arXiv subjects

Cheyanne Shariat

Publications and source records attributed to Cheyanne Shariat.

At least 19 recordsLinked to original sources

arXiv2026

Population demographics of post-interaction WDMS binaries: From common envelope evolution to stable mass transfer

Close white dwarf (WD) + main-sequence (MS) binaries are end products of mass transfer (MT) that occurred when the WD progenitor was a giant, making their population demographics a powerful probe of binary evolution. Several recent works have constructed samples of WD+MS binaries with well-understood selection functions using data from wide-field surveys. These include (a) au-scale astrometric binaries from Gaia that can be shown to contain a WD on dynamical grounds, (b) au-scale astrometric binaries in which a hot WD is detected through a GALEX UV excess, and (c) close binaries discovered through eclipses. Together, these samples probe outcomes of both stable MT and common-envelope evolution, and interactions on both the red giant branch (RGB) and asymptotic giant branch (AGB). We forward-model the three observed samples simultaneously. This approach produces robust constraints on uncertain binary evolution parameters because binaries removed from one population are predicted to appear in another. Our modeling includes a realistic initial binary population and treatments of the selection effects affecting all samples. We find that MT from AGB donors requires a critical accretor-to-donor mass ratio of $\sim0.4$ and is more stable than MT from RGB donors, for which we find a critical ratio of $\gtrsim0.65$. A common-envelope efficiency of $\alpha\lambda\sim0.3$ matches the relative numbers of close and wide systems and the period distribution of close systems. Most stable-MT products in the sample, including those with RGB donors, retain nonzero eccentricities ($\simeq0.1$). The model does not fully reproduce the mass distribution of main-sequence stars in post-common-envelope binaries, which exhibits a cliff well below the fully convective limit, pointing to missing physics that should be explored in future work.

astro-ph.SR↗

arXiv2026

Probing the IMF in the Early Universe -- Direct measurements in the Bo\"otes I UFD with JWST/NIRCam

The dependence of the stellar initial mass function (IMF) on star-formation environment, particularly at low metallicities and high redshifts, remains poorly constrained. Ultra-faint dwarf galaxies (UFDs) are local fossils of high-redshift galaxies hosting old, metal-poor populations, and their resolved stellar populations provide unique pathways to constrain the sub-solar IMF. We investigate the low-mass IMF in the Bo{\"o}tes I (Boo I) UFD with JWST/NIRCam, leveraging its capability to resolve over 10,000 stars reaching $\lesssim$0.15\msun, obtaining one of the largest, deepest resolved stellar samples for UFDs. We explore three different functional forms of the IMF with machine learning and statistical techniques, combining forward modeling of synthetic color-magnitude diagrams with simulation-based inference. We find that a single power-law IMF provides a poorer description of the observed luminosity function and yields a slope inconsistent with the canonical Salpeter IMF. Our best-fit broken power-law and lognormal IMF parameters are consistent with the Milky Way within 68\% confidence level, providing evidence that star formation at metallicities as low as $\mathrm{[Fe/H]}\approx-2.4$ follows a similar IMF as in the Milky Way. By treating Boo I as a local relic analogous to a high-redshift galaxy with a stellar mass of $\lesssim10^5\msun$ at $z\gtrsim6$, our results provide evidence for the universality of the IMF across both local and high-redshift environments.

astro-ph.GA↗

arXiv2026

OverCite: Add citations in LaTeX without leaving the editor

Adding citations while drafting in LaTeX often requires leaving the editor, searching for a paper in mind, copying its BibTeX entry into the project bibliography, renaming the cite key, and then returning to the sentence. \texttt{OverCite} is an open-source, lightweight tool that lets authors find, select, and insert citations without leaving the writing environment. In Overleaf, \texttt{OverCite} uses rough citation placeholders (e.g., $\texttt{\textbackslash citep\{Perlmutter1999\}}$) and local sentence context to query ADS/SciX-indexed literature, rank likely matches, and insert the selected reference, without leaving the editor. A companion \texttt{VS Code} extension provides the same functionality for local LaTeX projects. The ADS/SciX database includes astronomy, physics, computer science, mathematics, biology, and \emph{all} indexed arXiv e-prints, making \texttt{OverCite} useful across a broad range of scientific disciplines.

