arXiv subjects

Pier-Emmanuel Tremblay

Publications and source records attributed to Pier-Emmanuel Tremblay.

At least 19 recordsLinked to original sources

arXiv2026

Kilogauss magnetic fields from simulations of small-scale dynamo action in the convective envelope of a white dwarf

About 20% of white dwarfs are observed to host large-scale magnetic fields, but the origin of white dwarf magnetism remains uncertain. Small-scale turbulent dynamos (SSDs), which efficiently generate magnetic fields in solar and stellar convection simulations, have so far been studied in white dwarfs only through equipartition arguments in one-dimensional models. We therefore investigate whether turbulent convection in white dwarf surface layers can sustain SSD action through local three-dimensional radiation-magnetohydrodynamics simulations of a DA white dwarf with a convective pure-hydrogen atmosphere, including the full convection zone together with the underlying overshoot and stably stratified layers. Starting from a weak seed field of 1 mG, the magnetic energy undergoes exponential amplification before saturating at a magnetic-to-kinetic energy density ratio of about 5.5% at the visible surface, demonstrating that SSD action naturally generates kG-strength magnetic fields in convective white dwarf atmospheres. The resulting magnetic field is characterised by a mixed-polarity small-scale structure, with kG field concentrations contributing about 14% of the total unsigned magnetic flux at the visible surface. Despite a rate of magnetic energy generation amounting to roughly one-seventh of the bolometric flux, no significant modification of the mean stratification is found. Although these fields remain spatially unresolved for observations, they may contribute to spectral line broadening, suggesting that small-scale magnetism in white dwarfs could be more widespread than currently inferred from observations.

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arXiv2026

Investigating the Observational Progenitor Mass Gap in the White Dwarf Initial-Final Mass Relation. I. Cluster Census and Characterization of the First White Dwarfs in the Gap

In recent years, Gaia has been the primary driver of the expansion of the white dwarf (WD) initial-final mass relation (IFMR) in open clusters. The increased sample size has highlighted a pronounced observational gap at progenitor masses of $\simeq2$--$2.7\,M_\odot$, with no spectroscopically confirmed cluster-member WDs in this range. Analysis of the Milky Way open cluster census shows that this absence is primarily driven by the scarcity of appropriately aged, nearby clusters capable of hosting Gaia-detectable WDs, implying that deeper, targeted photometry will be required to build a substantial sample in this progenitor mass range. We further searched for previously unexamined Gaia WD candidates in clusters with ages consistent with producing gap progenitors and identified two viable targets, which we observed spectroscopically with Gemini GMOS-N. Both targets yield inferred progenitor masses within the observational gap, making them the first spectroscopically confirmed cluster-member WDs in this progenitor mass range. The NGC 6991 candidate, in particular, is confirmed as a DA WD with an inferred progenitor mass of $2.12^{+0.04}_{-0.15}\,M_\odot$, providing further support for a non-monotonic trend in the IFMR.

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arXiv2026

A Framework for Linking Pre- and Post-Common Envelope Binary Properties with Star Clusters: The First Demonstration with a Massive White Dwarf+M Dwarf Binary in Alessi 12

Common envelope (CE) evolution is a critical phase in the lives of binary stars, producing close binaries that are progenitors of type Ia supernovae and gravitational wave sources. Despite its importance, CE evolution remains poorly understood, largely due to the scarcity of systems with constrained pre- and post-CE properties. Here, we present a star cluster-based framework for reconstructing the evolutionary histories of white dwarf+main-sequence (WD+MS) post-CE binaries, where cluster membership can provide an independent age constraint and/or rule out a merger origin for the WD. We demonstrate this method with Alessi12-PCE, the first such binary in an open cluster with precisely determined pre- and post-CE properties. We classify the companion as an M4V and measure a WD mass of $1.06 \pm 0.02 M_{\odot}$, making it the most massive WD+MS binary associated with a cluster. A 6.99-hour periodicity detected in a light curve is confirmed as the binary orbital period via radial velocity monitoring. Combined with the WD mass, WD cooling age, and Alessi 12 cluster age, stellar evolution models imply a $5.40 \pm 0.10 M_{\odot}$ WD progenitor that entered a CE on the asymptotic giant branch (AGB). CE evolution models where convection is the dominant physical mechanism that sets $\alpha_{\text{CE}}$ reproduce the observed orbital separation in exactly two scenarios: either a mid-AGB interaction with $\alpha_{\text{CE}}\approx0.99$, or a late-AGB interaction with $\alpha_{\text{CE}}\approx0.05$. Applicable to other post-CE binaries in star clusters, our new framework enables empirical constraints on CE physics inaccessible from field binaries alone.

