The Roman exoplanet Imaging data challenge: a major community engagement effort

Organized by the Turnbull Science Investigation Team (SIT), the 2019-2020 Roman Exoplanet Imaging Data Challenge (EIDC) launched in mid October 2019 and ran for eight months. This data challenge was a unique opportunity for exoplanet scientists of all backgrounds and experience levels to get acquainted with realistic Roman CGI (coronagraphic) simulated data with a new contrast regimes at 10-8 to 10-9 enabling to unveil planets down to the Neptune-mass in reflected light. Participating teams had to recover the astrometry of an exoplanetary system combining precursor radial velocity data (also simulated across 15 years) with two to six coronagraphic imaging epochs (HLC and Star Shade). They had to perform accurate orbital fitting and determine the mass of any planet hidden in the data. It involved PSF subtraction techniques, post-processing and other astrophysics hurdles to overcome such as contamination sources (stellar, extragalactic and exozodiacal light). We organized four tutorial "hack-a-thon" events to get as many people on-board. The EIDC proved to be an excellent way to engage with the intricacies of the first mission to perform wavefront control in space, as a pathfinder to future flagship missions. It also generated a lot of positive interactions between open source package owners and a whole new set of young exoplanet scientists running them. As a community we are a few steps closer to being ready to analyze real CGI data

JWST/NIRCam Transmission Spectroscopy of the Nearby Sub-Earth GJ 341b

We present a JWST/NIRCam transmission spectrum from $3.9-5.0$ $\mu$m of the recently-validated sub-Earth GJ 341b ($\mathrm{R_P} = 0.92$ $\mathrm{R_{\oplus}}$, $\mathrm{T_{eq}} = 540$ K) orbiting a nearby bright M1 star ($\mathrm{d} = 10.4$ pc, $\mathrm{K_{mag}}=5.6$). We use three independent pipelines to reduce the data from the three JWST visits and perform several tests to check for the significance of an atmosphere. Overall, our analysis does not uncover evidence of an atmosphere. Our null hypothesis tests find that none of our pipelines' transmission spectra can rule out a flat line, although there is weak evidence for a Gaussian feature in two spectra from different pipelines (at 2.3 and $2.9\sigma$). However, the candidate features are seen at different wavelengths (4.3 $\mu$m vs 4.7 $\mu$m), and our retrieval analysis finds that different gas species can explain these features in the two reductions (CO$_2$ at $3.1\sigma$ compared to O$_3$ at $2.9\sigma$), suggesting that they are not real astrophysical signals. Our forward model analysis rules out a low mean molecular weight atmosphere ($< 350\times$ solar metallicity) to at least $3\sigma$, and disfavors CH$_4$-dominated atmospheres at $1-3\sigma$, depending on the reduction. Instead, the forward models find our transmission spectra are consistent with no atmosphere, a hazy atmosphere, or an atmosphere containing a species that does not have prominent molecular bands across the NIRCam/F444W bandpass, such as a water-dominated atmosphere. Our results demonstrate the unequivocal need for two or more transit observations analyzed with multiple reduction pipelines, alongside rigorous statistical tests, to determine the robustness of molecular detections for small exoplanet atmospheres.Comment: 25 pages, 18 figures, 6 tables. Accepted for publication in A

Double Trouble: Two Transits of the Super-Earth GJ 1132 b Observed with JWST NIRSpec G395H

The search for rocky planet atmospheres with JWST has focused on planets transiting M dwarfs. Such planets have favorable planet-to-star size ratios, enhancing the amplitude of atmospheric features. Since the expected signal strength of atmospheric features is similar to the single-transit performance of JWST, multiple observations are required to confirm any detection. Here, we present two transit observations of the rocky planet GJ 1132 b with JWST NIRSpec G395H, covering 2.8-5.2 $\mu$m. Previous HST WFC3 observations of GJ 1132 b were inconclusive, with evidence reported for either an atmosphere or a featureless spectrum based on analyses of the same dataset. Our JWST data exhibit substantial differences between the two visits. One transit is consistent with either a H$_2$O-dominated atmosphere containing ~1% CH$_4$ and trace N$_2$O ($\chi^{2}_{\nu}$ = 1.13) or stellar contamination from unocculted starspots ($\chi^{2}_{\nu}$ = 1.36). However, the second transit is consistent with a featureless spectrum. Neither visit is consistent with a previous report of HCN. Atmospheric variability is unlikely to explain the scale of the observed differences between the visits. Similarly, our out-of-transit stellar spectra show no evidence of changing stellar inhomogeneity between the two visits - observed 8 days apart, only 6.5% of the stellar rotation rate. We further find no evidence of differing instrumental systematic effects between visits. The most plausible explanation is an unlucky random noise draw leading to two significantly discrepant transmission spectra. Our results highlight the importance of multi-visit repeatability with JWST prior to claiming atmospheric detections for these small, enigmatic planets.Comment: 22 pages, 10 figures, 2 tables. Accepted for publication in ApJ Letters. Co-First Authors. Bonus materials and spectral data: https://doi.org/10.5281/zenodo.1000208