cs.DL↗

arXiv2026

Gaia astrometry disfavors a binary origin for long secondary periods

Approximately one-third of luminous pulsating red giant stars exhibit long secondary periods (LSPs): stable photometric variability with periods of several months to years in addition to their much shorter primary pulsation cycles. Now nearly a century after their discovery, the physical origin of LSPs remains unresolved. A leading explanation invokes binarity, in which the LSP corresponds to the orbital period of a low-mass companion responsible for both the photometric variability and the radial-velocity (RV) modulation. We test this hypothesis using a nearby sample of LSP stars from the {\it Gaia} Focused Product Release, which provides multi-epoch RVs and contemporaneous optical photometry. We find that interpreting the observed RV variability as orbital motion implies companion masses narrowly distributed around $M_2 \approx 0.1~{\rm M_\odot}$ with separations of 1--3 au, placing them squarely in the brown dwarf desert observed around their solar-type progenitors. Assuming such companions exist, we then forward-model the astrometric signature expected in {\it Gaia} DR3 and predict systematically elevated {\tt RUWE} values for nearby LSPs. In contrast, the observed {\tt RUWE} of nearby LSP stars is systematically lower than these predictions and consistent with most systems exhibiting LSPs being single. This discrepancy disfavors low-mass stellar or substellar companions as the dominant origin of LSPs in evolved stars, motivating a further exploration of alternative stellar mechanisms.

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arXiv2026

Thermally inflated accretors in post-mass transfer binaries: Abell 35 and its class revisited

A small but growing class of binaries containing hot ($T_{\rm eff}\sim10^5\ {\rm K}$) white dwarfs (WDs) and rapidly rotating, apparently subgiant companions -- including the prototype, Abell 35 -- show companions that are too large and luminous to be ordinary main-sequence stars yet too numerous to be explained as finely tuned near-twin binaries. We argue that these stars are instead main-sequence accretors temporarily inflated out of thermal equilibrium by recent mass transfer. For the subgiant of Abell 35, a new Gaia DR3 astrometric orbit ($P_{\rm orb}=790\ {\rm d}$), combined with updated photometric and spectroscopic constraints, yields $T_{\rm eff}\approx4925\pm75\ {\rm K}$, $R\approx3\pm0.05\ R_{\odot}$, near-solar metallicity, and rapid rotation aligned with the orbit ($v_{\rm rot}\approx195\pm3\ {\rm km\ s^{-1}}$), indicating substantial recent accretion and spin-up. Dynamical mass limits disfavor a coeval twin-binary origin, supporting the inflated-accretor interpretation. We test this scenario using self-consistent MESA binary evolution calculations with a new accretion prescription in which accreted material retains a fraction of its infall energy, rather than adopting the default assumption that its entropy equals that of the accretor's surface. The accretor expands to giant-like radii when $\dot{M}$ is high yet remains within its Roche lobe, allowing stable mass transfer even for mass ratios traditionally considered unstable. After mass transfer ceases, the star contracts on Myr timescales through a bloated, rapidly rotating phase whose temperatures, radii, and spins match those observed in Abell 35-type systems. This framework naturally explains the population and unifies Abell 35-type binaries with post-AGB binaries, blue lurkers, and wide WD+main-sequence systems as successive stages of the same post-mass-transfer evolutionary pathway.

