Sabrina Poulsen

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 μ m. This survey gathered observations for 56 white dwarfs within 25 pc at 10 and 15 μ m, probing each white dwarf for unresolved IR excesses, IR flux deficits indicative of collision-induced absorption, or resolved substellar companions. This paper presents observations of our first target, 2MASS J09424023−4637176 (also UCAC4 217-039132), henceforth called MEAD 62. This is a magnetic DA white dwarf with an estimated age of 6 . 5 − 2.0 + 4.0 Gyr. A red candidate companion, MEAD 62 B, about 2 mag fainter than its host white dwarf, is detected at an apparent separation of 1 . ″ 95. If confirmed, MEAD 62 B would be a 0.01 4 − 0.003 + 0.002 M _⊙ brown dwarf with T eff = 34 3 − 11 + 7 K, according to ATMO2020 evolutionary models. Also, at 20.48 ± 0.01 pc, it would be the third nearest substellar companion to a white dwarf. While the red F1000W − F1500W color of MEAD 62 B is similar to background galaxies, it is also consistent with being an unresolved point source from empirical point-spread function fitting. A false positive analysis yields an expectation number of 0.66 red (F1000W − F1500 ≥ +0.80 mag) unresolved sources within the same separation ( r ≤ 2″) for the entire MEAD survey. Thus, this candidate companion is as likely to be an actual companion as a false positive unresolved background galaxy. Follow-up JWST observations to measure common proper motion and sample the spectral energy distribution are warranted to confirm the nature of MEAD 62 B.

The MIRI Excesses Around Degenerates (MEAD) Survey is a Cycle 2 JWST program designed to image nearby white dwarfs with MIRI at 10 and 15 μ m. This survey targeted 56 white dwarfs within 25 pc to search for mid-infrared excesses, flux deficits from collision-induced absorption, and resolved substellar companions. In this paper we present our analysis of WD 0644+025, an unusually massive white dwarf (0.95 M _⊙ ) and the MEAD target exhibiting the most significant mid-infrared excess. The observed JWST MIRI photometry shows a 7.3 σ excess at 15 μ m and a 3.6 σ excess at 10 μ m, which may be associated with either a planetary companion or a circumstellar dust disk. This excess corresponds to a companion mass of 6.8 M _Jup ( T _eff = 261 ±9 K) with orbital distance M _Jup beyond ∼12 au. Metal pollution is confirmed in both archival Keck HIRES spectra from 1999 and new observations from 2025, with no evidence suggesting that the accretion rate has substantially changed over the decades. We explore possible dust disk morphologies to describe the observed IR excess and find that traditional debris disks struggle to fit our data. WD 0644+025 thus represents a compelling case study in the growing population of white dwarfs with cold infrared excesses and highlights JWST’s ability to probe planetary system remnants inaccessible to prior infrared observatories.

The MIRI Excess Around Degenerates (MEAD) Survey is a cycle 2 JWST program designed to image nearby white dwarfs with MIRI at 10 and 15 microns. This survey targeted 56 white dwarfs within 25 pc to search for mid-infrared excesses, flux deficits from collision-induced absorption, and resolved substellar companions. In this paper we present our analysis of WD 0644+025, an unusually massive white dwarf (0.95 Msun) and the MEAD target exhibiting the most significant mid-infrared excess. The observed JWST MIRI photometry shows a 7.3 sigma excess at 15 microns and a 3.6 sigma excess at 10 microns, which may be associated with either a planetary companion or a circumstellar dust disk. This excess corresponds to a companion mass of 6.8 Mjup (Teff=261 +/- 9 K) with orbital distance <11.8 au, although substantially lower masses are possible if we consider a closely orbiting insolated companion. No spatially resolved sources are detected within 200 au, with contrast curve analysis excluding planets more massive than 2 Mjup beyond ~12 au. Metal pollution is confirmed in both archival Keck HIRES spectra from 1999 and new observations from 2025, with no evidence suggesting the accretion rate has substantially changed over the decades. We explore possible dust disk morphologies to describe the observed IR excess, and find that traditional debris disks struggle to fit our data. WD 0644+025 thus represents a compelling case study in the growing population of white dwarfs with cold infrared excesses, and highlights JWST's ability to probe planetary system remnants inaccessible to prior infrared observatories.

