Year: 2026
Type: article
Abstract: Massive stars at cosmological distances can be individually detected during transient microlensing events, when gravitational lensing magnifications may exceed μ ≈ 1000. Nine such sources were identified in JWST NIRCam imaging of a single galaxy at redshift z = 0.94 known as the “Warhol arc,” which is mirror imaged by the galaxy cluster MACS J0416.1−2403. Here we present the discovery of two coincident and well-characterized microlensing events at the same location followed by a third event observed in a single filter approximately 18 months later. The events can be explained by microlensing of a binary star system consisting of a red supergiant ( T ≈ 4000 K) and a B-type ( T ≳ 13,000 K) companion star. The timescale of the coincident microlensing events constrains the estimated projected source-plane size to tens of astronomical units. The most likely binary configurations consistent with the observational constraints on the temperature and luminosity of each star are stars with initial masses M 1 init = 23 . 6 − 4.3 + 5.3 M ⊙ and an initial mass ratio between the two stars close to unity. A kinematic model that reproduces the observed light curves in all filters gives a relatively small transverse velocity of ∼50 km s −1 . This requires the dominant velocity component of several hundreds of kilometers per second to be roughly parallel to the microcaustic. An alternative possibility would be that the three microlensing events correspond to unrelated stars crossing distinct microcaustics, but this would imply a highly elevated rate of events at their common position, even though no underlying knot is present at the location.
Source: The Astrophysical Journal
Authors: Hayley Williams, Patrick L. Kelly, Emmanouil Zapartas, Rogier A. Windhorst, Christopher J. Conselice, Seth H. Cohen, Birendra Dhanasingham, José M. Diego, Alexei V. Filippenko, Brenda L. Frye, Benne W. Holwerda, Terry J. Jones, Anton M. Koekemoer, Ashish Kumar Meena, Massimo Ricotti, Clayton D. Robertson, Payaswini Saikia, Bangzheng Sun, S. P. Willner, Haojing Yan, Adi Zitrin
Institutions: University of Minnesota, FORTH Institute of Astrophysics, Foundation for Research and Technology Hellas, Arizona State University, University of Manchester, Instituto de Física de Cantabria, University of California, Berkeley, University of Arizona, University of Louisville, Space Telescope Science Institute, Ben-Gurion University of the Negev, University of Maryland, College Park, New York University Abu Dhabi, University of Missouri, Center for Astrophysics Harvard & Smithsonian
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $4,499
Funders: National Science Foundation, National Aeronautics and Space Administration, United States - Israel Binational Science Foundation, Space Telescope Science Institute, United States-Israel Binational Science Foundation, Israel Science Foundation, Hellenic Foundation for Research and Innovation, Goddard Space Flight Center
Awards: G103270039, G1055883707, G256731684, G3077354795, G4096137220, G433322167, G58316358, G6273510985, Luminous High-Redshift Stars and Dark Matter Substructure Using Galaxy Cluster Lenses, NEXT GENERATION FRONTIER STUDIES OF GALAXY FORMATI ON AND EVOLUTION WITH NEXT GENERATION SPACE TELES, G6608474652, G6722835988, G6909262500, THE PROPOSAL SEEKS TO ACCOMPLISH SEVERAL INVESTIGATIONS TO SIMULATE THE PERFORMANCE OF JWST DEEP FIELD SURVEYS, VARYING AS-YET-POORLY CHARACTERIZED P, NSF-BSF: Galaxies in the Reionization Era, G8067020961, IN 2002 WE WERE GRANTED 110 HOURS GTO TIME FOR A JWST MEDIUM-DEEP SURVEY. WITH HST AND SPITZER EXPERIENCE 14 YEARS LATER WE REDEFINE THIS SURVEY TO IMAGE~18 NIRCAM FIELDS IN 7 FILTERS TO AB<~ 29 29.3 MAG YIELDING 140 000 GALAXIES AT 0<~ Z<~ 12 15 IN 0.05 DEG2 (>~ 30 HUDFS!). WE WILL STUDY GALAXY ASSEMBLY + SUPER-MASSIVE BLACK-HOLE GROWTH AT Z 0 7 INCLUDING OBJECT VARIABILITY ON MONTHS YEARS TIMESCALES. WE STUDY THE REIONIZING POPULATION AT Z 2 8 AND USE THE BEST LENSING TARGETS TO OPTIMIZE OUR STUDY OF FIRST LIGHT OBJECTS AT Z 10 15. OUR SCIENCE GOALS ARE: 1. GALAXY ASSEMBLY; 2. SUPER-MASSIVE BLACK-HOLE GROWTH; 3. REIONIZATION; 4. FIRST LIGHT; 5. STUDY THE BEST LENSING CLUSTERS TO FIND JWST OBJECTS. MAP&REMOVE STRAYLIGHT GRADIENTS AND QUANTIFY SAMPLE COMPLETENESS IN RANDOM FIELD&CLUSTER IMAGES: WE WILL: A) USE HUDF AND HFF DATA TO SIMULATE MAP AND REMOVE A RANGE OF STRAYLIGHT AMPLITUDES AND GRADIENTS THAT COULD AFFECT RANDOM DEEP FIELDS (DFS) AND CLUSTER FIELDS WITH JWST; B) DETERMINE ACCURATE COMPLETENESS CORRECTIONS VS. GALAXY FLUX SIZE WAVELENGTH AND LOCATION IN JWST DFS OF VARIOUS DEPTH AND IN CLUSTER FIELDS WITH THEIR KNOWN GALAXY CLUSTER+ICL FOREGROUND; C) DETERMINE THE CLUSTER SELECTION FUNCTIONS BY FOLDING LENSING MAPS WITH SIMULATED BACKGROUND IMAGES YIELDING SIMULATED LENSED IMAGES AND THEIR COMPLETENESS CORRECTIONS FOR LENSED SOURCES WHICH WE SHOW CAN BE FACTORS 2 3; AND D) MODEL COSMIC VARIANCE IN HIERARCHICAL MODELS AT Z 6 15. WE WILL CORRECT THE LFS FOR THESE COMPLETENESS FUNCTIONS. WE WILL THEN USE A BAYESIAN CODE TO DETERMINE THE OPTIMAL SET OF LF EVOLUTION PARAMETERS FROM THE AVAILABLE JWST DATA TO QUANTIFY HOW GALAXIES ASSEMBLED SINCE Z<~ 15., G8380842850, G8401272922, G8552695075, G8684856318, G8835071962
OpenAlex ID: W7125968168