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arXiv2026

Direct detections of white dwarfs in four WD+dM post-common envelope binaries within 20 pc

Characterising post-common envelope binaries (PCEBs) containing a white dwarf and a main-sequence companion is essential for improving theories of binary evolution. This paper presents the first direct spectroscopic confirmations of the white dwarf components in four PCEB systems within 20 pc of the Sun: G 203-47, GJ 207.1, LHS 1817, and Wolf 1130. To detect the white dwarfs we obtained near-UV spectroscopy from STIS on the Hubble Space Telescope, fitting with white dwarf models and M dwarf proxy spectra. We provide estimates of the white dwarf effective temperatures, which range from approximately 5300 K to 6300 K. We compare these parameters to those determined from modelling with photometry alone, and find a 5 - 8 per cent discrepancy, due to emission features. Notably, 27 years after its initial detection, we confirm the presence of a white dwarf in G 203-47, which is the ninth closest white dwarf to the Sun. Using Swift XRT data, we find that despite the 14.9-day orbital period of G 203-47, it is not tidally locked, possessing a rotation period likely exceeding 100 days, and making it a rare example of a long-period PCEB formed via a brief common envelope interaction. We update the local white dwarf space density to (5.2 $\pm $0.4) $\times$ 10$^{-3}$ pc$^{-3}$, and compare our results to models from the Binary Populations and Spectral Synthesis (BPASS) framework, finding a good agreement with the predicted and observed numbers of PCEBs within 20 pc.

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arXiv2026

Physics of Eclipsing Binaries. VI. Hot, compact stars

Models of eclipsing binaries require the assignment of appropriate emergent intensities to the surface elements of the binary components. For distance-dependent modelling of flux-calibrated light curves, this necessitates an approximation of the absolute normal intensities of both components of the binary, as well as how their brightness varies across the stellar disks (limb darkening). Such surface intensities are often inferred from other physical properties of the synthetic binary (effective temperature, surface gravity, etc.) through the use of model atmospheres, which in turn are generally suited to a particular range of stellar types or parameters. Here, we present the major developments included in the PHOEBE 2.5 release (publicly available from http://phoebe-project.org), which improve the fidelity of model binaries comprising hot, compact stars. These developments include the incorporation model atmospheres produced using the Tubingen Model Atmosphere Package (TMAP) and Montreal/Tremblay codes (complementing the already incorporated PHOENIX and Castelli & Kurucz models, primarily suited to main sequences stars and low-temperature giants). Similarly, PHOEBE v2.5 now allows for blending/extrapolation of model atmospheres, meaning one can continue to make use of model atmospheres in cases when a small number of surface elements have parameters outside the model atmosphere grid. As an added value product, we also present tables of limb-darkening coefficients derived from the newly incorporated model atmospheres, such that they can be used as inputs in other binary modelling codes.

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arXiv2026

White dwarfs within 13 pc: insights from ultraviolet spectroscopy

We present a comprehensive multi-wavelength spectroscopic and photometric analysis of the 44 confirmed white dwarfs within 13 pc of the Sun. Combining flux-calibrated ultraviolet spectroscopy from the Hubble Space Telescope (STIS and COS) with ground-based optical spectroscopy, as well as photometry from Gaia, 2MASS, and WISE, we employ a combined fitting method to calculate atmospheric parameters. Each white dwarf is fitted with a bespoke model depending on its detailed atmospheric composition. Two strongly magnetic stars could not be fitted due to the complex splitting of their spectral lines. We find a systematic discrepancy in hydrogen-atmosphere white dwarfs with effective temperatures below 10,000K, where fits incorporating ultraviolet spectra result in effective temperatures that are 1 - 5 per cent higher than those derived from optical and infrared photometry alone. We re-classify three helium-atmosphere white dwarfs as metal enriched following a magnesium detection in their near-ultraviolet spectra: WD 0435-088, WD 1132-325 and WD 1917+386. In total, we identify five stars in the sample for which metals are only detected in the ultraviolet. Overall, we find that 30 per cent of the 13 pc white dwarfs show spectroscopic evidence of evolved planetary systems. Our analysis reveals no measurable difference between the hydrogen content of DQ and DC white dwarfs, although the upper limits of carbon in DCs are significantly below that of the DQ population. We find a multiplicity fraction of 33 per cent for the 13 pc white dwarfs.

