arXiv subjects

Nicholas J. Connors

Publications and source records attributed to Nicholas J. Connors.

4 recordsLinked to original sources

arXiv2026

GJ 3929 b as the First Complete Rocky Worlds DDT Data Set

Despite their large abundance, it is still unknown whether and under what conditions rocky planets around M dwarf stars can host atmospheres. This open question motivated the on-going Rocky Worlds DDT survey focused on searching for atmospheres on relatively low-temperature rocky exoplanets by systematically probing for the presence of day-night heat redistribution and CO2 absorption through JWST/MIRI 15 $\mu$m eclipse observations. Here we present the analysis of the first full data set from this survey, consisting of four observations of the warm Earth-size exoplanet GJ 3929 b, with a planetary mass of 1.75+0.44-0.45 M$_\oplus$ and instellation flux of 17.3+/-0.7 S$_\oplus$. In our analysis, we include two previously unpublished eclipse observations and find an overall eclipse depth of 118+/-22 ppm and a dayside surface brightness temperature of 641+59-64 K. This is marginally lower than the eclipse depth of 160+26-27 ppm previously reported based on only the first two observations. While the full data set remains consistent with bare rock scenarios, it also leaves more room for thin atmosphere scenarios. Only thick CO2 atmospheres without thermal inversion remain ruled out at greater than 3$\sigma$. We also continue with lessons-learned in robustly analyzing these kind of high-precision JWST/MIRI 15 $\mu$m eclipse observations. Notably, we find that the Frame Normalized Principal Component Analysis (FN-PCA) method appears more robust against the choice of extraction aperture size, which otherwise can have a significant impact on the inferred eclipse depth and scientific conclusions when using a standard polynomial baseline detrending method.

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arXiv2026

Uniform Reinterpretation of Rocky Exoplanet Secondary Eclipse Observations and the Impact of Stellar and Orbital Uncertainties

Secondary eclipse observations are a powerful way to investigate whether or not a rocky exoplanet hosts an atmosphere, as an atmospheric presence would transport heat to the nightside and render the dayside colder than anticipated. The interpretation of the secondary eclipse observations relies, however, on models based on imperfect knowledge of the host star properties and the system parameters. Any uncertainties in such astrophysical variables will propagate into both atmospheric and bare-rock models, potentially leading to poorly constrained results and erroneous conclusions. In this work, we introduce a framework to efficiently account for the stellar and orbital uncertainties when modeling the emission spectra of rocky exoplanets, and demonstrate its use by reanalyzing the current suite of rocky exoplanets with published eclipse observations. Our analysis reveals notable uncertainty in the predicted eclipse depth even for a simple dark ($A_{\mathrm{B}}=0$) bare rock as a result of the finite precision of the system's parameters and treatment of the host star's flux. In some cases, the model uncertainty is comparable to the observational uncertainty, further complicating our capability to constrain an atmospheric presence from secondary-eclipse observations. From our modeling schematic, we derive a linear correlation between the model uncertainty and the error in $R_{\mathrm{p}}/R_{\mathrm{*}}$, $ a_{\mathrm{p}}/R_{\mathrm{*}}$, and $T_{\mathrm{*}}$, therefore enabling a more robust compositional analysis in future studies. The model uncertainty serves as a fundamental precision limit to surface analyses, and must be mitigated to strongly constrain the composition of exoplanets in future eclipse observations.

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arXiv2025

Uniform Reanalysis of JWST MIRI 15{\mu}m Exoplanet Eclipse Observations using Frame-Normalized Principal Component Analysis

JWST MIRI 15 micron time-series eclipse photometry presents a powerful way to probe for the presence of atmospheres on low-temperature rocky exoplanets orbiting nearby stars. Here, we introduce a novel technique, frame-normalized principal component analysis (FN-PCA) to analyze and detrend these MIRI time-series observations. Using the FN-PCA technique, we perform a uniform reanalysis of the published MIRI 15 micron observations of LHS 1478 b, TOI-1468 b, LHS 1140 c, TRAPPIST-1 b, and TRAPPIST-1 c using our new data reduction pipeline (Erebus) and compare them to different potential atmospheric and surface compositions. We also investigate additional public data sets with the sole purpose of understanding the instrument systematics affecting MIRI. We identify and categorize important detector-level systematics in the observations that are generally present across all 17 analyzed eclipse observations, which we illustrate as eigenimage/eigenvalue pairs in the FN-PCA. One of these eigenimage/eigenvalue pairs corresponds to the prominent ramp effect at the beginning of the time-series observations which has widely been reported for JWST and Spitzer photometry. For JWST/MIRI, we show that the detector settling time scales exponentially with the apparent magnitude of the target star $T_\mathrm{set} \mathrm{[hours]} = 0.063\exp^{0.427\cdot m_K} -0.657$. This uniform reanalysis and investigation of JWST/MIRI systematics is done in preparation for the 500 hour Rocky Worlds DDT survey, to demonstrate a data-driven systematic model usable across all MIRI 15 micron datasets.

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arXiv2020

Primordial Radius Gap and Potentially Broad Core Mass Distributions of Super-Earths and Sub-Neptunes

The observed radii distribution of {\it Kepler} exoplanets reveals two distinct populations: those that are more likely to be terrestrials ($\lesssim1.7R_\oplus$) and those that are more likely to be gas-enveloped ($\gtrsim2R_\oplus$). There exists a clear gap in the distribution of radii that separates these two kinds of planets. Mass loss processes like photoevaporation by high energy photons from the host star have been proposed as natural mechanisms to carve out this radius valley. These models favor underlying core mass function of sub-Neptunes that is sharply peaked at $\sim$4--8$M_\oplus$ but the radial-velocity follow-up of these small planets hint at a more bottom-heavy mass function. By taking into account the initial gas accretion in gas-poor (but not gas-empty) nebula, we demonstrate that 1) the observed radius valley is a robust feature that is initially carved out at formation during late-time gas accretion; and 2) that it can be reconciled with core mass functions that are broad extending well into sub-Earth regime. The maximally cooled isothermal limit prohibits cores lighter than $\sim$1--2$M_\oplus$ from accreting enough mass to appear gas-enveloped. The rocky-to-enveloped transition established at formation produces a gap in the radius distribution that shifts to smaller radii farther from the star, similar to that observed. For the best agreement with the data, our late-time gas accretion model favors dust-free accretion in hotter disks with cores slightly less dense than the Earth ($\sim$0.8$ρ_\oplus$) drawn from a mass function that is as broad as $dN/dM_{\rm core} \propto M_{\rm core}^{-0.7}$.

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