arXiv subjects

J. J. Hermes

Publications and source records attributed to J. J. Hermes.

At least 19 recordsLinked to original sources

arXiv2026

Searching for Massive Remnant Planetary System Hosts with White Dwarf Gaia XP Spectra

Remnant planetary systems around massive white dwarfs ($M_{\rm WD} > 0.8\,{\rm M}_\odot$) are intrinsically rare and remain poorly characterized. As the evolutionary endpoints of intermediate-mass B- and A-type stars, these white dwarfs provide valuable constraints on the formation and survival of planetary systems around higher-mass progenitors. In the absence of large, dedicated spectroscopic surveys, extremely-low-resolution Gaia XP spectra provide a powerful means of identifying candidate metal-polluted white dwarfs. We obtained follow-up observations with low-resolution optical spectroscopy (R=500-4000) to search primarily for Ca II H & K absorption in massive, metal-polluted white dwarf candidates selected from Gaia XP spectra to increase the sample of massive remnant planetary system hosts among objects with effective temperatures below $\sim15{,}000$ K. We find that Gaia XP spectra recover metal-polluted white dwarfs efficiently, confirming 82$\pm$5% recovery of photospheric metals (59 of 72 targets) in high-confidence candidates of our sample (with classifier probability $P_{\rm DZ} > 0.65$). However, Gaia photometric masses derived from $G$, $G_{BP}$, and $G_{RP}$ broad-band photometry are not sufficient to identify the most massive systems, as reliable mass determinations require detailed metal-enriched atmospheric fits. We present a selection of cool white dwarfs confirmed to be both massive and metal polluted, demonstrating that Gaia XP spectra can substantially expand the sample of white dwarf exoplanet hosts. Our search led to the discovery of a new transiting debris system, SDSS J1624+5404, the 21st published system to date and eighth to show periodic transits.

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arXiv2026

Now you see me, now you don't: Deep, long-lived obscuration events of white dwarfs by dust and debris from disintegrating planetesimals

Transiting dust and debris around white dwarfs provide a direct view of planetary disruption. We report six previously non-variable white dwarfs that underwent single, deep obscuration events, including ZTF~J2327+0019, which fully disappeared for more than a year. These discoveries raise the number of confirmed debris-transit white dwarfs to 20. In addition, the systematic search of negative alerts from the Zwicky Transient Facility (ZTF), followed by photometric and spectroscopic observations, also identified three hot ($T\approx 55000$--$92000$ K) irregular variables as candidate debris hosts. The six confirmed events last weeks to years, reach transit depths of 25--100%, and show no recurrence over the 8-yr ZTF baseline. They are therefore much deeper and longer lived than the recurring, minute-scale transits typical of previously known systems. The observed reddening is consistent with dust extinction, and high-speed photometry reveals minute-scale structure in several systems, indicating rapidly moving material close to the white dwarf. ZTF~J2327+0019 also shows a simultaneous WISE infrared brightening, the first observed coincidence of infrared brightening and optical obscuration in a white dwarf. Two of the six hosts, one DAZ and one DBZ, are strongly metal enriched, with accretion rates among the highest known for their spectral types and minimum accreted masses of $3.5\times 10^{19}$ and $2\times 10^{24}$ g. We interpret the one-off transit events as collisions between planetesimal remnants and pre-existing circumstellar debris that trigger collisional cascades: short-timescale variability traces dust-producing fragments crossing the star, while slower changes trace the build-up and clearing of an optically thick dusty structure. In contrast, ZTF~J0436+5728 shows a coherent 5.910-h period, consistent with a rocky body shedding material near the tidal-disruption radius.

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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