astro-ph.SR↗

arXiv2026

A global view of post-interaction white dwarf-main sequence binaries

Common-envelope evolution (CEE) is among the most uncertain phases in binary evolution. To empirically constrain CEE, we construct a uniformly selected sample of eclipsing post--common-envelope binaries (PCEBs). Starting from an unresolved white dwarf-main-sequence (WDMS) candidate sample within 200 pc selected from the Gaia color-magnitude diagram, we identify 39 detached eclipsing WDMS binaries using ZTF light curves. The binaries contain cool M dwarfs orbiting warm white dwarfs with orbital periods ($P_{\rm orb}$) of 0.1-2 d. The sample's simple selection function allows us to model observational incompleteness and infer intrinsic properties of the PCEB population. We find an orbital-period distribution consistent with being log-uniform over 0.1-2 d, contrary to recent reports of a bimodal distribution. The companion-mass distribution peaks around $0.25~{\rm M_\odot}$ and declines steeply toward larger masses. The estimated local space density is $7.2\times10^{-5}~{\rm pc^{-3}}$, corresponding to a Galaxy-wide birth rate of 0.01 per year. Combining our results with recent Gaia-based constraints on wider WDMS binaries, we construct an empirical period distribution of post-interaction WDMS binaries spanning 0.1-1000 d. The emerging period distribution is roughly log-flat (d$N/{\rm d}\log P_{\rm orb}\propto P_{\rm orb}^0$) at $P_{\rm orb} < 2$ d and log-increasing (d$N/{\rm d}\log P_{\rm orb}\propto P_{\rm orb}^1$) at $P_{\rm orb} = 100-1000$ d. The 10-100 d regime remains poorly constrained, but a few nearby systems suggest it is also well-populated. Short-period PCEBs ($P_{\rm orb}<2$ d) with M dwarf companions are roughly 2-3 times more common than wide ($P_{\rm orb} = 100-1000$ d) WDMS binaries with FGK companions, which likely formed through stable mass transfer. These results provide direct observational constraints on CEE and an empirical benchmark for binary-population models.

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arXiv2025

Fast Radio Bursts from White Dwarf Binary Mergers: Isolated and Triple-Induced Channels

The detection of fast radio bursts (FRBs) in both young and old stellar populations suggests multiple formation pathways, beyond just young magnetars from core-collapse supernovae. A promising delayed channel involves the formation of FRB-emitting neutron stars through merger- or accretion-induced collapse of a massive white dwarf (WD). By simulating a realistic stellar population with both binaries and triples, we identify pathways to WD collapse that could produce FRB candidates. We find that (i) triple dynamics open new merger channels inaccessible to isolated binaries, significantly enhancing the overall merger rate; (ii) triple-induced mergers broaden the delay-time distribution, producing long-delay ($\gtrsim1$-8~Gyr) events largely independent of metallicity, alongside a shorter-delay population ($\lesssim100$~Myr) of rapid mergers; (iii) these long delays naturally yield FRBs in older environments such as quiescent host galaxies and galactic halos; (iv) when convolved with the cosmic star-formation history, binary channels track the star-formation rate ($z_{\rm peak} \sim 2$), while triple channels peak later ($z_{\rm peak} \sim 1$), giving a combined local source rate of $R_0 \approx 2\times10^4~{\rm Gpc^{-3}~yr^{-1}}$, consistent with observations; and (v) applying the same framework to Type~Ia supernovae, we find that triples extend the delay-time tail and roughly double the Ia efficiency relative to binaries, yielding rates and redshift evolution in good agreement with observations. If FRBs originate from the collapse of WDs, our results establish triples, alongside binaries, as a crucial and previously overlooked formation pathway whose predicted rates, host demographics, and redshift evolution offer clear tests for upcoming surveys.

astro-ph.HE↗

arXiv2025

How precisely can we measure the ages of subgiant and giant stars?

