Worlds Next Door: A Candidate Giant Planet Imaged in the Habitable Zone of $\alpha$ Cen A. II. Binary Star Modeling, Planet and Exozodi Search, and Sensitivity Analysis

Abstract

JWST observed our closest solar twin, $\alpha$ Cen A, with the MIRI coronagraph in F1550C (15.5 $\mu$m) at three distinct epochs between August 2024 and April 2025. For the first time with JWST, we demonstrate the application of reference star differential imaging to simultaneously subtract the coronagraphic image of a primary star and the point spread function (PSF) of its binary companion to conduct a deep search for exoplanets and dust emission. We achieve a typical 5$\sigma$ point source contrast sensitivity between $\sim$$10^{-5}$-$10^{-4}$ at separations $\gtrsim$ 1" and an exozodiacal disk (coplanar with $\alpha$ Cen AB) sensitivity of $\sim$5-8$\times$ the Solar System's zodiacal cloud around $\alpha$ Cen A. The latter is an extraordinary limit, representing the deepest sensitivity to exozodiacal disks achieved for any stellar system to date. Post-processing with the PCA-KLIP algorithm reveals a point source, called $S1$, in August 2024, detected at S/N $=$ 4-6 (3.3-4.3$\sigma$), a separation of $\approx$1.5" (2 au), and with a F1550C flux (contrast) of $\approx$3.5 mJy ($\approx 5.5\times 10^{-5}$). Various tests conducted with the data show that $S1$ is unlikely to be a detector or PSF subtraction artifact and confirm that it is neither a background nor a foreground object. $S1$ is not re-detected in the two follow-up observations (February and April 2025). If $S1$ is astrophysical in nature, the only explanation is that it has moved to a region of poor sensitivity due to orbital motion. We perform PSF injection-recovery tests and provide 2D sensitivity maps for each epoch to enable orbital completeness calculations. Additional observations are necessary to re-detect candidate $S1$ and confirm its nature as a planet orbiting our nearest solar-type neighbor.

arXiv commentAccepted to ApJL. 30 pages, 24 figures, 2 tables

References in corpus (41)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• Array Programming with NumPy
• Astropy: A Community Python Package for Astronomy
• The Astropy Project: Building an inclusive, open-science project and status of the v2.0 core package
• scikit-image: Image processing in Python
• The Astropy Project: Sustaining and Growing a Community-oriented Open-source Project and the Latest Major Release (v5.0) of the Core Package
• Angular Differential Imaging: a Powerful High-Contrast Imaging Technique
• A giant planet imaged in the disk of the young star Beta Pictoris
• astroquery: An Astronomical Web-Querying Package in Python
• Detection and Characterization of Exoplanets and Disks using Projections on Karhunen-Loeve Eigenimages
• The COBE Diffuse Infrared Background Experiment Search for the Cosmic Infrared Background: II. Model of the Interplanetary Dust Cloud
• A new algorithm for point spread function subtraction in high-contrast imaging: a demonstration with angular differential imaging
• The Science Performance of JWST as Characterized in Commissioning
• Fundamental limitations of high contrast imaging set by small sample statistics
• The Mid-Infrared Instrument for JWST, II: Design and Build
• VIP: Vortex Image Processing package for high-contrast direct imaging
• Detection and Characterization of Exoplanets using Projections on Karhunen-Loeve Eigenimages: Forward Modeling
• Substructure in the Circumstellar Disk around the Young Star AU Mic (GJ 803)
• HST/NICMOS detection of HR 8799 b in 1998
• Asteroseismology and calibration of alpha Cen binary system
• The HOSTS survey for exozodiacal dust: Observational results from the complete survey
• The Stability of Planets in the Alpha Centauri system
• The Orbit and Transit Prospects for $\beta$ Pictoris b constrained with One Milliarcsecond Astrometry
• The Mid-Infrared Instrument for the James Webb Space Telescope, V: Predicted Performance of the MIRI Coronagraphs
• High-Cadence, High-Contrast Imaging for Exoplanet Mapping: Observations of the HR 8799 Planets with VLT/SPHERE Satellite Spot-Corrected Relative Photometry
• Hubble Space Telescope UV and H$\alpha$ Measurements of the Accretion Excess Emission from the Young Giant Planet PDS 70 b
• The HOSTS survey - Exozodiacal dust measurements for 30 stars
• Classically and Asteroseismically constrained 1D Stellar Evolution Models of $\alpha$ Centauri A and B using Empirical Mixing Length Calibrations
• A temperate super-Jupiter imaged with JWST in the mid-infrared
• Close stellar conjunctions of alpha Centauri A and B until 2050 - An mK = 7.8 star may enter the Einstein ring of alpha Cen A in 2028
• Long-Term Stability of Planets in the $\alpha$ Centauri System
• Imaging low-mass planets within the habitable zone of α Centauri
• Planet Detectability in the Alpha Centauri System
• Precision Millimeter Astrometry of the $\alpha$ Centauri AB System
• Dust size and spatial distributions in debris discs: predictions for exozodiacal dust dragged in from an exo-Kuiper belt
• Efficiently Imaging Accreting Protoplanets from Space: Reference Star Differential Imaging of the PDS 70 Planetary System using the HST/WFC3 Archival PSF Library
• First Observations of the Brown Dwarf HD 19467 B with JWST
• Searching for Planets Orbiting Alpha Centauri A with the James Webb Space Telescope
• Optimal Fitting and Debiasing for Detectors Read Out Up-the-Ramp
• A PR drag origin for the Fomalhaut disk's pervasive inner dust: constraints on collisional strengths, icy composition, and embedded planets
• Worlds Next Door: A Candidate Giant Planet Imaged in the Habitable Zone of $\alpha$ Cen A. I. Observations, Orbital and Physical Properties, and Exozodi Upper Limits

Cited by in corpus (3)

• Worlds Next Door: A Candidate Giant Planet Imaged in the Habitable Zone of $\alpha$ Cen A. I. Observations, Orbital and Physical Properties, and Exozodi Upper Limits
• Astrometric exomoon detection by means of optical interferometry
• SPORES-HWO. II. Companion Mass Limits and Updated Planet Properties for 120 Future Exoplanet Imaging Targets from 35 yr of Precise Doppler Monitoring