A Galactic intermediate-mass stripped star with a Wolf-Rayet-like wind

Binary interaction in massive stars is expected to produce a large population of intermediate-mass ($2$-$8$ M$_\odot$) envelope-stripped stars, yet such objects have remained elusive in the Milky Way. We report the identification of an unambiguous Galactic example in a short-period ($P=5.94$ d), double-lined spectroscopic binary, discovered in the SDSS-V Milky Way Mapper survey. The system consists of a rapidly rotating O-type star and a hotter, lower-mass companion, which shows He II and N IV emission lines with large radial velocity variations, revealing its binary nature. Combined orbital constraints and joint spectroscopic and photometric modelling show that the companion is a hot ($T_\ast \approx 60$ kK), helium-rich star with a mass of $3.2$-$5.8$ M$_\odot$, placing it squarely in the intermediate-mass regime and below values typically inferred for classical Wolf-Rayet (WR) stars. The system's short period, negligible eccentricity, and rapidly rotating O-star point to a post-interaction configuration following efficient mass transfer and spin-up of the accretor. Comparison with binary evolution models suggests that the stripped star is observed in a brief inflated phase following mass transfer, which increases its optical flux contribution and facilitates its detection. The inferred mass-loss rate $\log \dot{M} = -6.3 \pm 0.1$ is in line with mass-loss rates observed for classical WR stars in the Milky Way and exceeds those measured for intermediate-mass stripped stars in the Magellanic Clouds, with the caveat that our target selection is biased towards systems with stronger emission features. As an unambiguous and well-characterised intermediate-mass stripped star, this system provides a key benchmark for models of binary evolution at solar metallicity, stripped-envelope supernova progenitors, and the formation of compact-object binaries.

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arXiv2026

SRG/eROSITA X-ray selected cataclysmic variable candidates observed in SDSS-V DR20

We report on the spectroscopic observations obtained during SDSS-V DR20 of accreting compact binaries (ACB), specifically the cataclysmic variables (CVs), that were identified as likely compact binary candidates from the SRG (Spectrum Roentgen Gamma) eROSITA eRASS1 and eRASS:3 observations. Our primary aim is to obtain a complete inventory of all CVs that were detected in eRASS1 and eRASS:3, with the goal to help better understand close-binary evolution, the population density, and demographics of these systems in the Galaxy. Previous population studies had their respective limitations, with volume-limited samples suffering from low-number statistics, while magnitude-limited observations were biased to only the brighter systems. All CVs are X-ray emitters, eROSITA, therefore, presents a unique opportunity to identify CVs based on their X-ray emission. Given eROSITA's sensitivity, we expect to find most X-ray active CVs within 500 pc, and magnetic CVs to several kpc. Using X-ray data from the eROSITA together with optical data from Gaia, three different approaches were explored to identify the Gaia optical counterpart to the eROSITA X-ray source of the likely ACB. From this, unique candidates were identified and were submitted in three different cartons to SDSS-V for optical spectroscopic observations as part of the Milky Way Mapper survey. From our submitted candidates, we found 538 likely CVs. We also identified CVs that were observed in other eROSITA based cartons, in which we identified an additional 49 systems that are likely CVs and which were not in our selection. We therefore identified 587 systems as CVs from the eROSITA based SDSS-V observations. We also attempted to sub classify the CVs as dwarf-novae, novalikes, or magnetic systems based on the eROSITA X-ray data, the emission line properties in the optical SDSS-V spectra, and other data in the public domain, if available.

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arXiv2026

The Twentieth Data Release of the Sloan Digital Sky Survey: First All-Sky BOSS Spectra, eROSITA-SDSS-V Mapper Coordinated Observations, and a Preview of the Local Volume Mapper

This paper presents the twentieth data release (DR20) from the Sloan Digital Sky Survey, the third data release of its fifth generation (SDSS-V). SDSS-V is a panoptic spectroscopy survey that is mapping the stars, gas, and galaxies through three scientific programs: the Milky Way Mapper (MWM), the Local Volume Mapper (LVM), and the Black Hole Mapper (BHM). DR20 presents the first optical (BOSS) SDSS-V spectra from southern hemisphere for the MWM and BHM surveys; new optical MWM and BHM data from the northern hemisphere are also available, for a total over 3 million spectra of 1.5 million stars and half a million galaxies and quasars, with galactic and extragalactic x-ray targets coordinate with eROSITA DR2. DR20 includes integral field spectroscopy maps from LVM of six targets and 169 tiles, spanning Galactic HII regions, planetary nebulae, and nearby galaxies. Additionally, eighteen value added catalogs are also released with DR20, based on SDSS-V MWM and BHM data, and we present a new LVM visualization tool including an RGB HiPS map as a value added product.

