Little red dot variability over a century reveals black hole envelope via a giant Einstein cross
Abstract
"Little red dots" (LRDs) represent a new population of astronomical objects uncovered by JWST whose nature remains debated. Although many LRDs are suspected as active galactic nuclei (AGN), they show little variability on days-years timescales. We report the discovery of two gravitationally lensed LRDs at redshift 4.3 behind the cluster RXCJ2211-0350, one of which (RX1) is quadruply imaged with time delays spanning 130 years. RX1 exhibits intrinsic color and brightness variations of up to 0.7 magnitude among its images. These changes are consistent with blackbody-temperature variations of a photosphere, indicating long-term variability analogous to Cepheid-like pulsations but in a far more extended ( AU) and massive () systems. These results suggest LRDs as a distinct class of AGN with stellar-like envelopes.
Keywords
Cite
@article{arxiv.2512.05180,
title = {Little red dot variability over a century reveals black hole envelope via a giant Einstein cross},
author = {Zijian Zhang and Mingyu Li and Masamune Oguri and Xiaojing Lin and Kohei Inayoshi and Catherine Cerny and Dan Coe and Jose M. Diego and Seiji Fujimoto and Linhua Jiang and Guillaume Mahler and Jorryt Matthee and Rohan P. Naidu and Keren Sharon and Yue Shen and Adi Zitrin and Abdurro'uf and Hollis Akins and Joseph F. V. Allingham and Ricardo Amorín and Yoshihisa Asada and Hakim Atek and Franz E. Bauer and Maruša Bradač and Larry D. Bradley and Zheng Cai and Sebastiano Cantalupo and Christopher Conselice and Liang Dai and Pratika Dayal and Eiichi Egami and Daniel J. Eisenstein and Andreas L. Faisst and Xiaohui Fan and Qinyue Fei and Brenda L. Frye and Yoshinobu Fudamoto and Lukas J. Furtak and Miriam Golubchik and Mauro González-Otero and Yuichi Harikane and Tiger Yu-Yang Hsiao and Yolanda Jiménez-Teja and Jeyhan S. Kartaltepe and Tomokazu Kiyota and Anton M. Koekemoer and Kotaro Kohno and Vasily Kokorev and Nimisha Kumari and Ivo Labbe and Claudia D. P. Lagos and Conor Larison and Yongming Liang and Ray A. Lucas and Jianwei Lyu and Nicholas S. Martis and Georgios E. Magdis and Matteo Messa and Minami Nakane and Gaël Noirot and Rafael Ortiz and Masami Ouchi and Justin D. R. Pierel and Marc Postman and Naveen Reddy and Massimo Ricotti and Daniel Schaerer and Raffaella Schneider and Charles C. Steidel and Wei Leong Tee and Roberta Tripodi and James A. A. Trussler and Hiroya Umeda and Francesco Valentino and Eros Vanzella and Feige Wang and Rogier Windhorst and Yunjing Wu and Zihao Wu and Hiroto Yanagisawa and Jinyi Yang and Fengwu Sun},
journal= {arXiv preprint arXiv:2512.05180},
year = {2025}
}
Comments
59 pages, 13 figures, 3 tables, submitted to a peer-reviewed journal; comments are welcome