Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>We present a method to determine sodium abundance ratios ([Na/Fe]) using the Na <jats:sc>i</jats:sc> D doublet lines in low-resolution (<jats:italic>R</jats:italic> ∼ 2000) stellar spectra. As stellar Na <jats:sc>i</jats:sc> D lines are blended with those produced by the interstellar medium, we developed a technique for removing the interstellar Na <jats:sc>i</jats:sc> D lines using the relationship between extinction, which is proportional to <jats:italic>E</jats:italic>(<jats:italic>B</jats:italic> − <jats:italic>V</jats:italic>), and the equivalent width of the interstellar Na <jats:sc>i</jats:sc> D absorption lines. When measuring [Na/Fe], we also considered corrections for nonlocal thermodynamic equilibrium (NLTE) effects. Comparisons with data from high-resolution spectroscopic surveys suggest that the expected precision of [Na/Fe] from low-resolution spectra is better than 0.3 dex for stars with [Fe/H] &gt; −3.0. We also present a simple application employing the estimated [Na/Fe] values for a large number of stellar spectra from the Sloan Digital Sky Survey (SDSS). After classifying the SDSS stars into Na-normal, Na-high, and Na-extreme, we explore their relation to stars in Galactic globular clusters (GCs). We find that while the Na-high SDSS stars exhibit a similar metallicity distribution function (MDF) to that of the GCs, indicating that the majority of such stars may have originated from GC debris, the MDF of the Na-normal SDSS stars follows that of typical disk and halo stars. As there is a high fraction of carbon-enhanced metal-poor stars among the Na-extreme stars, they may have a non-GC origin, perhaps due to mass-transfer events from evolved binary companions.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present optical and ultraviolet (UV) observations of a luminous type Ia supernova (SN Ia) SN 2015bq characterized by early flux excess. This SN reaches a <jats:italic>B</jats:italic>-band absolute magnitude at <jats:italic>M</jats:italic> <jats:sub> <jats:italic>B</jats:italic> </jats:sub> = −19.68 ± 0.41 mag and a peak bolometric luminosity at <jats:italic>L</jats:italic> = (1.75 ± 0.37) × 10<jats:sup>43</jats:sup> erg s<jats:sup>−1</jats:sup>, with a relatively small post-maximum decline rate [Δ<jats:italic>m</jats:italic> <jats:sub>15</jats:sub>(<jats:italic>B</jats:italic>) = 0.82 ± 0.05 mag]. The flux excess observed in the light curves of SN 2015bq a few days after the explosion, especially seen in the UV bands, might be due to the radioactive decay of <jats:sup>56</jats:sup>Ni mixed into the surface. The radiation from the decay of the surface <jats:sup>56</jats:sup>Ni heats the outer layer of this SN. It produces blue <jats:italic>U</jats:italic> − <jats:italic>B</jats:italic> color followed by monotonically reddening in the early phase, dominated iron-group lines, and weak intermediate-mass element absorption features in the early spectra. The scenario of enhanced <jats:sup>56</jats:sup>Ni in the surface is consistent with a large amount of <jats:sup>56</jats:sup>Ni (<jats:inline-formula> <jats:tex-math> <?CDATA ${M}_{{}^{56}\mathrm{Ni}}=0.97\pm 0.20$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:msup> <mml:mrow /> <mml:mrow> <mml:mn>56</mml:mn> </mml:mrow> </mml:msup> <mml:mi>Ni</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>0.97</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.20</mml:mn> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac323fieqn1.gif" xlink:type="simple" /> </jats:inline-formula> <jats:italic>M</jats:italic> <jats:sub>☉</jats:sub>) synthesized during the explosion. The properties of SN 2015bq are found to locate between SN 1991T and SN 1999aa, suggesting the latter two subclasses of SNe Ia may have a common origin.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Intrinsic iron abundance spreads in globular clusters (GCs), although usually small, are very common, and are signatures of self-enrichment: some stars within the cluster have been enriched by supernova ejecta from other stars within the same cluster. We use the Bailin self-enrichment model to predict the relationship between properties of the protocluster—its mass and the metallicity of the protocluster gas cloud—and the final observable properties today—its current metallicity and the internal iron abundance spread. We apply this model to an updated catalog of Milky Way GCs where the initial mass and/or the iron abundance spread is known to reconstruct their initial