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arXiv2026

Circumstellar interaction in the extreme white dwarf merger remnant ZTF\,J1901+1458: A new class of white dwarf merger remnants with X-ray emission

Double degenerate white dwarf (WD) mergers can exhibit extreme magnetic fields exceeding $10^{8}$ G and rapid rotation, but their spectral-energy distributions and high-energy emission mechanisms remain poorly characterised. ZTF J1901+1458 stands out as the most compact and strongly magnetised object discovered in this class to date. Recent Chandra observations have revealed that the white dwarf is also a source of soft X-ray emission, inconsistent with a photospheric origin. We analyse new phase resolved UV spectroscopy from the HST combined with optical and near-infrared photometry and spectroscopy, with newly developed magnetic atmosphere models to determine its effective temperature, radius, mass, average surface magnetic field strength, and cooling age. Our results demonstrate that the spectral break at $\approx$3000 Å, observed in several highly magnetised WDs, is well-reproduced by our new models, which take into account the effect of magnetic opacities on the structure of the atmosphere. Our best-fit parameters for the WD yield an effective temperature ($T_{\rm{eff}}=28,015\pm 20$ K) and larger radius ($2630\pm10$ km) than previously reported. Furthermore, the near-infrared data exclude the presence of a stellar or brown dwarf companion hotter than $\approx$700 K. We also jointly analyse the previously published Chandra data and new XMM-Newton X-ray spectra. The faint X-ray emission, $L_X =(1.3\pm0.2)\times10^{27}$ erg/s is very soft and highly pulsed on the rotation period of the WD. We suggest that the X-rays are powered by accretion or via the interaction of the WD magnetosphere with CSM. If the rapidly rotating magnetic field could power a weak wind along open field lines, material could be extracted directly from the surface of the WD. Alternatively, accretion of fallback material from the merger or the tidal disruption of a planetary body are possible sources of CSM.

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arXiv2026

Unveiling the properties of pulsating low-mass helium-core white dwarfs through TESS asteroseismology I. First results

Recent space-based photometry, particularly from TESS, has opened new possibilities for probing the internal structure of low-mass (LM) helium (He)-core white dwarfs (WDs). We present a homogeneous asteroseismological analysis of six pulsating LM WD stars, based on new and updated TESS photometry. We processed short- and ultra-short-cadence TESS observations of TIC 290904838 (J1112), TIC 156064657, TIC 33717565, TIC 344130696, TIC 72637474, and TIC 188087204, and analyzed the resulting pulsation spectra. We then carried out a detailed asteroseismological analysis using fully evolutionary models of LM He-core WDs that allow for varying hydrogen (H)-envelope thicknesses. We also estimated spectroscopic/photometric stellar masses when atmospheric parameters are available. We report the first TESS-based frequencies for J1112 and provide revised or expanded frequency solutions for the remaining targets. The asteroseismological analysis yields relatively well-constrained solutions for three stars, a representative but more tentative solution for one target, and constrained ranges for the remaining two. The inferred solutions span a broad range of H-envelope thicknesses, although some of the asteroseismological inferences remain tentative because of the limited number of observed periods available for the analysis. For most objects, the derived spectroscopic/photometric stellar masses are broadly compatible with the asteroseismological values. This is the first homogeneous TESS-based asteroseismological study of a small sample of pulsating LM WDs. Our results suggest that LM WDs can harbor H envelopes with a range of thicknesses, from canonical (thick) to very thin, as in average-mass H-rich pulsating WDs. They also provide a useful reference point for future studies of larger samples, which will hopefully benefit from richer mode sets and improved mode identification.

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arXiv2026

An Ultramassive White Dwarf with a Likely Oxygen-Neon Core

The core composition of ultramassive white dwarfs remains an open question in stellar evolution. The carbon content of white dwarf cores is critical to their role as progenitors of Type Ia supernovae. However, because the stellar photosphere only extends to the outermost layer of the star, observational probes of core compositions are limited. Here we present gravitational redshift measurements of an ultramassive white dwarf, SDSS J060851.44-005950.3, which indicate the likely presence of an oxygen-neon core. We measure the mass ($1.226_{-0.025}^{+0.024} M_\odot$) and radius ($0.491_{-0.009}^{+0.009}~R_\oplus$) of the white dwarf using gravitational redshifts from high-resolution UVES and MagE spectra paired with independent constraints from photometry. By comparing to state-of-the-art mass-radius relations for ultramassive white dwarfs, we find preference for a oxygen-neon core over a carbon-oxygen core, with a Bayes factor of $2.7$. This is a white dwarf which is likely structurally incapable of producing a Type Ia supernova, according to current understanding of supernova physics. This object provides evidence that white dwarfs which pass through the Q-branch without experiencing a delay in cooling compared to the normal white dwarf cooling sequence likely have oxygen-neon cores.