Precise stellar ages are fundamental to Galactic archaeology. However, obtaining reliable age estimates and uncertainties for field stars has been a long-standing challenge. We test the fidelity of ages from recent catalogs of giants and subgiants using wide binaries, whose components formed at the same time and thus should have consistent inferred ages. We find that subgiant ages based on spectroscopic metallicities from Xiang & Rix (2022) are generally consistent within their reported uncertainties, implying that fractional uncertainties of 5-10% are realistically achievable. In contrast, we find that published photometric subgiant ages underestimate true uncertainties by factors of 2-3. Spectroscopic age estimates for red giant and red clump stars also show reliable uncertainties, but are generally less precise (25-30%). These results demonstrate that accurate chemical abundance measurements are essential for precise subgiant ages and establish wide binaries as a powerful, model-independent benchmark for calibrating stellar age measurements in the era of large spectroscopic surveys.

astro-ph.SR↗

arXiv2025

Possible Dynamical Pathways to the Misalignment of the VHS 1256-1257 System

Circumbinary planets (CBPs) provide a unique window into planet formation and dynamical evolution in complex gravitational environments. Their orbits are shaped not only by the protoplanetary disk but also by the perturbations from two stellar hosts, making them sensitive probes of both early- and late-stage dynamical processes. In this work, we investigate the unusual architecture of the VHS J125601.92-125723.9 system, where a retrograde, nearly polar tertiary orbits an extremely low-mass substellar binary in a hierarchical triple configuration. We find that triple body dynamics can naturally reproduce the observed high eccentricity of the inner binary and the tertiary's near-polar obliquity. However, this configuration alone cannot account for the observed mutual inclination, which is both near-polar and retrograde. This tension suggests two possible formation pathways: either the planet formed in an aligned, protoplanetary disk-like configuration and was later tilted by an additional, undetected fourth companion (below current Gaia limits), or the system formed close to its current state. Stellar flybys, in contrast, are unlikely due to their long timescales. Our results highlight both the explanatory power and the limitations of triple dynamics, and the potential role of hidden companions in shaping extreme planetary architectures.

astro-ph.SR↗

arXiv2025

Wide binaries in an ultra-faint dwarf galaxy: discovery, population modeling, and a nail in the coffin of primordial black hole dark matter

We report the discovery and characterization of a wide binary population in the ultrafaint dwarf galaxy Bo\"{o}tes I using deep JWST/NIRCam imaging. Our sample consists of 52 candidate binaries with projected separations of 7,000 - 16,000 au and stellar masses from near the hydrogen-burning limit to the main-sequence turnoff ($\sim0.1$ - $0.8~{\rm M_\odot}$). By forward-modeling selection biases and chance alignments, we find that $1.25\pm0.25\%$ of Bo\"{o}tes I stars are members of wide binaries with separations beyond 5,000 au. This fraction, along with the distributions of separations and mass ratios, matches that in the Solar neighborhood, suggesting that wide binary formation is largely insensitive to metallicity, even down to [Fe/H] $\approx -2.5$. The observed truncation in the separation distribution near 16,000 au is well explained by stellar flyby disruptions. We also discuss how the binaries can be used to constrain the galaxy's dark matter properties. We show that our detection places new limits on primordial black hole dark matter, finding that compact objects with $M \gtrsim 5~{\rm M_\odot}$ cannot constitute more than $\sim1\%$ of the dark matter content. In contrast to previous work, we find that wide binaries are unlikely to provide robust constraints on the dark matter profile of ultrafaint galaxies given the uncertainties in the initial binary population, flyby disruptions, and contamination from chance alignments. These findings represent the most robust detection of wide binaries in an external galaxy to date, opening a new avenue for studying binary star formation and survival in extreme environments.

astro-ph.GA↗

arXiv2025

From Wide Triples to UCXBs: Multimessenger Signatures of Dynamically-formed Black Hole-White Dwarf Systems in the LISA Band