metallicities. We find that with the exception of the known anomalous bulge cluster Terzan 5 and three clusters strongly suspected to be nuclear star clusters from stripped dwarf galaxies, the model provides a good lens for understanding their iron spreads and initial metallicities. We then use these initial metallicities to construct age–metallicity relations for kinematically identified major accretion events in the Milky Way’s history. We find that using the initial metallicity instead of the current metallicity does not alter the overall picture of the Milky Way’s history because the difference is usually small but does provide information that can help distinguish which accretion event some individual GCs with ambiguous kinematics should be associated with and points to potential complexity within the accretion events themselves.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The recent Parker Solar Probe observations of type III radio bursts show that the effects of the finite background magnetic field can be an important factor in the interpretation of data. In the present paper, the effects of the background magnetic field on the plasma-emission process, which is believed to be the main emission mechanism for solar coronal and interplanetary type III radio bursts, are investigated by means of the particle-in-cell simulation method. The effects of the ambient magnetic field are systematically surveyed by varying the ratio of plasma frequency to electron gyrofrequency. The present study shows that for a sufficiently strong ambient magnetic field, the wave–particle interaction processes lead to a highly field-aligned longitudinal mode excitation and anisotropic electron velocity distribution function, accompanied by a significantly enhanced plasma emission at the second-harmonic plasma frequency. For such a case, the polarization of the harmonic emission is almost entirely in the sense of extraordinary mode. On the other hand, for moderate strengths of the ambient magnetic field, the interpretation of the simulation result is less clear. The underlying nonlinear-mode coupling processes indicate that to properly understand and interpret the simulation results requires sophisticated analyses involving interactions among magnetized plasma normal modes, including the two transverse modes of the magneto-active plasma, namely, the extraordinary and ordinary modes, as well as electron-cyclotron-whistler, plasma oscillation, and upper-hybrid modes. At present, a nonlinear theory suitable for quantitatively analyzing such complex-mode coupling processes in magnetized plasmas is incomplete, which calls for further theoretical research, but the present simulation results could provide a guide for future theoretical efforts.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We search for the isotropic stochastic gravitational-wave background, including the nontensorial polarizations that are allowed in general metric theories of gravity, in the Parkes Pulsar Timing Array (PPTA) second data release (DR2). We find no statistically significant evidence that the common-spectrum process reported by the PPTA collaboration has tensor transverse, scalar transverse, vector longitudinal, or scalar longitudinal correlations in PPTA DR2. Therefore, we place a 95% upper limit on the amplitude of each polarization mode, as <jats:inline-formula> <jats:tex-math> <?CDATA ${{ \mathcal A }}_{\mathrm{TT}}\lesssim 3.2\times {10}^{-15}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi mathvariant="italic"></mml:mi> </mml:mrow> <mml:mrow> <mml:mi>TT</mml:mi> </mml:mrow> </mml:msub> <mml:mo>≲</mml:mo> <mml:mn>3.2</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>15</mml:mn> </mml:mrow> </mml:msup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac35ccieqn1.gif" xlink:type="simple" /> </jats:inline-formula>, <jats:inline-formula> <jats:tex-math> <?CDATA ${{ \mathcal A }}_{\mathrm{ST}}\lesssim 1.8\times {10}^{-15}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi mathvariant="italic"></mml:mi> </mml:mrow> <mml:mrow> <mml:mi>ST</mml:mi> </mml:mrow> </mml:msub> <mml:mo>≲</mml:mo> <mml:mn>1.8</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>15</mml:mn> </mml:mrow> </mml:msup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac35ccieqn2.gif" xlink:type="simple" /> </jats:inline-formula>, <jats:inline-formula> <jats:tex-math> <?CDATA ${{ \mathcal A }}_{\mathrm{VL}}\lesssim 3.5\times {10}^{-16}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi mathvariant="italic"></mml:mi> </mml:mrow> <mml:mrow> <mml:mi>VL</mml:mi> </mml:mrow> </mml:msub> <mml:mo>≲</mml:mo> <mml:mn>3.5</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>16</mml:mn> </mml:mrow> </mml:msup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac35ccieqn3.gif" xlink:type="simple" /> </jats:inline-formula>, and <jats:inline-formula> <jats:tex-math> <?CDATA ${{ \mathcal A }}_{\mathrm{SL}}\lesssim 4.2\times {10}^{-17};$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi mathvariant="italic"></mml:mi> </mml:mrow> <mml:mrow> <mml:mi>SL</mml:mi> </mml:mrow> </mml:msub> <mml:mo>≲</mml:mo> <mml:mn>4.2</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>17</mml:mn> </mml:mrow> </mml:msup> <mml:mo>;</mml:mo> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac35ccieqn4.gif" xlink:type="simple" /> </jats:inline-formula> or, equivalently, a 95% upper limit on the energy density parameter per logarithm frequency, as <jats:inline-formula> <jats:tex-math> <?CDATA ${{\rm{\Omega }}}_{\mathrm{GW}}^{\mathrm{TT}}\lesssim 1.4\times {10}^{-8}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mi mathvariant="normal">Ω</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>GW</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>TT</mml:mi> </mml:mrow> </mml:msubsup> <mml:mo>≲</mml:mo> <mml:mn>1.4</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>8</mml:mn> </mml:mrow> </mml:msup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac35ccieqn5.gif" xlink:type="simple" /> </jats:inline-formula>, <jats:inline-formula> <jats:tex-math> <?CDATA ${{\rm{\Omega }}}_{\mathrm{GW}}^{\mathrm{ST}}\lesssim 4.5\times {10}^{-9}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mi mathvariant="normal">Ω</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>GW</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>ST</mml:mi> </mml:mrow> </mml:msubsup> <mml:mo>≲</mml:mo> <mml:mn>4.5</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>9</mml:mn> </mml:mrow> </mml:msup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac35ccieqn6.gif" xlink:type="simple" /> </jats:inline-formula>, <jats:inline-formula> <jats:tex-math> <?CDATA ${{\rm{\Omega }}}_{\mathrm{GW}}^{\mathrm{VL}}\lesssim 1.7\times {10}^{-10}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mi mathvariant="normal">Ω</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>GW</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>VL</mml:mi> </mml:mrow> </mml:msubsup> <mml:mo>≲</mml:mo> <mml:mn>1.7</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>10</mml:mn> </mml:mrow> </mml:msup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac35ccieqn7.gif" xlink:type="simple" /> </jats:inline-formula>, and <jats:inline-formula> <jats:tex-math> <?CDATA ${{\rm{\Omega }}}_{\mathrm{GW}}^{\mathrm{SL}}\lesssim 2.4\times {10}^{-12}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mi mathvariant="normal">Ω</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>GW</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>SL</mml:mi> </mml:mrow> </mml:msubsup> <mml:mo>≲</mml:mo> <mml:mn>2.4</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>12</mml:mn> </mml:mrow> </mml:msup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac35ccieqn8.gif" xlink:type="simple" /> </jats:inline-formula>, at a frequency of 1/yr.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Recent observations show activity in long-period comet C/2017 K2 at heliocentric distances beyond the orbit of Uranus. With this as motivation, we constructed a simple model that takes a detailed account of gas transport modes and simulates the time-dependent sublimation of supervolatile ice from beneath a porous mantle on an incoming cometary nucleus. The model reveals a localized increase in carbon monoxide (CO) sublimation close to heliocentric distance <jats:italic>r</jats:italic> <jats:sub> <jats:italic>H</jats:italic> </jats:sub> = 150 au (local blackbody temperature ∼23 K), followed by a plateau and then a slow increase in activity toward smaller distances. This localized increase occurs as heat transport in the nucleus transitions between two regimes characterized by the rising temperature of the CO front at larger distances and nearly isothermal CO at smaller distances. As this transition is a general property of sublimation through a porous mantle, we predict that future observations of sufficient sensitivity will show that inbound comets (and interstellar interlopers) will exhibit activity at distances far beyond the planetary region of the solar system.