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arXiv2026

Observing bright pulsating white dwarfs with PLATO: A new window into the late stages of stellar evolution

We present the scientific case for exploiting the capabilities of the PLATO mission to study bright pulsating white dwarfs across a wide spectral range, including hydrogen-deficient types (GW Vir and DBV stars) and hydrogen-rich classes (classical DAVs, pulsating extremely low-mass DA white dwarfs, and ultra-massive DA white dwarfs). PLATOs exceptional photometric precision, long-duration continuous monitoring, and extensive sky coverage promise transformative advances in white dwarf asteroseismology. Our key objectives include probing the internal structure and chemical stratification of white dwarfs, detecting secular changes in pulsation modes over extended timescales, and discovering rare or previously unknown classes of pulsators. To assess feasibility, we constructed a sample of 650 white dwarf candidates identified within PLATOs Southern LOPS2 field using the PLATO complementary science catalogue combined with Gaia DR3, and derived atmospheric parameters through photometric modeling. This sample comprises 118 DA white dwarfs (including 23 ZZ Ceti candidates), and 41 non-DAs (including 35 DBV candidates). Simulated observations using PlatoSim demonstrate that PLATO will be capable of detecting white dwarf pulsation modes with amplitudes as low as 0.1 mma depending on stellar magnitude, observation duration, pixel location, and the number of contributing cameras. We provide detailed detection limits and visibility forecasts for known pulsators across a representative range of these parameters. Furthermore, we emphasize strong synergies with Gaia astrometry, TESS photometry, and targeted spectroscopic campaigns, which together will enable robust mode identification and detailed stellar modeling. Collectively, these efforts will unlock unprecedented insights into white dwarf origins, evolution and internal physics, and the fate of their planetary systems.

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arXiv2026

Mode Instability and a Massive, Isolated Outburst in the Pulsating White Dwarf GD 1212

We analyze a large brightening event that lasted for roughly half a day in the pulsating hydrogen-atmosphere white dwarf GD 1212 during K2 Campaign 12 of the extended Kepler mission. For the other 80 days of K2 observations, GD 1212 exhibited a rich spectrum of long-period (~1100 s) pulsations that underwent rapid variations in frequency and amplitude but did not exhibit any additional outbursts. We refine previous attempts at mode identification and find a likely sequence of dipole and quadrupole splittings that reveal an overall rotation rate of roughly 17.0 hr. The outburst at Day 61 is fully resolved by the 60-second-cadence K2 data, with the entire white dwarf becoming up to 17.5% brighter overall, from an approximately 850 K increase in effective temperature, with pulsational variability during the outburst showing shorter periods and higher amplitudes. Outbursts are believed to be the result of nonlinear mode coupling via parametric instability, whereby energy stored in linearly excited parent modes is rapidly transferred to damped child modes that dissipate near the surface. Additionally, we characterize a "failed" outburst that caused correlated pulsation frequency changes, an approximately 5 microHz increase, with a small approximately 0.35% corresponding brightness increase. GD 1212 is now the eighth pulsating hydrogen-atmosphere DAV white dwarf to show outburst behavior, although it exhibited the largest outburst yet and has the longest inferred recurrence timescale. This high-signal-to-noise record tracing pulsations through both large and small temperature excursions in GD 1212 provides unique insights into parametric resonance and nonlinear mode coupling in white dwarf pulsations.

