of binary stars. Mergers are expected to produce a diversity of SN II progenitor characteristics, depending on the evolutionary timing and properties of the merger. Alternatively, SN II progenitors from interacting binaries may have accreted mass from their companion, and subsequently been ejected from the binary system after their companion exploded. We show that the overall fraction of SN II progenitors that are predicted to have experienced binary interaction is robust against the main physical uncertainties in our models. However, the relative importance of different binary evolutionary channels is affected by changing physical assumptions. We further discuss ways in which binarity might contribute to the observed diversity of SNe II by considering potential observational signatures arising from each binary channel. For supernovae which have a substantial H-rich envelope at explosion (i.e., excluding Type IIb SNe), a surviving non-compact companion would typically indicate that the supernova progenitor star was in a wide, non-interacting binary. We argue that a significant fraction of even Type II-P SNe are expected to have gained mass from a companion prior to explosion., Comment: The paper has been accepted for publication in Astronomy and Astrophysics

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 the main observables of Advanced LIGO. 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. By assuming efficient angular momentum transport, we are able to present a model that is capable of simultaneously predicting the three main gravitational-wave observables: the effective inspiral spin parameter $\chi_{eff}$, 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 around 80% of events with $\chi_{eff} < 0.1$, while the remaining 20% of events with $\chi_{eff} \ge 0.1$ are split into ~10% with $M_{chirp} < 15$ M$_\odot$ and ~10% with $M_{chirp} \ge 15$ M$_\odot$. In conclusion, 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., Comment: Accepted for publication in A&A on January 21th 2020, 19 pages, 9 figures

We present HST/WFC3 ultraviolet imaging in the F275W and F336W bands of the Type IIb SN 2001ig at an age of more than 14 years. A clear point source is detected at the site of the explosion having $m_{\rm F275W}=25.39 \pm 0.10$ and $m_{\rm F336W}=25.88 \pm 0.13$ mag. Despite weak constraints on both the distance to the host galaxy NGC 7424 and the line-of-sight reddening to the supernova, this source matches the characteristics of an early B-type main sequence star having $19,000 < T_{\rm eff} < 22,000$ K and $\log (L_{\rm bol}/L_{\odot})=3.92 \pm 0.14$. A BPASS v2.1 binary evolution model, with primary and secondary masses of 13 M$_{\odot}$ and 9 M$_{\odot}$ respectively, is found to resemble simultaneously in the Hertzsprung-Russell diagram both the observed location of this surviving companion, and the primary star evolutionary endpoints for other Type IIb supernovae. This same model exhibits highly variable late-stage mass loss, as expected from the behavior of the radio light curves. A Gemini/GMOS optical spectrum at an age of 6 years reveals a narrow He II emission line, indicative of continuing interaction with a dense circumstellar medium at large radii from the progenitor. We review our findings on SN 2001ig in the context of binary evolution channels for stripped-envelope supernovae. Owing to the uncrowded nature of its environment in the ultraviolet, this study of SN 2001ig represents one of the cleanest detections to date of a surviving binary companion to a Type IIb supernova., Comment: 8 pages, 3 figures. Resubmitted to ApJ after minor changes requested by referee

Massive stars in binaries can give rise to extreme phenomena such as X-ray binaries and gravitational wave sources after one or both stars end their lives as core-collapse supernovae. Stars in close orbit around a stellar or compact companion are expected to explode as "stripped-envelope supernovae", showing no (Type Ib/c) or little (Type IIb) signs of hydrogen in the spectra, because hydrogen-rich progenitors are too large to fit. The physical processes responsible for the stripping process and the fate of the companion are still very poorly understood. Aiming to find new clues, we investigate Cas~A, which is a very young ($\sim$340 \,yr) and near ($\sim$3.4\,kpc) remnant of a core collapse supernova. Cas~A has been subject to several searches for possible companions, all unsuccessfully. We present new measurements of the proper motions and photometry of stars in the vicinity based on deep HST ACS/WFC and WFC3-IR data. We identify stellar sources that are close enough in projection, but using their proper motions we show that none are compatible with being at the location of center at the time of explosion, in agreement with earlier findings. Our photometric measurements allow us to place much deeper (order of magnitude) upper limits on the brightness of possible undetected companions. We systematically compare them with model predictions for a wide variety of scenarios. We can confidently rule out the presence of any stellar companion of any reasonable mass and age (main sequence, pre main sequence or stripped). Although this finding is not in direct conflict with model predictions, it does rule out what many considered to be the most likely evolutionary scenario for type IIb supernova. (abstract abbreviated), Comment: 13 pages, accepted by A&A

Core-collapse supernovae (SNe), marking the deaths of massive stars, are among the most powerful explosions in the Universe, responsible, e.g., for a predominant synthesis of chemical elements in their host galaxies. The majority of massive stars are thought to be born in close binary systems. To date, putative binary companions to the progenitors of SNe may have been detected in only two cases, SNe 1993J and 2011dh. We report on the search for a companion of the progenitor of the Type Ic SN 1994I, long considered to have been the result of binary interaction. Twenty years after explosion, we used the Hubble Space Telescope to observe the SN site in the ultraviolet (F275W and F336W bands), resulting in deep upper limits on the expected companion: F275W > 26.1 mag and F336W > 24.7 mag. These allows us to exclude the presence of a main sequence companion with a mass >~ 10 Msun. Through comparison with theoretical simulations of possible progenitor populations, we show that the upper limits to a companion detection exclude interacting binaries with semi-conservative (late Case A or early Case B) mass transfer. The limits tend to favor systems with non-conservative, late Case B mass transfer with intermediate initial orbital periods and mass ratios. The most likely mass range for a putative main sequence companion would be ~5--12 Msun, the upper end of which corresponds to the inferred upper detection limit., Comment: 9 pages, 5 figures, accepted to appear in the Astrophysical Journal