Products and Models for "A JWST transmission spectrum of the nearby Earth-sized exoplanet LHS 475 b"

OVERVIEW: The critical first step in the search for life on exoplanets over the next decade is to determine whether rocky planets transiting small M-dwarf stars possess atmospheres and, if so, what processes sculpt them over time. Because of its broad wavelength coverage and improved resolution compared to previous instruments, spectroscopy with JWST offers a new capability to detect and characterize the atmospheres of Earth-sized, M-dwarf planets. Here we use JWST to independently validate the discovery of LHS 475 b, a warm (586 K), 0.99 Earth-radius exoplanet, interior to the habitable zone, and report a precise 2.9 − 5.3 μm transmission spectrum using the NIRSpec G395H instrument. With two transit observations, we rule out primordial hydrogen-dominated and cloudless pure methane atmospheres. Thus far, the featureless transmission spectrum remains consistent with a planet that has a high-altitude cloud deck (similar to Venus), a tenuous atmosphere (similar to Mars), or no appreciable atmosphere at all (akin to Mercury). There are no signs of stellar contamination due to spots or faculae. Our observations demonstrate that JWST has the requisite sensitivity to constrain the secondary atmospheres of terrestrial exoplanets with absorption features &lt; 50 ppm, and that our current atmospheric constraints speak to the nature of the planet itself, rather than instrumental limits

JWST/NIRCam Transmission Spectroscopy of the Nearby Sub-Earth GJ 341b -- Supplementary Material

Supplementary material for 'JWST/NIRCam Transmission Spectroscopy of the Nearby Sub-Earth GJ 341b' by Kirk et al., AJ (2024). This repository contains six categories of data products: Data reduction reproduction — Eureka! control files (.ecf) and parameter files (.epf) alongside Tiberius input parameter files. These allow replication of our data reduction, light curve fitting, and transmission spectra extraction using the open-source code Eureka! and Tiberius. Stellar spectra — (Non flux calibrated) observed stellar spectra of GJ 341 for all three NIRCam visits as extracted with Eureka! and Tiberius. We also include flux calibrated stellar spectra for all three visits as extracted with Tiberius. Light curves — Reduced white and spectroscopic light curves from three data reduction codes (Eureka!, Tiberius, and Tswift) for all three NIRCam visits. Transmission spectra — Reduced transmission spectra from three data reduction codes (Eureka!, Tiberius, and Tswift) for all three NIRCam visits. Forward models — Set of four atmosphere forward models as presented in Kirk et al. 2024. Retrieved models — The median retrieved atmosphere model for each of the three reductions (Eureka!, Tiberius, and Tswift) as presented in Kirk et al. 2024. For any additional data requests or questions, please contact: [email protected]

High Tide or Rip-Tide? GJ 486b JWST Transits with NIRSpec G395H - Supplementary Material, v3

Supplementary material for 'High Tide or Riptide on the Cosmic Shoreline? A Water-rich Atmosphere or Stellar Contamination for the Warm Super-Earth GJ 486b from JWST Observations' by Moran &amp; Stevenson et al., ApJL (2023). This repository contains four categories of data products: White light curves — White light curves produced for Visit 1 and 2, for detectors NRS1 and NRS2 via the FIREFLy pipeline and the open-source codes Eureka! and Tiberius Transmission spectra — Reduced transmission spectra from three data reduction codes (Eureka!, FIREFLy, and Tiberius) for both G395H visits. Stellar spectra and models — Flux calibrated observed stellar spectra of GJ 486 from each G395H visit, along with best-fit PHOENIX stellar models. Atmospheric models — Atmospheric forward models used to interpret the data, produced from the open source PICASO and CHIMERA codes. For any additional data requests or questions, please contact: [email protected] or [email protected]