Ultracompact X-ray binaries (UCXBs) are a subclass of low-mass X-ray binaries characterized by tight orbits and degenerate donors, which pose significant challenges to our understanding of their formation. Recent discoveries of black hole (BH) candidates with main-sequence (MS) or red giant (RG) companions suggest that BH-white dwarf (BH-WD) binaries are common in the Galactic field. Motivated by these observations and the fact that most massive stars are born in triples, we show that wide BH-WD systems can naturally form UCXBs through the eccentric Kozai-Lidov (EKL) mechanism. Notably, EKL-driven eccentricity excitations combined with gravitational wave (GW) emission and WD dynamical tides can effectively shrink and circularize the orbit, leading to mass-transferring BH-WD binaries. These systems represent promising multimessenger sources in both X-ray and GW observations. Specifically, we predict that the wide triple channel can produce $\sim3-27$ ($\sim1-5$) detectable UCXBs in the Milky Way (Andromeda galaxy), including $\sim1$ system observable by the mHz GW detection of LISA. If the final WD mass can reach sufficiently small values, this channel could contribute up to $\sim 10^3$ UCXBs in the Galaxy. Furthermore, the identification of tertiary companions in observed UCXBs would provide direct evidence for this formation pathway and yield unique insights into their dynamical origins.

astro-ph.HE↗

arXiv2025

10,000 Resolved Triples from Gaia: Empirical Constraints on Triple Star Populations

We present a catalog of $\sim 10,000$ resolved triple star systems within 500 pc of the Sun, constructed using Gaia data. The triples include main-sequence, red giant, and white dwarf components spanning separations of 10 to 50,000 au. A well-characterized selection function allows us to constrain intrinsic demographics of the triple star population. We find that (a) all systems are compatible with being hierarchical and dynamically stable; (b) mutual orbital inclinations are isotropic for wide triples but show modest alignment as the systems become more compact; (c) primary masses follow a Kroupa initial mass function weighted by the triple fraction; (d) inner binary orbital periods, eccentricities, and mass ratios mirror those of isolated binaries, including a pronounced twin excess (mass ratios greater than 0.95) out to separations of 1000+ au, suggesting a common formation pathway; (e) tertiary mass ratios follow a power-law distribution with slope $-1.4$; (f) tertiary orbits are consistent with a log-normal period distribution and thermal eccentricities, subject to dynamical stability. Informed by these observations, we develop a publicly available prescription for generating mock triple star populations. Finally, we estimate the catalog's completeness and infer the intrinsic triple fraction, which rises steadily with primary mass: from $5\%$ at $\lesssim 0.5\,{\rm M_\odot}$ to $35\%$ at $2\,{\rm M_\odot}$. The public catalog provides a robust testbed for models of triple star formation and evolution.

astro-ph.SR↗

arXiv2025

Cataclysmic Variables in Triples: Formation Models and New Discoveries

The formation of cataclysmic variables (CVs) has long been modeled as a product of common envelope evolution (CEE) in isolated binaries. However, a significant fraction of intermediate-mass stars -- the progenitors of the white dwarfs (WDs) in CVs -- are in triples. We therefore investigate the importance of triple star dynamics in CV formation. Using Gaia astrometry and existing CV catalogs, we construct a sample of $\sim50$ CVs in hierarchical triples within 1 kpc of the Sun, containing main-sequence (MS) and WD tertiaries at separations of 100 - 30,000 au. We infer that at least 10% of CVs host wide tertiaries. To interpret this discovery, we evolve a population of 2000 triples using detailed three-body simulations, 47 of which become CVs. We predict that 20% of CVs in triples form without ever experiencing CEE, where the WD and donor are brought together by the eccentric Kozai-Lidov (EKL) mechanism after the formation of the WD. These systems favor larger donor stars and longer birth orbital periods (8-20 hrs) than typical CVs. Among systems that do undergo CEE, about half would not have interacted without the presence of the tertiary. Triple formation channels both with and without CEE require initially wide inner orbits ($\gtrsim 1$ au), which in turn require larger tertiary separations to be stable. Consistent with this prediction, we find that the observed Gaia CV triples have wider separations on average than normal wide binaries selected in the same way. Our work underscores the importance of triples in shaping interacting binary populations including CVs, ultracompact binaries, and low-mass X-ray binaries.