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arXiv2026

The DECam MAGIC Survey $-$ Mapping the Ancient Galaxy in CaHK: Overview and Summary of Early Science

We present the DECam Mapping the Ancient Galaxy in CaHK (MAGIC) survey, a 54-night NOIRLab Survey Program to image $\gtrsim$5,000$\,$deg$^2$ of the southern hemisphere using a metallicity-sensitive narrow-band filter covering the Ca$\,$ii$\,$H&K lines centered at 3955$\,$A. This filter is installed on the Dark Energy Camera (DECam), mounted on the 4-m NSF Víctor M. Blanco Telescope. The survey reaches typical $10σ$ depths of $\text{mag}_{\text{CaHK}} \approx 22.5$, 3$-$4$\,$mag deeper than comparable surveys in the southern hemisphere. By combining photometry from this Ca$\,$ii$\,$H&K filter with existing DECam $g,r,i$ broadband photometry from the DECam Local Volume Exploration (DELVE) survey, MAGIC is deriving photometric metallicities for red giant branch stars down to the magnitude limit of usable proper motions from Gaia data release 3 (DR3). MAGIC has already imaged $\sim$3,000$\,$deg$^2$, supplemented by other affiliated observing programs that have used this filter to image star clusters, dwarf galaxies, and stellar streams. We overview MAGIC's survey strategy, describe data processing through the derivation of metallicities and photometric distances, and summarize early science results that have been published with this dataset. In addition, we present several new results, including the confirmation of a distant ($>5\,r_h$) member of the Reticulum II ultra-faint dwarf galaxy, on-sky density maps of low-metallicity stars into the distant Milky Way halo ($\sim150\,$kpc) recovering 13/14 ultra-faint dwarf galaxies in the current footprint, and a validation of our initial targeting of extremely metal-poor stars. Collectively, these results demonstrate that the MAGIC dataset enables cutting-edge studies of the faint, low-metallicity regime of the Milky Way and its substructures.

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arXiv2026

Kepler Discovery of GW Vir Pulsations of the Central Star of Planetary Nebula Kn 61

We report the discovery of pulsations in the N-rich PG 1159-type central star of the planetary nebula Kn 61 based on one month of Kepler Short Cadence observations. We detect four significant peaks in the frequency range consistent with g-modes excited in GW Vir stars. From the detected modes, we identify a mean period spacing of $ΔΠ=21.526(6)$ s for a sequence of three $\ell=1$ modes. This allows us to derive the asteroseismic mass of the star, which we estimate to be $0.551(6)~\mathrm{M}_{\odot}$, consistent with the one derived from the evolutionary tracks. We also characterize sporadic brightening events in the Long Cadence Kepler light curve of Kn 61. If we assume these are caused by increases in effective temperature, we estimate their energies to be $\sim10^{40}$ erg, though this may not be accurate as the mechanism for releasing so much energy is still unknown.

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arXiv2026

Constraints on White Dwarf Hydrogen Layer Masses Using Gravitational Redshifts

The hydrogen envelope is the outermost layer of a DA white dwarf; it makes up the entirety of the stellar photosphere, and yet its typical extent is difficult to model theoretically and remains poorly observationally constrained. As a result, hydrogen envelope mass is a substantial source of systematic uncertainty in physical properties of white dwarf, including overall masses and cooling ages. In this work, we fit a Gaussian mixture model to gravitational redshifts from high-resolution spectroscopy, paired with radius measurements from Gaia BP/RP spectra, to measure the mass-radius relation for a sample of 468 white dwarfs. Our results are in excellent agreement with the predicted mass-radius relations of state-of-the-art evolutionary models, including those from the MESA Isochrones and Stellar Tracks (MIST) library. We find that mass-radius relations such as MIST which assume a thick and mass-dependent hydrogen envelope are preferred by the observed probability density function over models which assume a constant hydrogen envelope mass. Proper treatment of the evolution of white dwarf progenitors is thus important for accurately modeling the mass-radius relation. Our results indicate that gravitational redshift measurements of large samples of white dwarfs in wide binaries are promising probes of the hydrogen envelope masses of DA white dwarfs.

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arXiv2026

White Dwarf Merger Remnants with Cooling Delays on the Q Branch Lack Strong Magnetism

A population of anomalous ultra-massive white dwarfs discovered with Gaia, often referred to as the Q branch, show high (multi-Gyr) cooling delays produced by exotic physical mechanisms. They are believed to be the products of stellar mergers, but the exact origin and formation channel remain unclear. We obtained a spectroscopically complete, volume-limited sample of the Q branch region within 100 pc, and found significant differences in atmospheric composition and rotation rates as a function of tangential velocity. In particular, we discover that stellar remnants with the longest cooling delays do not show strong magnetism nor detectable short-period rotational variability, as opposed to what is generally believed for double-degenerate mergers. This indicates that either these white dwarfs arise from a formation channel with no strong magnetism induced, or that the magnetism produced from the merger dissipates over the cooling delay timescales. Our follow-up photometry has also discovered pulsations in the second and third hydrogen-dominated DAQ white dwarfs, one hotter than 15,500 K, possibly extending the boundaries of the DAV instability strip for white dwarfs with thin hydrogen layers.