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arXiv2026

White dwarf planetary systems in the ultraviolet

Almost every known planet host will evolve into a white dwarf, and the surviving planetary material will continue to orbit this stellar remnant. Asteroids perturbed onto star-grazing orbits will become disrupted, forming an accretion disk which causes "enrichment" of the otherwise pure hydrogen or helium atmosphere. Measurements of these photospheric abundances give detailed insights into the interior compositions of exo-planetesimals with an accuracy not possible for intact exoplanets around main sequence stars. This method has revealed the diversity of rocky material in our solar neighborhood, including primitive, chondritic planetesimals, fragments of planetary cores, and even analogues of Kuiper belt objects. The planetesimal abundances can be used as an input to interior structure models. The far-ultraviolet is a key wavelength range for this field because it contains strong transitions for almost every element of interest, many of which are undetectable using ground-based optical spectroscopy. Without the FUV, we will no longer have access to the C, N, P, S content of exoplanetary bodies and thus will no longer be able to probe how volatiles interact with refractories, which is crucial to understanding planet formation-and even the origin of life. The medium resolution and high sensitivity of COS on HST has been indispensable in determining the compositions of dozens of exo-planetesimals. However, the only two medium resolution FUV-capable spectrographs are currently onboard HST, with no plans for replacements until the 2040s. An extension to the HST mission is critical for the field of white dwarf planetary systems, because the loss of FUV capability would leave us blind to volatiles. Boosting the orbit of HST would allow us to measure volatile abundances, determine the rocky planetary occurrence rate, investigate differentiation, and probe for photospheric abundance variability.

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arXiv2026

Detection of a weak magnetic field in the Balmer emission line white dwarf WDJ1653-1001

The small DAHe and DAe spectral classes comprise isolated, hydrogen-dominated atmosphere white dwarfs that exhibit variable photometric flux and Balmer line emission. These mysterious systems offer unique insight into the complex interplay between magnetic fields, stellar rotation and atmospheric activity in single white dwarfs. DAHe stars have detectable magnetic fields through Zeeman-split spectral lines, whereas DAe stars lack such splitting. We report the first discovery and characterisation of magnetism in the DAe white dwarf WDJ165335.21-100116.33 with new time-resolved spectropolarimetry from FORS2. We detect a weak but variable longitudinal magnetic field with values $\langle B_z \rangle > -9.2 \pm 2.4$ kG and $\langle B_z \rangle < -2.2 \pm 1.0$ kG. Independent ZTF and ATLAS photometry reveal a consistent period of P = 80.3070 $\pm$ 0.0007 h. Time-resolved optical spectroscopy obtained with six ground-based instruments demonstrates strong modulation in the strength of the H$\alpha$ and H$\beta$ Balmer line emission with P = 80.2922 $\pm$ 0.0108 h. The photometric flux and Balmer emission strength vary in antiphase, with the strongest magnetic detections coinciding with phases of low photometric flux and strong line emission. These characteristics support the theory that a magnetically active, temperature-inverted spot/region is producing an optically thin chromospheric emission region. Comparison with other DAe and DAHe white dwarfs reveals all systems have a strikingly similar antiphase phenomenology, reinforcing the theory that they are subject to a unified physical mechanism. With the detection of a weak magnetic field, we reclassify WDJ165335.21-100116.33 as a low-field DAHe white dwarf.

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arXiv2026

Classifying white dwarfs from multi-object spectroscopy surveys with machine learning

With tens to hundreds of spectra of white dwarfs being taken each night from multi-object spectroscopic surveys, automated spectral classification is essential as part of efficient data processing. In this study, we design a neural network to classify the spectral type of white dwarfs using a combination of spectra from the Dark Energy Spectroscopic Instrument (DESI) data release~1 and imaging from Pan-STARRS photometry. The trained network has a near 100% accuracy at identifying DA and DB white dwarf spectral types, while having an 85-95% accuracy for identifying all other primary types, including metal pollution. Distinct spectral or photometric features map into separate structures when performing a Uniform Manifold Approximation and Projection (UMAP) dimensionality reduction. Investigating further and looking at multiple epoch spectra, we performed a separate search for objects that have strongly changing spectral signatures using UMAP, discovering 3 new inhomogeneous surface composition ('double-faced') white dwarfs in the process. We lastly show how machine learning has the potential to separate single white dwarfs from double white dwarf binary star systems in a large dataset, ideal for isolating a single star population. The results from all of these techniques show a compelling use of machine learning to boost efficiency in analysing white dwarfs observed in multi-object spectroscopy surveys, at times replacing the need for human-driven spectral classifications. This demonstrates our techniques as powerful tools for batch population analyses, finding outliers as a form of rare subclass detection, and in conducting multi-epoch spectral analyses.