astro-ph.SR↗

arXiv2024

Triple Evolution Pathways to Black Hole Low-Mass X-ray Binaries: Insights from V404 Cygni

A recent discovery shows that V404 Cygni, a prototypical black hole low-mass X-ray binary (BH-LMXB) is a hierarchical triple: the BH and donor star are orbited by a $1.2$ M$_{\odot}$ tertiary at a distance of at least $3500$ au. Motivated by this system, we evolve a grid of $\sim50,000$ triple star systems, spanning a broad range of initial orbits. Our calculations employ {\tt MESA} stellar evolution models, using {\tt POSYDON}, and self-consistently track the effects of eccentric Kozai-Lidov (EKL) oscillations, mass loss, tides, and BH natal kicks. In our simulations, the progenitors of V404 Cygni-like systems have initial outer separations of $1000 - 10000$ au and inner separations of $\sim100$ au, such that they avoid Roche lobe overflow most of the time. Later on, EKL oscillations drive the inner binary to high eccentricities until tides shrink the orbit and mass transfer begins. Notably, such systems only form in simulations with very weak black hole natal kicks ($\lesssim 5\,{\rm km\,s^{-1}}$) because stronger kicks unbind the tertiaries. Our simulations also predict a population of BH-LMXB triples that form via the classical common-envelope channel, when the BH progenitor does overflow its Roche lobe. The formation rate for this channel is also higher in triples than in isolated binaries because early EKL oscillations cause inner binaries with a wider range of initial separations to enter and survive a common envelope. Our calculations demonstrate that at least some stellar BHs form with extremely weak kicks, and that triple evolution is a significant formation channel for BH-LMXBs.

astro-ph.SR↗

arXiv2024

Two Novel Hot Jupiter Formation Pathways: How White Dwarf Kicks Shape the Hot Jupiter Population

The origin of Hot Jupiters (HJs) is disputed between a variety of in situ and ex situ formation scenarios. One of the early proposed ex situ scenarios was the Eccentric Kozai-Lidov (EKL) mechanism combined with tidal circularization, which can produce HJs with the aid of a stellar or planetary companion. However, observations have revealed a lack of stellar companions to HJs, which challenges the importance of the binary star-driven EKL plus tides scenario. In this work, we explore so far unaccounted-for stellar evolution effects on HJ formation, in particular the effect of white dwarf (WD) formation. Gaia observations have revealed that WDs often undergo a kick during formation, which can alter a binary's orbital configuration or even unbind it. Based on this WD kick, in this letter we propose and explore two novel HJ formation pathways: 1) HJs that are presently orbiting single stars, but were initially formed in a binary that was later unbound by a WD kick; 2) Binaries that survive the WD kick can trigger enhanced EKL oscillations and lead to 2nd generation HJ formation. We demonstrate that the majority of seemingly single HJs could have formed in binary star systems. As such, HJ formation in binaries via the EKL mechanism could be one of the dominant HJ formation pathways, and our results highlight that unaccounted-for stellar evolution effects, like WD formation, can obscure the actual origin of observed exoplanet populations.

astro-ph.EP↗

arXiv2024

Once a Triple, Not Always a Triple: The Evolution of Hierarchical Triples that Yield Merged Inner Binaries

