Scott A. Diddams

We report the confirmation and characterization of four transiting giant planets orbiting early M dwarfs discovered by the Searching for GEMS survey: TOI-7189 b, TOI-7265B b, TOI-7393 b, and TOI-7394B b. Joint modeling of Transiting Exoplanet Survey Satellite and ground-based photometry with precision radial velocities from the Habitable-zone Planet Finder and NEID spectrographs yields self-consistent orbital and physical parameters for all systems. The planets have short orbital periods (P = 1.25–4.17 days), masses spanning from 0.5 M_J to 2.1 M_J, and radii comparable to Jupiter (0.95 R_J < R_p < 1.02 R_J). TOI-7189 b (0.50 M_J), TOI-7265B b (0.71 M_J), and TOI-7393 b (0.61 M_J) are Saturn-like in mass and density, whereas TOI-7394B b is a dense super-Jupiter (2.10 M_J, ρ_p ≈ 2.4 g cm⁻³) on a 1.25-day orbit. All hosts are early M dwarfs with a narrow range of stellar properties, enabling a controlled comparison of giant-planet outcomes around low-mass stars. Three systems orbit super-solar-metallicity stars, while TOI-7393 ([Fe/H] = −0.35 ± 0.16) is the most metal-poor GEMS host identified to date and exhibits kinematics approaching the thin/thick-disk transition, suggestive of an older stellar population. Together, these systems reveal substantial diversity in the masses and bulk properties of short-period giant planets orbiting early M dwarfs, demonstrating that markedly different planetary outcomes can arise around stars with otherwise similar fundamental properties.

We confirm the planetary nature of (1) TOI-5916 b and (2) TOI-6158 b, two giant exoplanets around M-dwarf stars (GEMS), both discovered by the Transiting Exoplanet Survey Satellite. Both systems were confirmed with ground-based photometry (Red Buttes Observatory and Swope, respectively) and radial velocity data from the Habitable-zone Planet Finder. Their radii are R 1 = 11 . 8 − 0.51 + 0.52 R ⊕ (1.05 ± 0.05 R _J ) and R 2 = 10 . 4 − 1.11 + 2.70 R ⊕ ( 0.9 3 − 0.10 + 0.24 R J ), their masses are M ₁ = 219 ± 28 M _⊕ ( 0.68 8 − 0.088 + 0.087 M J ) and M 2 = 13 5 − 18 + 19 M ⊕ ( 0.42 5 − 0.058 + 0.060 M J ), and their orbital periods are P 1 = 2.3671234 1 − 0.0000032 + 0.0000033 days and P 2 = 3.0446899 0 − 0.00000534 + 0.00000551 days . Both planets have Saturn-like densities ( ρ 1 = 0.7 3 − 0.13 + 0.14 g cm − 3 , ρ 2 = 0.6 6 − 0.23 + 0.41 g cm − 3 ), which is consistent with the densities of most other GEMS, and with warm gas giants in general. In confirming both of these exoplanets, we add to the growing evidence for a population of Saturn-density planets among the GEMS systems. We also find evidence for a preliminary trend in which GEMS exhibit systematically closer orbits compared to FGK giants.

We demonstrate a self-referenced and optically-stabilized Er:fiber frequency comb that does not require external amplification. The 100 MHz frequency comb operates with only 250 mW of optical pump power. This advance employs a low-noise polarization-maintaining mode-locked laser that outputs 100 pJ, 100 fs pulses to drive octave generation and self-referencing with integrated nanophotonics. Multi-day optical phase locking and outdoor operation in the Colorado mountains highlight the robustness required for future use on transportable and airborne platforms beyond the research lab, where power and space are at a premium.