White dwarfs with metal pollution are caused by the accretion of rocky dust from tidally disrupted minor bodies and are signposts for planetary systems. These minor bodies are perturbed by planets that have survived post-main-sequence evolution. Open questions exist as to the typical mass of the perturbers and the specific planetary architectures that cause metal pollution. JWST’s sensitivity in the mid-IR has opened new doors to deciphering polluted white dwarfs. We present JWST Cycle 1 mid-infrared instrument imaging of four nearby metal-polluted white dwarfs with the goal of detecting and characterizing planetary companions. With deep mid-IR imaging we are sensitive to cold Jupiter-mass planet analogs. In addition to finding two candidate planetary companions, for the first time we detect significant excesses above the expected photospheric emission at 21 μm for two of our targets, WD 2149+021 and WD 2105−820. WD 2105−820 has a candidate planetary companion at a projected separation of 34 au and an IR excess—if both candidates are confirmed, it would represent the first WD multiplanet system. We investigate whether these excesses could be caused by very low luminosity warm dust disks or planets. While both are likely, we argue that the most likely explanation for the excesses is that they are the thermal emission from Jovian-mass planets in orbits with semimajor axes <10 au, using a combination of observational constraints. If most of the candidate planets presented here are confirmed, it would suggest that metal-polluted white dwarfs are frequently orbited by at least one giant planet.

The launch of JWST has ushered in a new era of high-precision infrared astronomy, allowing us to probe nearby white dwarfs for cold dust, exoplanets, and tidally heated exomoons. While previous searches for these exoplanets have successfully ruled out companions as small as 7–10 Jupiter masses (M _Jup), no instrument prior to JWST has been sensitive to the likely more common sub-Jovian-mass planets around white dwarfs. In this paper, we present the first multiband photometry (F560W, F770W, F1500W, F2100W) taken of WD 2149+021 with the Mid-Infrared Instrument on JWST. After a careful search for both resolved and unresolved planets, we do not identify any compelling candidates around WD 2149+021. Our analysis indicates that we are sensitive to companions as small as ∼0.5 M _Jup outwards of 1.″263 (28.3 au) and ∼1.0 M _Jup at the innermost working angle (0.″654, 14.7 au) at 3 Gyr with 5σ confidence, placing significant constraints on any undetected companions around this white dwarf. The results of these observations emphasize the exciting future of sub-Jovian planet detection limits by JWST, which can begin to constrain how often these planets survive their host stars' evolution.

We report the discovery of two directly imaged, giant planet candidates orbiting the metal-rich, hydrogen atmosphere white dwarfs WD 1202−232 and WD 2105−82. JWST’s Mid-Infrared Instrument (MIRI) data on these two stars show a nearby resolved source at a projected separation of 11.47 and 34.62 au, respectively. Assuming the planets formed at the same time as their host stars, with total ages of 5.3 and 1.6 Gyr, the MIRI photometry is consistent with giant planets with masses ≈1–7 M _Jup. The probability of both candidates being false positives due to red background sources is approximately 1 in 3000. If confirmed, these would be the first directly imaged planets that are similar in both age and separation to the giant planets in our own solar system, and they would demonstrate that widely separated giant planets like Jupiter survive stellar evolution. Giant planet perturbers are widely used to explain the tidal disruption of asteroids around metal-polluted white dwarfs. Confirmation of these two planet candidates with future MIRI imaging would provide evidence that directly links giant planets to metal pollution in white dwarf stars.

The launch of JWST has ushered in a new era of high precision infrared astronomy, allowing us to probe nearby white dwarfs for cold dust, exoplanets, and tidally heated exomoons. While previous searches for these exoplanets have successfully ruled out companions as small as 7-10 Jupiter masses, no instrument prior to JWST has been sensitive to the likely more common sub-Jovian mass planets around white dwarfs. In this paper, we present the first multi-band photometry (F560W, F770W, F1500W, F2100W) taken of WD 2149+021 with the Mid-Infrared Instrument (MIRI) on JWST. After a careful search for both resolved and unresolved planets, we do not identify any compelling candidates around WD 2149+021. Our analysis indicates that we are sensitive to companions as small as ~0.34 MJup outwards of 1."263 (28.3 au) and ~0.64 MJup at the innermost working angle (0."654, 14.7 au) with 5 sigma confidence, placing significant constraints on any undetected companions around this white dwarf. The results of these observations emphasize the exciting future of sub-Jovian planet detection limits by JWST, which can begin to constrain how often these planets survive their host stars evolution.