More than half of all main-sequence (MS) stars have one or more companions, and many of those with initial masses <8 M$_\odot$ are born in hierarchical triples. These systems feature two stars in a close orbit (the inner binary) while a tertiary star orbits them on a wider orbit (the outer binary). In hierarchical triples, three-body dynamics combined with stellar evolution drives interactions and, in many cases, merges the inner binary entirely to create a renovated `Post-Merger Binary' (PMB). By leveraging dynamical simulations and tracking binary interactions, we explore the outcomes of merged triples and investigate whether PMBs preserve signatures of their three-body history. Our findings indicate that in 26-54% of wide double WD binaries (s>100 au), the more massive white dwarf (WD) is a merger product, implying that these DWD binaries were previously triples. Overall, we estimate that $44\pm14\%$ of observed wide DWDs originated in triple star systems and thereby have rich dynamical histories. Additionally, our results suggest that the separations of inner and outer binaries are uncorrelated at birth, providing insights into stellar formation processes. We also examine MS+MS and MS+Red Giant mergers manifesting as Blue Straggler stars (BSSs). These PMBs have orbital configurations and ages similar to most observed BSS binaries. While the triple+merger formation channel can explain the observed chemical abundances, moderate eccentricities, and companion masses in BSS binaries, it likely only accounts for $\sim$20-25% of BSSs. Meanwhile, we predict that the majority of observed single BSSs formed as collisions in triples and harbor long-period (>10 yr) companions. Furthermore, both BSS binaries and DWDs exhibit signatures of WD birth kicks.

astro-ph.SR↗

arXiv2024

Predicting the Dominant Formation Mechanism of Multi-Planetary Systems

Most, if not all, sun-like stars host one or more planets, making multi-planetary systems commonplace in our galaxy. We utilize hundreds of multi-planet simulations to explore the origin of such systems, focusing on their orbital architecture. The first set of simulations assumes in-situ assembly of planetary embryos, while the second explores planetary migration. After applying observational biases to the simulations, we compare them to 250+ observed multi-planetary systems, including 13 systems with planets in the habitable zone. For all of the systems, we calculate two of the so-called statistical measures: the mass concentration ($S_{c}$) and orbital spacing ($S_{s}$). After analytic and empirical analyses, we find that the measures are related to first-order with a power law: $S_{c} \sim S_{s}^\beta$. The in-situ systems exhibit steeper power-law relations relative to the migration systems. We show that different formation scenarios cover different regions in the $S_{s} - S_{c}$ diagram with some overlap. Furthermore, we discover that observed systems with $S_{s} < 30$ are likely dominated by the migration scenario, while those with $S_{s} \geq 30$ are likely dominated by the in-situ scenario. We apply these criteria to determine that a majority (62%) of observed multi-planetary systems formed via migration, whereas most systems with currently observed habitable planets formed via in-situ assembly. This work provides methods of leveraging the statistical measures ($S_{s}$ and $S_{c}$) to disentangle the formation history of observed multi-planetary systems based on their present-day architectures.

astro-ph.EP↗

arXiv2023

Dynamical Evolution of White Dwarfs in Triples in the Era of Gaia

The $Gaia$ mission has detected many white dwarfs (WDs) in binary and triple configurations, and while observations suggest that triple stellar systems are common in our Galaxy, not much attention was devoted to WDs in triples. For stability reasons, these triples must have hierarchical configurations, i.e., two stars are on a tight orbit (the inner binary), with the third companion on a wider orbit about the inner binary. In such a system, the two orbits torque each other via the eccentric Kozai-Lidov mechanism (EKL), which can alter the orbital configuration of the inner binary. We simulate thousands of triple stellar systems for over $10$ Gyr, tracking gravitational interactions, tides, general relativity, and stellar evolution up to their WD fate. As demonstrated here, three-body dynamics coupled with stellar evolution is a critical channel to form tight WD binaries or merge a WD binary. Amongst these triples, we explore their manifestations as cataclysmic variables, Type Ia supernovae, and gravitational-wave events. The simulated systems are then compared to a sample of WD triples selected from the $Gaia$ catalog. We find that including the effect of mass loss-induced kicks is crucial for producing a distribution of the inner binary-tertiary separations that is consistent with $Gaia$ observations. Lastly, we leverage this consistency to estimate that, at minimum, $30\%$ of solar-type stars in the local $200$ parsecs were born in triples.

astro-ph.SR↗