The nearby ( d = 7.7 pc) M4V star GJ 3378 is a target of our radial velocity (RV) exoplanet survey of fully convective stars in the solar neighborhood with the near-IR Habitable-zone Planet Finder (HPF) spectrometer on the Hobby–Eberly Telescope (HET) at McDonald Observatory. Recently, C. Moutou et al. announced the discovery of an m sin i = 5.2 6 − 0.97 + 0.94 M ⊕ planet, GJ 3378 b, with an orbital period of 24.73 ± 0.06 days, based on SPIRou RV data. Here, we present our HPF RVs for GJ 3378, as well as additional Doppler spectroscopy from the extreme-precision NEID spectrometer on the WIYN telescope at Kitt Peak National Observatory. We have analyzed the HPF + NEID RVs jointly with the published RVs from the CARMENES and SPIRou spectrometers. We present an orbital model for GJ 3378 b that differs significantly from the C. Moutou et al. solution. The joint RV model reduces the orbital period to P = 21.45 ± 0.01 days and the minimum mass to m sin i = 2.3 ± 0.4 M ⊕ . The shortened orbital distance remains within the conservative circumstellar liquid-water habitable zone (HZ), while the reduced mass increases the likelihood that the planet has a terrestrial composition. The revised planet properties place it near the “cosmic shoreline,” where planets in the HZs of M dwarfs may lose their atmospheres due to radiative stripping.

Manipulating the quantum noise of continuous-wave lasers through squeezing has reshaped optical interferometry. However, progress in optical frequency comb interferometry with pulsed squeezed sources has been limited, despite the role of frequency combs in ultraprecise optical metrology. Here, we introduce a new time-domain approach to characterizing squeezed femtosecond light pulses using dual-comb interferometry. Time-domain interferograms are generated via multiheterodyne beating between the modes of a Kerr soliton-squeezed frequency comb and a coherent state comb. The interferogram noise reveals phase-dependent squeezing and antisqueezing, dipping as much as 3.8 ± 0.2 dB below the shot noise level at alternating zero crossings. We model this nonstationary quantum noise as a periodic optical displacement of the squeezed comb by the coherent comb. These results support a route toward quantum-enhanced dual-comb timing applications and high-speed quantum state tomography with dual-comb interferometers.

We present results from a systematic search for transiting short-period giant exoplanets around M dwarf stars (GEMS; P < 10 days, R _p ≳ 8 R _⊕ ) within a distance-limited 100 pc sample of 149,316 M dwarfs using TESS-Gaia Light Curve (or TGLC) data. We describe the development and application of the TESS-miner package and associated vetting procedures used in this analysis. To assess detection completeness, we conducted ∼72 million injection-recovery tests across ∼26,000 stars with an average of ∼3 sectors of data per star, subdivided into early-type (M0–M2.5), mid-type (M2.5–M4), and late-type (M4 or later) M dwarfs. Our pipeline demonstrates high sensitivity across all subtypes within the injection bounds. We estimate the occurrence rates of short-period GEMS as a function of stellar mass, and combine our measured rates with those derived for FGK stars, fitting an exponential trend with stellar mass, consistent with core-accretion theory predictions. We find GEMS occurrence rates of 0.118% ± 0.068% for early-type M dwarfs, 0.153% ± 0.069% for mid-type M dwarfs, and 0.036% ± 0.024% for late-type M dwarfs, with a mean rate of 0.068% ± 0.024% across the full sample. While our search spanned 1.0 day < P < 10.0 days, these rates were calculated using planets orbiting with 1.0 day < P < 5.0 days. This work establishes the basis for future occurrence-rate studies of transiting GEMS.

Broadband and high-resolution spectroscopy in the visible and ultraviolet is central to advances in multiple fields, including fundamental quantum physics, biology, atmospheric science and astronomy. Traditionally, these measurements are performed with grating or Fourier-transform spectrometers using incoherent light sources. Leveraging coherent light enables powerful frequency-comb-based techniques, but is limited by the technical complexity of efficiently generating broad spectral bandwidths from relatively narrowband and spectrally distant laser sources. Current visible dual-comb spectrometers require implicit compromises between optical bandwidth, experimental simplicity, and acquisition speed. In this work, we introduce a simple and efficient dual-comb spectrometer that converts robust Er:fiber frequency combs from the near-infrared to the ultraviolet and visible with thin-film lithium niobate (TFLN) nanophotonic waveguides. Using real-time signal processing, we retrieve coherently averaged dual-comb spectra over nearly 120 THz of simultaneous bandwidth in the visible with 100 MHz spectral resolution. With these capabilities, we measure the broadband absorption spectrum of molecular iodine (I2), demonstrating the broadest visible spectral coverage of a dual-comb spectrometer to date. Additional measurements of NO2, atomic rubidium, and atomic sodium further illustrate the achievable combination of spectroscopic bandwidth, resolution, and intrinsic frequency accuracy. Our results demonstrate the powerful integration of low-power frequency combs, nonlinear nanophotonics, and digital signal processing to enable a compact, efficient and versatile approach to high-resolution mapping of complex absorption spectra across 500 THz in the UV-visible and near-infrared spectral regions for multiple applications beyond the research lab

