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Two Lensed Star Candidates at z ≃ 4.8 behind the Galaxy Cluster MACS J0647.7+7015

Authors :
Ashish Kumar Meena
Adi Zitrin
Yolanda Jiménez-Teja
Erik Zackrisson
Wenlei Chen
Dan Coe
Jose M. Diego
Paola Dimauro
Lukas J. Furtak
Patrick L. Kelly
Masamune Oguri
Brian Welch
Abdurro’uf
Felipe Andrade-Santos
Angela Adamo
Rachana Bhatawdekar
Maruša Bradač
Larry D. Bradley
Tom Broadhurst
Christopher J. Conselice
Pratika Dayal
Megan Donahue
Brenda L. Frye
Seiji Fujimoto
Tiger Yu-Yang Hsiao
Vasily Kokorev
Guillaume Mahler
Eros Vanzella
Rogier A. Windhorst
Source :
The Astrophysical Journal Letters, Vol 944, Iss 1, p L6 (2023)
Publication Year :
2023
Publisher :
IOP Publishing, 2023.

Abstract

We report the discovery of two extremely magnified lensed star candidates behind the galaxy cluster MACS J0647.7+015 using recent multiband James Webb Space Telescope (JWST) NIRCam observations. The star candidates are seen in a previously known, z _phot ≃ 4.8 dropout giant arc that straddles the critical curve. The candidates lie near the expected critical curve position, but lack clear counter-images on the other side of it, suggesting these are possibly stars undergoing caustic crossings. We present revised lensing models for the cluster, including multiply imaged galaxies newly identified in the JWST data, and use them to estimate background macro-magnifications of at least ≳90 and ≳50 at the positions of the two candidates, respectively. With these values, we expect effective, caustic-crossing magnifications of ∼[10 ^3 –10 ^5 ] for the two star candidates. The spectral energy distributions of the two candidates match well the spectra of B-type stars with best-fit surface temperatures of ∼10,000 K, and ∼12,000 K, respectively, and we show that such stars with masses ≳20 M _⊙ and ≳50 M _⊙ , respectively, can become sufficiently magnified to be observable. We briefly discuss other alternative explanations and conclude that these objects are likely lensed stars, but also acknowledge that the less-magnified candidate may alternatively reside in a star cluster. These star candidates constitute the second highest-redshift examples to date after Earendel at z _phot ≃ 6.2, establishing further the potential of studying extremely magnified stars at high redshifts with JWST. Planned future observations, including with NIRSpec, will enable a more detailed view of these candidates in the near future.

Details

Language :
English
ISSN :
20418213 and 20418205
Volume :
944
Issue :
1
Database :
Directory of Open Access Journals
Journal :
The Astrophysical Journal Letters
Publication Type :
Academic Journal
Accession number :
edsdoj.3ba23f1784364355ab45e16dc4e1bcf7
Document Type :
article
Full Text :
https://doi.org/10.3847/2041-8213/acb645