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>TOI-216 is a pair of close-in planets with orbits deep in the 2:1 mean motion resonance. The inner Neptune-class planet (TOI-216b) is near 0.12 au (orbital period <jats:italic>P</jats:italic> <jats:sub>b</jats:sub> ≃ 17 days) and has a substantial orbital eccentricity (<jats:italic>e</jats:italic> <jats:sub>b</jats:sub> ≃ 0.16) and large libration amplitude (<jats:italic>A</jats:italic> <jats:sub> <jats:italic>ψ</jats:italic> </jats:sub> ≃ 60°) in the resonance. The outer planet (TOI-216c) is a gas giant on a nearly circular orbit. We carry out <jats:italic>N</jats:italic>-body simulations of planet migration in a protoplanetary gas disk to explain the orbital configuration of TOI-216 planets. We find that TOI-216b's migration must have been halted near its current orbital radius to allow for a convergent migration of the two planets into the resonance. For the inferred damping-to-migration timescale ratio <jats:italic>τ</jats:italic> <jats:sub> <jats:italic>e</jats:italic> </jats:sub>/<jats:italic>τ</jats:italic> <jats:sub> <jats:italic>a</jats:italic> </jats:sub> ≃ 0.02, overstable librations in the resonance lead to a limit cycle with <jats:italic>A</jats:italic> <jats:sub> <jats:italic>ψ</jats:italic> </jats:sub> ≃ 80° and <jats:italic>e</jats:italic> <jats:sub>b</jats:sub> &lt; 0.1. The system could have remained in this configuration for the greater part of the protoplanetary disk lifetime. If the gas disk was removed from inside out, this would have reduced the libration amplitude to <jats:italic>A</jats:italic> <jats:sub> <jats:italic>ψ</jats:italic> </jats:sub> ≃ 60° and boosted <jats:italic>e</jats:italic> <jats:sub>b</jats:sub> via the resonant interaction with TOI-216c. Our results suggest a relatively fast inner-disk removal (∼10<jats:sup>5</jats:sup> yr). Another means of explaining the large libration amplitude is stochastic stirring from a (turbulent) gas disk. For that to work, overstable librations would need to be suppressed, <jats:italic>τ</jats:italic> <jats:sub> <jats:italic>e</jats:italic> </jats:sub>/<jats:italic>τ</jats:italic> <jats:sub> <jats:italic>a</jats:italic> </jats:sub> ≃ 0.05, and very strong turbulent stirring (or some other source of large stochastic forcing) would need to overcome the damping effects of gas. Hydrodynamical simulations can be performed to test these models.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We investigate observable signatures of a first-order quantum chromodynamics (QCD) phase transition in the context of core-collapse supernovae. To this end, we conduct axially symmetric numerical relativity simulations with multi-energy neutrino transport, using a hadron–quark hybrid equation of state (EOS). We consider four nonrotating progenitor models, whose masses range from 9.6 to 70 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>. We find that the two less-massive progenitor stars (9.6 and 11.2 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>) show a successful explosion, which is driven by the neutrino heating. They do not undergo the QCD phase transition and leave behind a neutron star. As for the more massive progenitor stars (50 and 70 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>), the proto-neutron star (PNS) core enters the phase transition region and experiences the second collapse. Because of a sudden stiffening of the EOS entering to the pure quark matter regime, a strong shock wave is formed and blows off the PNS envelope in the 50 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> model. Consequently the remnant becomes a quark core surrounded by hadronic matter, leading to the formation of the hybrid star. However, for the 70 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> model, the shock wave cannot overcome the continuous mass accretion and it readily becomes a black hole. We find that the neutrino and gravitational wave (GW) signals from supernova explosions driven by the hadron–quark phase transition are detectable for the present generation of neutrino and GW detectors. Furthermore, the analysis of the GW detector response reveals unique kHz signatures, which will allow us to distinguish this class of supernova explosions from failed and neutrino-driven explosions.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We characterize protostellar multiplicity in<jats:fn id="apjac36d2fn2a"> <jats:label> <jats:sup>20</jats:sup> </jats:label> <jats:p> Current address: Niels Bohr Institute, University of Copenhagen, Øster Voldgade 5–7, DK-1350, Copenhagen K, Denmark.