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arXiv2025

The Future of Evolved Planetary Systems

Understanding the formation, evolution, and chemical diversity of exoplanets are now central areas of astrophysics research. White dwarfs provide a uniquely sensitive laboratory for studying the end stages of planetary-system evolution and for probing the bulk composition of both rocky and volatile-rich exoplanetary material. In the 2030s new facilities will transform our ability to carry out \textit{``industrial-scale''} astrophysics, leading to fundamental results and new challenges for the next decade. By combining the volume of data surveyed by the ESA {\em Gaia} mission and Vera C. Rubin Observatory with the next-generation of spectroscopic facilities, the European Southern Observatory (ESO) community will be in a position to obtain an unbiased census of evolved planetary systems, constrain the composition of thousands of disrupted planetesimals, and connect these signatures to Galactic populations and stellar birth environments. Thus, it is now the time for assessing those challenges and preparing for the future. This white paper outlines key science opportunities arising in the next decade and the technological requirements of future ESO facilities in enabling transformative discoveries in the 2040s. These future facilities will have to combine a number of features that are crucial for studying evolved planetary systems at white dwarfs, such as broad optical to near-infrared coverage, a high sensitivity at blue wavelengths, multi-resolution capability, massive multi-plexing, and time-domain reactivity.

astro-ph.IM↗

arXiv2025

The Galactic White Dwarf Population

The ESA Gaia mission has revolutionized our understanding of the white dwarf population, delivering an unprecedented census of these nearby remnants and revealing previously unseen structures in the Hertzsprung-Russell (HR) diagram. However, while Gaia has expanded the scope of white dwarf astrophysics, it has also exposed new questions related to atmospheric composition, spectral evolution, crystallization, magnetism, and merger-driven pathways. Many of these open problems are encoded in the detailed morphology of the Gaia HR diagram, where precise spectroscopic characterization is essential for interpreting the underlying physical processes. Spectroscopic characterization, obtainable with current and future ESO facilities, can provide the effective temperatures and surface gravities that are required to derive accurate white dwarf masses, cooling ages, and luminosities. These fundamental parameters not only enable studies of spectral evolution, interior physics, and the origin of magnetic and high-mass white dwarfs, but also guarantee the construction of robust mass distributions and luminosity functions, essential for constraining the initial-to-final mass relation, probing the initial mass function, and reconstructing the star formation history of the local Galaxy, among other applications. Looking toward the 2040s, future multi-fiber spectrographs operating in survey mode on 10--15 meter class telescopes will be able to collect a complete spectroscopic sample of white dwarf, enabling the detailed characterization of their population. Achieving spectroscopic completeness for the nearby Galactic population and securing high signal-to-noise, moderate-to-high resolution spectra across the HR diagram with ESO instrumentation will be critical steps toward resolving these longstanding questions in white dwarf astrophysics.

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arXiv2025

Re-evaluating Lyman $\alpha$ wing opacities and the low mass-problem in cool white dwarfs

