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  • Identifying Close-in Jupiters that Arrived via Disk Migration: Evidence of Primordial Alignment, Preference of Nearby Companions and Hint of Runaway Migration
    Two leading hypotheses for hot Jupiter migration are disk migration and high-eccentricity migration (HEM). Stellar obliquity is commonly used to distinguish them, as high obliquity often accompanies HEM. However, low obliquity does not guarantee disk migration, due to possible spin–orbit realignment or coplanar HEM. Seeking a proxy for disk migration, we investigate the idea that when the circularization timescale of a planet on circular orbit is longer than its age (τcir > τage), HEM would not have had sufficient time to complete, favoring disk migration. We empirically calibrate the reduced planetary tidal quality factor to be using the eccentricity distribution of 500+ Jovian mass (0.2MJ < Mp < 13MJ) planets with measured masses and radii, a value consistent with solar system Jupiter. We then calculate τcir and identify dozens of disk migration candidates (τcir > τage, e < 0.1). These planets show three notable trends. We first find a clear cutoff of obliquity at τcir ∼ τage, suggesting the primordial alignment of protoplanetary disks. Second, we find that among hot Jupiters (a < 0.1 au), nearby companions are preferentially found around disk migration candidates, suggesting that either HEM dominates hot Jupiter formation, or disk migration also disrupts nearby companions at short separations. Finally, we find a possible dearth of disk migration candidates around mass ratio , consistent with a similar dip suggested at longer orbits from microlensing. The lack of planets across different orbital distance, if true, could be interpreted as a hint of runaway migration.

  • Revised Mass and Orbit of ε Eridani b: A 1 M Jup Planet on a Near-circular Orbit
    The mature Jovian planet ε Eridani b (ε Eri b) orbits one of the closest Sun-like stars at a moderate separation of 3.5 au, presenting one of the best opportunities to image a true analog to a solar system planet. We perform a thorough joint reanalysis and cross-validation of all available archival radial velocity (RV) and astrometry data, combining data from eight RV instruments and four astrometric sources (Hipparcos, the Hubble Space Telescope’s Fine Guidance Sensor, Gaia Data Release 2, and Gaia Data Release 3). We incorporate methodological advances that impact our findings, including a principled treatment of correlation between Gaia DR2 and DR3 velocity. We revise the planet’s mass upward to 1.00 ± 0.10 MJup and find that its orbit is nearly circular and likely to be to coplanar with the outer debris disk. We further present one of the first models of an exoplanet orbit exclusively from absolute astrometry and independently confirm the planet’s orbital period. We make specific predictions for the planet’s location at key imaging epochs from past and future observing campaigns. We discuss and resolve tensions between previous works regarding the eccentricity, inclination, and mass. Our results further support that ε Eri b is one of the closest analogs to a solar system planet yet detected around a nearby star.

  • MEGA Mass Assembly with JWST: The MIRI EGS Galaxy and Active Galactic Nucleus Survey
    We present the Mid-Infrared Instrument (MIRI) Extended Groth Strip (EGS) Galaxy and Active Galactic Nucleus (MEGA) survey, a four-band MIRI survey with 25 pointings in the EGS extragalactic field. Three pointings utilized only the three reddest bands (F1000W, F1500W, and F2100W), while the remainder also included a blue filter (F770W). MEGA builds upon the existing observations in the EGS field by providing MIRI imaging for 68.9% of CEERS NIRCam imaging, filling a crucial gap in order to understand galaxy evolution by observing the obscured Universe. Here, we present the technical design, data reduction, photometric catalog creation for our first data release, and science drivers of the MEGA survey. Our data reduction starts with the standard James Webb Space Telescope calibration pipeline but adds additional warm pixel masking and custom background subtraction steps to improve the quality of the final science image. We estimate the image depth of the reduced mosaics and present new galaxy number counts in four MIRI bands.

  • An Independent Search for Small Long-period Planets in Kepler Data. I. Detection Pipeline
    The unprecedented photometric precision of the Kepler mission allows searches for Earth-like planets. However, it remains difficult to distinguish these low signal-to-noise-ratio planets from the false alarms originating from correlated and non-Gaussian noise. It reduces the resulting planetary catalog reliability and makes it hard to measure the occurrence rate of small long-period planets. We aim to obtain a more reliable catalog of small long-period planet candidates from Kepler data and use it to improve their occurrence rate estimates. This work develops an independent search pipeline for small (Kepler multiple-event statistic (MES) ≲ 12) long-period (50–500 days) planets. We design and implement a detection statistic that takes into account noise non-Gaussianity and physical priors. For every threshold-crossing event, we run permutation and injection procedures to calculate the probability of it being caused by a real planet. The provided detection statistic has a tailless background distribution with a rate of ∼1 false alarm per search for MES ∼ 7.8. We demonstrate an increase in detection efficiency for MESs of 7.5–9 and >4 transits due to the background distribution control. The pipeline was tested and found to be able to detect most of the faint confirmed Kepler planets. The pipeline was applied to the entirety of Kepler data and detected ∼50 candidate events with a high probability of originating from real planets, which will be presented in our future work.

  • Characterizing Temperatures of Flares on the M Dwarf Wolf 359 from Simultaneous Multiband Optical Observations
    We present a flare temperature study of the highly active M dwarf Wolf 359 using simultaneous multiband (u, g, r, i, and z) photometric observations from the Lulin 1 m and 41 cm telescopes. Twelve flares were detected over five nights, with significant brightness increases in the u, g, and r bands; only three were seen in i, and none in z. From broadband spectral energy distribution fitting and g/r color ratio, we derive an average flare temperature of 5500 ± 1600 K, significantly cooler than the canonical 10,000 K. We obtained a power-law relation between FWHM flare temperature and energy in the solar-class flare regime and extrapolated it to higher energies, superflare regime. This power-law is consistent with the trends reported for M dwarf superflares in previous studies, suggesting a common temperature–energy scaling across several orders of magnitude. However, the scatter in the superflare regime increases, indicating that such energetic events may involve more complex physical mechanisms and limiting the applicability of simple blackbody models at the high-energy flares. Using our FWHM flare temperature–TRIPOL g energy relation and the reported flare energy frequency distribution of Wolf 359, we evaluated the potential flare contribution to photosynthetically active radiation (PAR) in the habitable zone. We find that typical solar-class giant flares (Efl,bol ∼ 9 × 1031 erg, Tfl,fwhm ∼ 6800 K) are not frequent enough to sustain Earth-like net primary productivity. Even under the extreme superflare condition (∼1036 erg, ∼16,500 K), flare activity remains far from meeting the PAR threshold.