</jats:p> </jats:fn> the Orion molecular clouds using Atacama Large Millimeter/submillimeter Array 0.87 mm and Very Large Array 9 mm continuum surveys toward 328 protostars. These observations are sensitive to projected spatial separations as small as ∼20 au, and we consider source separations up to 10<jats:sup>4</jats:sup> au as potential companions. The overall multiplicity fraction (MF) and companion fraction (CF) for the Orion protostars are 0.30 ± 0.03 and 0.44 ± 0.03, respectively, considering separations from 20 to 10<jats:sup>4</jats:sup> au. The MFs and CFs are corrected for potential contamination by unassociated young stars using a probabilistic scheme based on the surface density of young stars around each protostar. The companion separation distribution as a whole is double peaked and inconsistent with the separation distribution of solar-type field stars, while the separation distribution of Flat Spectrum protostars is consistent solar-type field stars. The multiplicity statistics and companion separation distributions of the Perseus star-forming region are consistent with those of Orion. Based on the observed peaks in the Class 0 separations at ∼100 au and ∼10<jats:sup>3</jats:sup> au, we argue that multiples with separations &lt;500 au are likely produced by both disk fragmentation and turbulent fragmentation with migration, and those at ≳10<jats:sup>3</jats:sup> au result primarily from turbulent fragmentation. We also find that MFs/CFs may rise from Class 0 to Flat Spectrum protostars between 100 and 10<jats:sup>3</jats:sup> au in regions of high young stellar object density. This finding may be evidence for the migration of companions from &gt;10<jats:sup>3</jats:sup> au to &lt;10<jats:sup>3</jats:sup> au, and that some companions between 10<jats:sup>3</jats:sup> and 10<jats:sup>4</jats:sup> au must be (or become) unbound.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Using ground-based gravitational-wave detectors, we probe the mass function of intermediate-mass black holes (IMBHs) wherein we also include BHs in the upper mass gap at ∼60–130 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>. Employing the projected sensitivity of the upcoming LIGO and Virgo fourth observing run (O4), we perform Bayesian analysis on quasi-circular nonprecessing, spinning IMBH binaries (IMBHBs) with total masses 50–500 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, mass ratios 1.25, 4, and 10, and dimensionless spins up to 0.95, and estimate the precision with which the source-frame parameters can be measured. We find that, at 2<jats:italic>σ</jats:italic>, the mass of the heavier component of IMBHBs can be constrained with an uncertainty of ∼10%–40% at a signal-to-noise ratio of 20. Focusing on the stellar-mass gap with new tabulations of the <jats:sup>12</jats:sup>C(<jats:italic>α</jats:italic>, <jats:italic>γ</jats:italic>)<jats:sup>16</jats:sup>O reaction rate and its uncertainties, we evolve massive helium core stars using <jats:monospace>MESA</jats:monospace> to establish the lower and upper edges of the mass gap as ≃<jats:inline-formula> <jats:tex-math> <?CDATA ${59}_{-13}^{+34}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>59</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>13</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>34</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac3130ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> and ≃<jats:inline-formula> <jats:tex-math> <?CDATA ${139}_{-14}^{+30}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>139</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>14</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>30</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac3130ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> respectively, where the error bars give the mass range that follows from the ±3<jats:italic>σ</jats:italic> uncertainty in the <jats:sup>12</jats:sup>C(<jats:italic>α</jats:italic>, <jats:italic>γ</jats:italic>)<jats:sup>16</jats:sup>O nuclear reaction rate. We find that high resolution of the tabulated reaction rate and fine temporal resolution are necessary to resolve the peak of the BH mass spectrum. We then study IMBHBs with components lying in the mass gap and show that the O4 run will be able to robustly identify most such systems. Finally, we reanalyze GW190521 with a state-of-the-art aligned-spin waveform model, finding that the primary mass lies in the mass gap with 90% credibility.</jats:p>