Gaia observations have reignited interest in the optical and ultraviolet (UV) opacity problems of cool white dwarfs ($T_{\rm eff} \leq 6000$ K), which were thought to be resolved nearly two decades ago through the inclusion of Lyman $\alpha$ red wing opacity arising from H-H$_2$ collisions in atmospheric models. Recent studies have revealed that their masses derived from Gaia optical photometry are 0.1$-$0.2 M$_{\odot}$ lower than expected from single-star evolution. Since the Ly $\alpha$ H-H$_2$ wing opacity significantly affects the blue end of their optical spectra, it may contribute to the mass discrepancy. To investigate this hypothesis, we revisited the Ly $\alpha$ opacity calculations in the quasi-static single and multi-perturber approximations by explicitly using the ab initio potential energy data of H$_3$ while fully accounting for the H-H$_2$ collision angle. We find that the opacity is slightly smaller than the standard models at the shortest wavelengths ($\leq5000$ angstrom), but larger at longer wavelengths. Comparing synthetic magnitudes (GALEX, Gaia, WISE) to the observations of the 40 pc white dwarf sample, we note that the revised models tentatively reproduce the observed $NUV-G$ colours for stars cooler than 6000 K, but still fail to match $G_{\rm BP} - G_{\rm RP}$ colours, resulting in similarly low inferred masses ($\leq 0.5$ M$_{\odot}$) as obtained with the standard Ly $\alpha$ opacity. Exploring other dominant opacity sources, we discover that decreasing the strength of the bound-free H$^-$ opacity in existing models better reproduces the optical and infrared colours, while collision-induced absorption (CIA) opacity is ineffective in resolving the low-mass problem. We highlight the need for improved opacities and multi-wavelength observations in future studies.

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arXiv2025

The White Dwarf Initial-Final Mass Relation from Open Clusters in Gaia DR3

The initial-final mass relation (IFMR) links a star's birth mass to the mass of its white dwarf (WD) remnant, providing key constraints on stellar evolution. Open clusters offer the most straightforward way to empirically determine the IFMR, as their well-defined ages allow for direct progenitor lifetime estimates. We construct the most comprehensive open cluster WD IFMR to date by combining new spectroscopy of 22 WDs with an extensive literature review of WDs with strong cluster associations. To minimize systematics, we restrict our analysis to spectroscopically confirmed hydrogen-atmosphere (DA) WDs consistent with single-stellar origins. We separately analyze a subset with reliable Gaia-based astrometric membership assessments, as well as a full sample that adds WDs with strong cluster associations whose membership cannot be reliably assessed with Gaia. The Gaia-based sample includes 69 spectroscopically confirmed DA WDs, more than doubling the sample size of previous Gaia-based open cluster IFMRs. The full sample, which includes 53 additional literature WDs, increases the total number of cluster WDs by over $50\%$ relative to earlier works. We provide functional forms for both the Gaia-based and full-sample IFMRs. The Gaia-based result useful for $M_i \geq 2.67\,\mathrm{M}_\odot$ is $$M_f = \left[0.179 - 0.100 H(M_i-3.84\,\mathrm{M}_\odot) \right ] \times (M_i-3.84\,\mathrm{M}_\odot)+0.628\,\mathrm{M}_\odot$$ where $H(x)$ is the Heaviside step function. Comparing our IFMR to recent literature, we identify significant deviations from best-fit IFMRs derived from both Gaia-based volume limited samples of field WDs and double WD binaries, with the largest discrepancy occurring for initial masses of about $5\,\mathrm{M}_\odot$.

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arXiv2025

Assessing the star formation history of all-sky and part-sky 100pc white dwarf samples

Thanks to Gaia and large-scale spectroscopic follow-up surveys (4MOST, DESI, WEAVE, SDSS-V), it is now possible to build representative and minimally biased samples of the local white dwarf population. Here we analyse several volume-limited 100pc samples of white dwarfs, constructed from different surveys and studies, to evaluate their completeness and residual biases. We model the underlying star formation history and Galactic disc age via comparison with simulated populations of white dwarfs to quantitatively characterise completeness. We assess whether the benefit of Gaia XP spectra in datasets outweighs the reduction in sample size, and to what extent targeted, part-sky, and magnitude limited surveys can be used in comparison to all-sky volume limited surveys. Additionally, we simulate the 4MOST 100PC sub-survey and discuss its use to better understand the local star formation history.

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arXiv2025

Exogeological inferences from white dwarf pollutants: the impact of stellar physics

Many white dwarfs have accreted material from their own planetary systems. These objects can be used to infer the composition of exoplanetary material and identify evidence for key geological processes. However, the white dwarf atmospheric physics distorts the inferred material composition away from the true composition, mainly through differential atomic diffusion of the accreted metals. Correcting for this effect is essential, but is dependent on various physical assumptions associated with the white dwarf itself. We first focus on the effect of assumptions related to convective overshoot and thermohaline mixing on the atomic diffusion timescales. For white dwarfs with H-dominated atmospheres between 12000 K and 18000 K, we find that including a complete treatment of convective overshoot decreases the inferred Fe and O abundances in accreted material. For these white dwarfs, we also find that including thermohaline mixing decreases Fe and O abundances. For He-dominated systems, the effect of convective overshoot is comparatively minor. We then explore the overall effect of other physical assumptions by comparing publicly available grids of diffusion timescales. We find that the choice of model grid can have a large impact for white dwarfs with He-dominated atmospheres, notably on the inferred core to mantle ratio of accreted material. We identify several systems for which the geological interpretation is robust against these systematics. We also present a `discrepancy metric' which can be used to estimate the potential impact of changing the stellar physics without requiring detailed modelling.