Recent observations with the LOw Frequency ARray (LOFAR) have revealed 19 nearby M dwarfs showing bright circularly polarized radio emission. One of the possible sources of such emission is through magnetic star-planet interactions (MSPIs) with unseen close-in planets. We present the initial results from a spectroscopic survey with the Habitable-zone Planet Finder (HPF) and NEID spectrographs designed to characterize this sample and further investigate the origin of the radio emission. We provide four new insights into the sample. I) We uniformly characterized the stellar properties, constraining their effective temperatures ( T _eff ), surface gravities (log g ), metallicities ([Fe/H]), projected rotational velocities ( v sin i _⋆ ), rotation periods ( P _rot ), stellar radii ( R _⋆ ), and stellar inclinations ( i _⋆ ) where possible. Further, from a homogeneous analysis of the HPF spectra, we inferred their chromospheric activity and spectroscopic multiplicity states. From this, we identified GJ 625, GJ 1151, and LHS 2395 as single, quiescent stars amenable to precise radial velocity follow-up, making them strong MSPI candidates. II) We show that the distribution of stellar inclinations are compatible with an isotropic distribution, providing no evidence for a preference to pole-on configurations. III) We refined the radial velocity solution for GJ 625 b, the only currently known close-in planet in the sample, reducing the uncertainty in its orbital period by a factor of three, to facilitate future phase-dependent radio analysis. IV) Finally, we identified GJ 3861 as a spectroscopic binary with an orbital period of P = 14.841181 _−0.00010 ^+0.00011 d and with a mass ratio of q = 0.7663 _−0.0018 ^+0.0020 , making it the only confirmed binary with a relatively short orbit in the sample, where we surmise the radio emission is likely related to magnetospheric interactions between the two stars. These results advance our understanding of radio-emitting M dwarfs and establish an observational foundation for identifying MSPIs.

We report the confirmation and analysis of TOI-5349 b, a transiting, warm, Saturn-like planet orbiting an early M dwarf with a period of ∼3.3 days, which we confirmed as part of the Searching for GEMS survey. TOI-5349 b was initially identified in photometry from NASA’s Transiting Exoplanet Survey Satellite mission and subsequently confirmed using high-precision radial velocity (RV) measurements from the Habitable-zone Planet Finder and MAROON-X spectrographs, and from ground-based transit observations obtained using the 0.6 m telescope at Red Buttes Observatory and the 1.0 m telescope at the Table Mountain Facility of Pomona College. From a joint fit of the RV and photometric data, we determine the planet’s mass and radius to be 0.40 ± 0.02 M _J ( 127 . 4 − 5.7 + 5.9 M ⊕ ) and 0.91 ± 0.02 R _J (10.2 ± 0.3 R _⊕ ), respectively, resulting in a bulk density of ρ _p = 0.66 ± 0.06 g cm ⁻³ (∼0.96 the density of Saturn). We determine that the host star is a metal-rich M1-type dwarf with a mass and radius of 0.61 ± 0.02 M _⊙ and 0.58 ± 0.01 R _⊙ , and an effective temperature of T _eff = 3751 ± 59 K. Our analysis highlights an emerging pattern, exemplified by TOI-5349, in which transiting Giant Exoplanets around M dwarf Stars (GEMS) often have Saturn-like masses and densities and orbit metal-rich stars. With the growing sample of GEMS planets, comparative studies of short-period gas giants orbiting M dwarfs and Sun-like stars are needed to investigate how metallicity and disk conditions shape the formation and properties of these planets.