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arXiv2025

Stellar physics at sub-nanoradian angular resolution

Many stars -- if they could be imaged with enough angular resolution -- would exhibit features expected from theory but not possible to extract from spectra. We may group these by increasing complexity as follows. First, smooth variations in brightness across the surface, resembling solar limb darkening but much more prominent and involving more processes in stars with fast spin or external tides. Next, there are periodic features: not only oscillations, but also convective cells and starspots, which appear to transit across a star as its spins, and exoplanets that really do transit across the star. Then, there are transients like flares. Current optical interferometers provide synthetic apertures of a few hundred metres and angular resolutions down to about nanoradian ($\simeq 0.2\,$milliarcsecond), enough to resolve some of the above features on the nearest upper main-sequence stars, giants and supergiants. Ongoing projects aims to km-scale synthetic apertures, enough to measure the radius of the nearest white dwarf. In this White Paper we briefly discuss what could be observed with synthetic apertures over $\sim20\,$km -- resolving detail on white dwarfs at the level currently possible on supergiants.

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arXiv2025

Follow-up Observations of Candidate White Dwarf Planets with MIRI

We report on second-epoch imaging of two candidate planet-hosting white dwarfs stars, WD2105-82 and WD1202-232. Both stars showed evidence of resolved, planet-mass candidate companions in observations using the MIRI mid-infrared imager on JWST. WD2105-82 also showed evidence of an infrared excess consistent with an unresolved 1.4 Jupiter mass companion with an orbital separation of <4 au. Our second epoch observations confirm that the source of the excess shares common proper motion with the star. The excess is almost certainly due to a companion planet or debris disk. However, neither of the two resolved sources with projected separations of >1" in the first epoch of JWST observations show measurable proper motion and are thus likely faint, unresolved background galaxies. We also search for common proper motion companions out to hundreds of au, but find no evidence of widely separated companions.

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arXiv2025

The MIRI Excesses around Degenerates (MEAD) Survey I: A candidate cold brown dwarf in orbit around the nearby white dwarf 2MASS J09424023-4637176

The MIRI Excesses Around Degenerates Survey is a Cycle 2 James Webb Space Telescope (JWST) Survey program designed to image nearby white dwarfs in the mid-IR with the MIRI imaging mode. Only a handful of white dwarfs have previously been observed beyond 8~\micron. This survey gathered observations for 56 white dwarfs within 25~pc at 10 and 15~\micron, probing each white dwarf for unresolved IR excesses, IR flux deficits indicative of collision induced absorption, or resolved substellar companions. We present in this paper observations of our first target, 2MASS J09424023-4637176, (also UCAC4 217-039132), henceforth called MEAD 62. It is a magnetic DA white dwarf with an estimated age of $7.6^{+1.7}_{-2.2}$\,Gyr. A red candidate companion, MEAD 62B, about 2 magnitudes fainter at 15\,$μ$m than the white dwarf is detected at an apparent separation of 1.95". If confirmed, MEAD 62B, would be a $0.014^{+0.002}_{-0.003}$\,\Msun\, brown dwarf with T$_{\rm eff} = 343^{+7}_{-11}$\,K, according to ATMO2020 evolutionary models. Although its red F1000W$-$F1500W color is similar to background galaxies, MEAD 62B, is consistent with being an unresolved point-source from empirical PSF fitting. A false positive analysis yields an expectation number of 0.66 red (F1000W$-$F1500$ \geq +0.80$\,mag) unresolved sources within the same separation (r$\leq2$ arcsec) for the entire MEAD survey. Thus, this candidate companion as likely to be an actual companion as a false-positive unresolved background galaxy. Additional observations to measure common proper motion or sample the SED are warranted to confirm the nature of MEAD 62B. A deep near-infrared imaging detection is achievable from the ground while JWST is needed at longer infrared wavelengths.

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