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arXiv2025

MESA Isochrones and Stellar Tracks (MIST) III. The White Dwarf Cooling Sequence

We present a substantial update to the MESA Isochrones and Stellar Tracks (MIST) library, extending the MIST model grids and isochrones down the white dwarf (WD) cooling sequence with realistic physics for WD cooling timescales. This work provides a large grid of MESA models for carbon-oxygen core WDs with hydrogen atmospheres (spectral type DA/DC), descended from full prior stellar evolution calculations. The model tracks, isochrones, and WD cooling timescale contours are available on the MIST project website and at https://doi.org/10.5281/zenodo.15242046. Our WD models provide a very large, publicly available grid with detailed physics for WD cooling timescales: realistic interior and envelope compositions, with element diffusion and heavy-element sedimentation, nuclear burning at the base of the WD hydrogen envelope, core crystallization, and C/O phase separation. As a large grid of open-source stellar evolution models, these WD models provide both out-of-the-box model tracks for comparison with observations and a framework for building further WD models to investigate variations in WD physics.

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arXiv2025

A hot white dwarf merger remnant revealed by an ultraviolet detection of carbon

Atmospheric carbon has been detected in the optical spectra of six hydrogen-rich ultra-massive white dwarfs, revealing large carbon abundances (log C/H > $-$0.5) attributable to the convective dredge-up of internal carbon into thin hydrogen surface layers. These rare white dwarfs likely originate from stellar mergers, making them "smoking guns" for one of the binary evolution channels leading to thermonuclear supernovae. However, optical spectroscopy can uncover only the most carbon-enriched objects, suggesting that many more merger remnants may masquerade as normal pure-hydrogen atmosphere white dwarfs. Here, we report the discovery of atmospheric carbon in a Hubble Space Telescope far-ultraviolet spectrum of WD$\,$0525+526, a long-known hydrogen-rich ultra-massive white dwarf. The carbon abundance (log C/H = $-$4.62) is 4$-$5 dex lower than in the six counterparts and thus detectable only at ultraviolet wavelengths. We find that the total masses of hydrogen and helium in the envelope ($10^{-13.8}$ and $10^{-12.6}$ of the total white dwarf mass) are substantially lower than those expected from single-star evolution, implying that WD$\,$0525+526 is a merger remnant. Our modelling indicates that the low surface carbon abundance arises from an envelope structure in which a thin hydrogen-rich layer floats atop a semi-convection zone$-$a process that has been largely overlooked in white dwarfs. Our study highlights the importance of ultraviolet spectroscopy in identifying and characterising merger remnants.

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arXiv2025

The DBL Survey II: towards a mass-period distribution of double white dwarf binaries

Double white dwarf binaries are an important remnant of binary evolution as they are possible type Ia supernova progenitors and strong sources of gravitational waves in the low-frequency regime. The double-lined double white dwarf (DBL) survey searches for compact double white dwarfs where both stars are spectrally disentangleable. Candidates are identified by being overluminous compared to the cooling sequence of a typical mass, single white dwarf. In this second DBL survey instalment, we present full orbital solutions of 15 double white dwarf binaries from our ongoing campaign to accurately measure a magnitude-limited mass-period distribution. 12 of these systems are fully solved for the first time. A long-standing bias in the full population has been evident, favouring systems with orbital periods up to a few hours, with little exploration of the majority of the compact double white dwarf population, whose orbital period distribution centres at approximately 20hr. The 15 systems in this study span the orbital period range 5-75hr, significantly augmenting the number of well-characterised systems over these periods, and in general have two similar mass stars combining to approximately 1.0 solar masses. We witness that the orbitally derived mass ratios generally show an excellent agreement with those deduced from atmospheric fits to double-lined spectra in previous work, emphasising the power of wide-scale spectroscopic surveys to efficiently locate the highest mass, double-lined double white dwarfs in the local Galaxy.

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